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