Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Path: utzoo!mnetor!uunet!seismo!sundc!pitstop!sun!decwrl!ucbvax!A.ISI.EDU!CERF From: CERF@A.ISI.EDU Newsgroups: comp.protocols.tcp-ip Subject: Re: TCP performance limitations Message-ID: <[A.ISI.EDU].3-Oct-87.06:36:14.CERF> Date: Sat, 3-Oct-87 06:36:00 EDT Article-I.D.: <[A.ISI.EDU].3-Oct-87.06:36:14.CERF> Posted: Sat Oct 3 06:36:00 1987 Date-Received: Wed, 7-Oct-87 01:11:55 EDT References: Sender: daemon@ucbvax.BERKELEY.EDU Organization: The ARPA Internet Lines: 34 As you move upward in the bandwidth range, you have decreasing amounts of time to process each object passing through - the high speed switching fabrics developed at Bell Labs and Bell Core have the characteristic that very little per packet processing is being done and, as you surmise, a kind of virtual circuit is set up; however, the switching fabric is able to share the bandwidth of the transmission resources, despite the VC set-up, because the VCs are just table entries and not reservations of actual capacity within each trunk. At the terminations of such a switching fabric, however, I think one still will need some end/end checking. Moreover, if we contemplate the kind of linking of networks we have today (vastly different internal operation), we may still need the end/end checking that TCP does. Rather than putting the TCP in the mainframe, anymore, though, it is fair to consider the sort of DMA interface which permits the TCP and perhaps other layers of protocol to be housed on an external board, equipped with special purpose logic or at least dedicated processing, placing data or taking data from the main processor's memory. Communications becomes a matter of placing buffers in memory and possibly signalling their arrival to the communications processor. I suspect that this description is not far away from the kinds of equipment already made and sold by companies like EXCELAN and ACC. Forgive me if I failed to mention the dozens of other companies whose products may work this way - I'm not up to speed on all the commercial products now flowering in the TCP/IP fields. At an IP switch point, you are still faced with at least full IP level processing and handling 45 Mb/s and up at that point is still a big processing load, unless we re-think the IP level and try to find a way to fabricize it, as the Bell folks have with the lower level packet switching. Hmm. Vint