"First Internet message" and ...

[Noel Chiappa]

    > From: Brent Hilpert

    > Roughly, IP took care of a common addressing scheme and a common
    > packet presentation, TCP took care of end-to-end flow control.

Yes on IP, but TCP's main function is reliability - much of the mechanism of
TCP (sequence numbers, acknowledgements, timeouts and retransmissions, and
checksums) is all there for that.

    > As so much nowadays is about throwing ethernet frames around on
    > different types of links and network formats (not what ethernet was
    > originally designed for), some of the earlier diversity that made
    > 'interneting' necessary may no longer be there.

There is one aspect of internetworking (the original term - I probably should
have described PUP/CHAOS/XNS as 'internetworking protocols') which _is_
crucial, though - the multi-layer address space. We'd need that even if
_everything_ in the world used Ethernet frame headers.

If one tried to do path selection (usually called 'routing', but I don't use
that term as it can be confused with packet forwarding) using only 48-bit
interface identifiers, it just wouldn't scale to the size network we have
now. The ability to aggregate groups of hosts, so that a distant routing
table contains only a single entry for all of them, is crucial for scaling
purposes. Without that, routing tables would have to have billions
(literally; add up the numbers of different kinds of end-user devices -
laptops, etc) of entries.

(Heck, even XNS had network numbers, precisely for this reason. Although one
could build a system which has aggregatable addresses, used for path
selection, but hid them from the hosts, and used an 'invisible' mapping
system to translate from them to the aggregatable 'true' addresses. The LISP
networking system does this, as does the 800 and inter-provider portability
capability in the 'phone system - although in both cases the input and output
to the mapping system have identical syntax.)

Originally, IP had only two layers in the addressing - network # and 'rest',
then we added a third layer with 'subnets', and finally went to a potentially
multi-layer system with CIDR. (I'm not sure what ISPs are actually doing with
them now - I'm now out of touch with that world.)

    > It might be arguable whether we have an 'internet' any longer or just a
    > great big 'network' with different types of links.

I found Jack Haverty's message to the internet-history list about the
changing nature of 'the Internet', but alas the list archives are broken at
the moment, so no URL.

	Noel