Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!usc!apple!salt.acc.com!opal!art
From: art@opal.acc.com (Art Berggreen)
Newsgroups: comp.protocols.tcp-ip
Subject: Re: Packet Sizes
Message-ID: <1991Mar28.171539.17232@salt.acc.com>
Date: 28 Mar 91 17:15:39 GMT
References: <7741@uceng.UC.EDU> <9103151236.AA05472@asylum.sf.ca.us> <17724@sdcc6.ucsd.edu>
Sender: news@salt.acc.com
Reply-To: art@opal.acc.com (Art Berggreen)
Organization: Advanced Computer Communications, Santa Barbara, California
Lines: 22

In article <17724@sdcc6.ucsd.edu> jclark@sdcc6.ucsd.edu (John Clark) writes:
>In article <9103151236.AA05472@asylum.sf.ca.us> romkey@asylum.sf.ca.us writes:
>+If you're looking at raw ethernet packet lengths (as opposed to IP
>+datagram lengths), you'll see lots of 60 byte packets on the net
>+because ethernet has a minimum packet length of 60 bytes. Any packets
>+that are shorter are padded out to 60. IP can tell how many bytes it
>
>Sometime ago I had a ethernet analyzer on a line with both TCP/IP
>and DECNET traffic. It seems to me that there were some DECNET
>packets shorter than the minimum. It could have been a halucination
>or does DEC violate the standard.
>-- 
>
>John Clark
>jclark@ucsd.edu

Is it possible that your ethernet analyzer was reporting the length of the
DECNET packet?  DECNET uses a length field immediately after the Ethertype
to define the size of the encapsulated DECNET packet.  The Ethernet packet
is always supposed to be padded out to minimum size (if neccessary).

Art