Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!rutgers!usc!apple!sun-barr!decwrl!ucbvax!WSMR-SIMTEL20.ARMY.MIL!WANCHO From: WANCHO@WSMR-SIMTEL20.ARMY.MIL ("Frank J. Wancho") Newsgroups: comp.protocols.tcp-ip Subject: Comments on your RFC 1106 Message-ID: Date: 29 Jun 89 03:54:00 GMT Sender: daemon@ucbvax.BERKELEY.EDU Organization: The Internet Lines: 36 Richard, A reading of your RFC gives a good impression on the surface, and in a closed, high-speed network, it would probably be a "good thing" to allow very large windows. However, my concern, from the point of view of running a host with a high volume of ftp activity, is that I don't believe proper window value are being used now, and that opening up the possibility of even higher windows will clog all available bandwidth, especially when several connections are active with several retransmissions in progress. Case in point: there are hosts connecting to us with connections through a local high speed network, which negotiate 8K, 16K, and even 64K windows. What does not appear to be taken into account is that the connections in the middle are at much lower speeds (or the opposite case where the connected net is some medium-to-high speed, but the host connection is at some lower speed). The result is that we try to keep the pipe full as requested, but the inevitable retransmissions are tying up the limited bandwidth for the other connections. Even now I'm not sure we should blindly accept any legal max packet and window size, just because it's legal for a single connection. It seems to me that we should be exercising some overall management of the aggregate of all the connections as to both timely serviceability and available bandwidth on our end. Unfortunately, the only tools we have as a measure are connection-by-connection round-trip times to use to compute retransmission intervals, and, although we seem to be getting closer, it still ignores the overall picture. I guess I'm not ready to accept requests for gigabyte windows when some hosts still don't know a reasonable window to request under 64K now...(not to mention *where* we're going to find the address space to hold the retransmission buffers)... --Frank