Re: Internet Exchanges supporting jumbo frames?

[joel jaeggli <joelja () bogus com>]

On 3/9/16 7:58 AM, Mikael Abrahamsson wrote:
> On Wed, 9 Mar 2016, Nick Hilliard wrote:
>
> > used.  Some will want 9000, some 9200, others 4470 and some people
>
> I have a strong opinion for jumboframes=9180bytes (IPv4/IPv6 MTU),
> partly because there are two standards referencing this size (RFC 1209
> and 1626), and also because all major core router vendors support this
> size now that Juniper has decided (after some pushing) to start
> supporting it in more recent software on all their major platforms
> (before that they had too low L2 MTU to be able to support 9180 L3 MTU).
>
> In order to deploy this to end systems, I however thing we're going to
> need something like
> https://tools.ietf.org/html/draft-van-beijnum-multi-mtu-04 to make this
> work on mixed-MTU LANs. The whole thing about PMTUD blackhole detection
> is also going to be needed, so hosts try lower PMTU in case larger
> packets are dropped because of L2 misconfiguration in networks.
>
> With IPv6 we have the chance to make PMTUD work properly and also have

The prospects for that seem relatively dire. of course whats being
discussed here is the mixed L2 case, where the device will probably not
sent icmp6 ptb anyway but rather simply discard the packet as a giant.

> PMTU blackhole detection implemented in all hosts. IPv4 is lost cause in
> my opinion (although it's strange how many hosts that seem to get away
> with 1492 (or is it 1496) MTU because they're using PPPoE).

if your adv_mss is set accordingly you can get away with
 a lot.
>

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