Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Path: utzoo!mnetor!uunet!seismo!rutgers!sri-spam!ames!ucbcad!ucbvax!TOPAZ.RUTGERS.EDU!hedrick
From: hedrick@TOPAZ.RUTGERS.EDU (Charles Hedrick)
Newsgroups: comp.protocols.tcp-ip
Subject: Re: Ethernet meltdowns
Message-ID: <8707140733.AA09249@topaz.rutgers.edu>
Date: Tue, 14-Jul-87 03:33:45 EDT
Article-I.D.: topaz.8707140733.AA09249
Posted: Tue Jul 14 03:33:45 1987
Date-Received: Wed, 15-Jul-87 04:19:24 EDT
Sender: daemon@ucbvax.BERKELEY.EDU
Distribution: world
Organization: The ARPA Internet
Lines: 36

Well, I know the cure for broadcast storms, and I think plenty of
other people do as well.  I mostly give it in the message.  You simply
have to be very careful to do validity checking before forwarding
packets or generating ICMP error messages.  As far as I can tell, 4.3
is fairly good, so it's mostly a matter of waiting for vendors to
catch up to 4.3.  All the Unix vendors we deal with have either just
released 4.3-based network code or are about to do so.  I agree with
your implication that validation of TCP/IP implementations would be
useful.  I understand that it is hard to design a test setup that will
make sure a TCP follows all the best performance guidelines.  But it
is not at all hard to make sure that an IP is designed so it won't
contribute to broadcast storms.  

My first inclination is to say that it will be easy for ISO to avoid
this problem.  It isn't hard to come up with a set of implementation
guidelines that avoid broadcast storms.  What really triggered this
was the Internet changing its idea of the broadcast address.  I mean,
it shouldn't have been hard to forsee this problem when 0 was changed
to -1.  (On the other hand, subnetting probably required enough of a
change that things would have broken anyway, so there might have been no
way to avoid problems.)

However this may be giving too much credit to people.  The people who
will be implementing ISO are exactly the same people who have ignored
the TCP/IP implementation guidelines.  If people can do IP's that
don't respond to ICMP echo, presumably they can find ways to mess up
ISO as well.  It seems to me that ISO's equivalent of the broadcast
address change is going to be the incredibly complex address
structure.  It seems likely that few people will implement every
possible address format.  (Indeed probably they couldn't if they
wanted to.)  My intuition says that when different implementations
implement different sets of address formats, there are bound to be
some interesting interactions somewhere.  And with the worldwide PTT
network built into the addressing structure, I'll bet at some point
we'll manage to see some sort of storm that involves several
continentne