Three-Way Handshake for Intermediate System to Intermediate System (IS-IS) Point-to-Point Adjacencies

The IS-IS routing protocol (ISO 10589) requires reliable protocols at the link layer for point-to-point links. As a result, it does not use a three-way handshake when establishing adjacencies on point-to-point media. This paper defines an backward-compatible extension to the protocol that provides for a three-way handshake. It is fully interoperable with systems that do not support the extension. Additionally, the extension allows the robust operation of more than 256 point-to-point links on a single router. This extension has been implemented by multiple router vendors; this paper is provided as information to the Internet community in order to allow interoperable implementations to be built by other vendors.