Re: MTU to CDN's

[George Michaelson <ggm () algebras org>]

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.

-G

On Fri, Jan 19, 2018 at 9:50 AM, Mark Andrews <marka () isc org> wrote:
> Because the CDN delivers to your customers not you.  It’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 <— > 6RD <— > 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 () 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 () telecurve com> wrote:
> > > Vincent,
> > >
> > > Thanks. That URL explained a lot.
> > >
> > > On Tue, Jan 9, 2018 at 3:11 AM, Vincent Bernat <bernat () luffy cx> wrote:
> > >
> > > > ❦  8 janvier 2018 15:08 -0800, joel jaeggli <joelja () 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 () isc org