This document defines the Subscriber and Performance Policy Identifier Context Headers.  These Variable-Length Context Headers can be
     carried in the Network Service Header (NSH) and are used to inform Service
     Functions (SFs) of subscriber- and performance-related information for the
     sake of policy enforcement and appropriate Service Function Chaining (SFC)
     operations. The structure of each Context Header and their use and
     processing by NSH-aware nodes are described.