[j-nsp] ISIS and BFD

[Mark Tinka]

On Tuesday 29 December 2009 06:29:27 pm 
martin.mogensen at bt.com wrote:

> The feedback I've had previously from Juniper is the
>  re-establishment of the adjacency even though BFD is
>  filtered is intended behaviour. A BFD session isn't a
>  requirement for re-establishing the adjacency - BFD is
>  instead used for tearing down the adjacency in case of
>  BFD timeout *after* the BFD session has been
>  established.

This would make sense to me, and perhaps, something I'd 
support if BFD decided to "go off the rails".

However, all things being equal, in most cases, failure of 
BFD packets to be sent/received across a link would likely 
lead to a failure of the IGP frames/packets from being 
sent/received on the link anyway.

While BFD is meant to be more aggressive than the IGP with 
regard to link liveliness checking, with the exception of 
massive network or device instability, I'm trying to think 
up a situation where BFD packets are traversing a link, then 
suddenly stop doing so, but all other packets (including 
IGP) are traversing the link just fine.

Nonetheless, such a fail-safe (independence of link state 
adjacency formation from BFD up/down status) would be 
useful, but only if I had a knob to turn such a sub-feature 
of BFD on or off. 

Cheers,

Mark.
-------------- next part --------------
A non-text attachment was scrubbed...
Name: not available
Type: application/pgp-signature
Size: 836 bytes
Desc: This is a digitally signed message part.
URL: <https://puck.nether.net/pipermail/juniper-nsp/attachments/20091229/193a32eb/attachment.bin>