Optional Checksums in Intermediate System to Intermediate System (ISIS)

This draft describes an optional extension to IS-IS protocol, used today by several ISPs for routing within their clouds. IS-IS is an interior gateway routing protocol developed originally by OSI and used with IP extensions as IGP. IS-IS originally does not provide CSNP and PSNP checksums, relying on the underlying layers to verify the integrity of information provided. Experience with the protocol shows that this precondition does not always hold and scenarios can be imagined that impact protocol functionality. This document introduces a new optional TLV providing checksums.