Segment Routing is the evolution of traditional MPLS, and here we look at SR-MPLS and Traffic Engineering across multiple domains with an SR-PCE (Path Computation Element). Traffic Engineering has been around for many years as RSVP-TE; however, being very cumbersome and complex, it has gained very little popularity with few deployments. Segment Routing Traffic Engineering adds a new dimension to Segment Routing, including the ability to perform end-to-end traffic engineering across discontiguous IP networks.
SR-MPLS TE has dramatically simplified the implementation, removing the state from the network and placing it in the packet. SR-MPLS has added several new capabilities to traffic engineering, including delay-based forwarding demonstrated in the SR-MPLS with Flex-Algo Lab, Centralized Traffic Engineering as seen in the SR-MPLS Traffic Engineering Lab and several features we will explore in subsequent labs.
In previous labs, we explored Segment Routing and Segment Routing Traffic Engineering, also called SR-MPLS and SR-TE. We also introduce you to the concept of a traffic engineering controller known in the Cisco world as SR-PCE to perform centralized SR-TE. In this lab, we utilize an SR-PCE again for centralized traffic engineering, but we will do it across multiple IGP domains.
This lab provides a hands-on environment with Cisco XRv9000 routers to demonstrate the use of SR-MPLS Traffic Engineering with a centralized traffic engineering controller. We will build an end-to-end path from PE1 to PE3 and traverse three isolated IS-IS IGP domains devoid of IP reachability. We will rely on the SR-PCE receiving IGP domain database information from all three domains to create the SR-TE path from PE1 to PE3.