Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!ames!lll-winken!gauss.llnl.gov!casey
From: casey@gauss.llnl.gov (Casey Leedom)
Newsgroups: comp.protocols.tcp-ip
Subject: Re: IP Multicasting in SunOS
Message-ID: <43650@lll-winken.LLNL.GOV>
Date: 9 Jan 90 02:10:48 GMT
References: <43507@lll-winken.LLNL.GOV> <9001080653.AA24474@ucbvax.Berkeley.EDU>
Sender: usenet@lll-winken.LLNL.GOV
Reply-To: casey@gauss.llnl.gov.UUCP (Casey Leedom)
Organization: Lawrence Livermore National Laboratory
Lines: 39

| From: cire@CISCO.COM
| 
| Except for the problems with Casey's proposal it is fine.  :-)

  Yes, I know that it's really too late to get rid of Ethernet
broadcasts, but I had to bring it up because too many people think that
Ethernet broadcasts are the Right Way to do things (for instance all the
&^*%&*^ groady broadcast license schemes floating around).

| Given that ARP is a cached protocol (I don't think 'lazy' applies)
| extending it to use multicast doesn't seem like a big win.

  "Lazy" refers to Lazy Evaluation which is an algorithm technique that
can often work wonders for theoretically large polynomial or even
non-polynomial problems.  The basic idea is that instead of always trying
to be prepared at every stage of an algorithm with every possible value
one might need to compute the next stage of the algorithm, you don't pre-
compute anything.  Instead you fault when you need a value that hasn't
been compute yet.  It's called Lazy Evaluation because of the analogy of
a Lazy Person not doing anything until it's needed.

  In this particular case I'm comparing the non-Lazy Hello type Address
Resolution Protocols to the Lazy Ethernet/IP Address Resolution
Protocol.  In the ARPs of the former type, every station constantly
screams its Ethernet/Network address pairing to the entire net to make
sure everyone knows how to get to it.  This technique doesn't scale up
well at all for larger networks.  Unfortunately it's used by a lot of
network protocols.  The IP/Ethernet ARP on the other hand scales up very
nicely.

  Thus, I essentially agree with you that there's not a lot to be gained
in converting IP/Ethernet ARP to Ethernet multicasting.  But I still hate
the use of Ethernet broadcasts.  I just don't think they ever should have
existed, or their use should have been specifically described for use in
an Ethernet level Control Message Protocol (and even then that should
simply have been yet another multicast address; thus I can't find any
good reason to support Ethernet broadcasts).

Casey