Re: [Idr] Review of draft-ietf-large-community-06.txt

heasley <heas@shrubbery.net> Sat, 05 November 2016 18:35 UTC

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Date: Sat, 5 Nov 2016 18:35:17 +0000
From: heasley <heas@shrubbery.net>
To: Robert Raszuk <robert@raszuk.net>
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Subject: Re: [Idr] Review of draft-ietf-large-community-06.txt
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Sat, Nov 05, 2016 at 06:55:22PM +0100, Robert Raszuk:
> Heas,
> 
> All true .. I posted my question as perhaps it really makes sense to modify
> the defaults for both 1997 and large.
> 
> To share the experience from a lot of global deployments of SAFI 128
> propagation of extended communities was the biggest pain for 100s customers
> to keep remembering to enable send-community extended|both knob on each
> session.
> 
> And as you know SAFI 128 is pretty useless without RTs so keeping such
> defaults there on both IBGP and EBGP sessions was just wrong.
> 
> Here in the case of Large Communities folks clearly indicated need to use
> it across multiple ASNs. And that is cool. Except you have zero control how
> peer of your provider will handle it.
> 
> So today non upgraded eBGP router will propagate it. When new OS is loaded
> (maybe for completely different reason) which can recognize LC attribute
> unless the knob is in place it will be dropped.
> 
> Perhaps it make sense to spell this out in the draft that large communities
> attribute should be propagated by default unless otherwise suppressed by
> policy ?

rfc4360 also does not make such a recommendation about a 'send-community
extended' (in cisco-ese) feature.  As I recall, it is one vendor who started
that, though I can not recall why, and many who copy their CLI have followed
suit.  One vendor has no such knob that I know of; communities are always
sent unless removed by RPL.  And, I believe there are a few open
implementations that also send communities by default.

I do wish that implementations that have this feature would default to
enabled/send, rather than disabled/filter.

However, given the heated discussion about prescribing a canonical
representation for -large-communities, is this a subject for an IDR rfc?
Isn't it a subject for a customer-vendor meeting?  Is changing the language
about propagating recognized transitive attributes going to change these
vendor's defaults?