| Internet-Draft | Secure Vector Routing (SVR) | September 2022 |
| Menon, et al. | Expires 24 March 2023 | [Page] |
This document describes Secure Vector Routing (SVR). SVR is an overlay inter-networking protocol that operates at the session layer. SVR provides end-to-end communication of network requirements not possible or practical using network header layers. SVR uses application layer cookies that eliminate the need to create and maintain non-overlapping address spaces necessary to manage network routing requirements. SVR is an overlay networking protocol that works through middleboxes and address translators including those existing between private networks, the IPv4 public internet, and the IPv6 public internet. SVR enables SD-WAN and multi-cloud use cases and improves security at the networking routing plane. SVR eliminates the need for encapsulation and decapsulation often used to create non-overlapping address spaces.¶
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Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet-Drafts is at https://datatracker.ietf.org/drafts/current/.¶
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This Internet-Draft will expire on 24 March 2023.¶
Copyright (c) 2022 IETF Trust and the persons identified as the document authors. All rights reserved.¶
This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (https://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document.¶
There exists a need to communicate network requirements between IP routers and networks to provide an end-to-end experience. Selection of specific paths whose attributes meet or exceed the networking requirements are an objective of SVR. There is also a need for applications to communicate their requirements to networks. This need is increasing as workloads move to public clouds and the numbers of cloud locations increase. The standard practice today is to use an overlay network of tunnels to create a virtual network. SVR overlay is being proposed as an alternative to using tunnels. SVR simplifies the network by virtue of having only one network layer. SVR securely transports traffic with authentication and adaptive encryption. The absence of tunneling overhead reduces bandwidth. Since SVR specifies requirements abstractly, it also has the capability to interwork policies between different networks and address spaces.¶
Most WAN networks are deployed with a virtual private network (VPN) across IP backbone facilities. VPNs have the significant disadvantage of carrying additional network layers increasing packet size and leading to IP fragmentation as well as reduced bandwidth.¶
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all capitals, as shown here.¶
+---------+
|Network2 |
+----------+ | | +----------+
| SVR<---->+<-L3-IP->+<---->SVR |
| | +---------+ | |
|Network1 | +---------+ |Network 4 |
| SVR<--->SVR SVR<--->SVR |
+----------+ | | +----------+
|Network3 |
+----------+ | |
|Client SVR|<---->SVR |
+----------+ +---------+
An SVR implementation describes a network requirement semantically and shares this as metadata with a routing peer. The requirement to a peer is conveyed by means of a cookie, often referred to as first packet metadata, which is placed in the first packet of a session that is targeted towards the SVR peer. SVR requires session state on every participating SVR router and sets up a bi-flow (matching forward and reverse flows) based on the requirement. Once the session is established bi-directionally, the cookie is not sent in subsequent packets, resulting in elimination of additional overhead.¶
Benefits from this approach include:¶
The following terms are used throughout this document.¶
Secure Vector Routing is a session stateful routing overlay that operates at edges of networks where stateful NATs are normally performed. It is at these same locations where multi-path routing is being deployed. These locations include edge routers located at branches, data centers, and public clouds. SVR maps local network requirements into administratively defined text strings that have global meaning. These are communicated or signaled by insertion of a networking cookie called SVR metadata directly into IP Packets in transit.¶
SVR metadata is inserted into existing packets directly after the L4 header (see Section 4.2) The metadata in the first packet of a new session (TCP or UDP bidirectional flow) can be used for path selection and security. Metadata can be inserted in any subsequent packet to change/update the networking requirements. The metadata is inserted into the payload portion of a packet to guarantee it makes it unchanged between SVR routers.¶
Sessions supported by SVR include TCP, UDP, UDP Unicast, point-to-point ethernet, and ICMP. Sessions are characterized by having an initial first packet that is unique to an SVR router. Often this is described as a unique 5-tuples as seen by the router. Sessions start when the first packet is processed, and end when either the L4 protocol indicates the session is completed (TCP FIN/FIN ACK) or there has been no activity for a length of time (UDP, ICMP, UDP Unicast, point-to-point ethernet).¶
SVR utilizes the concept of session direction. The direction of the session is what creates a Secure Vector. Routing policies include a Tenant (source) and Service (destination) pair that exactly match the direction of sessions. When describing metadata in this document, direction is either forward or reverse; it is not tied to network topology, but rather the direction of session establishment. For TCP, the forward direction is always the client side towards the server side. For UDP, the forward direction is from the sender of the first packet. Reverse is the opposite direction. On a given pathway Secure Vector Routes could be traversing on the same pathways with opposite directions.¶
Metadata formats described in this document will be labeled as "forward" or "reverse". Forward metadata is inserted in packets going from client to server. Reverse metadata is inserted in packets that travel from server to client.¶
SVR co-exists with traditional routing. In fact, the router interface addresses known as Waypoints in this document MUST be reachable via traditional networking for every peer relationship. When packet routing is being decided in the router, should the route resolve to an SVR capable router (i.e., the next hop address returned in the route equals a known Waypoint address of an SVR Peer) then metadata MAY be inserted and session stateful SVR is performed. Otherwise, the packet is forwarded like any traditional IP router.¶
To ensure the metadata is received and understood between peers, a handshake is performed. A router that supports SVR peer pathways inserts metadata for each packet flow in the following circumstances:¶
These two comprise what is known as the "metadata handshake" -- that is, the initiating router includes metadata in all packets it sends to the recipient router until it receives a reverse packet with metadata from that recipient. Likewise, the recipient continues to send metadata to the initiating router until it receives a packet without metadata. This is how two routers acknowledge receipt of metadata from their counterparts: the absence of metadata in a packet indicates that it has received metadata from its counterpart.¶
Firewalls and middleboxes that sit along a peer pathway may not propagate TCP SYN messages with data in the payload (Despite being valid), or may verify sequence numbers in TCP streams (which are invalidated due to the inclusion of SVR metadata). The two devices that represent the peer pathway endpoints may determine through testing if there is a firewall, NAT, or other active middlebox between the two routers. The BFD protocol with metadata can be used to detect the presence of a NAT. See Section 5.1.2. Additional procedures like STUN [RFC8489], TURN [RFC6062], and ICE [RFC8445] are well-known, and not included in this document.¶
If a NAT is detected on the Peer Pathway, the SVR Router that determines its Waypoint address is being changed saves this as an attribute of the pathway. The NAT will change the port address assignment, and require NAT keep alives as exemplified in Section 6.3.¶
If a middlebox is detected, the packets can be UDP-transformed i.e., the protocol byte can be changed from TCP to UDP by the transmitting router and restored to TCP by the receiving router for packets flowing in both directions. See Section 4.2.7 and Section 4.6.3 for more information.¶
When routers use IP addresses that are dynamic, such as DHCP served addresses or PPPoE network attachments, it's possible to be assigned a new address. If this happens all existing sessions using that Waypoint address must be updated to use the new address. For existing sessions this can be performed in real time be reviewing the sending address. If the address is changed internal references to the old address can be updated. For idle circuits, BFD with metadata is used to detect address changes. See Section 5.1.3 for details.¶
To prevent breaking any applications, there MUST be a 100% guarantee that metadata inserted by a participating SVR device is removed prior to the consumption of the data by the application service. If the client and server support metadata, then SVR metadata can be sent end-to-end. When a mid-stream packet router wants to insert SVR metadata, it must guarantee that the packet is directed to a next hop device that will understand and remove the metadata.¶
A router can be certain an SVR capable router is on the path when the next-hop address returned from a FIB table exactly matches a known peer Waypoint address. Before sending the packet with metadata to the Waypoint address, the originating SVR router should determine the Peer reachability as exemplified in Section 3 and Section 5.¶
If the next-hop is not a known reachable peer, SVR metadata insertion MUST NOT be performed.¶
To guarantee that the packet will go to a specific router, the destination address for the packet is changed to the Waypoint Address of the chosen peer. The original addresses are stored in the forward context (see Section 7.4.1) and can be recovered when needed. This is similar to IPv6 segment routing (see [RFC8986]) or a LISP (see [RFC6830]) RLOC with the exception that the original addresses are stored in metadata within the payload portion of the packet, and not the IP Network Header.¶
Selection of the Waypoint Address to direct sessions to is implementation specific. In the general case a standard FIB lookup returns one or more IP Address(es) (Waypoints) of the next SVR peer. When more than one Waypoint address is returned from the FIB, additional logic can be applied to select the best Waypoint based on observed peer pathway quality OR session layer load balancing. See Section 3 for exemplary details.¶
To provide a return path for the return flow the source SVR peer changes the source address to be its own egress Waypoint address. This provides a guarantee of a symmetric flow. The state of the session MUST be held in both the source SVR router and the destination SVR peer.¶
The address translation rules for the session become state information that is processed on every packet after the metadata handshake. All 5 tuples of addressing information are updated bidirectionally for the session. This action replaces tunnel encapsulation and decapsulation (tunnel compression), and is an order of magnitude simpler computationally.¶
SVR metadata contains contextual IP Addresses (sources, destinations, and Waypoints) along with textual service names (i.e., Zoom, Office365, etc.). The SVR routers can apply policies and route sessions based on the textual names if they have a route information base that contains service names. When performing name based routing, a destination NAT is often required when exiting the SVR network. The primary use case for this is networking between public clouds such as AWS and Azure.¶
With semantic based routing, the use of Dynamic DNS to locate a service can be eliminated if clients support SVR. Clients can simply request the service by name, and the SVR router can resolve the route, and deliver the session to the best location. The last SVR Router on egress performs a destination NAT for the chosen best instance of a service.¶
A local DNS server resolving service addresses to a nearby SVR router can also provide semantic based routing. This can eliminate the need to use dynamic DNS for locating services inside data centers.¶
To avoid sharing a hash with all traffic, and to make sessions completely independent on peer pathways, the source port and destination port can be assigned any values that are unique by the source router. When there are no NATs between the two router interfaces, this permits 2^32 (4,294,967,296) different unique sessions on a peer pathway. If there are source NATs, this will be reduced to 2^16 (65,536) different unique sessions. Ports can be reassigned if not in active use. It is also possible that middle boxes will limit what destination ports are permissible, reducing the number of possibilities. Due to all these reasons, range of ports that can be used on a peer pathway are provisioned by an administrator.¶
The ingress SVR peer (client side) assigns both source and destination ports, even ports for local (source port) and odd ports for remote (destination port). This provides total uniqueness between any two peers, with no negotiation or collision possibilities. This reduces the number of sessions originating by a router to half of the total sessions (or 2^30). Think of the two ports as a Session Identification Tag. Even if a session traveling in the opposite direction was allocated the same exact ports, because the source address and destination addresses would be swapped, the 5-tuples on the wire remain unique.¶
This unique tuple per TCP/UDP session also allows any DSCP or QoS scheme to work properly. Those fields in the original packet were not modified and the underlay network routers will see those fields on a session-by-session basis.¶
After the metadata handshake has been completed. all subsequent packets are simply translated (all 5-tuples, bidirectionally). This is a very efficient process compared to IPSEC encapsulation which requires memory copies, new header creation, completely new packet checksums, and mandatory encryption.¶
Each participant (peer) in secure vector routing must maintain state for every active session. This includes the full set of original addresses and translations required. This allows participants to stop sending metadata once it has been received by the peer. There are two possible scenarios for how state could be lost. Either the ingress of the SVR session (source peer) could lose state, or an intermediate (downstream peer) SVR peer could lose state.¶
Determining if an SVR router is an ingress verses a peer SVR router is based on the arriving packet's destination address. If the address is NOT the interface address of the router, it is an ingress SVR router. Alternatively, if the address matches the interface address of the router, there are two possibilities.¶
After determining if the router is an ingress or egress SVR router when there is a flow miss, the state recovery techniques for each type of lost state is listed below.¶
Each SVR router (peer) must statefully remember the source address that a session with metadata was received on. This may not be the same address the router sent a packet from due to a NAT or Firewall in the pathway. Routers use both provisioned and learned Waypoint Addresses. Routers MUST store the actual Waypoint Addresses received on the wire from a peer.¶
When a firewall or middlebox is detected, the SVR router behind such a device must send metadata packets periodically on idle sessions to keep any firewall pinholes translations from being removed. For every UDP and TCP session that has seen no packets after a programmable length of time (20 seconds is recommended), then the SVR Peer should send an SVR Control Message on the peer path with the source and dest ports from the idle session's saved state. See Section 7.3.6 for more information and see Section 6.3 for an example.¶
BFD [RFC5880] is used to verify Peer Pathways. BFD is used to determine reachability, presence of NATs, changes of Waypoint Addresses, determination of MTU size, current quality on idle circuits, authentication of peers, and maintenance of peer cryptographic keys. Alternative methods can be used for each of these if both peers agree. The use of BFD is included in this specification as a preferred technique for Peer Pathway management.¶
BFD metadata is defined and required to measure quality, perform authentication, and maintain keys because standard BFD authentication fields are insufficient. BFD metadata is different than SVR metadata because it is inserted at the very end of a BFD control packet, and not at the end of the layer 4 header. BFD metadata is never encrypted. To make processing easy, protobufs are used to transmit the BFD metadata instead of TLV's. The specifics of BFD metadata can be found in Section 5.¶
The example below shows two SVR capable routing peers with multiple peer pathways.¶
Client
LAN
10.x.x.x
|
| +--------+ +---------+
