TCP chokes between Ultrix 4 and 3.1c systems

[Dan Levin]

lgy at phys.washington.edu (Laurence G. Yaffe) writes:
> gamiddle at 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They are now badly outdated, it isn't clear they did any good to start with,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 at mips.com (No, Really! Trust Me.)