SR-MPLS - SRTE Traffic Steering (per destination)

As indicated in RFC 9256, there are several approaches that a headend router may use to take a given flow and place it into an SR policy, one of them being per‐destination steering. This architecture allows service operators to create separate forwarding paths, commonly known as candidate paths, and optimally distribute the traffic across several network links or even prioritize some paths for high‐priority services. A spine‐and‐leaf topology with two spine routers and several PEs was deployed to perform the test. It allowed us two paths for every PE for IPv4 and IPv6 traffic. As shown in the figure below, two different paths reach each headend.

From each edge, we advertised a “color” community from each PE router to the destination router over BGP, where color and the address of the endpoint could be matched by an SR policy to generate an appropriate SID list.
With the application of the color tag, the respective SR policy implemented in the network directed packets through a specific designated SR‐TE path. Upon removing the color tag, the traffic switched to an alternate SR path, and if there was no SR path, it just dropped the traffic as it should. All the source‐destination pairs within the network were tested, and it was confirmed that there was no packet loss in any of the SR‐TE tunnels tested.
In general, the results disclosed in this section stress the strength of per‐destination SRTE forwarding over SR‐MPLS methods: Such development provides operators with the tools they need to implement routing schemes that balance traffic loads and prioritize the critical or most important traffic while also ensuring high service availability in IP/MPLS networks.