Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!mailrus!purdue!mentor.cc.purdue.edu!dls
From: dls@mentor.cc.purdue.edu (David L Stevens)
Newsgroups: comp.protocols.tcp-ip
Subject: Re:  Using the 4.2 broadcast addr with 4.3 systems
Message-ID: <3836@mentor.cc.purdue.edu>
Date: 2 Sep 89 01:08:26 GMT
References: <8909011422.AA06811@interlan.interlan.com>
Reply-To: dls@mentor.cc.purdue.edu (David L Stevens)
Organization: PUCC UNIX Group
Lines: 27


	Since Phil Karn will point it out, I will first; over such a SLIP
link, where link-level addresses are implicit, you don't have broadcasts,
anyway.
	From PK's second posting, it seems to me that he isn't so radical
as I thought in that (and I know I'll be corrected if wrong) I THINK he
was suggesting an additional flag (only) and not a replacement for IP broadcast/
multicast addressing. That seems perfectly reasonable to me and would allow
traps for "telnet <broadcast addr>" without losing anything else.

	On the topic of single IP address per host: I used to think so too,
but I suspect it would result in routing chaos and poor choices in other ways.
Multi-connected hosts would likely suffer unnecessary outages or (just as bad)
poor routing decisions (close hosts going the long way around) because of it.
Hosts on the same network, but with different network addresses would suffer
from different levels of service-- a nightmare to keep straight-- because
distant gateways have incomplete or inconsistent information about the
"different" networks.
	After all, the whole point of IP addresses is to make routing easy;
if everything else works, humans shouldn't even have to deal with them...
	Finally, directed broadcasts (again) break; suppose you have a network
where every host on it is a gateway and each's IP address is taken from its
other network. You have a network that is not addressable, so, though you
could send packets to individual hosts, you could not broadcast to all of
them with one packet, like you can now.
-- 
					+-DLS  (dls@mentor.cc.purdue.edu)