An Extensible Architecture for Service Modeling

This document describes problems with the currently published IETF service modules and defines a modular service modeling structure that extracts technology-agnostic constructs into a base ietf-svc module, separates Ethernet-specific treatment into ietf-eth-svc, and layers VPN-oriented intent in ietf-vpn-svc, with bis versions of the L2SM and L3SM augmenting the shared foundation.