MSD Consideration in Path Computation Element Communication Protocol (PCEP)

Segment Routing (SR) allows a node to steer a packet flow along any path. SR Policy is an ordered list of segments (i.e., instructions) that represent a source-routed policy. The packets steered into an SR Policy carry an ordered list of segments associated with that SR Policy. An SR Policy can be instantiated SR-MPLS and SRv6 data planes. Maximum SID Depth (MSD) is first introduced for SR-MPLS to indicate the number of SIDs supported by a node or a link on a node. This concept is further extended for SRv6 with more types of MSD. MSD may become one of the limitations that need to be considered when computing an SR-TE path for PCE. This draft specifies some MSD considerations PCE needs to take into account when computing an SR-TE path.