Martin Pels wrote on 10/3/2016 4:15 μμ:
On Thu, 10 Mar 2016 08:23:30 +0200 Tassos Chatzithomaoglou <achatz@forthnet.gr> wrote:
Niels Bakker wrote on 10/3/16 02:44:
* nanog@nanog.org (Kurt Kraut via NANOG) [Thu 10 Mar 2016, 00:59 CET]:
I'm pretty confident there is no need for a specific MTU consensus and not all IXP participants are obligated to raise their interface MTU if the IXP starts allowing jumbo frames. You're wrong here. The IXP switch platform cannot send ICMP Packet Too Big messages. That's why everybody must agree on one MTU.
Isn't that the case for IXP's current/default MTU? If an IXP currently uses 1500, what effect will it have to its customers if it's increased to 9200 but not announced to them? None. Until someone actually tries to make use of the higher MTU. Then things start breaking.
I can understand the above issue. But as i said that's customer's decision. Exactly the same will happen if the customer increases its mtu now.
In order for Jumboframes to be successful on IXPs _on a large scale_ the technology has to change. There needs to be a mechanism to negotiate MTU for each L2 neighbor individually. Something like draft-van-beijnum-multi-mtu-03, which was mentioned before in this thread. With this in place individual sets of peers could safely use different MTUs on the same VLAN, and IXPs would have a migration path towards supporting larger framesizes.
Agreed. But that doesn't forbid the IXPs to use the max MTU now. -- Tassos