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MTU to CDN's

thanks. good answer. low risk answer. "it will work" answer.

If its a variant of "the last mile is your problem" problem, I'm ok
with that. If its a consequence of the middleware deployment I feel
like its more tangibly bad decision logic, but its real.


On Fri, Jan 19, 2018 at 9:50 AM, Mark Andrews <marka at isc.org> wrote:
> Because the CDN delivers to your customers not you.  Itâ??s your customers link
> requirements that are the ones you need to worry about.  If you support
> jumbo frames to all of your customers and their gear also supports jumbo
> frame then sure go ahead and use jumbo frames otherwise use the lowest
> common denominator MTU when transmitting.  This is less than 1500 on
> today Internet and encapsulated traffic is reasonable common.
>         embedded CND <--> NAT64 <--> CLAT <--> client
>                      1500       14XX     1500
>         embedded CDN <--> B4 <â?? > 6RD <â?? > client
>                      1500.   14XX     1500
> Now you can increase the first 1500 easily.  The rest of the path not so
> easily.
>> On 19 Jan 2018, at 9:53 am, George Michaelson <ggm at algebras.org> wrote:
>> if I was an ISP (Im not) and a CDN came and said "we want to be inside
>> you" (ewww) why wouldn't I say "sure: lets jumbo"
>> not even "asking for a friend" I genuinely don't understand why a CDN
>> who colocates and is not using public exchange, but is inside your
>> transit boundary (which I am told is actually a bit thing now) would
>> not drive to the packet size which works in your switching gear.
>> I understand that CDN/DC praxis now drives to cheap dumb switches, but
>> even dumb switches like bigger packets dont they? less forwarding
>> decision cost, for more throughput?
>> On Fri, Jan 19, 2018 at 6:21 AM, Dovid Bender <dovid at telecurve.com> wrote:
>>> Vincent,
>>> Thanks. That URL explained a lot.
>>> On Tue, Jan 9, 2018 at 3:11 AM, Vincent Bernat <bernat at luffy.cx> wrote:
>>>> â?¦  8 janvier 2018 15:08 -0800, joel jaeggli <joelja at bogus.com> :
>>>>>> N00b here trying to understand why certain CDN's such as Cloudfare have
>>>>>> issues where my MTU is low. For instance if I am using pptp and the MTU
>>>> is
>>>>>> at 1300 it wont work. If I increase to 1478 it may or may not work.
>>>>> PMTUD has a lot of trouble working reliability when the destination of
>>>>> the PTB  is a stateless load-balancer.
>>>> More explanations are available here:
>>>> https://blog.cloudflare.com/path-mtu-discovery-in-practice/
>>>> --
>>>> Don't comment bad code - rewrite it.
>>>>            - The Elements of Programming Style (Kernighan & Plauger)
> --
> Mark Andrews, ISC
> 1 Seymour St., Dundas Valley, NSW 2117, Australia
> PHONE: +61 2 9871 4742              INTERNET: marka at isc.org