RINA - scott whaps at the nanog hornets nest :-)

Mans Nilsson mansaxel at besserwisser.org
Mon Nov 8 12:36:49 CST 2010


Subject: RE: RINA - scott whaps at the nanog hornets nest :-) Date: Mon, Nov 08, 2010 at 08:53:47AM -0800 Quoting George Bonser (gbonser at seven.com):
> > 
> > Even if larger MTUen are interesting (but most of the time not worth
> > the work) the sole reason I like SDH  as my WAN technology is the
> > presence of signalling -- so that both ends of a link are aware of its
> > status near-instantly (via protocol parts like RDI etc). In GE it is
> > legal to not receive any packets, which means that "oblivious" is a
> > possible state for such a connection. With associated routing
> > implications.
> 
> I wasn't talking about changing anything at any of the edges.  The idea was just to get the "middle" portion of the internet, the peering points to a place that would support frames larger than 1500.  It is practically impossible for anyone to send such a packet off-net until that happens.

Know what? We have not one, but five or so Internet Exchange points in
Sweden, where there are 802.1q VLANS setup for higher MTU (4470 for
hysterical raisins) . My impression is that people use them, but I'm
also being informed by statistics that there is a _very_ steep drop in
packet count vs size once 1500 is reached. It is setup, but the edge is
where packets are made, not the core. Thus, noone can send large
packets. Anyway. 

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.

-- 
Måns Nilsson     primary/secondary/besserwisser/machina
MN-1334-RIPE                             +46 705 989668
I was making donuts and now I'm on a bus!
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