This document specifies an integrated routing protocol, based on the OSI Intra-Domain IS-IS Routing Protocol, which may be used as an interior gateway protocol (IGP) to support TCP/IP as well as OSI. This allows a single routing protocol to be used to support pure IP environments, pure OSI environments, and multi-protocol environments. This specification was developed by the IS-IS working group of the Internet Engineering Task Force. The final international standard version of the OSI IS-IS protocol is contained in ISO 10589 [1]. Comments should be sent to 'isis@merit.edu'.