Advertising IGP Measurement Group using TLV

This document defines an IS-IS capability sub-TLV for advertising measurement group membership for Active Measurement Protocols (AMPs) such as TWAMP and STAMP. The mechanism allows IGP routers to discover other routers participating in different measurement groups, enabling automatic discovery of measurement endpoints across IGP areas. The solution uses interface addresses (IPv4 or IPv6) to identify measurement group membership, where the same interface address may be used for multiple measurement groups.