major change to 1822 (IMP) software


Mark Crispin (MRC%PANDA@SUMEX-AIM.ARPA)
Tue 18 Mar 86 19:09:33-PST


     All sites should be aware of the changes to the ARPANET, Milnet, DRENET,
and other BBN IMP-based networks using the 1822 protocol that are announced
in RFC 979. This report, "PSN END-TO-END FUNCTIONAL SPECIFICATION" is a MUST
read by the site personnel responsible for the network software for every
host on these networks.

     This report succumbs to the popular tradition of changing terminology
just as we've gotten accustomed to the old terminology. Basically, an IMP
is now called a PSN (Packet Switch Node) and the protocol/software that runs
on the IMP is now called EE (End-to-End protocol and module).

     The most important changes are as follows:
(1) VDH hosts are no longer supported. If you're still a VDH, you had better
    replace your VDH with a pair of ECU boxes, etc. I think VDH's are extinct
    animals these days though.
(2) Uncontrolled (subtype 3) regular messages will no longer be supported.
    This is being replaced by a new Datagram service.

     All the other changes are upwards compatible and in general are wins.

     I am concerned about change (2) above. TOPS-20 uses uncontrolled
regular messages and other operating systems may do so as well. For what
TOPS-20 does with uncontrolled regular messages it is alright to substitute
the datagram service for uncontrolled regular messages, but since there will
be no period of overlap between the two I'm concerned about flag days. I
would like to lobby for the new datagram service to be accessed by using a
subtype 3 regular message.

     Incidentally, I am wondering whether or not it would be a good idea to
always use datagrams for TCP/IP packets. Perhaps this would increase
performance on the network if 1822 was spared the overhead of reliable
delivery?
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