[183364] in North American Network Operators' Group
Re: PMTUD for IPv4 Multicast - How?
daemon@ATHENA.MIT.EDU (Chris Marget)
Mon Aug 31 17:28:50 2015
X-Original-To: nanog@nanog.org
In-Reply-To: <55E4C450.7070004@necom830.hpcl.titech.ac.jp>
From: Chris Marget <chris@marget.com>
Date: Mon, 31 Aug 2015 17:28:27 -0400
To: Masataka Ohta <mohta@necom830.hpcl.titech.ac.jp>
Cc: "nanog@nanog.org list" <nanog@nanog.org>
Errors-To: nanog-bounces@nanog.org
>> I'll probably come around, but I've not yet concluded that "screw it,
>> fragment my traffic, I don't care" is the stance that a conscientious
>> application should be taking.
>
> Don't you care, for routers, generating ICMP PTB is as burdensome
> as generating fragments?
I don't think so. If PMTUD is working (big IF, I know), the ICMP PTB
generation is a one-time thing (or once per 10 minutes or whatever)
and can be rate limited with little impact. Fragmenting transit
traffic, on the other hand, needs to be done for every transit packet.
