Understanding Routing Protocol Extensions in SSO/NSF, GR, and NSR

[Brandon Marr]

Quick question is  What exactly is a "routing protocol extension"? I am reading through the HA Technologies section of the ENCOR book and specifically when talking about SSO/NSF, GR, and NSR im seeing that some are being refered to as using routing protocol extensions and some dont. 

Im understanding that SSO/NSF can use either GR or NSR or both of these, GR is stated to use routing protocol extensions where NSR does not use extensions, i think if you were able to explain why each of those do and dont use extensions would help clear it up. As of now im having a hard time understaind what these peotocol extension actaully mean. I tried a google search and came across RFC 5073 but this seems to discuss something related to MPLS which iv not learned yet. 

Any help and expanation to get this point understood would be welcomed. Thanks.

[Ramblin Tech]

A Cisco Press book provides a good summary of NSF/SSO vs GR vs NSR: https://www.ciscopress.com/articles/article.asp?p=1395746&seqNum=2

OSPF GR extensions: RFC 3623

BGP GR extensions: RFC 4274, RFC 8538

[Brandon Marr]

I am wondering if I added to much to my question, i think im really just wanting to know what a "routing protocol extension" is in general, im startinbg to think this is not even specific to SSO/NSF. Thanks for the RFC's though I will bookmark for later.

[Ramblin Tech · Accepted solution]

Routing protocols start out with some baseline capabilities as described in their original RFCs (and updated by the subsequent RFCs that “obsolete” them). Dev teams implement these capabilities and deliver them to market. At some point, the market may want more capabilities than the baseline can provide and so the protocol must be extended, providing the new capabilities via new RFCs issued to describe the additions. OSPF capabilities can be extended by adding new LSAs. BGP can be extended by adding Address Families to the Network Layer Reachability Information. IS-IS can be extended by adding new TLVs. Some protocols are not extensible and are essentially replaced by a later baseline version (eg, RIPv1 vs RIPv2).

[Brandon Marr]

This is exactly what i needed that makes sense, thank you!