6-Sep-82 16:30:41-PDT,2623;000000000001
Mail-from: ARPANET host SRI-NIC rcvd at 6-Sep-82 1630-PDT
Date:  6 Sep 1982 1521-PDT
From: Nic at SRI-NIC
Subject: Network News No. 14 - Please Read - Important Announcement!!
To:   ANEWS-DIST:
cc:   NIC-STAFF:

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ANEWS-14                                                DCA Code B645
6 August 1982                                        (DCACODE252@ISI)
                                                     (202) 692-6175/6

                  DoD NETWORK NEWSLETTER


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      ATTENTION!  - Netwide TCP Experiment - October 1, 1982

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On October 1, from 12:00 to 16:00 EDT, a TCP-only experiment will be 
conducted on the ARPANET.  During this period, the ARPANET IMPs will be 
disabled from sending NCP Host-to-Host traffic, and network traffic 
measurements will be made.

The method that will be used to disable the NCP traffic will be for the 
IMPs to reject any messages submitted by the hosts that use link 0 
(i.e., that have bits 65-72 in the 1822 leader set to zero).  If an IMP 
receives such a message, it will respond to the host with a type 7 
(destination host or IMP dead) subtype 3 (communication with the 
destination host is administratively prohibited) message (see BBN Report
1822, Page 3-30).  This response is consistent with the IMP's present 
behavior, and this is similar to the method that was used when short 
leaders were removed from the network.

During the test, hosts that are running NCP and TCP in parallel with 
shared remote host state tables may encounter some problems unless their
NCP is turned off for the duration.  Several TOPS-20 TCP implementations
fall into this category, and other hosts may as well.  TCP-only hosts 
should encounter no difficulties, and NCP-only hosts will be unable to 
use the network.

It is important to note that this method of disabling NCP traffic will 
be used once the network passes the TCP-only date next year (1 Jan 83), 
so your host software should (if it cannot now) be able to correctly 
recognize and handle type 7, subtype 3 messages from the IMP.

Any technical questions concerning the test may be directed to Andrew 
Malis (Malis@bbn-unix).  Any administrative questions should be directed
to DCA Code B645 (formerly Code 252) (DCACODE252USC-ISI).

Regards,
Jack Snively
DCA Code B645(252)
ARPANET Managment

Telephone: (202) 692-6175/6176 or (AV) 222-6175/6176.

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