| | | | |
| | | | |
+->] East [203.0.113.1<---MPLS---->203.0.113.89] West |
| SVR | | SVR |
| Router[198.51.100.2<--Inet-+--->198.51.100.8] Router|
| | | | |
| [192.0.2.1<-----LTE--+ | [<--+
| | | | |
+--------+ +---------+ |
<========= Peer Pathways ========> |
|
172.15.11.x
LAN
Servers
Note: The client, server, and MPLS network support the private address space 172.15.x.x natively, but the internet and LTE networks do not. This is an example of using secure vectors to join networks together.¶
The first step is that routers would apply any locally defined static L3 routes, and begin advertising and receiving routes using L3 networking protocols (BGP, OSPF, etc.) from their IP peers to build a forward information base or FIB. This is required initially to ensure that the Waypoints are reachable bidirectionally allowing SVR Peer Paths to be established.¶
The second step is for both the East and West routers to establish the authenticated peer pathways that make up the SVR Peer relationship. It is recommended that each peer pathway must be authenticated bi-directionally before the SVR pathway is used.¶
Authentication of peers is recommended. It is technically possible to send SVR metadata and determine a key for peers without authentication, but this is discouraged. Either peer could require authentication, and declare the peer relationship invalid should authentication fail.¶
Authentication is based on a certificate signature request created by the router that contains its name and authority that is signed by a trusted CA (The Router Certificate). The device registration, creation, signing, and the secure installation of this certificate are omitted from this specification. Please refer to [RFC4210].¶
Elliptical Curve encryption (see [RFC8422]) techniques are used in SVR. These are more efficient, and have smaller footprints than RSA which is necessary to efficiently operate inside the BFD protocol. The SVR Curve that is to be used is defined globally by an administrator. It is recommended that NIST Curve P-256 be used for all SVR metadata cryptography. All participating routers in an SVR network must use the same elliptic curve.¶
Each peer sends a BFD packet that contains BFD Metadata in clear text that contains an x509 Router Certificate in PEM format (see [RFC5758]). See Section 5.1.7 for specifications. Upon receipt, this certificate is verified like any other x509 certificate. The common name in the certificate provides the authenticated name of the peer router. The router must verify that the name identified in the certificate is a valid peer in its routing configuration. The certificate should have a locally verifiable chain to a trusted certificate authority.¶
In our example above, there are three pathways. The BFD message with the x509 certificate is sent by each side (East and West) on each pathway. Each side verifies the certificate, and then determines if the peer pathway is valid and should be used between peers. To communicate that the peer has received the certificate, and to stop sending it in subsequent BFD packets, a BFD packet without a certificate is sent. This defines the handshake for the local and remote peer. If a certificate is ever required (for example when a routers IP address changes) a peer can request it be transmitted by sending its certificate.¶
The public key of the router is stored and saved to verify signatures used in subsequent keying procedures (see Section 3.1.2. If the routers certificate is updated, this process must be repeated. Any outstanding valid keys remain operational, preventing outages during recertification.¶
In the above example Figure 2 there are three pathways that define the peer relationship between East and West. Assuming that all three pathways have been authenticated, the East West peer relationship has three transport pathways that are authenticated.¶
To securely send SVR that can't be intercepted by a man-in-the-middle an elliptical curve Peer Key needs to be determined that can only be known to the authenticated peers. Elliptical curve method requires each peer previously authenticated create a new key pair (see Section 5.1.8) every time a key is required or needs updated. The public keys for each side are signed by each router (ECDSA signature using the same public key from the routers authentication certificate above) and sent as BFD metadata inside BFD messages on one of the authenticated peer paths. This is transmitted once per second until a corresponding BFD message arrives without the BFD metadata. This provides the handshake guaranteeing delivery.¶
As soon as both sides have each other's public key, an ECHD based peer key can be calculated that can be used bidirectionally to encrypt all SVR metadata on any of the peer paths that represent the peer relationship. See [RFC8422] for more information on ECDH and ECDSA.¶
To rekey, at any time, either party can generate a new key pair, and send a BFD message with a new public key. The peer will then respond with a newly computed public key, and the SVR peer key can be recomputed.¶
With each new key computed, the security ID TLV Section 7.3.2 sent in SVR metadata is incremented to indicate which key version is to be used for decryption. This solves transitory race conditions that are theoretically possible.¶
The same SVR Peer Key is used for all pathways between peers. This is beneficial when sessions move from one pathway to another during multipath routing use cases.¶
When a peer has at least one working authenticated pathway, and has calculated an Elliptical Curve Peer Key (ECPK), the SVR Peer is assumed ready for transport traffic bidirectionally, and the peer is declared operational and in service.¶
When in service, East and West independently communicate using BFD to each other's interfaces to ensure operational status and measure path characteristics such as jitter, latency, and packet loss. In our example, assuming 100 percent success, the resulting peer pathways would be:¶
PEER: East -> West Authenticated/In Service Name Description Characteristics MPLS 203.0.113.1->203.0.113.89 20ms Lat, 0 Loss, 2 Jit Internet 198.51.100.2->198.51.100.8 30ms Lat, 0 Loss, 3 Jit LTE 192.0.2.1->198.51.100.8 50ms Lat, 0 Loss, 15 Jit PEER: West -> East Authenticated/In Service Name Description Characteristics MPLS 203.0.113.89->203.0.113.1 20ms Lat, 0 Loss, 2 Jit Internet 198.51.100.8->198.51.100.2 30ms Lat, 0 Loss, 3 Jit LTE 198.51.100.8->192.0.2.1 50ms Lat, 0 Loss, 15 Jit
BFD is also used on in service Peer Pathways to determine MTU size and detect address changes, and monitor quality when idle.¶
To route packets and sessions of packets onto SVR Peer Pathways, a route lookup must return an indication of either which peer pathway to use, or which peer to use.¶
In the example shown below our assumption is that there are servers that are located inside 172.15.11.0/24 at the West location. West publishes or otherwise advertises this route to East on each path available to it. Subsequently East's FIB will look like this:¶
East's Forward Information Base (FIB)
Route Next-Hop IP Addr
---------------- -----------------
172.15.11.0/24 203.0.113.89
172.15.11.0/24 198.51.100.8
....
[FIB Entries to reach Waypoints omitted]
Additionally, we will assume there exists a network policy created by the authority Example that defines a tenant "engineering" as 10.0.0.0/25 VLAN2, and "github.example" as 172.15.11.23 using TCP port 22. The provisioning and/or discovery of this policy is outside the scope of this protocol description.¶
A first packet from an engineering client with github as a destination received at the East SVR Router will result in a search of the FIB and result in two possible next-hop IP Addresses. East will consult its SVR Peer Pathway list and recognize that three of its peer pathways have an exact match of this next-hop IP Address. These represent the three possible pathways that may be used for routing this session. The resulting potential routes are:¶
Possible Routes
MPLS 20ms Latency, 0 Loss, 2 Jitter
Internet 30ms Latency, 0 Loss, 3 Jitter
LTE 50ms Latency, 0 Loss, 15 Jitter
The East router can now choose which pathway (peer pathway) is desired for the specific session. If the East router has quality service levels to maintain, it can choose from any of the peer pathways based on their current quality metrics. If all things are equal, the East router could load balance using approaches like "least busy" or other techniques. Once a peer pathway is chosen, the first packet metadata is constructed, inserted into the first packet, and sent down the chosen pathway to the West peer router.¶
For this example, the private address space in the LAN supported by the East Router is different. This is often the case with large networks. This is illustrative of a branch router performing network address translation (NAT) on a source address to solve overlapping address problems.¶
In this specific case, assuming MPLS was chosen, East would perform first packet processing resulting in the insertion of metadata in the first packet (see Section 3.7.1) and send it out East's interface with a source address of 203.0.113.1 and a destination address of 203.0.113.89. These are the exact addresses of the MPLS Peer Pathway.¶
Both the East and West routers would use the same address pairs (only reversed) for the bidirectional session, using the allocated source and destination ports to recognize the specific session. All packets from all sessions on a peer path will have the same exact IP addresses, differentiated solely by their port numbers.¶
SVR first packet metadata contains text strings that contain service names. SVR routing can route traffic by these names if the FIB contained text entries. There are some use cases where this might make sense:¶
Below is an example FIB that contains named services and traditional FIB entries. The next-hop addresses were changed to Waypoint Addresses to reflect the FIB is now an SVR fib containing service names, protocols, and ports.¶
East's Extended SVR Forward Information Base (OPTIONAL)
Egress
Service Name Route Waypoint Action
-------------- ------------------ ------------ --------
github.example 172.15.11.23:TCP:22 203.0.113.89 FWD
github.example 172.15.11.23:TCP:22 198.51.100.8 FWD
logsvc.example 172.15.11.20:UDP:514 203.0.113.89 DNS
logsvc.example 172.15.11.20:UDP:514 198.51.100.8 DNS
https.example 172.15.11.24:TCP:443 203.0.113.89 DEST NAT
-196.168.1.1
-196.168.1.2
-196.168.1.3
[FIB Entries to reach Waypoints omitted]
Longest prefix matching (LPM), protocol and port will be used to match Routes for packets intended for github on ingress to SVR. The text string "github.example" will be used by all other SVR routers until egress from SVR. The SVR fib can be used to LPM match on IP addresses and exactly match protocol and ports. In the above illustrative example, only three protocols are supported (SSH, Syslog, and HTTPs). All other packets will be denied by default.¶
The egress action in the SVR fib can be used to support three different egress actions:¶
These named routes can co-exist with traditional FIB entries shown above. SVR will always matched a named route first, and fall through to the generic routes second.¶
For basic SVR functionality to work between peers, there must be a Authority wide provisioned set of rules. These rules include:¶
SVR does not limit the use of ciphers and techniques to just those listed. The requirements for both signatures and encryption are that the results are fixed well-known block sizes.¶
Security Policies are used during session setup to setup payload encryption specifically for individual sessions. These are exchanged in first packet metadata.¶
For this example will use the following SVR security definitions.¶
HMAC: (On, time-based, SHA256-128, ALL Packets)
Metadata Encryption (On, AES256)
Elliptical Curve: Curve 256P (NIST)
To positively authenticate and provide integrity for SVR session, SVR peers use Time Based HMAC signatures. HMAC signatures are defined in [RFC2104]. Please see Section 4.5.1.¶
In our example, we are using SHA256-128 with a size of 16 Bytes.¶
Every metadata transaction includes a security ID header TLV (see Section 7.3.2).¶
Each SRV Peer will have its initial Peer Key (version 1) established during the peering establishment. The key may be updated at any time, and the key version will be incremented. The security key version is always sent in metadata to ensure the peer knows which key to use to decrypt the metadata just sent. If a peer only has version 1 of a key, and metadata arrives specifying it is now at version 2, the SVR router must obtain the new key before it can process any packets. Please see Section 3.1.2).¶
For networks that are large and actively performing key management, there may be multiple versions of a key active for very brief moments in time, and SVR routers MUST be able to utilize any key for a reasonable amount of time.¶
The diagram below shows the example github TCP session flowing between a client and server through the East and West routers in our example network.¶
Ladder Diagram for SSH Example:¶
Engineering Github
Client . . . . . . . . . . . . . . . . . . . . . Server
| |
+ East Router West Router |
| | | |
+---SYN----->| | |
| |--SYN[MD]-------------->| |
| | |--SYN----->|
| | | |
| | |<--SYN/ACK-|
| |<------SYN/ACK[RMD]-----| |
|<--SYN/ACK--| | |
| | | |
| | | |
|<==== Session Packets Flow with No Metadata ====>|
¶
The East Router MUST construct and insert metadata (MD) in the first packet of the SSH session, which will be a TCP SYN packet. The West Router must remove the metadata, and forward the SYN packet, and wait for the server to respond with a SYN/ACK. Upon receipt of the SYN/ACK, the West Router will create reverse metadata (RMD), and insert it into the SYN/ACK. This will create the metadata handshake for the SSH session. All forward and reverse metadata are inserted into existing packets if possible.¶
When a client or router detects that a new session is being established, the East Router will insert metadata into the first packet to communicate intent to the West Router. At both East and West Routers, the first packet will require specialized handling. Detecting a first packet for a session is protocol specific. For TCP, it's a new 5-Tuple packet (new flow) with the just the SYN flag set. For UDP, it's simply a new 5-Tuple packet not currently in active use.¶
Utilizing the same example, assume that the packet shown below arrives on the East Router from the Client LAN. The packet is the result of an engineer attempting to access a github service via SSH.¶
Arriving Packet at East Router¶
Packet received on LAN side East Router
Engineer using SSH to access Github
+---------+---------------------+--------------+----------+
|L2 HDR | IP Header | TCP Header | PAYLOAD |
| VLAN=2 | SRC=10.0.1.1 | Sport=6969 | Data |
| | DST=172.15.11.23 | Dport=22 | (N/A) |
+---------+---------------------+--------------+----------+
¶
Determine the Tenant. The tenant is a text name which describes the routes and policies that are available for a group of source IP addresses. Tenants are like security zones. In our example, the "engineer" is based upon VLAN 2, and the tenant will be "engineer" as named by the authority "example". The configuration and data models to map physical network attributes to named tenants is implementation specific. Associating a default tenant with every logical interface on a SVR Router is recommended.¶
There are multiple ways to determine what an intended service is. Application Identification technology is used that understands all popular SaaS offerings. These techniques use combinations of IP address ranges and ports, SNI fields in TLS, Common Name from Certificates, and extraction of URLs from http requests. Most popular SaaS vendors today publish and update frequently their CIDR blocks and ports used by their services. This is out of scope for this document.¶
Longest prefix matching algorithms are used to extract the major and key services at a site. If there is traffic which cannot be identified accurately, often it will be placed into a "catch-all" service called "internet".¶
We will assume for this document, that the address 172.15.11.23 is a well-known address for git servers at Example, and port 22 is known to be SSH.¶
Once the tenant and service have been determined, a lookup for network requirements can be determined. The requirements should include¶
Example Network Requirements¶
SERVICE: github
Access Policies:
Tenants Allowed: engineering
Tenants Denied: release.engineering
Quality Policy: latency < 40ms
Security Policy:None
¶
The above definition for github defines an example network requirement. Access policies determine which tenants are allowed, and if any specifically denied. The Quality policy defines the service level experience requirements. Secure Vector Routing exchanges tenants, services, and security policies using character strings in metadata. Access and quality policies are defined and used locally within a router and logically tied to the service. The implementation of quality and access policy controls are site specific. For example, VLAN based subnets may have different meanings at various locations. Also, QoS management schemes may be different for different network areas.¶
