Subject: Re: ATM drivers...
To: None <firstname.lastname@example.org>
From: None <Havard.Eidnes@runit.sintef.no>
Date: 04/08/1998 12:55:55
> I use the Adaptec card with OC3 on an i386 at or about 1.3... It's
> basically point-to-point IP over a PVC with an interface
> route... I've run ttcp through it at 152mbit/sec to a SS5 with a
> FORE card at the other end.... My machine is a PII/233.
Isn't that breaking the theoretical "speed limit"?
If I'm not much mistaken, the SDH STM-1 (which for these purposes
should be the same as SONET OC-3) section overhead removes 9/270 of
the bandwidth and the path overhead consumes another 1/270, giving you
155.520Mbit/s * 260/270 which comes out to 149.760Mbit/s which can be
used for ATM cells. If the above mentioned value was observed with
ttcp you'd have to additionaly take into account the ATM cell header
overhead (which comes out to approx. 10%), possible AAL5 encapsulation
overhead and the overhead possibly caused by the last cell in the IP
packet not being completely filled with "user" data.