Xref: utzoo comp.unix.ultrix:4881 comp.sys.mips:1095 Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!wuarchive!zaphod.mps.ohio-state.edu!mips!costello!djl From: djl@mips.COM (Dan Levin) Newsgroups: comp.unix.ultrix,comp.sys.mips Subject: Re: TCP chokes between Ultrix 4 and 3.1c systems Message-ID: <42043@mips.mips.COM> Date: 10 Oct 90 23:50:43 GMT References: <1990Oct9.031736.2569@hayes.fai.alaska.edu> Sender: news@mips.COM Followup-To: comp.unix.ultrix Lines: 32 lgy@phys.washington.edu (Laurence G. Yaffe) writes: > gamiddle@maytag.waterloo.edu (Guy Middleton) writes: > > >Aha. That seems to fix the problem. I'll disable trailers on all our mips > >boxes; they are evil in any case. > > Why? Basically because they are non-standard, not documented, and don't do any good for modern machines. The former is a general no-no in networking. The latter because that means many new machines don't bother implementing them, which can open them up to all kinds of errors. You have to recognize and reorganize trailer packets, even if you never send them. Since you never send them, however, they tend to lose mind- share. The receiving implementation, which is important, can get broken by other changes - and since you aren't thinking about them (or likely testing vs. them often) you may not catch the bug. If you have pages larger than 1500 bytes (and we almost all do these days), then you actually pay a penalty on every incoming packet to deal with trailers. They do you no good at all. In short, trailers were a quick hack for machines with small page sizes. They are now badly outdated, it isn't clear they did any good to start with, and they are a danger to any ethernet because they are non-standard and very poorly documented. -- ***dan {decwrl,pyramid,ames}!mips!djl djl@mips.com (No, Really! Trust Me.)