Scope of Communities [was: Re: Last call for bgp-redistribution]

[Joe Provo]

[way behind, but this thread piqued interest as an operator]

On Fri, Jul 26, 2002 at 12:01:28PM -0400, William Waites wrote:
[snip]
> Is there a compelling reason to strip comminities off of the
> routes at all in the transit path?

To not have straggling bits of control data that one did not intend 
in one's network altering things nondeterministically. If one is using 
any specific attributie gfor control, one needs to have an FSM of 
sorts (why one vendor got beat up badly for their BGP tie-breaker 
varying from what they published for many years).

Operators who are not using certain control knobs may be letting them
trickle unmolested and in their ignorance allowing folks to remote-
control their networks. Just because something is a common control 
knob (like well-known communikties) doesn't mean everyone uses them. 
But you can be sure the folks who intend to use them scrub everything 
but the ones they intend to use. That's just simple engineering of the 
steady-state.

Of course, there will be operators who decide for/against (and change 
one way or the other based on customer demand) the use of any control 
knobs. As with bogon filtering, a leaf ASes isn't going to be *guarenteed* 
any action (honouring of prefixes, communities, etc) beyond the reach
of your contracts.  

IMO, putting the capability out there knowing it will address some 
of the problems and will be used some of the time is compelling. 
Major providers have been trending toward expanding and publishing 
their existing act-on-peer communities (two I watch have updated their 
public docs in the last two weeks).  I think that represents a strong 
trend of desire for leaf ASes to have control without the tragedy of 
the commons triggered by other approaches; the concept is widely 
accepted and it would be easier for the leaf ASes to manage (and the
network operators) should these approaches be standardized.

Wow, I guess a long way of agreeing yes that "all intended transitive 
communities should be blessed as Well-Known".

Hope was relevant, back to my hole now.

joe

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 crimson at sidehack.gweep.net * jprovo at gnu.ai.mit.edu * jzp at rsuc.gweep.net
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