[c-nsp] does duplex mismatch affect UDP throughput?

[Reuben Farrelly]

On 2/08/2011 8:45 PM, Mark Tinka wrote:
> On Sunday, July 31, 2011 02:47:38 PM Gert Doering wrote:
>
>> If you order a cross-city ethernet link from a telco,
>> they usually force duplex/speed settings on their gear
>> and turn off autonegotiation.
>
> Funny, we tend to do the opposite these days :-).
>
> I can understand closed networks and enterprise/corporate
> networks still going the "hard-coding" route, but it'd be
> interesting to learn if a vast majority of service providers
> are still doing the same these days (yes, it's still common
> to find hard-coding in service provider environments as well
> these days, but I just wonder whether the number is falling,
> rising or stagnant).
>
> I suspect thoughts on this are bound to be academic :-).
>
> Mark.

Even more odd is that while many enterprises still insist on hard 
setting speed and duplex between network devices (which are typically 
manufactured by vendors in single vendor environments with the best hope 
of it working properly anyway) they frequently don't force the speed and 
duplex on the end node server or non-network ports to match the switch 
port end.  These are not so easy to spot if there are mismatches as most 
servers don't seem to make the counters quite so easily visible as they 
are on switches (where -are- those settings in Windows you may ask?) - 
and by definition fixing the speed and duplex on a switch port means you 
never see *any* collisions or broken frames on that specific end of the 
link anyway.

But back to the Telco question.  Based on my experiences here in 
Australia it isn't changing all that much.  I know that Telstra 
(Wholesale and Retail) and I believe Optus Wholesale here in Australia 
still force these settings this as a matter of operational policy.  That 
covers the majority of telco services offered here.  Most of the smaller 
carriers and ISPs are more flexible with this though and will do 
auto/auto if asked (if not by default).

In my experience as a field engineer the number of duplex problems 
caused by telcos' hard setting these parameters versus autonegotiation 
problems is about 100:1.  Not to mention it also breaks MDI-X... grrr.

We had a fight with Telstra Wholesale over this very thing earlier this 
week. As a background - one of our shiny new ME3600's refused to link up 
on the port at all when it was hard set to 100/FULL (to match Telstra's 
ME3400) on the latest code, but it worked fine at 100/HALF when our port 
was configured as auto/auto**.  Telstra flatly refused to set the port 
on their switch to auto/auto to match ours so that it would work, 
telling us it was "management policy" that it was hard set this way and 
that there is no way they would change it for us.  They have insisted on 
this setting on all of our services including both old and brand new 
installations.

[** And yes, it was a crossover cable, and yes after an IOS downgrade it 
linked up again, but that's a separate matter]

Reuben