[TUHS] BerkNet

Clem Cole clemc at ccc.com
Thu Nov 27 06:16:10 AEST 2014


On Wed, Nov 26, 2014 at 1:49 PM, Noel Chiappa <jnc at mercury.lcs.mit.edu>

>     > From: Clem Cole
> A few comments on aspects I know something of:
>     > BTW: the Arpanet was not much better at the time
> The people at BBN might disagree with you... :-)

​Fair enough...

> But seriously, throughout its life, the ARPANET had 'load-dependent
> routing',
> i.e. paths were adjusted not just in response to links going up or down,
> but
> depending on load (so that traffic would avoid loaded links).
> The first attempt at this (basically a Destination-Vector algorithm, i.e.
> like
> RIP but with non-static per-hop costs) didn't work too well, for reasons I
> won't get into unless anyone cares. The replacement, the first Link-State
> routing algorithm, worked much, much, better; but it still had minor issues
> damping fixed most of those too).
​You're right of course.  I was referring more to the fact that changes
tended to be an issue​.

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.   Dave once quipped:  "Why does a change at CMU have to
affect MIT?"  I've forgotten what we did at CMU at the time, but I remember
the MIT folk were not happy about it.

>     > DH11's which were a full "system unit"
> Actually, two; they were double (9-slot, I guess?) backplanes.

>     > The MIT guys did ARP for ChaosNet which quickly migrated down the
> street
>     > to BBN for the 4.1 IP stack.
> Actually, ARP was jointly designed by David Plummer and I for use on both
> TCP/IP and CHAOS (which is why it has that whole multi-protocol thing
> going);
> we added the multi-hardware thing because, well, we'd gone half-way to
> making
> it totally general by adding multi-protocol support, so why stop there?
Thanks, ​I never knew that.  Makes sense.

> As soon as it was done it was used on a variety of IP-speaking MIT machines
> that were connected to a 10MBit Ethernet; I don't recall them all, but one
> kind was the MIT C Gateway multi-protocol routers.
​Thought, didn't you guys have the 3Mbit stuff like we did at CMU and UCB
first?  ​

>     > Hey it worked just fine at the time.
> For some definition of 'work'! (Memories of wrapping protocol A inside
> protocol B, because some intervening router/link didn't support protocol A,
> only B...)

​Hey when we did it, we were trying to a UNIX machine to talk to CDC Cyber
and an VMS/VAX.   No routers.  We were happy to just have those systems
communicating ;-)

I was not smart enough to see something like ARP - which later seemed like
such a D'oh moment.

Then again -- at the time 48 bits of Ethernet was supposed to me "enough"
and you were not going to need anything else.  Funny how it all worked out.​
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