As stated previously, the East Router has three peer paths that can reach the destination based on L3 reachability. The next step is to apply the network requirements to see which of the peer paths remain. Our policy requires latency to be less than 40 Msecs, and this effectively eliminates East's LTE pathway from consideration. The remaining two pathways MPLS and Internet are both possible. We will choose MPLS as it has the lowest latency, offering the user the best experience.¶
Many different criteria can be used in selecting a peer pathway. In practice, how busy a peer path is and its capacity result in new sessions routing to 2nd best options. Often simple load balancing is used. In cases where there are higher costs (such as LTE or 5G networking), these may be held in reserve for backup or disaster recovery. The actual algorithms for picking peer pathways are outside the scope of this protocol.¶
In this github example, there is a source NAT at the East Router on the MPLS interface to the datacenter. This by design allows all of the remote branch sites to use overlapping addresses, and is very common in larger networks. Routers that perform source NAT have two options: use the interface address and allocate a new source port, or use an IP address pool and allocate full IP addresses for each session. Either way, this allocated address only needs to be placed into metadata, as the existing packet address will be translated to Waypoint Addresses shortly. The egress SVR router will apply the source NAT.¶
The next step is to allocate new ports for the SVR session. The ports being allocated must not be in use, and should not have been used recently to avoid any issues with middleboxes. See Section 4.2.¶
The range of ports that can be used may be site specific and tied to policies that exist in upstream firewalls or middleboxes. For these reasons, the actual pool of available addresses is provisioned on every SVR router. The East router has ports 8000 to 24000 available for both the source and destination ports. In this example we will allocate an even source port of 8000, and an odd destination port of 8001.¶
The router now has reached a point where it can forward the packet. It has valid network requirements, available peer paths, and has available SVR ports. The next step is to create and save all session state information for subsequent packet processing. A session UUID is created for end-to-end tracking of sessions. The table below refers to metadata TLVs and specific contents that are documented in Section 7.¶
Session State Table Entry¶
State Information & Mappings to Metadata Fields
Metadata TLV |------TLV------|
Category -Field VALUE Type Len Hdr
-------- ------------------ ----------------
Header 12
Header TLVs
Security ID 1 16 4 4
Path Metrics 26 10 4
-Tx Color 5
-Tx TimeValue 4200 MSecs
-Rx Color 3
-Rx TimeVlue 3950 MSecs
-Drop No
-Prev Color Count 950 Packets
--- ---
Total Header Length = 34 (26+8) 26 8
Payload TLVs
Forward Context 2 13 4
- Source IP Addr 10.0.0.1
- Dest IP Addr 172.15.11.23
- Protocol TCP
- Source Port 6969
- Dest Port 22
Tenant Name engineering 7 11 4
Service Name github 10 6 4
UUID ABCDEFGHIJKLMNOP 6 16 4
Source Router Name East Router 14 11 4
Source NAT Address 203.0.113.1 25 4 4
Security Policy NONE 15 4 4
Peer Path 19 22 4
- Source Addr 203.0.113.1
- Dest Addr 203.0.113.89
--- ---
Total Payload Length = 119 (87+32) 87 32
To West Fr West
Allocated Ports Router Router
-Source Port 8000 8001
-Dest Port 8001 8000
Session HMAC Key [Peer Key at session start]
¶
The required and optional metadata attributes that must be inserted in a first packet of a new sessions are defined in Section 4.3.1.¶
One optional metadata attribute is included in this example for the pathway metrics. This is documented in Section 7.3.7.¶
The order of the TLVs is arbitrary, but header TLVs must be before any payload TLVs. If a TLV is received that is unknown to a peer, it MUST ignore it. In this example, the header length including the two header TLVs is 34, and the 8 payload TLV's are 119 bytes long.¶
The Session HMAC Key is state information retained by the router. The Session HMAC Key is set to the current Peer Key at session initiation. This key is used for the life of a session.¶
The next step is to encrypt the metadata block as defined in Section 4.4. In our example, our provisioned security definitions include AES256 for metadata encryption. AES has a 128-bit block size for all key lengths. In our example, the metadata payload TLVs are 119 bytes large. Padding will be added during encryption to make it 128 bytes (or 9 bytes of padding). In addition, to make the encrypted data stateless, we must also include a 16 byte initialization vector directly after the encrypted block. The resultant encrypted metadata block is 178 bytes and looks like this:¶
Metadata Block¶
+--------------+--------------+---------+----------------+
| Metadata | Metadata |Padding | Initialization |
| Header ) | Payload TLVs | | Vector |
| (Unecrypted) | Payload TLVs | | Vector |
| 34 Bytes | 119 Bytes | 9 Bytes | 16 Bytes |
+--------------+--------------+---------+----------------+
|<---Clear---->|<---Encrypted Portion-->|
|<----------------178 Byte Metadata Block--------------->|
¶
The metadata block is inserted into the packet directly after the L4 Header. The total length of this specific metadata block is 178 bytes, 34 of which are header bytes and 119 for payload TLVs. If there is data in the payload portion of the IP Packet, the payload data is moved down to make room for the metadata. The packet structure will now look like:¶
Metadata Added¶
Packet with metadata inserted
+---------------------+--------------+----------+-----------+
| IP Header | TCP Header |Metadata | PAYLOAD |
| SRC=10.0.1.1 | Sport=6969 |Block | Data |
| DST=172.15.11.23 | Dport=22 |178 Bytes | (optional)|
+---------------------+--------------+----------+-----------+
¶
The transport addresses in the packet are updated to use the selected peer path.¶
Transport Addresses Updated¶
Final Transformed Packet with metadata inserted
+---------------------+--------------+----------+-----------+
| IP Header | TCP Header |Metadata | PAYLOAD |
| SRC=203.0.113.1 | Sport=8000 |Block | Data |
| DST=203.0.113.89 | Dport=8001 |178 Bytes | (optional)|
+---------------------+--------------+----------+-----------+
¶
The packet containing metadata is now signed with a HMAC signature (See Section 3.5). The HMAC signature is placed at the very end of the packet, extending the packet size by the signature's length. The IP header is excluded from the signature. The current peer key is used (see Section 5.1.8) for signing and verifying the authenticity of the packet. In this case the HMAC is 16 bytes.¶
HMAC Signature Added¶
Packet with metadata inserted
+-------------------+--------------+----------+---------+-----+
|IP Header | TCP Header |Encrypted | PAYLOAD | HMAC|
| SRC=203.0.113.1 | Sport=8000 | metadata | Data | 16 |
| DST=203.0.113.89 | Dport=8001 | | |Bytes|
+-------------------+--------------+----------+---------+-----+
| |
|<=========HMAC Signed Data========>|
¶
The packet length and checksum is corrected, and the packet is transmitted. The sending side will include the same exact metadata on every packet until a packet in the opposite direction (reverse direction) arrives with reverse metadata indicating a complete handshake. For TCP, the SYN packet contains metadata, and typically a SYN-ACK from the server side responds with metadata, and there is no further metadata inserted in a session.¶
Client ----> TCP SYN w/Metadata ----> Server
Server <---- TCP SYN-ACK w/Metadata <---- Server
¶
For UDP, metadata can be inserted in packets until there is a reverse flow packet with metadata, except for unidirectional flows as noted in Section 3.5.7.¶
If a packet arrives at the West Router having the West Routers Waypoint (interface address) as a destination address (i.e., the packet was sent to the router, and not to a destination beyond the router) the packet may likely contain metadata. When this occurs, the following steps are taken.¶
Packets arriving on the routers must be verified to be valid before they are processed (see xref target="std_metadata_checking" />). These simple checks that can eliminate any potential attack vectors. If the packet fails authentication or validation the packet MAY be dropped or responded to with an ICMP Destination Unreachable packet.¶
In the example case we are using, there are only three source addresses that could be possible:¶
Possible Source Addresses¶
203.0.113.1 MPLS Peer Pathway
198.51.100.2 Internet Peer Pathway
169.254.231.106 LTE Peer Pathway
¶
The very first and most efficient test is to verify that the metadata is present is to look for header magic number (see Section 4.6.1).¶
The next verification step is to check the HMAC signature (see Section 4.5.1). If the signature is invalid, the packet should be dropped and a security event noted. If valid, processing continues.¶
The unencrypted portions of the metadata header should be verified for reasonableness. The Header Length and Payload Length must be less than the metadata block size.¶
The next step is to decrypt the metadata (See Section 4.6.2.2). If there are any reasons why the metadata block can not be decrypted, or the decryption fails, the packet is dropped.¶
The payload TLVs can now be parsed and the necessary state and translations loaded into memory. If there is a failure to parse all TLV's, the packet is dropped.¶
Next the metadata block and HMAC signatures are removed from the packet.¶
The metadata information is used to restore the original context to the packet. The packet is then recursively processed exactly like the first packet described in Section 3.7.1 with a few differences. The Context, Tenant, Service, Security Policy and Session UUID strings are used from the metadata (as opposed to locally determining them) eliminating these steps. These are then used for applying policy and routing decisions locally. The end result is the packet may go through another SVR Peer Pathway or be delivered via standard networking techniques. In this example, the West Router delivers the packet to the Server LAN.¶
When the packet is forwarded to another SVR Peer, there are some differences. The Tenant, Service, Session UUID, Security Policy and the original 5-tuple addresses are all cloned. This provides consistent data across a multi-hop SVR network. It should be noted that the metadata must be decrypted at every SVR Router and then re-encrypted because the Waypoint addresses are different for each selected peer pathway.¶
Because every hop between SVR Routers utilizes the same session UUID, a looping first packet is easy to detect. There MUST never be two sessions with the same UUID. Any session that loops must be dropped. By detecting looping packets during the first packet transmitted, subsequent packets can be dropped on ingress by the SVR Router that detected the looping behavior. SVR routers must also decrement the TTL and operate in all ways like a traditional router to prevent looping packets that are not detected by SVR.¶
When a packet arrives with metadata after the metadata handshake has been completed, it is assumed to be an update and not classified as looping. Updates can be used to change any attribute, but most commonly to change a peer pathway for a session. See Section 6.1.¶
After processing the first forward packet at both East and West routers, both the East and West routers have established packet forwarding rules and translations for both directions. This means that eastbound rules and westbound rules are all established and installed. The router is thus capable now of recognizing 5-tuples in either direction and acting on the packets without consulting routing tables. This is known as fast path processing.¶
On a session-by-session basis, SVR Routers must know the status of a metadata handshake. If a packet for a session arrives and the metadata handshake is not complete, the SVR Router must insert metadata for the session. This will continue until there is verification that the SVR Peer has received the information. As stated previously, for TCP SYN this is normally the first reverse packet which is a TCP SYN/ACK. The purpose of reverse metadata is:¶
In this example, the reverse metadata includes:¶
Reverse Metadata Response¶
Reverse Metadata Response
State Information & Mappings to Metadata Fields
Metadata TLV |------TLV------|
Category -Field VALUE Type Len Hdr
-------- ------------------ ----------------
Header 12
Header TLVs
Security ID 1 16 4 4
Path Metrics 26 10 4
-Tx Color 3
-Tx TimeValue 4100 MSecs
-Rx Color 5
-Rx TimeVlue 4050 MSecs
-Drop No
-Prev Color Count 1950 Packets
--- ---
Total Header Length = 34 (26+8) 26 8
Payload TLVs
Reverse Context 4 13 4
- Source IP Addr 203.0.113.1
- Dest IP Addr 172.15.11.23
- Protocol TCP
- Source Port 7891
- Dest Port 6969
Peer Path 19 22 4
- Source Addr 203.0.113.89
- Dest Addr 203.0.113.1
--- ---
Total Payload Length = 43 (35+8) 35 8
To East From East
Allocated Ports Router Router
- Source Port 8001 8000
- Dest Port 8000 8001
Session HMAC Key [Peer key used by remote peer]
¶
See Section 4.3 for required and optional TLVs in reverse metadata.¶
One optional metadata attribute is included in this example for the pathway metrics. This is documented in Section 7.3.7.¶
The Session HMAC Key is state information retained by the router. The Session HMAC Key is set to the Peer Key version specified in the SVR Metadata (Security ID). This is most like the current Peer Key but it is possible ReKeying could create a race condition. To solve this problem, the Session State for routers terminating SVR sessions uses the Peer Key indicated by the initiator. This key is used for the life of a session.¶
One of the outstanding benefits of SVR is the complete tracking end-to-end of sessions. In this example, the metadata state located in the SVR router contains all addresses used. The forward context provides the egress SVR router with the addresses being used pre-NAT, and the source NAT information. The reverse context would likewise supply the ingress SVR destination NAT addresses. Also knowing the Waypoint Addresses used along with the ports used provides a complete end-to-end visibility of each session.¶
This metadata will be encrypted, inserted, and an HMAC checksum will be computed and attached as per the previous example. The reverse packet in this example will have 34 bytes of header data, and 43 bytes of payload data, 5 bytes of padding, and a 16 byte initialization vector resulting in a metadata block that is 98 bytes long.¶
As soon as an SVR peer receives a packet of a session from another SVR peer and there is no metadata, the SVR Handshake is complete, and it can stop sending metadata. This work for both the East Router and the West Router. Both will transmit metadata until they receive a packet without metadata.¶
No metadata is sent upon normal session termination. The router can monitor the TCP state machine and have a guard timer after seeing a FIN/ACK or RST exchange. After the guard timer, the session can be removed from the system. If a new session arrives during this period (a TCP SYN), then it will cause immediate termination of the existing session. In addition, all protocols also have an associated inactivity timeout, after which the session gets terminated if no packets flow in either direction. Should an existing session send a packet after the inactivity timeout, it will be processed as a new session.¶
When there are unidirectional flows, or path asymmetry (e.g. TCP sequence numbers advance with no reverse packets observed), and there is end-to-end communication, one can stop sending metadata. For UDP asymmetry, the sending router will send a maximum of 11 packets with metadata; if no reverse packets are seen during that time, the receiving peer router generates and sends a disable metadata packet to the originating router to complete the metadata handshake.¶
The diagram below shows a typical normal TCP session flowing between a client and server through routers in a network.¶
Ladder Diagram for Session Initiation with Metadata:¶
Client . . . . . . . . . . . . . . . . . . . . . . Server
| |
+ RouterA RouterB RouterC |
| | | | |
+---SYN----->| | | |
| |--SYN[MD1]-->| | |
| | |--SYN[MD2]->| |
| | | |--SYN----->|
| | | | |
| | | |<--SYN/ACK-|
| | |<--SYN/ACK--| |
| |<--SYN/ACK---| [RMD2] | |
|<--SYN/ACK--| [RMD1] | | |
| | | | |
| | | | |
|<===== Session Packets Flow with No Metadata =====>|
¶
Note that each router constructs metadata for the next chosen peer in the routed pathway as depicted by MD1 and MD2 in the above diagram. Upon receipt of first reverse packet, reverse metadata RMD2 and RMD1 is inserted. Each router allocates its own transport addresses (Waypoints) for each session. The context, service name, tenant name, and session UUID are sent unchanged between all routers, and can be used for determining routing policies to apply. The session UUID is the same in MD1, MD2, RMD1, and RMD2 in the above diagram.¶
Likewise, the diagram below shows a session teardown sequence for a typical TCP session.¶
Ladder Diagram for Session Teardown Metadata:¶
Client . . . . . . . . . . . . . . . . . . . . . . Server
