Path: utzoo!mnetor!uunet!husc6!tut.cis.ohio-state.edu!uwmcsd1!ig!agate!ucbvax!A.ISI.EDU!CERF
From: CERF@A.ISI.EDU
Newsgroups: comp.protocols.tcp-ip
Subject: Re:      Conversion to ISO - Number of NCP Hosts
Message-ID: <[A.ISI.EDU]23-Mar-88.07:39:45.CERF>
Date: 23 Mar 88 12:39:00 GMT
References: <MAB@CORNELLC.CCS.CORNELL.EDU>
Sender: usenet@ucbvax.BERKELEY.EDU
Organization: The Internet
Lines: 19

I can't give firm numbers but there were on the order of 20-25 different
operating system implementations of NCP and somewhat fewer for TCP at the
time the conversion was done - some hosts never made the change and were
simply retired (good excuse...).

The NCP/TCP and TCP/ISO analogies are not exact. For one thing, NCPwas
never a commercial product. TCP is. For another, only ARPANET hosts did NCP because
that was NOT an internet protocol, so a single administration could insist on
the conversion and was even able to turn off NCP capability within the 
subnet as a forcing function. This is not possible for TCP/ISO except perhaps
at the gateways (and maybe for the subnets if packet types for ISO IP and DoD IP
are distinct, as I suppose they are likely to be).

There must be literally tens of thousands of TCP/IP hosts by now compared to
at most a couple of hundred NCP hosts in Jan 83. 

Somehow I think the analogy is not very apt.

Vint