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From: malis@BBN.COM (Andy Malis)
Newsgroups: comp.protocols.tcp-ip
Subject: Re: IP and Coloured Book Software in the UK
Message-ID: <9106241935.AA09855@ucbvax.Berkeley.EDU>
Date: 24 Jun 91 16:22:46 GMT
References: <1991Jun21.043649.21000@milton.u.washington.edu>
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Organization: The Internet
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> ... let me assure you that the transition from NCP to TCP was
> done in a great rush, occupying virtually everybody's time 100% in the
> year 1982.  *Nobody* was ready.

To the contrary - we (the enforcers) were! :-)

> On January 1, DCA had the ARPANET IMP software modified so that they
> would not pass NCP traffic.  

I wrote the IMP code to make this happen.  We had a configuration
bit for each host, to allow or disallow NCP on a host-by-host
basis, plus a master switch for each IMP.  To enforce the
cutover, we preset all the configuration bits ahead of time, and
then just flipped the master switches at cutover time.

> There was a hue and cry, and thus for several months afterwards
> a number of sites (both NCP-only and NCP/TCP sites which needed
> to be able to talk to NCP-only sites) had "reclama" to use NCP.

We had a long list of hosts that were granted permission, for one
reason or another, to continue to use NCP.  As I recall, we had a
good number of hosts on the list from day 1, and it grew quite a
bit before it started to shrink.

Eventually, the list grew shorter and shorter, until (probably
eight months or so after the cutover) the last hosts had their
NCP permission turned off.  That particular code is now long gone
from the PSN.  However, upon reflection, it was probably the
first protocol-based filtering ever built into a packet switch.
It used the 1822 "link number" protocol identifier to determine
which messages were carrying NCP.

> It was a major painful ordeal, and one that those who experienced it
> are not eager to repeat.  You can tell who we are -- the old farts who
> smirk knowingly when "ISO transition" gets mentioned.

I'm looking forward to it already.

Andy