| |
+ RouterA RouterB RouterC |
| | | | |
+---FIN----->| | | |
| |-----FIN---->| | |
| | |----FIN---->| |
| | | |-----FIN-->|
| | | | |
| | | |<--FIN/ACK-|
| | |<--FIN/ACK--| |
| |<--FIN/ACK---| | |
|<--FIN/ACK--| | | |
| | | | |
| | | | |
¶
No metadata is sent or required when sessions terminate. Each router keeps its state information for a programmed length of time in case a FIN/ACK is delayed or dropped, then the state information is removed.¶
This section provides the normative requirements for SVR Metadata to achieve interoperability.¶
SVR implementations MUST support TCP, UDP, and ICMP. SVR implementations SHOULD support UDP Unicast. Sessions are characterized by having an initial first packet that is a unique to an SVR router. Often this is described as a unique 5-tuples as seen by the router. Sessions start when the first packet is processed, and end when either the L4 protocol indicates the session is completed (TCP FIN/FIN ACK) or there has been no activity for a length of time (UDP, ICMP, UDP Unicast, point-to-point ethernet).¶
SVR is always OPTIONAL. SVR implementations can choose when to use SVR on a session-by-session basis. SVR implementations MUST support non-SVR traffic.¶
SVR implementations MUST insert metadata into packets directly after the L4 header, even if the resulting increase in packet size would cause the packet to require fragmentation. For Ethernet point-to-point and ICMP error messages, IP Headers and L4 headers MUST be created, and if associated with an existing session MUST share the exact transport 5-tuples (SVR Waypoints and Ports) as the session the ICMP error message relates to. The metadata MUST be in the very first packet of a new session (TCP or UDP bidirectional flow) to have any role in path selection or security. Metadata SHALL be sent in any subsequent packet in any direction to change or update the networking requirements. The metadata is inserted into the payload portion of a packet to guarantee it makes it unchanged through the network. Packet lengths and checksums MUST be adjusted accordingly. TCP sequence numbers MUST NOT be adjusted.¶
A prerequisite for SVR metadata insertion is that a Peer Pathway MUST be selected relating to a specific session. This is similar to choosing a tunnel between two networks. This Peer Pathway has IP addresses on either side (Waypoint Addresses), and these addresses will always be the transport IP addresses for packets containing SVR metadata.¶
The SVR peer originating the session (client side) MUST allocate both source and destination ports. The ingress side MUST choose even ports for local (source port) and odd ports for remote (destination port) This provides total uniqueness between any two peers, with no negotiation or collision possibilities. The range of ports to use for allocation is provisioned. Ports in use MUST be excluded from allocation. Ports MUST be unallocated when session state is removed. Ports MUST have a 60 second guard time before being reallocated¶
SVR implementations MAY need to send metadata to a peer at a time when there are no existing packets. In these cases an IP packet MUST be created and inserted into the appropriate existing session with an indication the packet should be dropped. See Section 6.3 for an example. The packet MUST be processed, interpreted, and dropped by the directly adjacent peer and not forwarded to any other SVR peer.¶
Existing IP Packet with metadata inserted +------------------+-----------------+---------+----------+----+ | Existing IP Hdr | Existing L4 Hdr |Metadata | PAYLOAD |HMAC| | Source IP Addr | Source Port |Block | Data | | | Dest IP Addr | Dest Port | |(optional)| | +------------------+-----------------+---------+----------+----+ GeneratedIP Packet with metadata inserted +-------------------+------------------+---------+----+ | Created IP Hdr | Created L4 Hdr |Metadata |HMAC| | Source IP Addr | Source Port |Block | | | Dest IP Addr | Dest Port | | | +-------------------+------------------+---------+----+ ICMP Packet with metadata inserted +-----------------+----------------+----------+--------+----+ | Created IP Hdr |Created UDP Hdr |Metadata | ICMP |HMAC| | Source IP Addr| Source Port |Block | MSG | | | Dest IP Addr | Dest Port | | | | +-----------------+----------------+----------+--------+----+ Ethernet Packet with metadata inserted +-----------------+----------------+---------+---------+----+ | Created IP Hdr |Created UDP Hdr |Metadata | Ethernet|HMAC| | Source IP Addr| Source Port |Block | MSG | | | Dest IP Addr | Dest Port | | | | +-----------------+----------------+---------+---------+----+¶
If UDP protocol, the UDP Header MUST be updated to have the correct packet length.¶
The Layer 4 header (TCP/UDP) MUST have its checksum recalculated per the appropriate procedures.¶
The IP Packet length field MUST be updated to reflect the number of bytes added for the metadata block AND the HMAC signature.¶
The IP Header Checksum MUST be updated after the IP Packet length is adjusted.¶
If TCP protocol, the TCP Sequence numbers MUST NOT be changed.¶
Metadata is sent inside the payload portion of TCP and UDP packets. Given that no byte sequence is truly unique in the payload of a packet, in the scenario where the original payload after the L4 header contained the same byte sequence as the SVR magic number, false positive logic is enacted on the packet. This guarantees downstream SVR routers will not confuse metadata magic number signatures.¶
False positives SHALL NOT occur when first packets are processed, since valid metadata will always be inserted regardless of the contents of the first 8 bytes of the payload. False positive can only occur during existing valid SVR sessions between peers.¶
To implement false positive logic, SVR implementations MUST insert an empty metadata header (12 byte header with 0 TLVs). This creates a contract with downstream SVR routers that if the magic number is present, there MUST be valid metadata that requires processing and removal.¶
The structure of a false positive metadata includes just a header of length 12 bytes, with zero header TLVs and zero payload TLVs. The SVR router receiving a packet with false positive metadata will strip out the metadata header and any TLV's as is normally expected. The inserted metadata header has no TLV's and is not encrypted.¶
Metadata Location¶
Received Midstream SVR Packet matching SVR Magic Number +-------+--------+-------------------------+ |IP Hdr | L4 Hdr |0x4c48dbc6ddf6670c ..... | +-------+--------+-------------------------+ Midstream SVR Packet with False Positive metadata inserted +--------+--------+--------+---------------------------+ | IP Hdr | L4 Hdr |Metadata| 0x4c48dbc6ddf6670c ...... | | | | HDR | | +--------+--------+--------+---------------------------+¶
Insertion of header or payload TLV's is OPTIONAL and at the discretion of the implementation. If adding TLV's, standard procedures MUST be applied including encryption if payload TLV's are added.¶
TCP to UDP transformation is required when a middlebox blocks certain TCP packets that contain metadata. SVR implementations typically test Peer Pathways to ensure metadata insertion into TCP SYN packets will pass through any middleboxes. If TCP SYN packets with metadata are dropped by a middle box, then TCP packets are transformed to UDP for SVR processing, and restored when exiting SVR processing. The steps to transform TCP to UDP are:¶
The protocol field in the IP header MUST be changed from 0x06 (TCP) to 0x11(UDP).¶
The UDP checksum will write over the sequence number. To save the sequence number, it is copied to the 32-bit checksum/urgent pointer location of the TCP header.¶
To positively communicate that TCP to UDP transformation has occurred, one must add TLV 12 to the metadata being transmitted. See Section 7.4.9.¶
The UDP transformation is for every packet in a session, not just the packets with metadata. The restoration process is depicted in Section 4.6.3.¶
The metadata TLVs that MUST be inserted in a first forward metadata packet of a new sessions includes:¶
Optional metadata TLV's that MAY be included in forward metadata are:¶
The order of the TLVs is arbitrary, but header TLVs must be before any payload TLVs. If a TLV is received that is unknown to a peer, it MUST ignore it.¶
The metadata TLVs that MUST be inserted in a first reverse packet of a new sessions include:¶
Optional metadata TLV's that MAY be included reverse metadata are:¶
The metadata TLVs that MUST be inserted when returning an ICMP Error include:¶
Optional metadata TLV's that MAY be included reverse metadata are:¶
Encryption of metadata utilizes block mode ciphers. Cipher's MUST have a consistent block size. The cipher to use and its block size MUST be provisioned and known to peers in advance. The provisioning methodology is outside the scope of this document. The Peer Key used for encryption is specific to all Peer Pathways between any two peers and is obtained using BFD with metadata (See Section 5.1.8). When data is encrypted with block mode ciphers, the block will be padded with zeros (0x0's) to equal an increment of the block size used by the cipher. An initialization vector allows the decryption to be performed without any state.¶
Metadata Block¶
Cipher Block Size IV Size
------- ----------------- -------
AES256 128 Bits(16 Bytes) 16 Bytes
AES128 128 Bits(16 Bytes) 16 Bytes
+----------+--------+---------+--------+----------------+
| Metadata | Header | Payload |Padding | Initialization |
| Header | TLVs | TLVs | | Vector |
+----------+--------+---------+--------+----------------+
|<------Clear------>|<-- Encrypted --->|
|<---------------------- Metadata Block ---------------->|
¶
The padding can be computed as the length of the metadata payload TLVs MOD block size.¶
Through provisioning (outside the scope of this document), an SVR Authority MUST define if HMAC signatures are to be used. An SVR Authority MUST also define if Time Based HMAC is to be used. AN SVR Authority MUST determine if ALL packets are signed, or just packets containing metadata. Due to the possibility of replay attacks, it is RECOMMENDED that Time Based HMAC signatures be used on ALL SVR packets. The Session HMAC Key is determined at session initialization and defaults to the Peer Key (see Section 5.1.8).¶
SVR Peers SHOULD sign all packets with HMAC signatures defined in [RFC2104]. The Session HMAC Key should be used when creating an HMAC signature. When present there MUST be only one HMAC signature in an IP packet even if it fragments across multiple physical IP packets. Time-based HMAC signatures are RECOMMENDED. For time-based HMAC signatures, SVR routers append the current time since epoch (measured in seconds) divided by 2 to the data being signed. SVR routers MUST have clocks synchronized accurately. Methods for synchronizing clocks and measuring any differences or drifts are outside the scope of this document. Minimally NTP [RFC5905] should be implemented. In cases where the current time cannot be relied on, one may need to disable the time based HMAC and use a standard HMAC, but this is NOT RECOMMENDED.¶
The HMAC signature is always added to the very end of a packet. The size of the HMAC signature depends on which signature is used. Well known HMAC types are used with SVR including SHA1, SHA256-128, and SHA256.¶
SVR Packet with metadata inserted
+-----------+--------------+---------+----------+-------+
|IP Header | L4 Header |Metadata | PAYLOAD | HMAC |
| | | |(optional)| |
+-----------+--------------+---------+----------+-------+
| |
|<======= HMAC Signed Data ========>|
Subsequent SVR Packet
+-----------+--------------+---------+-------+
|IP Header | L4 Header |Payload | HMAC |
| | | | |
+-----------+--------------+---------+-------+
| |
|<== HMAC Signed Data ==>|
HMAC TYPE LENGTH OF SIGNATURE
------------------ ----------------------
SHA1 20 Bytes
SHA256-128 16 Bytes
SHA256 32 Bytes
¶
If HMAC signatures are present in an SVR implementation, SVR implementations MUST verify and remove the signature. Verification provides both authentication of the SVR router that sent the packet, and integrity that the packet has not been modified in any way intentionally, or through transmission errors between two SVR routers.¶
Through provisioning (outside the scope of this document), an SVR Authority MUST define if HMAC signatures are present. An SVR Authority MUST also define if Time Based HMAC is to be used. AN SVR Authority MUST determine if ALL packets are signed, or just packets containing metadata. Due to the possibility of replay attacks, it is RECOMMENDED that Time Based HMAC signatures be used on ALL SVR packets. The Session HMAC Key associated with the session state is used for all HMAC signatures and verification.¶
To verify the HMAC signature, a new signature is generated on the packet and bytewise compared to the signature transmitted in the packet.¶
SVR Packet with HMAC Signature
+-----------+--------------+----------+-------+
|IP Header | L4 Header | PAYLOAD | HMAC |
| | |(optional)| |
+-----------+--------------+----------+-------+
| |
|<== Signed Data ========>|
SVR Packet with HMAC Signature removed
+-----------+--------------+----------+
|IP Header | L4 Header | PAYLOAD |
| | |(optional)|
+-----------+--------------+----------+
¶
For efficiency reasons, when verifying an Time Based HMAC signature, implementers SHOULD compute the HMAC on the packet (not including the IP header) and save the preliminary result. Then try updating the HMAC signature with the current window value. If this fails to match the signature, one must try updating the preliminary result using the next time window by adding 2 seconds (or previous by subtracting 2). If the time window is determined to be the next time window; it will remain that way for all packets received from a particular peer until it advances with clock time. Keeping an active time window per peer can make this process much more efficient.¶
If the signature does not match after checking adjacent time windows and newly issued keys, then the packet is dropped and a security event noted.¶
If the signature matches exactly the signature in the packet, then the packet has been authenticated as being sent by the previous SVR router, and assured that the packets integrity between the two routers is good. The HMAC signature MUST be removed from the packet.¶
The IP Packet length field MUST be updated to reflect the number of bytes removed.¶
The IP Header Checksum MUST be updated after the IP Packet length is adjusted.¶
Routers MUST process SVR traffic and non-SVR traffic. SVR Routers MUST keep track of sessions that are using SVR. Only sessions setup with SVR may use the procedures described below. Traffic that is using SVR will always originate and terminate on Waypoint addresses (known peer pathways). This provides efficient separation of non-SVR traffic and SVR traffic.¶
Packets received on known Peer Pathways MUST be assumed to either have metadata or be packets associated with existing SVR sessions.¶
Any packet could arrive at any time with metadata. DPI MUST be used to scan for the presence of metadata on every packet. Metadata MAY be expected and required for first packet processing, and the absence of metadata will result in dropped packets.¶
The HMAC verification step (defined above) MUST be performed prior to performing any other metadata verification steps. This prevents attacks by modifying packet on the wire.¶
If the first 8 bytes of the payload (TCP or UDP) exactly matches the SVR magic number (0x4c48dbc6ddf6670c) it indicates that packet MUST have metadata. If the first 8 bytes do not match, the packet does not contain metadata. If metadata is not present the packet SHOULD be routed if part of an existing session (See Section 4.6.4). If not part of an existing session the packet MUST be dropped and a security event noted.¶
The metadata header is parsed (see Section 7.1). If the header length and payload length are both zero, the metadata is simply removed and the packet is forwarded. Please see Section 4.2.6 for description of false positive metadata header insertion. The next step is to walk the header TLV's to ensure they are reasonable. If the payload length is zero, then the metadata can be accepted and processed. Decryption of metadata is only required when there are payload TLV's.¶
If a TLV is sent that is unknown to the implementation, the TLV should be skipped and the TLV MUST NOT be forwarded.¶
If the metadata TLVs are not reasonable, the packet MUST be dropped and security events noted.¶
If the peers have been provisioned to encrypt metadata with a specific cipher AND the payload length in the header is non-zero, then the SVR implementation MUST assume that an encrypted metadata block was transmitted.¶
To decrypt the encrypted metadata block, an SVR implementation MUST have the pre-provisioned Cipher, block size, and initialization vector size. Once these are known, it is possible based on the payload length in the metadata header to determine the exact structure of the packet, and how to decrypt it.¶
Encrypted Metadata Block¶
Known in advice: Cipher, Block Size, IV size
From Metadata Header: Payload TLV size
+----------+--------+-------+-------+----------------+--~~~
| Metadata | Header |Payload|Padding| Initialization | Rest...
