27 Nov
2014
27 Nov
'14
2:38 p.m.
From: jnc(a)mercury.lcs.mit.edu (Noel Chiappa)
The replacement, the first Link-State routing
algorithm, worked much,
much, better; but it still had minor issues
damping fixed most of those too).
Oop, the editor 'ate' a line there (or, rather the editor's operator
spaced
out :-): it should say "it still had minor issues, such as oscillation
between two equal-cost paths, with the traffic 'chasing itself' from path to
path; proper damping fixed most of those too".
I always give Dave Clark credit (what I call
"Clark's Observation") for
the most powerful part of the replacement for the ARPAnet - aka the
idea of a network of network.
Not sure exactly what you're referring to here (the concept of an internet
as a collection of networks seems to have occurred to a number of people,
see the Internet Working Group notes from the early 70s).
Dave once quipped: "Why does a change at CMU have
to affect MIT?"
Subnets (which first appeared at MIT, due to our, ah, fractured
infrastructure) again were an idea which occurred to a number of people all
at the same time; in part because MIT's CHAOSNET already had a collection of
subnets (the term may in fact come from CHAOSNET, I'd have to check) inside
MIT.
I've forgotten what we did at CMU at the time,
but I remember the MIT
folk were not happy about it.
I used to know the answer to that, but I've forgotten what it was! I have this
bit set that CMU did something sui generis, not plain ARP sub-netting, but I
just can't remember the details! (Quick Google search...) Ah, I see, it's
described in RFC-917 - it's ARP sub-netting, but instead of the first-hop
router answering the ARP based on its subnet routing tables, it did something
where ARP requests were flooded across the entire network.
No wonder we disapproved! :-)
Thought, didn't you guys have the 3Mbit stuff
like we did at CMU and
UCB first?
MIT, CMU and Stanford all got the 3Mbit Ethernet at about the same time, as
part of the same university donation scheme. (I don't recall UCB being part
of that - maybe they got it later?)
The donation included a couple of UNIBUS 3Mbit Ethernet cards (a hex card,
IIRC) the first 3MB connections at MIT were i) kludged into one of the MIT-AI
front-end 11's (I forget the details, but I know it just translated CHAOS
protocol packets into EFTP so they could print things on the Dover laser
printer), and ii) a total kludge I whipped up which could forward IP packets
back and forth between the 3M Ethernet, and the other MIT IP-speaking LANs.
(It was written in MACRO-11, and with N interfaces, it used hairy macro
expansions to create separate code for each of all 'N^2' possible forwarding
paths!) Dave Clark did the Alto TCP/IP implementation (which was used to
create a TFTP->EFTP translating spooler for IP access to the Dover).
I can give you the exact data, if you care, because Dave Clark and I had
a competition to see who could be done first, and the judge (Karen Sollins)
declared it a draw, and I still have the certificate! :-)
Noel