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Path: euryale.cc.adfa.oz.au!newshost.carno.net.au!harbinger.cc.monash.edu.au!nntp.coast.net!news.dacom.co.kr!arclight.uoregon.edu!enews.sgi.com!decwrl!usenet.cisco.com!iverson From: iverson@cisco.com (Tim Iverson) Newsgroups: comp.unix.bsd.freebsd.misc Subject: Re: FTP performance with pppd Date: 8 Aug 1996 22:20:50 GMT Organization: cisco Lines: 26 Message-ID: <4udp82$69m@cronkite.cisco.com> References: <32037C10.41C67EA6@solidsys.com> <32041EE6.8F6@www.play-hookey.com> <4u1rrj$6b2@ucthpx.uct.ac.za> <32090B80.2781E494@www.play-hookey.com> NNTP-Posting-Host: rottweiler-ether.cisco.com In article <32090B80.2781E494@www.play-hookey.com>, Ken Bigelow <kbigelow@www.play-hookey.com> wrote: |S Marquard wrote: |> I have got throughput of about 2700bps using pppd, vs 3100bps using ijppp |> (with 28.8 modems). Adjusting the mtu/mru values hasn't helped. |> I'd also like to know what the difference is. | |mtu/mru = maximum transmit/receive unit. This is basically the block |size for your TCP/IP packets. If you don't specify something smaller, |default is typically 1500 bytes per block. On a dialup link, large |blocks can cause slowdowns and increased re-transmits if the line is |noisy or collisions or other problems occur. A smaller block size |reduces the likelihood of error, and also the size of the re-transmitted A minor note -- you can't get collisions on a dialup line (full duplex and point to point) and modem error correction should guarantee a clean line. In general, a larger MTU will increase throughput on transfer protocols and increase latency on interactive protocols (vice-versa for smaller MTU). If you only use a single network protocol at a time, use 1500. If you telnet with ftp in the background, you'll probably want to use something much smaller (576 is a favorite for many people). - Tim Iverson iverson@lionheart.com