Dual-plane disjoint path in Segment Routing

Recently created a article on how simply the use of Anycast-SID can be used to enforce traffic to disjoint paths in dual-plane architecture. SO , thought of sharing here.

Dual-plane Disjoint paths | In this article we will discuss how Anycast-SID can be used to send different traffic types across dual-plane disjoints path networks. Though, there are other SR based methods to achieve same functionality , one of them is using IGP Flex-algo and other is by dynamic SR policy using SDN controller (SR-PCE) . In today’s discussion , will see how to use Anycast-SID and define Explicit candidate path to achieve the same functionality .

A brief on Anycast-SID , it is a Node Prefix-SID that is advertised by more than one node (typically two or more ). The set of nodes advertising the same anycast-SID form a group called as anycast set. By using an Anycast-SID in the SID list of an SR policy path , it helps achieving traffic load-sharing and resiliency. Apart from this, it can be used to have traffic engineered path through a set of nodes or region (can be called as plane in the network)

Understand Dual-plane vs Single-plane in context with Segment Routing

Dual-plane is the mechanism to enforce disjointness in the network , where , the traffic path towards destination node stays within a set of nodes ( called plane). There can be multiple planes in the network, so that different planes in the network can be. used for different kind of traffic types depending upon the SLA, a service provider signs with customer. Anycast-SID allows creation of such macro policies, such as , “flow of traffic 1 from node A to B must go via plane 1” and “flow of traffic 2 from node A to B must go via plane 2.” This is practically called dual-plane disjoint path architecture.

Dual-plane disjoint path use case

Assume there is L3 VPN service required between nodes S1 and S10 with two VRFs. These two VRFs should be carried over disjoint paths. Traffic of first VRF should be send across orange plane and traffic of second VRF should be carried via green plane.This can be simply achieved by steering traffic of first VRF into SR-Policy of orange plane , similarly, steering traffic of second VRF into SR-Policy of green plane.

If you are interested further in step-by-step details, how this is done , you can visit here