Path: utzoo!utgpu!watserv1!watmath!att!rutgers!dimacs.rutgers.edu!seismo!uunet!mcsun!hp4nl!svin02!eba!al.ele.tue.nl!raymond
From: raymond@ele.tue.nl (Raymond Nijssen)
Newsgroups: comp.unix.sysv386
Subject: Re: ISC 2.2 SL/IP throughput?
Message-ID: <545@al.ele.tue.nl>
Date: 29 Aug 90 19:17:30 GMT
References: <25@astph.UUCP> <3694@wb3ffv.ampr.org> <26@astph.UUCP> <1990Aug23.160013.1199@scuzzy.mbx.sub.org>
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Organization: Eindhoven University of Technology, The Netherlands
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In article <1990Aug23.160013.1199@scuzzy.mbx.sub.org> src@scuzzy.mbx.sub.org (Heiko Blume) writes:
>can someone tell me what throughput i can expect with sl/ip over
>a modem connection with HST modems (14400bps)? we talk to the modems
>at 19200 and use hardware flow control (FAS with 16550 chips). we did
>a ftp and the throughput was ~0.2 KB/s on a 600KB file, which is unacceptable.

The bottleneck causing such low performance is not your system, but your modem.
HST modems are '14400' bps modems, 'but not as we know it'; in fact these
modems are just half-duplex 9600 baud modems, and they are not V32 compatible
at all, although many vendors 'forget' to mention this subtlety, just like
IBM 'forgot' to tell potential customers that the PS/2 model 30 cannot run 
OS/2. (Excuse me for referring to it in this newsgroup)
SLIP _needs_ a full-duplex connection, and since the line-turnaround times
of HST modems are very slow, the throughput will be very disappointing.

To make things even worse, turning the line around at a high rate virtually 
eliminates the effect of the data-compression performed by the modem, so the
effective connection-throughput might be even lower than 500 cps (ca. 9600/2 
baud). Any ordinary MNP-5 class modem would perform about the same, which 
explains, if you take SL/IP overhead into account, your 200 cps rate.

>did we do something wrong? (of course we did sldialup/attach 19200 ttyF01).
I'm afraid you made the wrong choice when you bought the HST modem.
But maybe your vendor didn't know himself that it isn't V32 compatible.

______________________________________________________________________________
Raymond X.T. Nijssen  / Don't speak if you  / Oh VMS, please forgive me all
raymond@ele.tue.nl   / speak for yourself  / unfriendly things I said about you