Re: MTU to CDN's

[Mark Andrews <marka () isc org>]

Which doesn’t work with IPv6 as UDP doesn’t have the field to clamp. 

-- 
Mark Andrews

> On 20 Jan 2018, at 03:35, Radu-Adrian Feurdean <nanog () radu-adrian feurdean net> wrote:
>
> > On Fri, Jan 19, 2018, at 01:14, Jared Mauch wrote:
> > If you’re then doing DSL + PPPoE and your customers really see a MTU
> > of 1492 or less, then another device has to fragment 5x again.
>
> In this part of the world we have even worse stuff around: PPP over L2TP over over IP with 1500 MTU interconnection. 
> Remove another 40 bytes. Add some more headers for various tunneling scenarios and you may get into a situation where 
> even 1400 is too much.  But it usually works with MSS clamping to the correct value. Some small ISPs don't even make 
> the effort to check if the transport supports "more than 1500" in order to give the 1500 bytes to the customer - they 
> just clamp down MSS.