Re: other comments for single-hop bfd [Re: I-D ACTION:draft-ietf-bfd-v4v6-1hop-01.txt]

[Pekka Savola <[e-mail]>]

On Wed, 23 Feb 2005, Dave Katz wrote:
> It does raise the question of whether we want to continue to add text into 
> this document for other protocols, or whether it would be worth having 
> additional documents to cover them so that this one can be put to bed.  I 
> would prefer to avoid further significant technical changes to this doc and 
> to have additional stuff be put into a separate one, in order to advance this 
> stuff without too much more tinkering.  This should probably be discussed in 
> Minneapolis.

Right.  Obviously, I'm a proponent of putting it here (well, I asked 
if I should make it a separate draft back in July or so, but then it 
was felt ok to include it here).

>> .. in fact it would preclude the operation of the IGP in the particular 
>> BFD-enabled _interface_.  The text seems to be implying that having BFD 
>> would be an IGP domain-wide toggle like IS-IS authentication.  But in 
>> reality, it is an interface toggle, so this argument is irrelevant.
>
> It is not irrelevant on multipoint media.  Perhaps it would more correctly 
> read "...preclude the *correct* operation of the IGP..."  It's not that it 
> makes the IGP completely fail, but it can create large-scale black holes if 
> the topology is particularly unlucky.  I could add the extra word if you feel 
> strongly about it.

No, this clarification would also be misleading.  It would prevent the 
correct operation of the IGP *on that particular interface*.  So, you 
must enable BFD on all the systems you have adjacencies to on a 
multipoint link.

I'm not sure how common those multipoint links are (we certainly have 
only one with more than 1 neighbor with which we would like to run 
BFD; the most common are probably Ethernet IX's but folks don't run 
IGP there), so unless our setup differs radically from what's out 
there, this shouldn't be a problem.

-- 
Pekka Savola                 "You each name yourselves king, yet the
Netcore Oy                    kingdom bleeds."
Systems. Networks. Security. -- George R.R. Martin: A Clash of Kings