| Header | TLVs |TLVs | | Vector (IV) | of ...
| | | | | | Pkt ...
+----------+--------+-------+-------+----------------+--~~~
|<------Clear------>|<- Encrypted ->|
|<------------------ Metadata Block ---------------->|
¶
The padding is equal to the payload length from the header MOD cipher block size. The "block" is then decrypted assuming that the IV size bytes following the "block" is the Initialization vector.¶
If the decryption fails, then the packet MUST be assumed invalid and dropped. When this happens a security event is noted.¶
After the decryption succeeds, the payload TLV's MUST be reviewed for reasonableness and completeness. See Section 4.3 for minimum required TLV's. If there are insufficient TLV's present for the SVR implementation, the packets MUST be dropped and errors noted.¶
After review of the TLV's, the metadata is considered valid and accepted by the SVR implementation. The metadata block is removed from the packet, and the IP header length and checksum MUST be corrected. The packet signatures and decryption provide a very high degree of assurance that the metadata is authentic and has integrity.¶
If the received metadata block contains a TCP SYN Packet TLV (see Section 7.4.9) then the following procedures MUST be performed on EVERY packet of the session. This also signals to the SVR Router that packets flowing in the opposite direction MUST also be UDP transformed. See Section 4.2.7. The steps performed are:¶
The protocol field in the IP header MUST be changed from 0x11 (UDP) to 0x06 (TCP).¶
Copy the 32-bit integer in the checksum/urgent pointer location of the TCP header to the sequence number, effectively restoring it.¶
The TCP Checksum MUST be recalculated.¶
Any packet that is has a source and destination IP address that maps to a Peer Pathway is an SVR packet. SVR Packets that do not have metadata are SVR session packets. Each of these MUST have corresponding known session state. If no session state exists, these packets MUST be dropped, or there must be an attempt to restore session state (see Section 2.10).¶
Packets ingressing to a peer pathway that are part of existing SVR sessions that do not contain metadata MUST be translated (all 5-tuples, bidirectionally). The source address MUST be replaced with the local Waypoint address associated with the peer pathway. The destination address MUST be replaced with the Waypoint of the SVR Peer chosen. The protocol either remains the same, or is modified if UDP Transformation is required (See Section 4.2.7). The source and destination port fields MUST be replaced with the ports allocated for this SVR session. For efficiency, implementors SHOULD save a single checksum delta as part of the session state because the address/protocol/port modifications will always be identical for each packet of a session.¶
Packets egressing from a peer pathway must have their addresses restored. SVR session state MUST contain the original packet context 5-tuples for every SVR session. The original Source IP Address MUST be restored. The original Destination IP Address MUST be restored. The original protocol must be restored, and if it is changes from UDP to TCP then one MUST follow the procedures defined in Section 4.6.3. The source port MUST be restored. The destination port MUST be restored.¶
A provisioned SVR Policy SHOULD include both a tenant and service. Absence of an applicable SVR policy SHOULD prevent SVR sessions from being established. Traditional IP routing can be used when SVR policies do not apply.¶
Services are textual names for sets of CIDR blocks, protocols, and ports. Services map directly to our human understanding of a network use case. Examples include "Zoom" or "Office365".¶
Service Definition¶
svc_name
protocol:TCP/UDP
port ranges[]
CIDR Blocks[]
¶
When a packet arrives with metadata at an SVR Router the name of the service MUST be in first packet metadata.¶
When a first packet arrives without metadata, the service must be determined through a lookup of the IP destination address, port, and protocol. The resultant string becomes the service name. If this fails to result in a service, the name of the service can be determined by using application recognition techniques. These are omitted from this document, but include HTTP Request Analysis, TLS SNI, and Common names in certificates.¶
Services can have associated quality policies and security policies associated with them via provisioning. This is outside the scope of this document.¶
When egressing an SVR Peer Pathway, the service name can be used to route the packet to another SVR Peer, or to the final destination. If another SVR peer is chosen, the service name MUST be used as provided by the previous SVR peer. When exiting SVR and returning to traditional network routing, the textual service name MUST be resolved to an IP address. SVR supports several options:¶
Services SHOULD be provisioned to have lists of Tenants that are permitted to use a Service, and tenants that are denied using a service. These access controls are RECOMMENDED.¶
Tenant is a text string hierarchy delimited by periods. Tenants are logically similar to VLANs, CIDR block subnets, and Security Zones. The entire text string, including the full hierarchy is used to define a tenant, and for policy application, the tenant MAY match right to left in full segments (delimited by periods). The longest match will always be used (the most segments).¶
Tenants SHOULD be referenced and associated with Services to create a from-to vector. This has the benefits of associating ACLs directly with Destinations. A provisioned SVR Policy SHOULD include both a tenant and service. Absence of a applicable SVR policy prevents SVR sessions from being established. The deny by default approach is RECOMMENDED.¶
It is RECOMMENDED that a tenant be associated with physical interfaces and logical interfaces (VLANs) as a default for arriving sessions. CIDR block-based tenants SHOULD override these defaults. Tenant definitions directly from clients that self-assert their tenancy SHOULD override all other tenant definitions.¶
All network interface-based tenant definitions are local to an SVR router. The tenant definitions on ingress to SVR MAY not match those on egress from SVR. This permits the use of different segmentation techniques in different networks.¶
If payload encryption is required, a Security Policy is used to describe all aspects of the agreed upon methods. The Security Policy meaning must be valid and equal at the point of encryption and decryption in multi-hop use cases. The current Peer Key is the default key used for encryption. The security policy may require a new key be created for every session, replacing the Peer Key. Either way, the Security KEY TLV (see Section 7.4.15) contains the key for encryption/decryption in the first packet. This allows the key for decryption to go end-to-end in multi-hop router cases. The key is safe because metadata is encrypted hop-by-hop through the network. Thus each payload encrypted packet is decrypted once at the end of the SVR route. Using a semantically named Security Policy permits implementations to use whatever ciphers and techniques they wish, as long as they can be named.¶
If a router that has originated an SVR session that required payload encryption rekeys with the peer handling the session (see Section 5.1.8) it can send the new key in metadata in the very first packet encrypted with the new key. Packets coming from the remote peer will continue to arrive encrypted with the old key. When the remote router responsible for decryption receives the new key, it begins using it for the session. The key is included in reverse metadata when the first packet is encrypted with this new key in the reverse direction.¶
If the security policy agreed up has an alternative key methodology, the initial and subsequent keys are treated the same way. The responsibility for the key is always the source of the SVR session, and communication of the key is always using SVR metadata.¶
Peer Pathways are similar to Tunnels. They represent virtual transport pathways between routers. BFD is an excellent way to very reachability, measure quality of a pathway, and to perform authentication and key management.¶
It is RECOMMENDED for every configured or discovered SVR Peer pathway, A UDP BFD session be used to monitor the state of the pathway, and through extensions, measure path quality.¶
BFD Control messages are sent by each router on each peer path. The BFD message is constructed with appropriate timers for the Peer Pathway which are administratively determined. BFD as defined in [RFC5880] does not support certificates or exchange of public keys. To overcome this, BFD metadata is used.¶
BFD Metadata is inserted into existing BFD messages for the following purposes:¶
BFD Metadata is added to the end of the BFD packet when required. If BFD metadata is added, the length field in the IP Header, UDP Header, and BFD Control message are all adjusted to be accurate.¶
BFD Metadata Location:¶
BFD Control Packet with Metadata
+-----------+--------+---------+----------+
|IP Header | UDP | BFD | protobuf |
| | Header | Control | BFD |
| | | Packet | Metadata |
+-----------+--------+---------+----------+
| |
|<== BFD Pkt Len ==>|
¶
In all cases, BFD packets will be defined as BFD Control Packets. When sending MeasureData messages which behave like BFD Echo packets, the Required Min Echo RX Interval (see [RFC5880]) is greater than zero.¶
The metadata is described by as follows:¶
BFD Metadata Protobuf Definition:¶
syntax = "proto2";
package pb.bfd;
import "ip.proto";
message PeerAuth {
required string certificate = 1;
}
message PeerPublicKey {
required string signed_key = 1;
}
message SessionData {
required ip.Tuple original_ipTuple = 1;
required ip.Tuple received_ipTuple = 2;
optional string peername = 3;
optional string routername = 4;
}
message MeasureData {
message Request {
required uint32 transId = 1;
}
message Response {
required uint32 request_transId = 1;
required uint32 response_transId = 2;
}
oneof type {
Request request = 1;
Response response = 2;
}
optional bool mtu_discovery = 3;
}
message NodeInfo {
required uint32 id = 1;
required uint64 create_timestamp = 2;
optional uint64 time_value = 3;
}
message Metadata {
optional SessionData sessionData = 1;
optional MeasureData measure = 2;
optional NodeInfo nodeInfo = 3;
optional PeerAuth peerAuth = 4;
optional PeerKey peerKey = 5;
}
¶
The SessionData message can be used to determine the source address a remote peer router receives on a Peer Pathway. This is required to establish a peer path. Configuration will be tied to a router hostname, and not a dynamic address associated with a hostname. Remote Peers will create a local address resolution table (i.e. /etc/hosts) to resolve the hostname in configuration to the dynamic IP address. This action can be performed simultaneously with Detection of NAT between Peers below.¶
Determination of Peer Received Address:¶
Router-A Router-B Local
[Addr-A -> -Addr-B] DNS
| | |
|BFD ------------------>| |
| original_ipTuple=A | |
| hostname="Router-A" | |
| |DNS Update------------>|
| | Router-A: Address A |
| | |
| | |
Router-B has hostname lookup for Router-A
¶
The SessionData message can optionally be used to detect NATs between two routing peers. Typically, this is performed during initial peer pathway establishment, and often grouped together with sending Peer Authorization certificates. Similarly to STUN, the IP address of the originating interface is stored in the field SessionData.original_ipTuple. If the router has received any BFD packets from its peer router, it will store the IP address of the received BFD packet in this field. When sending the SessionData BFD metadata, a router OPTIONALLY places its own name in the peername field. Through the process of comparing real addresses seen on the wire with addresses used by the routers interfaces, one can detect when there is a NAT on a Peer Pathway.¶
BFD NAT Detection on Pathway:¶
Router-A NAT Router-B
Addr-A Addr-N Addr-B
| | |
|BFD ------------------>| |
| original_ipTuple=A | |
| | |
| |BFD ------------------>|
| | original_ipTuple=N |
| | |
| | |
NAT Detected
Router-B gets N
address on the wire
and it doesn't match
original_ipTuple
| | |
| | |
| |<-------------------BFD|
| | original_ipTuple=B |
| | received_ipTuple=N |
|<-------------------BFD| |
| original_ipTuple=B | |
| received_ipTuple=N | |
| | |
No NAT detected
Router-A gets B's address
on the wire which matches
the original_ipTuple
¶
If a NAT is detected in a Peer Pathway as in the above example, care must be taken to associate address N with the Peer Pathway to Router-A. Sessions that are traversing this Peer Pathway may require NAT Keep Alive processing. See Section 6.3.¶
Often branch data routers are connected to networks and receive their IP Address dynamically from DHCP, LTE or PPPoE procedures. Although it is rare, sometimes these addresses change unexpectedly. This may be the result of a lease running out, or a router reestablishing connectivity after a failure. When this happens, any peer that was using the old address will lose connectivity to this peer. By including SessionData BFD Metadata, learning the address of the peer and recovery occur very quickly.¶
BFD Detection on Router Address Change:¶
Router-A DHCP Router-B
[Addr-A -> Server <-Addr-B]
| | |
|BFD -------------------------------------->|
| original_ipTuple=A | |
| received_ipTuple="" | |
| | |
|<---------------------------------------BFD|
| | original_ipTuple=B |
| | received_ipTuple=A |
|BFD -------------------------------------->|
| original_ipTuple=A | |
| received_ipTuple=B | |
Both routers have learned each other's IP Address
and have confidence there are no NAT's between them
|DHCP Lease Exp ---->| |
|<-------New Address C| |
| | |
|BFD -------------------------------------->|
| original_ipTuple=C | |
| received_ipTuple=B | |
|<---------------------------------------BFD|
| | original_ipTuple=B |
| | received_ipTuple=C |
Both routers have the correct IP Address and
confidence there are no NATs between them
¶
Knowing the MTU size on a path is important for routers so they can fragment packets when necessary. After a peer pathway is established, a series of BFD MeasureData packets that increase in size can help us find the limit of packet size between peers. To make the BFD packet larger the lengths are adjusted in the IP header, UDP header, and BFD header. A peer receiving a BFD request with the MTU Discovery field equal to TRUE that is fragmented simply does not respond.¶
Often there is an entire network between peers. As such, the MTU size may change over time. It is recommended that the MTU size be measured routinely, and updated if it should change.¶
BFD MeasureData for Determining Pathway MTU:¶
Router-A Router-B
[Addr-A -> <-Addr-B]
| |
|BFD MeasureData (id=1, size 1200)-------------->|
|BFD MeasureData (id=2, size 1250)-------------->|
|BFD MeasureData (id=3, size 1300)-------------->|
|BFD MeasureData (id=4, size 1350)-------------->|
|BFD MeasureData (id=5, size 1400)-------------->|
|BFD MeasureData (id=6, size 1450)-------------->|
|BFD MeasureData (id=7, size 1500)-{fragmented}->|
| |
|<----(req_id=1, resp_id=1)-------BFD MeasureData|
|<----(req_id=2, resp_id=2)-------BFD MeasureData|
|<----(req_id=3, resp_id=3)-------BFD MeasureData|
|<----(req_id=4, resp_id=3)-------BFD MeasureData|
|<----(req_id=5, resp_id=3)-------BFD MeasureData|
|<----(req_id=6, resp_id=3)-------BFD MeasureData|
MTU Size = 1450
¶
After a Peer Pathway is authenticated, and ready for use, BFD can be used to measure latency and packetloss. This is performed by sending BFD packets with BFD MeasureData metadata. Both sides of a Peer Pathway can test for quality if desired. The number of packets in a burst is determined by configuration. The frequency of quality tests is also determined by configuration. Quite often routers with a large number of Peer Pathways (such as a data center hub router) may never perform quality tests, and rely solely on observations made by its peer spoke routers.¶
These quality measurements are only required when circuits are idle. When sessions are traversing a peer path, quality measurements can made for existing sessions using SVR Path Metrics (See Section 7.3.7).¶
The receiving side generates a response message by re-writing the BFD metadata and supplies information if requested. Each "request" generates a "response". Each request has a transaction ID, and so does each response. This solves a problem of exact symmetry where by a peer may not know if a message is a response or a request from a peer.¶
BFD MeasureData for Measuring Pathway Quality:¶
Router-A Router-B
[Addr-A -> <-Addr-B]
| |
|BFD MeasureData (req_id=1)------------------>|
|BFD MeasureData (req_id=2)------------------>|
|BFD MeasureData (req_id=3)------------------>|
.......
