[e2e] node addresses vs. interface addresses

[J. Noel Chiappa]

    > From: Roop Mukherjee <bmukherj at shoshin.uwaterloo.ca>

    > Why do IP interfaces have addresses not the nodes themselves? Is there
    > an architectural reason for this? I thought since people here seem to
    > have a better perspective of the history of IP

Actually, in the beginning (especially back in the ARPANet), the distinction
between the two wasn't at all clear. That lack of clarity carried across to
the early TCP/IP work. To the best of my (admittedly now dim due to the
passage of time) memory, the question of whether to name them from separate
namespaces simply never even came up.

The first person I know of to clarify that we needed to think of them
separately was (as usual!) Jerry Saltzer, in his 1982 paper "On the Naming
and Binding of Network Destinations", now available as RFC 1498.

As things stand, it's not completely true that interfaces completely "own"
the addresses - there are many places in the architecture (e.g. the TCP
checksum pseudo-header) where the IP address is used to identify a host
(with consequent problems).

This continuing confusion over whether IP addresses name hosts or interfaces
causes problems in numerous places, e.g. multi-homing, mobility, etc, etc.
Had we to do it all over again, I suspect we'd have a separate namespace for
each of them.

	Noel