The document describes the design of p4srv6, a P4 program that implements SRv6 (Segment Routing for IPv6) functions. It discusses p4srv6's pipeline design based on the v1model.p4 architecture and includes details on the parser, ingress control, transit and end tables for SRv6, and handling of variable length SID lists. It also provides examples of configuring p4srv6 for GTP to SRv6 encapsulation and decapsulation.