Path: utzoo!mnetor!uunet!husc6!rutgers!bellcore!faline!ulysses!ggs
From: ggs@ulysses.homer.nj.att.com (Griff Smith)
Newsgroups: comp.unix.wizards
Subject: Re: rdump, Ethernet slowness
Message-ID: <3265@ulysses.homer.nj.att.com>
Date: 10 Dec 87 16:25:19 GMT
References: <788@hsi.UUCP> <1268@laidbak.UUCP> <411@anuck.UUCP>
Organization: AT&T Bell Laboratories, Murray Hill
Lines: 38
Summary: mostly software delays

In article <411@anuck.UUCP>, jrl@anuck.UUCP writes:
> > The network transfer rate is good, but the latency is poor.
> 
> How good is this? I know that the network bandwidth is 10Mb,
> but when I transfer a 1 MB file, instead of the 10 seconds that
> the true bandwidth suggests I might get on an unloaded net, 
> I find that it takes a minute or more.

10 Mbit/sec == 1.2 Mbyte/sec.  True, I never see speeds anywhere near
that.  I do see 110 Kbyte/sec when I use a CCI POWER 6/32 running
4.3BSD to dump to a DEC VAX 8650, also running 4.3BSD.  I think this
comes to 9 seconds/Mbyte.  I just tried a file copy between those two
processor and got 10 seconds/Mbyte, which is just what you wanted.

> Is this software delay,

Probably; protocol delay, and sometimes processor overload.  TCP/IP
can chew up a lot of a processor.  Our CCI machine has speeded up
by a factor of 6 since we first started using 4.3BSD on our VAXen.
The first factor of 2 was a windowing strategy mismatch between
4.3BSD and the version of 4.2BSD that was running on the CCI processor.
A further factor of 3 resulted when we upgraded to a 4.3BSD+ beta
distribution from Berkeley.

> maybe someone will make [a controller] that can really feed the
> net, which would change my mind about being somewhat put off of
> ethernet because it fails to deliver on the single-user throughput.
> 
> John R. Lupien
> ihnp4!mvuxa!anuxh!jrl

You don't say what flavor of UNIX you are using.  Protocol implementations
can have a lot of effect on the speed.
-- 
Griff Smith	AT&T (Bell Laboratories), Murray Hill
Phone:		1-201-582-7736
UUCP:		{allegra|ihnp4}!ulysses!ggs
Internet:	ggs@ulysses.uucp