Path: utzoo!attcan!uunet!zaphod.mps.ohio-state.edu!usc!apple!agate!shelby!portia.stanford.edu!jessica.stanford.edu!morgan
From: morgan@jessica.stanford.edu (RL "Bob" Morgan)
Newsgroups: comp.dcom.lans
Subject: Re: How many physical addresses belong to 1 Ethernet station?
Message-ID: <1990Oct23.071021.2317@portia.Stanford.EDU>
Date: 23 Oct 90 07:10:21 GMT
References: <1990Oct18.172918.24929@forwiss.uni-passau.de> <9380@orca.wv.tek.com>
Sender: news@portia.Stanford.EDU (USENET News System)
Organization: Academic Information Resources
Lines: 19

In article <9380@orca.wv.tek.com> alanj@nevermore.WV.TEK.COM (Alan Jeddeloh) writes:

>The National 83932 SONIC uses a 16-entry content-addressable memory to filter
>incoming packets.  The enties in the CAM can be any combination of multicast
>addresses or physical addresses.  This limits you to 16 different addresses,
>but eliminates the need to do the software check.  

It seems as though 16 entries will get used up in a hurry once
multicast gets going.  And since the software that's wanting the
different addresses lives at many different layers (eg, Ethernet, IP,
some application like file service), and in many protocols (eg, IP,
AppleTalk, OSI, etc), and the failure condition (running out of
multicast slots) occurs at a very low level, I can foresee some very
obscure error messages, and confused users.  I'd suggest that any chip
without a at least fallback to some soft-failure solution (like the
AMD and Intel hash bucket scheme) would be a major lose.

 - RL "Bob" Morgan
   Stanford