|BFD MeasureData (req_id=n)------------------>|
|<----(req_id=1, resp_id=1)----BFD MeasureData|
|<----(req_id=3, resp_id=2)----BFD MeasureData|
|<----(req_id=1, resp_id=3)----BFD MeasureData|
......
|<----(req_id=N, resp_id=N-1)--BFD MeasureData|
Latency = Sum of RTT(pkt 1-n)/(2*n)
Jitter = Std Dev RTT(pkt 1-n)
Packet Loss = 1-(Pcks_Sent-Pcks_recv/Pkts_Sent)
¶
Router-B responds to each BFD MeasureData message it receives by responding to the original message and adding a serialized resp_id. To measure latency, the sending (measuring) side (Router-A in this case) can measure the elapsed time between each req_id sent, and its response. Absence of a responce counts as a packet lost. The variability in latency provides a method of calculating jitter, and MoS scores can be computed once latency, packetloss, and jitter are known.¶
Both Router-A and Router-B must send their own BFD MeasureData messages to get their own quality measurements from their own specific point of view. The actual network quality between these two routers can vary based on direction.¶
If one side of a Peer Pathway fails, and there is a redundancy action that automatically takes over, BFD NodeInfo metadata can be used to detect this event. Knowledge of a Peer Pathway failover may be required by routers in certain feature scenarios.¶
For redundancy, routers are often grouped into a cluster of active/active modes. Responsibility for a Peer Pathway may change from one member of a cluster to another. When sending BFD with Metadata, by including the Node ID (instance number in a cluster) and a timestamp of when the Peer router started, one can detect redundancy events at the far end side of a Peer Pathway.¶
Inclusion of this is optional. There may be features that require special actions by a remote peer where redundancy events impact them. If this is the case, you may need to use this method.¶
SVR Routers will authenticate with each other using their textual names. This is similar to how servers authentic using their domain names. In SVR, Authorities have name space control over router names, and as such SVR Router names for authentication will consist of "name/authority". For example, if an authority named "example" created a router named "router1", the name used for authentication will be "router1/example". All configuration referencing this specific router would use this name.¶
Names are used for authentication because router IP Addresses often change. This is true when transport addresses of branch routers are established using DHCP and leases expire. Names are also used for authentication between routers to avoid duplicate certificate verification for multiple pathways for a single router peering relationship.¶
When a router is initialized, if it does not have a signed authentication certificate that is valid, it must obtain one from a certificate authority. The router will create an elliptic-curve public/private key pair (see [RFC8422]). The public key is used to create an x.509 certificate signing request (CSR) with the common name field set to the routers name. Elliptic-curve is used to ensure the x509 certificate is as small as possible. A certificate signing request is initiated to a known and trusted CA through a secure connection. The CA will digitally sign (ECDSA) the the CSR and return it to the requesting router. The specific details of this process is omitted from this specification, but it is recommended that it follow the procedures and guidelines defined in [RFC4210]. Certificates and Public Keys are stored locally on each router in PEM format defined by [RFC7468].¶
Creating Router Authentication Certificate:¶
RouterA
Certificate
RouterA Authority
| |
+------+------+ |
|Cert Missing,| |
| Invalid | |
| or Expiring | |
+-------------+ |
| |
+-----+-----+ |
| Create | |
|Curve-P256 | |
| Pub/Priv | |
| Key Pair | |
+-----------+ |
| |
+-----+-----+ |
| Create | |
| x.509 Cert| |
| CN=RouterA| |
+-----------+ |
| |
+------CSR------>|
| |
|<--x509 Signed--|
¶
The certificate is stored on the router persistently in PEM format. The private key associated with the certificate should be stored in a secure non-volatile storage, such as a Trusted Platform Module (TPM).¶
When establishing a peer pathway, The routers authentication certificate (encoded in PEM format is inserted as BFD Metadata into a BFD message and the BFD message is sent to a peer. The certificate MUST be included in all BFD messages until the remote peer successfully sends its certificate in response, and the certificate has been validated. This provides a handshake guaranteeing delivery for both local and remote peers.¶
The diagram below shows two routers, with two peer pathways. The certificates are sent by both routers on both pathways, but only need to be validated one time for each router peer.¶
Router Authentication:¶
RouterA RouterA RouterB RouterB
Peerpath1 Peerpath2 Peerpath1 Peerpath2
| | | |
=============ALL PEER PATHS ARE DISCONNECTED==========
| | | |
|--BFD w x509 Cert------>| |
| |--BFD w x509 Cert------->|
| | | |
....Delay between retransmissions .......
| | | |
|--BFD w x509 Cert------>| |
| | RouterA |
| | Validated |
| | | |
| |--BFD w x509 Cert------->|
| | | |
|<----BFD w x509 Cert----| |
RouterB | | |
Validated | | |
| |<-----BFD w x509 Cert----|
| | | |
=============ALL PEER PATHS ARE OPERATIONAL==========
| | | |
....Delay between retransmissions .......
| | | |
|----BFD---------------->| |
| |-------BFD-------------->|
|<-------------BFD-------| |
| |<-------------BFD--------|
¶
When a certificate is received from a peer, it must be validated. The validation includes the following checks:¶
The validation for a peer only needs to be done one time. When a certificate is received from a peer on multiple peer paths, if the certificate is identical to a previously validated certificate, a cached validation response can be used.¶
When receiving a certificate from a peer router, after validation, the receiving router must extract the peer routers public key and save it. This will be used for validating Peer Key/rekey requests authenticity.¶
Each router should update its authentication certificate before the current certificate expires utilizing the same exact steps identified herein.¶
Elliptic-Curve Diffie-Hellman is used between two peers to compute a key for cryptography. See [ECDH_Key_Exchange] for details on key calculation, and see [RFC8422] for examples on how ECDH is used in TLS. For example, a 256 Bit key can be computed from the public key exchange for a peer relationship between two routers.¶
A single key is used for all paths between two routers. The key is kept and considered valid until a new key is accepted as a replacement. This includes across network outages and path failures. If a key is lost, or doesn't appear to function correctly, a new key must be obtained before processing of traffic with SVR metadata can occur.¶
Anytime a key is needed, a new public/private key pair is generated locally for the peer relationship. The public key is signed, and stored locally as a PEM formatted text string. The PEM string is inserted as BFD metadata and transmitted to the peer UDP BFD Control packet. Upon receipt the remote peer will respond by creating a new public/private key pair for the same peer relationship, and then return its public key, signed with its router public key formatted as a PEM string.¶
The key is shared on all peer paths between two peers. Once calculated on one peerpath, it can be used immediately on all others with the same remote peer.¶
When both local and remote peers have their newly created public keys, then a new shared peer key can be computed using Elliptic-Curve Diffie-Hellman techniques. The key can be immediately used for encrypting metadata after incrementing the Security ID (see Section 7.3.2).¶
Peer Path Key/Rekeying:¶
RouterA RouterA RouterB RouterB
Peerpath1 Peerpath2 Peerpath1 Peerpath2
| | | |
........NO Current Key Exists...............
| | | |
|--BFD w KEY Req-------->| |
| | | |
|<----BFD w KEY Req------| |
| | | |
Key | Key |
Computed | Computed |
| | | |
......Security ID=1, 1st Key Exists........
| | | |
...........At Rekeying Interval............
| | | |
| |--BFD w Key Req--------->|
| |<---BFD w Key Req--------|
| | | |
........... 2nd Key Exists.................
| | | |
..........Transition Guard Time.............
| | | |
.......Security ID=2, 2nd Key used..........
¶
SVR Payload Metadata uses encryption. During the rekeying period prior to both sides exchanging new public keys, and computing their new peer key, the old key is used. A reasonable guard time should be added post key computation to prevent any retransmitted packets, delayed packets or long latency packets not having a key ready for use.¶
If a peer sends BFD with Key Request to a peer for which there is not a current valid key, and there is no response, then the peer path remains out of service until there is a valid response.¶
If a peer sends a BFD with Key Request to a peer, and there is no response, the peer continues to resend it at periodic intervals. If there is no response after a very long period of time, the peer path can be declared not valid, and removed from service based on administrative timers.¶
Metadata can be inserted and used to share network intent between routers. Below are examples for specific use cases. The metadata is not limited to these use cases, these are just illustrative.¶
To change the pathway of a session between two routers, any SVR Router simply reinserts the metadata described in section Section 3.7.1.7 and transmits the packet on a different peer path, but retains the same Session UUID of the existing session that is being moved.¶
After 5 seconds the old path state entries can be removed. By keeping the old and new fast path entries during this 5 second transition, no packets in flight will be dropped. The diagram below shows the sequence for moving sessions around a failed mid-pathway router.¶
Ladder Diagram for Existing Session Reroute with Metadata:¶
RTR-A RTR-B RTR-C RTR-D
Client . . . . . . . . . . . . . . . . . . . . . . . . Server
| | | | | |
|--PUSH--->| | | | |
| |--PUSH-------------->| | |
| | | |--PUSH--->| |
| | | | |--PUSH--->|
| | | | |<---ACK---|
| | | |<---ACK---| |
| |<--------------ACK---| | |
|<---ACK---| | | | |
| | | | | |
......................RTR-C Fails.......................
|--PUSH--->| | | | |
| |--PUSH--->| | | |
| | [MD1] | | | |
| | |--PUSH[MD2]--------->| |
| | | | |--PUSH--->|
| | | | |<--ACK----|
| | |<-----ACK[RMD2]------| |
| |<--ACK----| | | |
|<--ACK----| [RMD1] | | | |
| | | | | |
|<======== Session Packets Flow without Metadata =====>|
¶
When router C fails, metadata MD1,MD2 can be included in the very next packet being sent in either direction. Confirmation that the move was completed is confirmed with reverse metadata RMD2, RMD1. For established TCP sessions, this is either a PUSH (as shown) or an ACK (Not shown). This can reestablish the SVR session state into a new router (Router B in this example) that previously did not have any involvement in the session. This technique can also be used to modify paths between two routers effectively moving TCP sessions from one transport (MPLS for example) to another (LTE). A session move can be initiated by any router at any time.¶
Ladder Diagram for Session Reroute Between Peers with Metadata:¶
+-------+ +--------+
| +-----MPLS-----+ |
Client--| Rtr-A | | Rtr-B +----Server
| +------LTE-----+ |
+-------+ +--------+
Client . . . . . . . . . . . . . . . . . . . . . . Server
| |
| RouterA RouterB |
| | | |
|---PUSH---->| | |
| |---PUSH over MPLS-------->| |
| | |---PUSH--->|
................MPLS has Poor Quality ................
