Path: utzoo!utgpu!water!watmath!clyde!att!pacbell!rtech!hoptoad!gnu From: gnu@hoptoad.uucp (John Gilmore) Newsgroups: comp.mail.uucp Subject: Re: 'g' packet size Message-ID: <5463@hoptoad.uucp> Date: 26 Sep 88 08:01:27 GMT References: <212@jato.Jpl.Nasa.Gov> Organization: Grasshopper Group in San Francisco Lines: 33 The packet size is negotiated in powers of two; it is possible to negotiate larger packet sizes. I have not tried it in gnuucp, but it should work. Last time this was mentioned though, someone reported that old Unix uucp's would happily try to send you larger packets, but had statically allocated buffers of the old size -- so they end up overrunning an array, writing into random memory, and crashing. It's not clear what effect larger packet sizes would have. On links that have high delay (e.g. PC Pursuit), the more data you can shove into the pipe before stalling awaiting an ack, the better off you are -- so since the protocol limits you to 7 packets, making them larger is a possible way to increase thruput. On links with fast acks (any Telebit link, and links to quick systems), it probably doesn't matter much. Somebody pointed out a problem if uucico "swaps out" and you use large packets, the tty drivers won't have room to keep all the characters. That depends on your tty drivers of course, but regardless, if your uucico is swapping out, your thruput is going to go to shit anyway because your acks are delayed and the sender stops sending. I recommend that if anyone implements larger packet sizes, you call it the "G" protocol rather than the "g" protocol. That is, the "G" protocol is a "g" protocol that has no bugs around large packet sizes. Advertise as supporting both; if you call another site with no bugs, you'll use large packets, and if you call an older site, you'll use the old standby 64 byte packets. John Gilmore -- John Gilmore {sun,pacbell,uunet,pyramid,amdahl}!hoptoad!gnu gnu@toad.com there's still time to change the road you're on. --LZ: "Stairway to Heaven"