From: bmanning@ISI.EDU (Bill Manning) Subject: Re: Cisco's AIP vs HSSI To: freedman@netaxs.com (Avi Freedman) Date: Tue, 15 Oct 1996 07:55:50 -0700 (PDT) Cc: bmanning@ISI.EDU, salo@msc.edu, kri@bellcore.com, nanog@merit.edu [...] The orginal question can be paraphrased as; "which board is better" (see the subject line). Tim S. couched his replies in the form of an ATM only solution. I feel that the HSSI board was not designed as such. Your comments seem to back up my assertions.

The HSSI card was not designed as an ATM solution. The HSSI ATM solution involved, in some sense, making the ATM network look like a frame relay network to the HSSI card.

I would claim that for raw throughput, and assuming the DS3 daughtercard for the AIP, that the HSSI board delivers more useful bits at the expense of an outboard CSU. This is based on my feeling that HDLC is more efficent than ATM signaling/framing.

If the context of the question is the most appropriate interface for a point-to-point connection between two routers, I would worry more about throughput than, for example, issues of ATM versus HDLC functionality and overhead. The AIP card can obviously clock out data a lot faster than can a HSSI board, (assuming you don't intentionally put a slow interface on the AIP card). However, I think it is also important to understand the throughput of the two boards and how well they are integrated into the Cisco (or, in general, your favorite vendor's) router. I was under an impression that the HSSI card was a lower-performing board, but someone with some more detailed understanding should provide some insight. I suppose my answer could be refined as: o If you need an ATM solution, use the AIP card. o If you merely want a DS-3 or slower point-to-point link between two routers, test both solutions, (or talk to someone who has), to determine which solution has better performance; or o If you want a point-to-point connection between two routers at speeds faster than HSSI can support (a bit more than 45 Mbps, I think) use the AIP card. Again, you should also consult your router vendor. They should be giving you all this information and more. For example, you might discuss a OC-3c IP over SONET solution for point-to-point connections. -tjs