Path: utzoo!attcan!uunet!lll-winken!lll-tis!ames!pasteur!ucbvax!spider.UUCP!ian
From: ian@spider.UUCP
Newsgroups: comp.protocols.tcp-ip
Subject: default broadcast address
Message-ID: <6315.8807212019@brahma.cs.hw.ac.uk>
Date: 21 Jul 88 20:19:04 GMT
Sender: daemon@ucbvax.BERKELEY.EDU
Organization: The Internet
Lines: 17

I'm surprised to hear that RFC 922 isnt generally supported (I implemented
it for our routers).  RFC 1009 certainly pushes it, it's straightforward to 
implement, and without it you can't handle network broadcasts over subnets.  

I can see an issue with network broacasting from an embedded gateway or
multihomed host with two (or more) interfaces onto subnets of the same
network, viz. what IP source address do you use for the multiple
outgoing datagrams?

If a network broadcast is transmitted on an unbound socket, do you use the 
local IP address for each interface?  In this case you get different datagrams 
transmitted on each interface.  A consequence of the suboptimality of reverse 
path forwarding is that hosts on some subnets will receive one datagram 
(with varying IP source address) and hosts on others may receive two datagrams 
with different IP source addresses.  The number of datagrams and source
address of the datagrams received by a particular host may change as the 
routing tables change.  Multihomed hosts suffer from identity crises,
I suppose.