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Path: sserve!newshost.anu.edu.au!munnari.oz.au!yoyo.aarnet.edu.au!myall.awadi.com.au!myall!blymn From: blymn@awadi.com.au (Brett Lymn) Newsgroups: comp.os.386bsd.questions Subject: Re: CSLIP questions Date: 13 Mar 93 19:14:59 Organization: AWA Defence Industries Lines: 36 Message-ID: <BLYMN.93Mar13191459@mallee.awadi.com.au> References: <RUSSO.93Mar1104607@bogon.lanl.gov> <RUSSO.93Mar1112911@bogon.lanl.gov> NNTP-Posting-Host: mallee.awadi.com.au In-reply-to: russo@lanl.gov's message of Mon, 1 Mar 1993 18:29:11 GMT >>>>> On Mon, 1 Mar 1993 18:29:11 GMT, russo@lanl.gov (Thomas Russo) said: T> In article <RUSSO.93Mar1104607@bogon.lanl.gov> russo@lanl.gov (Thomas Russo) writes: >Oh, and I'd be interested in hearing from anybody who's using a >v.32+v.42bis modem (not v.32bis) and who is getting anything close to >the supposed peak transmission speed --- I seem to be getting an >effective transfer rate of about 8000bps over a nice clean phone line. T> I should probably have been more specific --- I mean I'd like to hear T> from people who are getting high transfer rates using SLIP with modems T> of this sort. I have found that the slip MTU has a big effect on the throughput of the slip link, especially when using higher baud rates. I was able to ftp at 1.4Kbyte/s on a v.42 modem by increasing the slip MTU to 900 bytes. With v.42bis my transfer speeds were not as fast as they should be so it looks like I need to increase the MTU, I reckon 1500 bytes will be my next step. To increase the size of the slip MTU you need to hack the following file: /usr/src/sys.386bsd/net/if_sl.c, find the line that has '#define SLMTU'. The original size is 296, increase it to whatever you like and recompile, install and reboot the new kernel. You should notice a big improvement in the speed of ftp, note though that the MTU size is a tradeoff between interactive and non-interactive traffic, if you make the MTU too big your telnet sessions will feel sluggish because more keystrokes will be sent in one packet, on the other hand a MTU too small makes ftp inefficient. The current MTU is set for a 9600 baud line so some tweaking is in order if you have a faster modem. I also have a copy of a hacked slattach that was posted a while ago which enables the VJ header compression. If you cannot find a copy elsewhere then mail me and I will send you a copy. -- Brett Lymn