Re: MTU to CDN's

[Mike Hammett <nanog () ics-il net>]

Wouldn't those situations be causing issues now, given the likelihood that someone with a less than 1,500 byte MTU is 
communicating with you now? 




----- 
Mike Hammett 
Intelligent Computing Solutions 
http://www.ics-il.com 

Midwest-IX 
http://www.midwest-ix.com 

----- Original Message -----

From: "Mikael Abrahamsson" <swmike () swm pp se> 
To: "Mike Hammett" <nanog () ics-il net> 
Cc: "NANOG list" <nanog () nanog org> 
Sent: Friday, January 19, 2018 8:05:17 AM 
Subject: Re: MTU to CDN's 

On Fri, 19 Jan 2018, Mike Hammett wrote: 

> Other than people improperly blocking ICMP, when does PMTUD not work? 
> Honest question, not troll. 

Mismatch of MTU interface settings between interfaces, mismatch of MTU 
between L3 devices and intermediate L2 devices, anycast services, ECMP 
based services where the ICMP error is delivered to the wrong node. 

So yes, there are plenty reasons that PMTUD doesn't work without anyone 
doing it because of ill will or incompetence. 

-- 
Mikael Abrahamsson email: swmike () swm pp se