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C00002 00002		  COMPATIBILITY OF A FUTURE ARPANET AND A FUTURE DIALNET
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	  COMPATIBILITY OF A FUTURE ARPANET AND A FUTURE DIALNET

	Here are some comments relevant to the future of the ARPAnet in
reply to the message from Elizabeth Feinler of SRI (FEINLER@OFFICE-1).

	We at SU-AI have been considering the possibility of using the
dial-up telephone network to achieve a subset of the capabilities of
ARPAnet.  The problem is that the ARPAnet is too expensive for many of the
people with whom we would like to communicate, and many of them have to
little interest to the Defense Department to justify connection to
ARPAnet.

	The idea is to equip computers with telephone dialers (SU-AI has a
dialer rented from the phone company) and to develop protocols allowing
communication among any computers equipped with telephone connections and
implementing the protocols.  We call this proposal Dialnet.  Like ARPAnet,
Dialnet would provide for person-to-person messages, file transfer, and
terminal access.  As with ARPAnet, the host could limit this access.
While the facilities would be similar, the data rates would be much
smaller, and one dialer would support only one interaction at a time.
Unlike ARPAnet, any installation that implemented the system would be
automatically a "member" and a user would only have to know the telephone
number of the installation, the login name of the recipient and a password
(if required) in order to communicate.

	We are considering two levels of Dialnet protocol capable of
communicating with each other.  The first is for time-sharing systems, and
the second is for single user systems down to the level of the hobbyist
computer.  The small computer would need to be capable of answering the
telephone when unattended for the message service to be useful.

	It has occured to us that the Defense Department also has
installations for which the cost of an ARPAnet connection is not justified
by the size of computer or its expected frequency of network use.  For
these installations, Dialnet would also be appropriate.  Moreover, it
seems that Dialnet and ARPAnet should be compatible, and this
compatibility is readily achieved if the need for it is taken into account
in the design of ARPAnet.

	The requirements for compatibility seem to be the following:

	1. The protocols are divided into high level protocols that know
about messages, file transfer, etc. and those that know about
communication, error control, etc.  Communication between the high level
and low level programs it done by protocols that don't assume packet
switching and are compatible with either a packet switching or a dial-up
connection.

	2. The ARPAnet programs which are capable of handling multiple
dialogs are also capable of communicating with Dialnet programs that can
handle only a single dialog.

	There are many issues concerning error control, flexibility in
communication rate, and core protocols that remain to be identified and
resolved.  We think the basic facility should be that a program in one
computer can ask to have a program in another computer waked up and then
exchange messages with it.

	The Stanford AI Lab is currently soliciting NSF support for
implementing Dialnet, but it will probably be done anyway at a slower pace
even if support isn't forthcoming, because there is much aspiration for
ARPAnet like facilities among people who use computers that will never be
part of ARPAnet.

	The Defense Department should co-operate because

	1. It has developed much of the basic technology that will be
used.

	2. It will need Dialnet-like facilities in some form for smaller
DoD computers.

	3. ARPAnet users will need to communicate with non-ARPAnet users.

	4. It can relieve some of the pressure to join ARPAnet on the part
of installations which are either too small or whose DoD connection is too
small to justify it.

	Replies to this communication should be sent to

MCCARTHY@SU-AI

Professor John McCarthy
Artificial Intelligence Laboratory
Stanford University
Stanford, California 94305

(415) 497-4430

This memo is ARPANE[F76,JMC]@SU-AI