| | | |
|---PUSH---->| | |
| |---PUSH over LTE[MD]----->| |
| | |---PUSH--->|
| | |<---ACK----|
| |<---ACK over LTE[RMD]-----| |
|<---ACK-----| | |
| | | |
|<===== Session Packets Flow without Metadata =====>|
¶
The diagram shows moving an active TCP session from one transport network to another by injecting metadata (MD) into any packet that is part of the transport in either direction. Reverse metadata is sent on any packet going in the reverse direction to confirm that the move was successful (RMD).¶
Certain sessions may be idle or packets may create a one-way information flow (TCP Pushes) with one way acknowledgement (TCP ACKS). In these scenarios, insertion of metadata into existing packets may not be possible.¶
After moving a session, if an SVR router determines no packets are received or sent for an active session over an elapsed time of 1 second, the SVR router will generate an SVR Control Message to the peer.¶
Ladder Diagram for One Way Media Move with Metadata:¶
+-------+ +--------+
| +-----MPLS-----+ |
Client--| Rtr-A | | Rtr-B +----Server
| +------LTE-----+ |
+-------+ +--------+
Client . . . . . . . . . . . . . . . . . . . . . . Server
| |
| RouterA RouterB |
| | | |
| | |<---PUSH---|
| |<---PUSH over MPLS------->| |
|<---PUSH----| | |
|----ACK---->| | |
| |------ACK over MPLS------>| |
| | |---ACK---->|
| X RouterA MPLS FAILS | |
| X RouterB MPLS OK| |
| X | |
..............RouterA Moves Session to LTE..........
| | |<---PUSH---|
| X<---PUSH over MPLS------->| |
| | |<---PUSH---|
| X<---PUSH over MPLS------->| |
| | | |
.......NO Packets at Router A for Moved Session......
| | | |
| |-----[MD over LTE]------->| |
...............RouterB Moves Session to LTE..........
| | |<---PUSH---|
| |<--PUSH over LTE [RMD]--->| |
|<---PUSH----| | |
|----ACK---->| | |
| |------ACK over LTE------->| |
| | |---ACK---->|
|<======== Session Packets Continue flowing =======>|
¶
The SVR Control Message uses the new SVR router interface addresses (Waypoints) and contains the standard first packet metadata fields with the SVR Control Message TLV added to the header with drop reason "FLOW MOVED". Also added is a TLV attribute with the remaining session time. This is essential to ensure mid-stream routers remove sessions from their tables roughly at the same time. This message will be transmitted once every second for 5 seconds OR reverse metadata has been received. If no reverse metadata has been received in 5 seconds the session is torn down. For a quiescent flow, the RMD is a generated SVR Control Message as well as shown below:¶
Ladder Diagram for Quiescent Moved Session with Metadata:¶
+-------+ +--------+
| +-----MPLS-----+ |
Client--| Rtr-A | | Rtr-B +----Server
| +------LTE-----+ |
+-------+ +--------+
Client . . . . . . . . . . . . . . . . . . . . . . Server
| |
| RouterA RouterB |
| | | |
|<========== Quiescent Session Established ========>|
| | | |
| X RouterA MPLS FAILS | |
| X RouterB MPLS OK| |
| X | |
..............RouterA Moves Session to LTE..........
| | | |
| |-----[MD over LTE]------->| |
| | | |
...............RouterB Moves Session to LTE..........
| | | |
| |<-----[RMD over LTE]----->| |
| | | |
|<=========== Quiescent Session Continues =========>|
¶
If an SVR Router determines there is one or more NATs on a peer pathway (See Section 2.4, the SVR Peer must maintain the NAT bindings for each active session by sending keep alive metadata in the direction of the NAT. For keep alive, SVR utilizes a packet that matches the L4 header of the idle session that includes metadata type 24 with the drop reason set to Keep Alive.¶
Ladder Diagram for NAT Keep Alive with Metadata:¶
RTR-A NAT RTR-B
Client . . . . . . . . . . . . . . . . . . Server
| | | | |
...................Existing SVR Session......
|--PUSH--->| | | |
| |--PUSH--->| | |
| | |---PUSH-->| |
| | | |--PUSH--->|
| | | |<---ACK---|
| | |<---ACK---| |
| |<--PUSH---| | |
|<--PUSH---| | | |
.........NO PACKETS EITHER DIRECTION FOR 20 SECS........
| | | | |
| |--[MD1]-->| | |
| | |--[MD1]-->| |
| | | | |
.........NO PACKETS EITHER DIRECTION FOR 20 SECS........
| | | | |
| |--[MD1]-->| | |
| | |--[MD1]-->| |
| | | | |
¶
The metadata attributes that MUST be inserted in a keep alive for existing packet sessions includes:¶
Because there are only header attributes, encryption is not required.¶
Unlike a tunnel where all packets must be encrypted, each session in SVR is unique and independent. Most of the modern applications sessions are already using TLS or DTLS. SVR Routers have the capability of encrypting only sessions that are not already encrypted. Below is an example of adaptive encryption. With adaptive encryption, every session begins unencrypted. By analyzing the first 4 packets, the router can determine that encryption is required or not. If the fourth packet in a TLS Client hello message, encryption is NOT required. Any sequence of packets that does not indicate TLS or DTLS setup would immediately toggle encryption on.¶
Ladder Diagram of Adaptive Encryption with Client Hello:¶
Client . . . . . . . . . . . . . . . . . . Server
| |
+ RouterA RouterB |
+---SYN----->| | |
| |----SYN[MD1]----->| |
| | |--SYN----->|
| | |<--SYN/ACK-|
| |<----SYN/ACK------| |
|<--SYN/ACK--| [RMD1] | |
|---ACK----->| | |
| |------ACK-------->| |
| | |--ACK----->|
|--Client--->| | |
| Hello |<== ENCRYPTION===>| |
| | Not Required | |
| | | |
| |-----Client------>| |
| | Hello |--Client-->|
| | | |
¶
If the fourth packet is not an indication that encryption will be performed by the transport layer, then the ingress SVR Routers must encrypt and the egress SVR router must decrypt the session bidirectionally. This ensures that any data between the SVR Routers is encrypted.¶
Ladder Diagram of Adaptive Encryption with data:¶
Client . . . . . . . . . . . . . . . . Server
| |
+ RouterA RouterB |
+---SYN----->| | |
| |--SYN[MD1]--->| |
| | |--SYN----->|
| | |<--SYN/ACK-|
| |<--SYN/ACK----| |
|<--SYN/ACK--| [RMD1] | |
|---ACK----->| | |
| |----ACK------>| |
| | |--ACK----->|
|---Data---->| | |
| |<==ENCRYPT===>| |
| | Required | |
| | | |
| |--Encrypted-->| |
| | Data |---Data--->|
¶
Adaptive encryption is part of the security provisioning. Security policies are associated with services, and as such certain applications can mandate encryption; others may allow adaptive encryption, and still others may specify no encryption.¶
When a fragmented packet is presented to a SVR Router, the packet must be completely assembled to be processed. The SVR Router routes IP packets, and as all SVR actions require the entire packet. As such, the HMAC must be applied to the entire packet, and the entire packet must be routed as a whole. Each resulting fragment must be turned into an IP packet with 5-tuples that match the corresponding session to ingress and pass through an SVR. The SVR Router will simply use the same L4 header on all fragments from the session state table (peer pathway and transit ports). a time based HMAC signature is created for the entire packet and appended to the last fragment. Each fragment must also have metadata inserted that clearly identifies the fragment to the SVR routing peer.¶
Ladder Diagram Fragmented Packets:¶
Client . . . . . . . . . . . . . . . . . . . . . . Server
| |
| RouterA RouterB |
| | | |
|--Frag 1--->| | |
|--Frag 3--->| | |
|--Frag 2--->| | |
| +---+----+ | |
| |Assemble| | |
| +---+----+ | |
| |----Frag 1[L4/MD]-------->| |
| | | |
| |----Frag 2[L4/MD]-------->| |
| | | |
| |----Frag 3[L4/MD]-------->| |
| | +--------+ |
| | |Assemble| |
| | +--------+ |
| | |--Frag 1-->|
| | |--Frag 2-->|
| | |--Frag 3-->|
¶
In the diagram above, Router A collects all the fragments 1 2, and 3. Reassembly is performed. Router A records two things from the inbound fragments: The Original ID, and the largest fragment size received. Router A then proceeds to send the jumbo packet by fragmenting it again, but this time sending each piece inside a packet with a newly created L4 which maps exactly to the peer pathway chosen with ports assigned from the session state table. The fragment size will be the lesser of the smallest MTU on the path OR the largest fragment seen, whichever is smaller. The Metadata header and header TLV's are not encrypted. The packet construction looks like this:¶
SVR Fragment Packet Layout¶
Fragment 1
+-----+-----+----------+----------+---------+
|Peer |Peer | Metadata | Header | First |
|IP |L4 | Header | TLV-1,16 | Fragment|
|HDR |HDR | 12 Bytes | 22 Bytes | |
+-----+-----+----------+----------+---------+
Fragment 2
+-----+-----+----------+----------+---------+
|Peer |Peer | Metadata | Header | Second |
|IP |L4 | Header | TLV-1 | Fragment|
|HDR |HDR | 12 Bytes | 14 Bytes | |
+-----+-----+----------+----------+---------+
Fragment 3
+-----+-----+----------+----------+---------+----------+
|Peer |Peer | Metadata | Header | Third | PKT |
|IP |L4 | Header | TLV-1 | Fragment| HMAC |
|HDR |HDR | 12 Bytes | 14 Bytes | | SIGNATURE|
+-----+-----+----------+----------+---------+----------+
¶
The metadata type 1 inside the SVR fragment will have its own extended ID assigned. This allows a different number of fragments to be between router A and B than the Client and Server have. It also allows independent fragmentation by SVR should it be required. Router B will process the fragments from router A. Router B will look at its egress MTU size, and the largest fragment seen recorded by RouterA and transmitted in Metadata to determine the proper size fragments to send, and the packet is fragmented and sent.¶
There are no other metadata fields required. All information about the session state is tied to the 5-tuple peer pathway and transports ports.¶
The details on packet fragmentation are identical to what is standardly performed in IP fragmentation, exception for the full L4 headers and metadata insertion.¶
If a packet traversing an SVR needs to be fragmented by the router for an SVR segment for any reason, including the insertion of metadata, the initiating router inserts metadata on the first packet and duplicates the L4 header (either TCP or UDP) on subsequent fragments and inserts metadata. In this case the Largest Fragment Seen and Original ID field in the metadata is left blank.¶
Ladder Diagram Fragmented Packets:¶
Client . . . . . . . . . . . . . . . . . . . . . . Server
| |
| RouterA RouterB |
| | | |
|--Lg Pkt--->| | |
| |--------Frag 1[MD]------->| |
| | | |
| |----Frag 2[L4 Hdr|MD]---->| |
| | |--Lg Pkt-->|
| | | |
¶
There are two types of ICMP messages. There are messages associated with specific packet delivery network errors. This includes:¶
These messages have information from the packet that generated the error by including the IP header + 8 bytes in the ICMP message (See [RFC0792]. It is important to deliver the ICMP message back to the origin. For these ICMP messages, the router MUST determine what active session the ICMP message belongs to by parsing the IP header information inside the ICMP message. Once a session is found, the ICMP message is transported across the SVR and reverse metadata is applied by having its destination address changed to the Waypoint Addresses of the routers.¶
Metadata type 20 and 21 are used to send the source of the ICMP error backward through the networks. See Section 7.3.4 and Section 7.3.5 for information about these metadata formats. This repeats until the ICMP packet arrives at the initial SVR router. At this point the ICMP packet is recreated and the source address is changed to the address communicated through metadata type 20 and 21.¶
SVR Fragment Packet Layout¶
+------------+------------+----------------+--------------+
| IP HEADER | UDP HEADER | Metadata 20/21 | ICMP Packet |
+------------+------------+----------------+--------------+
¶
ICMP over SVR for Network Failures¶
Client . . . . . . . . . . . . . . . . . . . . . . .No Network
| Found
| RouterA RouterB |
| | | |
|----PKT---->| | |
| |------PKT[MD]------------>| |
| | |<--ICMP------|
| | | (Router B) |
| |<--UDP[ICMP[RMD]]---------| |
|<--ICMP-----| | |
| (Client) | | |
| | | |
¶
The first ICMP message is directed to Router B. Router B examines the ICMP error to find the session, and forwards backwards to the correct Waypoint for Router A. Router A recreates the ICMP message, and sends to the Client. The address of where the error was detected is in¶
The second type of ICMP message is not related to any specific sessions. These types of messages include ICMP ECHO for example. These are always encapsulated as UDP, and a session is created for the ICMP message. The identifier field in ICMP and the IP addresses are used as the 5-tuple session key. This includes:¶
ICMP over SVR for Information¶
Client . . . . . . . . . . . . . . . . . . . . . . . Target
| |
| RouterA RouterB |
| | | |
|--ICMP ECHO---->| | |
| |---UDP[ICMP ECHO]->| |
| | [MD1] | |
| | |---ICMP ECHO--->|
| | |<--ECHO RESP----|
| |<--UDP[ECHO RESP]--| |
| | [RMD1] | |
|<--ECHO RESP----| | |
¶
The ICMP message creates a session on Router A directed towards Router B. Metadata MD1 is inserted just like any UDP session to establish the return pathway for the response. Reverse metadata is inserted into the ECHO Response, effectively creating an ICMP session. Subsequent identical ICMP messages will utilize this path without metadata being inserted. This session state MUST be guarded with an inactivity timer and the state deleted.¶
The format of metadata has both Header attributes as well as Payload attributes. Header attributes are always guaranteed to be unencrypted. These headers may be inspected by intermediate network elements but can't be changed. Header attributes do not have a forward or reverse direction. Header attributes are used for router and peer pathway controls.¶
Payload attributes optionally can be encrypted by the sender. Payload attributes are associated with sessions, and as such have a forward and reverse direction. For encryption, the pre-existing security association and key sharing is outside the scope of this document. Each SVR attribute defined will indicate whether it is a header attribute (unencrypted) or payload attribute (optionally encrypted). There are no attributes that can exist in both sections.¶
The metadata header is shown below. A well-known "cookie" (0x4c48dbc6ddf6670c in network byte order byte order) is built into the header which is used in concert with contextual awareness of the packet itself to determine the presence of metadata within a packet. This is an eight-byte pattern that immediately follows the L4 header and is an indicator to a receiving router that a packet contains metadata. NOTE: Normal IP traffic will never have the Waypoint Address as its destination. If a packet arrives at a SVR Router Waypoint it has to have Metadata or be associated with an active SVR session. Please see Section 2.10 for a discussion of state recovery techniques.¶
0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | + Cookie + | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |Version| Header Length | Payload Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Header TLVs ... | Payload TLVs ... | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Given that no byte sequence is truly unique in the payload of a packet, in the scenario where the original payload after the L4 header contained the same byte sequence as the cookie, false positive logic is enacted on the packet. If the metadata HMAC signature can't verify that the metadata is valid, then a false positive metadata header is added to the packet to indicate that the first eight bytes of the payload matches the cookie.¶
The structure of a false positive metadata includes just a header of length 12 bytes, with zero header TLVs and zero payload TLVs. The receiving side of a packet with false positive metadata will strip out the metadata header.¶
In the scenario where a router receives a false positive metadata header but intends to add metadata to the packet, the false positive metadata header is modified to contain the newly added attributes. Once attributes are added, the metadata header is no longer considered to be false positive.¶
Payload metadata attributes may be valid in the forward direction, the reverse direction, or both. If not valid, it is ignored quietly by the receiving side.¶
All metadata attributes are expressed as Tag Length Values or TLV's. This includes Header and Payload TLVs. It is recommended that Payload TLVs be encrypted, but not mandatory. When debugging networks, or if mid-stream routers need to consult the TLV's, they can be transmitted in clear text. The entire metadata block is signed, and thus the integrity of the data can be verified. No midstream router or middlebox can modify any aspect of the metadata. Doing so will invalidate the signature, and the metadata will be dropped.¶
0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Variable Length Values ..... | \/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/
