Re: Communities

[Iljitsch van Beijnum <iljitsch () muada com>]

On Mon, 15 Oct 2001, E.B. Dreger wrote:

> Let's say that I have transit from 6347 and 2914.  Now let's say
> that I'm stupid, and start advertising routes that I learn from
> 2914 into 6347, and that 6347 isn't filtering my as-paths or
> netblocks.  [Note: 6347 does know better in the real world.]

Ok, I understand. There was a problem along these lines a few weeks ago.
"Sorry guys, a circuit came into service unexpectedly, we hadn't installed
any filters yet." (AS#s withheld to protect the guilty.)

But then the question is: which is worse, having traffic flow over an
inferior path, or taking the chance that two people who both should know
better screw up?

> *** Message #2 ***

> [ snip ]

> > So a community that indicates "you don't want to use this route
> > unless you absolutely have to--trust us" would have been very
> > welcome. Such a community would be especially useful in the
> > face of congestion:

> I see and agree.  Good idea, IMHO.

> > But is it worth the trouble to try to "standardize" communities
> > for this?

> I should think that this would be trivial.  0x0000:* and 0xffff:*
> are reserved per RFC1997... release a new RFC with your "you
> don't want this route!" communities added, participants would
> benefit, non-participants would observe no change, and there
> would be no interoperability troubles.

Yes, why not. If anyone has something to contribute or wants to co-author
such a draft or RFC, contact me off-list.

> I think I like this better than my prior geography-based post...
> you're suggesting that MED-like info be advertised via standard
> communities.  And who would know better than the originating
> provider?  Makes sense to me...

I've been thinking about other information that could be conveyed in
communities. For instance, bandwidth, delay and packet loss. If each
router along the way modifies such a community (should probably be an
extended one) then a much richer set of information would be available to
multihomers to aid in route selection.

Iljitsch