BGP communities attached to prefix issue

[Ondrej Zajicek]

On Mon, Jul 04, 2016 at 12:15:18PM +0200, Job Snijders wrote:
> On Mon, Jul 04, 2016 at 12:02:59PM +0200, Ondrej Zajicek wrote:
> > By RFC 4271, BGP message is limited to 4 kB of length. BIRD internally
> > limits attribute part of a transmitted message to 2 kB. This is
> > equivalent of 1024 (4 kB) or 512 (2 kB) communities.
> > 
> > You could replace constants 3072 [1] and 2048 [2] with say 3840 and 3584,
> > that would allow 3.5 kB of attributes (~ 900 communities).
> > 
> > [1] proto/bgp/packets.c:372 and proto/bgp/packets.c:465
> > [2] proto/bgp/packets.c:385 and proto/bgp/packets.c:481
> 
> Do you have https://tools.ietf.org/html/draft-ietf-idr-bgp-extended-messages-12 on
> your roadmap? This draft bumps the 4 kB limit to ~ 65 kB.

It is already mostly [*] supported in 1.6.0, but it needs to be supported
by both sides and does not solve this issue for route servers of IXPs
unless everyone has the support.

[*] well, it allows 64 kB messages but i forgot about the internal 2 kB
limit for attributes, so it is currently not much useful. Will be fixed
in the next version.

-- 
Elen sila lumenn' omentielvo

Ondrej 'Santiago' Zajicek (email: santiago at crfreenet.org)
OpenPGP encrypted e-mails preferred (KeyID 0x11DEADC3, wwwkeys.pgp.net)
"To err is human -- to blame it on a computer is even more so."
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