When a packet is fragmented to insert metadata, a new fragmentation mechanism must be added to prevent fragmentation attacks and to support reassembly (which requires protocol and port information). If a packet is received that IS a fragment, and it must transit through a metadata signaled pathway, it must also have this metadata attached to properly bind the fragment with the correct session.¶
All fragments will have a metadata header and the fragment TLV added to the guaranteed unencrypted portion of the metadata header. If the original packet already has a metadata header on it, the fragment TLV will be added to it. See [RFC0791] for information about IP Fragmentation. For a detailed example of packet fragmentation in SVR please see Section 6.5¶
0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type = 1 | Length = 10 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Extended ID | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Original ID |Flags| Fragment Offset | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Largest Seen Fragment | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Field used for identifying fragment attributes. They are (in order, from most significant to least significant):¶
A versioning identifier used to determine which security key version should be used when handling features dealing with security and authenticity of a packet.¶
0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type = 16 | Length = 4 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Security Key Version | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
An indication that forward metadata should be disabled. This is sent in the reverse metadata to acknowledge receipt of the metadata. This is the second part of the metadata handshake.¶
0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type = 18 | Length = 0 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
No other data is required. The specific session that is being referred to is looked up based on the 5-tuple address of the packet. See metadata handshake in Section 2.3.¶
This is exclusively used to implement ICMP messages that need to travel backwards through SVR pathways. See Section 6.6 for more information. The IPv4 address of the source of the ICMP message is placed into metadata. This metadata travels in the reverse direction backwards to the originating SVR, which restores the information and sends an ICMP message to the originator of the packet.¶
0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type = 20 | Length = 4 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Source Address | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
This is exclusively used to implement ICMP messages that need to travel backwards through SVR pathways. See Section 6.6 for more information. The IPv6 address of the source of the ICMP message is placed into metadata. This metadata travels in the reverse direction backwards to the originating SVR, which restores the information and sends an ICMP message to the originator of the packet.¶
0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type = 21 | Length = 16 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | + + | | + Source Address + | | + + | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The SVR Control Message is used for protocol specific purposes that are limited to a single peer pathway. This message is sent by an SVR router to a peer. This metadata is always sent in a UDP message originating by the SVR control plane.¶
0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type = 24 | Length = 1 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Drop Reason | +-+-+-+-+-+-+-+-+
Reason why this packet should be dropped.¶
This metadata type is used to allows peers to measure and compute inline flow metrics for a specific peer pathway and a chosen subset of traffic. class. The flow metrics can include jitter, latency and packet loss. This is an optional metadata type.¶
When a peer sends this metadata, it provides the information for the period of time to the peer.¶
When a peer receives this metadata type 26, it responds with metadata type 26.¶
After several exchanges, each side can compute accurate path metrics for the traffic included. This metadata can be sent at any time, but is normally sent when metadata is being sent for other reasons. The metadata includes "colors" which represent blocks of packets. Packet loss and latency can be determined between routers using this in line method. Using colors to measure inline flow performance is outside the scope of this document. Please refer to [RFC8321]¶
0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type = 26 | Length = 10 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Tx Co | Transmit TimeValue | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Rx Co | Received TimeValue | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |D| Previous Rx Color Count | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Payload attributes are used for session establishment and SHOULD be encrypted to provide privacy. Encryption can be disabled for debugging.¶
The context contains a five-tuple associated with the original addresses, ports, and protocol of the packet. This is also known as the Forward Session Key.¶
0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type = 2 | Length = 13 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Source Address | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Destination Address | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Source Port | Destination Port | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Protocol | +-+-+-+-+-+-+-+-+
A five-tuple associated with the original addresses, ports, and protocol of the packet for IPv6.¶
0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type = 3 | Length = 37 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | + + | | + Source Address + | | + + | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | + + | | + Destination Address + | | + + | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Source Port | Destination Port | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Protocol | +-+-+-+-+-+-+-+-+
Five-tuple associated with the egress (router) addresses, ports, and protocol of the packet. Forward context and reverse context session keys are not guaranteed to be symmetrical due to functions which apply source NAT, destination NAT, or both to a packet before leaving the router.¶
0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type = 4 | Length = 13 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Source Address | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Destination Address | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Source Port | Destination Port | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Protocol | +-+-+-+-+-+-+-+-+
Five-tuple associated with the egress (router) addresses, ports, and protocol of the packet. Forward and reverse session keys are not guaranteed to be symmetrical due to functions which apply source NAT, destination NAT, or both to a packet before leaving the router.¶
0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type = 5 | Length = 37 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | + + | | + Source Address + | | + + | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | + + | | + Destination Address + | | + + | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Source Port | Destination Port | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Protocol | +-+-+-+-+-+-+-+-+
Unique identifier of a session. The UUID MUST be conformant to [RFC4122]This is assigned by the peer that is initiating a session. Once assigned, it is maintained through all participating routers end-to-end.¶
The UUID is used to track sessions across multiple routers. The UUID also can be used to detect a looping session. The UUID metadata field is required for all session establishment.¶
0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type = 6 | Length = 16 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | + + | | + UUID + | | + + | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
An alphanumeric ASCII string which dictates what tenancy the session belongs to.¶
0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type = 7 | Length = variable | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Name (1 - n bytes) .... | \/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/
An alphanumeric string which dictates what service the session belongs to.¶
0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type = 10 | Length = variable | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Service Name (1-n bytes) ..... | \/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/
Indicates if the session is having its payload encrypted by the SVR router. This is different from having the metadata encrypted. The keys used for payload encryption are dependent on the Security Policy defined for a session.¶
This field is necessary because often traffic is already encrypted before arriving at an SVR router (making DPI a poor choice). Also in certain use cases, re-encryption may be required. This metadata TLV is always added when SVR encrypts the payload.¶
0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type = 11 | Length = 0 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Indicates if the session is being converted from TCP to UDP to enable passing through middle boxes that are TCP session stateful. A SVR implementation must verify that metadata can be sent inside TCP packets through testing the Peer Pathway. If the data is blocked, then all TCP sessions must be converted to UDP sessions, and restored on the destination peer.¶
Although this may seem redundant with the Forward Context that also has the same originating protocol, this refers to a specific peer pathway. In a multi-hop network, the TCP conversion to UDP could occur at the second hop. It's important to restore the TCP session as soon as possible after passing through the obstructive middlebox.¶
When TCP to UDP conversion occurs, no bytes are changed other than the protocol value (TCP->UDP). Because the UDP message length and checksum sit directly on top of the TCP Sequence Number, the Sequence number is overwritten. The Sequence number is saved by copying it to the TCP Checksum. The Checksum is recalculated upon restoration of the packet. The packet integrity against bit loss or malicious activity is provided through the HMAC signature.¶
0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type = 12 | Length = 0 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Note: This type does not contain any value as its existence in metadata indicates a value.¶
An alphanumeric string which dictates which source router the packet is originating from. This attribute may be present in all forward metadata packets if needed.¶
0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type = 14 | Length = variable | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Router Name (1-n bytes) .... | \/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/
An alphanumeric string containing the Security Policy to use for a particular session. This is used only when payload encryption is being performed. The Security Policy describes the specifics about Ciphers used for payload encryption.¶
0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type = 15 | Length = variable | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | SECURITY POLICY | \/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/
An ASCII string which dictates which router peer pathway has been chosen for a packet. This name is the hostname or IP address of the egress interface of the originating router. This can be used to determine the peer pathway used exactly when there may be multiple possibilities. This enables association of policies with specific paths.¶
0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type = 19 | Length = variable | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Peer Pathway Name (1-n bytes) .... | \/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/
Routers may be provisioned to perform source NAT functions while routing packets. When a source NAT is performed by an SVR Peer, this metadata TLV MUST be included. When the far end router reconstructs the packet, it will use this address as the source address for packets exiting the SVR.¶
0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type = 25 | Length = 4 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | IPv4 Source Nat Address | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
After a path failure, it may become necessary to transmit a SVR Control Message when there are one-way flows waiting for a packet to be transmitted. In these cases, the metadata includes an attribute defining the remaining session time so intermediate routers creating new session entries will expire the session at the correct time.¶
0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type = 42 | Length = 4 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Remaining Session Time (seconds) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
An alphanumeric string containing the cryptographic key to use for a payload encryption of a particular session. This is used only when payload encryption is being performed. Unless specified in the Security Policy, the key used will default to the Peer Key (see Section 5.1.8). The key is encrypted in SVR metadata hop-by-hop through a network, preventing any party from obtaining the key. The router terminating the session utilizes this key to decrypt payload portions of packets. This prevents re-encryption penalties associated with multi-hop routing scenarious. To support the widest array of keys, the key is sent in PEM format.¶
To rekey a session, this SVR metadata can be included in any subsequent packet with the new key to use. When rekeying, the SVR that initiated the encrypted session must compute a new key, and include the key as SVR metadata. Upon receipt, the terminating router must create a reverse metadata packet containing the same key to indicate when to switch to the new key for decryption. This solves race conditions with packets in flight.¶
0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type = 45 | Length = variable | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | SECURITY KEY | \/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/
HMAC signatures are REQUIRED for the packets that contain metadata to guarantee the contents were not changed, and that the router sending it is known to the receiver. Any HMAC algorithm can be used, from SHA128, or SHA256 as long as both sides agree. HMAC is always performed on the layer 4 payload of the packet. The signature is placed at the end of the existing packet.¶
Optional HMAC signatures are RECOMMENDED for every packet. This prevents any mid-stream attempts to corrupt or impact sessions that are ongoing. This also helps detect and correct lost state at egress SVR routers. See Section 2.10. The signature must include all of the packet after Layer 4, and include a current time of day to prevent replay attacks. The signature is placed at the end of the existing packet.¶
Both the sending and receiving routers must agree on these optional HMAC signatures, details of which are outside the scope of this document.¶
Payload encryption can use AES-CBC-128 or AES-CBC-256 ciphers which can be configured. Since these are block-ciphers, the payload should be divisible by 16. If the actual payload length is divisible by 16, then the last 16 bytes will be all 0s. If the actual payload is not divisible by 16, then the remaining data will be padded and the last byte will indicate the length.¶
Waypoint addresses could be addressed by any client at any time. IP packets that arrive on the router's interface will be processed with the assumption that they MUST contain metadata OR be part of an existing established routing protocol.¶
Routers will only accept metadata from routers that they are provisioned to speak with. As such an ACL on incoming source addresses is limited to routers provisioned to communicate. All other packets are dropped.¶
When a packet is received the "cookie" in the metadata header is reviewed first. If the cookie isn't correct, the packet is dropped.¶
The HMAC signature is checked. If the signature validates, the packet is assumed to be good, and processing continues. If the HMAC fails, the packet is dropped.¶
These methods prevent distributed denial of service attacks on the Waypoint Addresses of routers.¶
This document does not require any IANA involvement.¶
The authors would like to thank Anya Yungelson, Scott McCulley, and Chao Zhao for their input into this document.¶
The authors would like to thank Tony Li for his extensive support and help with all aspects of this document.¶
The authors want to thank Ron Bonica, Kireeti Kompella, and other IETFers at Juniper Networks for their support and guidance.¶