The IS-IS protocol is specified in ISO 10589 [1], with extensions for supporting IPv4 specified in RFC 1195 [3]. Each Intermediate System (IS) (router) advertises one or more IS-IS Link State Protocol Data Units (LSPs) with routing information. Each LSP is composed of a fixed header and a number of tuples, each consisting of a Type, a Length, and a Value. Such tuples are commonly known as TLVs, and are a good way of encoding information in a flexible and extensible format.