From: Jim Van Baalen <vansax@atmnet.net> Subject: Re: NAP/ISP Saturation WAS: Re: Exchanges that matter... Date: Fri, 20 Dec 1996 03:57:47 -0800 (PST)

... Why does everybody seem to be so sold on Gigaswitch based Xchange points? ...

A few random thoughts: o I believe that the DEC GigaSwitch has been demonstrated, under very heavy production loads, to be far superior to any other available technology. Technology superior to the GigaSwitch might exist, but I don't believe anyone has demonstrated that technology under heavy, 24x7 load. The alternative technology needs someone to bet their exchange on putting 200-400 mbps of continuous Internet traffic across the new technology. o When the GigaSwitch was first selected for an exchange, alternative technology was not as well developed. ATM switches still had, (with somewhere between zero and two exceptions), small buffers. A lot of ATM equipment was simply bad, at least for wide-area applications. The fact that the Cisco AIP card did not have a DS-3 interface also hurt, (fairly seriously, it turns out). o Note that if an exchange bets on ATM, its fate also depends upon the quality of the ATM interfaces in the attached routers. In particular, the Cisco AIP card becomes a critical component in the exchange. Before I placed too heavy of a bet on an ATM exchange, I would want to see a good performance analysis of the Cisco AIP card and the ATM interfaces for any other router which might attach. If the router ATM interfaces are not as good as the router FDDI interfaces, an ATM exchange, as a whole, is likely to be less successful than an FDDI exchange. By the way, I would assume that router vendors have spent more resources on improving the performance of FDDI interfaces than ATM interfaces.

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. ...

I think several unfortunate events plagued the PacBell and AADS exchanges. o Because it was not clear that a Cisco DS-3 AIP card would be available in the required timeframe, a decision was made to use ATM DSUs and the Cisco HSSI interface, (a decision in which I played a modest role). o It turns out that the selected ATM DSU had implementation problems which took a while to work out. ATM DSUs in general, I believe, also have the problem that they simply aren't designed for the sort of load that is experienced at an Internet exchange. The Cisco HSSI card might also be weaker than the Cisco AIP card. o It is possible that the two exchanges remained committed to an ADSU solution longer than they should have, particularly when it became apparent that the Cisco DS-3 AIP card was available (something I had no role in). So, history may play a bit of a role in the current position of the PacBell and AADS exchanges. On the other hand, it appears that the Internet operational folks are unlikely to try anything as new and as unproven as ATM until they have no other choice. I suspect that the next time ATM products and standards are called upon to carry production Internet traffic, they will be ready to support a heavy duty Internet load. I think ATM products and standards are [perhaps almost, perhaps just] ready to support the traffic loads experienced at Internet exchanges. It would be nice to see a heavily loaded ATM exchange or perhaps a mixed ATM/FDDI exchange. -tjs