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- Path: sparky!uunet!elroy.jpl.nasa.gov!ames!network.ucsd.edu!ucsbcsl!spectrum.CMC.COM!fennel.acc.com!art
- From: art@acc.com (Art Berggreen)
- Newsgroups: comp.protocols.tcp-ip
- Subject: Re: satellite link file transfers
- Message-ID: <1992Jul27.215151.22407@acc.com>
- Date: 27 Jul 92 21:51:51 GMT
- References: <1992Jul27.190345.22868@Arco.COM> <1992Jul27.194447.23444@Arco.COM>
- Organization: ACC, Advanced Computer Communications
- Lines: 27
-
- In article <1992Jul27.194447.23444@Arco.COM> Gary White writes:
- >In article <1992Jul27.190345.22868@Arco.COM> Gary White <gwhite@arco.com>
- >writes:
- >>Hi-
- >>Between Texas and Alaska via a satellite -linked communications link, we
- >>find that FTP goes awfully slowly. Has anybody learned how to tune FTP,
- >>or come up with some other software, to go fast on a satellite link?
- >>
- >>Thanks-
- >>Gary White
- >>
- >More information: this is with a T1 link with two RS/6000 560 machines
- >both running AIX 3.2; FTP performance is similar to a 56Kb terrestial
- >hookup.
-
- Do you have any idea what the TCP window size is on the RS/6000s?
- Assuming a single satellite hop, that's about 1/2 sec. RTT.
- This requires a window of 96KB at full T1 (24X64Kbps). Since the best
- you can do with TCP (without the large window option) is 64KB,
- the T1 will max around 128KBps. With a default window size of 4KB,
- you should see about 8KBps (64Kbps). This is close to what you appear
- to be getting.
-
- Art
-
- KBps = KiloBytes/sec
- Kbps = KiloBits/sec
-