[188099] in North American Network Operators' Group
Re: Internet Exchanges supporting jumbo frames?
daemon@ATHENA.MIT.EDU (Nick Hilliard)
Wed Mar 9 10:52:11 2016
X-Original-To: nanog@nanog.org
X-Envelope-To: nanog@nanog.org
Date: Wed, 09 Mar 2016 15:51:59 +0000
From: Nick Hilliard <nick@foobar.org>
To: Kurt Kraut <listas@kurtkraut.net>
In-Reply-To: <CAPbn28kHTxBvXgOiguxcXp8+d15+LHXcqmFUBZ-61t3vfJ7dzQ@mail.gmail.com>
Cc: "nanog@nanog.org" <nanog@nanog.org>
Errors-To: nanog-bounces@nanog.org
Kurt Kraut wrote:
> Thank you for replying so quickly. I don't see why the consensus for an
> MTU must be reached. IPv6 Path MTU Discovery would handle it by itself,
> wouldn't it? If one participant supports 9k and another 4k, the traffic
> between them would be at 4k with no manual intervention. If to
> participants adopts 9k, hooray, it will be 9k thanks do PMTUD.
>
> Am I missing something?
for starters, if you send a 9001 byte packet to a router which has its
interface MTU configured to be 9000 bytes, the packet will be
blackholed, not rejected with a PTB.
Even if it weren't, how many icmp PTB packets per second would a router
be happy to generate before rate limiters kicked in? Once someone
malicious works that out, they can send that number of crafted packets
per second through the IXP, thereby creating a denial of service situation.
There are many other problems, such as pmtud not working properly in the
general case.
Nick
