tcp-ip@ucbvax.ARPA (07/30/85)
From: jbn@FORD-WDL1.ARPA
Someone needs to nail this down. The meaning of ``broadcast
addressing'' in IP space is not well defined at present, and needs
to be.
Incidentally, it is probably a bad idea to have special addresses
that only can be decoded after you know how many bits of subnet information
apply. This applies to [0.0.0.x], [0.0.x.x], and [0.x.x.x], which seem
to be of marginal utility.
Nagletcp-ip@ucbvax.ARPA (07/30/85)
From: POSTEL@USC-ISIF.ARPA See the bottom of page 3 of RFC 943. --jon. -------
tcp-ip@ucbvax.ARPA (07/30/85)
From: Jeff Mogul <mogul@Navajo>
Someone needs to nail this down. The meaning of ``broadcast
addressing'' in IP space is not well defined at present, and needs
to be.
Right. How about taking as a starting point either RFC919, "Broadcasting
Internet Datagrams", or RFC922, "Broadcasting Internet Datagrams in
the Presence of Subnets". The latter might be slightly out-of-synch
with the RFC940 scheme for subnetting, but the intelligent reader
will not miss the point.
There has been a thundering silence on the topic ever since I wrote
these RFCs last year. Neither memo requires the use of broadcast
(something that some people failed to understand), but merely
specifies a mechanism to be used if desired. Remember, "RFC"
stands for "Request for Comments".
Incidentally, it is probably a bad idea to have special addresses
that only can be decoded after you know how many bits of subnet
information apply. This applies to [0.0.0.x], [0.0.x.x], and
[0.x.x.x], which seem to be of marginal utility.
You're mostly right. The idea (see RFC917) is that the use of subnets
should be invisible outside the network. Therefore, any "special"
address that requires such decoding must be used only within a single
network. The only such address for which I can see a use is "broadcast
to a specific non-local subnet of this network".
The use of [0.0.0.x] et al in the "Information Request" ICMP suffers
from this decoding problem, and several others, and is one reason
why a group of us proposed the "Reverse Address Resolution Protocol"
(RFC903), to obviate this ICMP.