NAP/ISP Saturation WAS: Re: Exchanges that matter...

Jim Van Baalen vansax at
Fri Dec 20 11:57:47 UTC 1996

I have a question that fits this topic. Why does everybody seem to be so
sold on Gigaswitch based Xchange points? I know that the busiest, highest
membership NAPs are of this design, but with all the associated problems
(head of line blocking, tiny buffers, and less than ideal flow control
mechanisms (token withholding during congestion for example)) why are all 
the new Xchanges using this architecture? Based on membership and traffic it 
appears that there is still a stigma associated with Xchanges (PBnap and AADS 
for example) that have chosen different architectures. It was also my 
impression that people were much more critical of these "other" NAPS at the 
recent NANOG than SprintNAP and the MAEs.

It is my opinion that the most promising architecture today is PBNap. The
StrataCom switches far exceed Gigaswitch in addressing issues such as flow 
control, buffering, and aggregate throughput (which may not be comparable
when, as with Gigaswitch, port congestion is such a bottleneck). In addition, 
with new line cards due out early next year, the BPXs will support ABR and,
relatively speaking, huge buffers at high density OC3 and 2 port OC12.

I know that ATM is a nasty word (or should I say acronym) to many on this list,
but even some of the greatest ATM critics admit that it is a reasonable LAN
technology. As far as the popular packet shredder (sp?) argument goes, I don't 
think that it relevant on any switch that supports EPD.

Just curious to see other perspectives.


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