[131930] in North American Network Operators' Group
Re: RINA - scott whaps at the nanog hornets nest :-)
daemon@ATHENA.MIT.EDU (Jack Bates)
Mon Nov 8 15:29:54 2010
Date: Mon, 08 Nov 2010 14:29:44 -0600
From: Jack Bates <jbates@brightok.net>
To: Mans Nilsson <mansaxel@besserwisser.org>
In-Reply-To: <20101108183648.GK15266@besserwisser.org>
Cc: nanog@nanog.org
Errors-To: nanog-bounces+nanog.discuss=bloom-picayune.mit.edu@nanog.org
On 11/8/2010 12:36 PM, Mans Nilsson wrote:
> I'd concur that links where routers exchange very large routing tables
> benefit from PMTUD (most) and larger MTU (to some degree), but I'd
> argue that most IXPen see few prefixes per peering, up to a few
> thousand max. The large tables run via PNI and paid transit, as well as
> iBGP. There, I've seen drastical improvements in convergence time once
> PMTUD was introduced and arcane MSS defaults dealt with. MTU mattered
> not much.
>
> Given this empirical data, clearly pointing to the fact that It Does
> Not Matter, I think we can stop this nonsense now.
>
His point wasn't to benefit the BGP routers at the IX, but to support
those who need to transmit > 1500 size packets and have the ability to
create them on the edge. In particular, the impact of running long
distances (high latency) with higher packet drop probability. In such a
scenario, it does matter.
Even if you don't see that many > 1500 byte packets, doesn't imply that
it doesn't matter. I have v6 peerings and see very little traffic on
them compared to v4. Should I then state that v6 doesn't matter? If
people have an expectation of not making it through core networks at
>1500, they won't bother trying to send >1500. If the IX doesn't
support >1500, why would people connecting to the IX care if their
backbones support >1500?
Jack
