Is a BGP Open message longer or shorter than a BGP Keepalive?

[Specop 007]

I assume a BGP Open message is quite a bit longer than a BGP Keepalive message, but I'm not positive on that so wanted to get some confirmation on it.

Based upon these 2 links (Which I dont know how accurate it is) it would seem an Open could potentially be smaller than a Keepalive which was a bit surprising to me....

http://www.inetdaemon.com/tutorials/internet/ip/routing/bgp/operation/messages/open.shtml

http://www.inetdaemon.com/tutorials/internet/ip/routing/bgp/operation/messages/keepalives.shtml

 

[m1ldslide1]

Not sure if you have two routers to test with, but Wireshark FTW...

 

[Specop 007]

Not sure if you have two routers to test with, but Wireshark FTW...

Wish I could. I might try to swipe 2 from our test lab if I make it by there though. If I had 2 routers sitting around I'd have already done that!

 

[mcmilljb]

Keepalive is always the smallest. Each message has a 19 byte header. The Keepalive is just the 19 byte header, while the Open message is 19 bytes plus its message format. The RFC says its minimum is 29 bytes including the header. Plus you get a Keepalive as a response to the Open message if the Open message is acceptable.

Link for the RFC
Latest BGP-4 - http://tools.ietf.org/html/rfc4271