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Date: 17 Jun 1983 2014-PDT
From: NIC at SRI-NIC
Subject: DDN Newsletter No. 27
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cc: NIC at SRI-NIC
======================================================================
DDN-NEWS 27 NETWORK INFO CENTER for
17 June 1983 DCA DDN Program Mgmt Office
(415) 859-3695 (NIC@SRI-NIC)
DEFENSE DATA NETWORK NEWSLETTER
(Maximum Distribution Requested. The DDN Newsletter is published by
the Network Information Center under DCA contract. For on-line
subscription, contact NIC@SRI-NIC. Back issues obtainable by FTP from
the directory <DDN-NEWS> at SRI-NIC [10.0.0.73].)
======================================================================
Section I. OFFICIAL
Topic: - More Details on the MILNET/ARPANET Split
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FURTHER DETAILS ON THE ARPANET/MILNET SPLIT
Introduction
As previously discussed in DDN Newsletter 26, the existing ARPANET
will soon be split into two separate networks - the experimental
ARPANET and the operational MILNET. Hosts on the two networks will
intercommunicate via mail bridges, using the internet gateway
mechanisms to pass mail traffic between hosts on the two networks.
The mail bridges will, on a controlled basis, provide full internet
gateway services for MILNET hosts that request it.
The Logical Split
Because it takes a large amount of time and effort to physically split
a network in a coherent manner, the ARPANET will initially, on 4
October 1983, be logically partitioned by the use of existing
mechanisms in the IMPs to enforce segregation of hosts and TACs into
separate communities of interest. Each community of interest (COI)
becomes a virtual network, i.e., hosts (including TACS) in the same
community can fully interoperate as is currently the case, while hosts
in different communities cannot directly intercommunicate. This, in
effect, transforms the ARPANET into an Internet in which the MILNET
will assume a new class A network number, network 26, while the
ARPANET remains network 10. (Details of the host renumbering
procedures will be covered in a later newsletter from the Network
Information Center (NIC).)
Intercommunication between the MILNET and ARPANET is via mail bridges
which use standard internet protocols and mechanisms to pass data
between hosts in the two networks. This is why the conversion from
NCP to TCP/IP is so important; any host with a fully working TCP/IP
implementation (including ICMP, the host-gateway protocol), should see
no loss in service because of the split. However, hosts using
incomplete TCP/IP implementations (those that do not include ICMP as a
part of IP, or have no provision for using gateways) will be
restricted to communicating with other TCP/IP hosts in the same
network. In particular, this means that they will not be able to send
(or receive) mail traffic through the bridges to hosts in the other
network.
THERE CAN BE NO EXEMPTIONS TO THE SPLIT!!
Unlike the NCP-to-TCP conversion which is still underway for a few
hosts, once the split occurs, there is nothing that can be done to
allow a host with an incomplete TCP/IP to fully intercommunicate with
the other network other than helping them to convert to a fully
working TCP/IP as soon as possible.
Future DDN Newsletters will discuss in greater detail how the split
affects the users and host software maintainers, and how the split
will be tested before it is finally implemented in October.
The Physical Split
Concurrent with the logical split the network is being physically
split as well. Many new trunks are being added to support each
network, and a number of trunks will eventually be removed once
replacement trunks have been installed. The first quarter of CY 1984
has been established as the goal for completion of the physical split,
but this is dependent upon delivery of new circuits from the TELCOs,
some of which have very long lead times (over a year in some cases).
To complete the physical split, hosts and terminals which are homed on
the wrong IMP or TAC must be rehomed. In some cases, a new IMP on the
proper network will be used; in other cases, a host may need to use
HDH (the HDLC-based replacement for VDH) in order to gain access to
its network via a remote IMP. In either case, the host must change
its network address, and the TAC users of these hosts must be made
aware of the change. Both host and terminal rehoming will be kept to
the absolute minimum possible.
Sources of Additional Information
To obtain additional copies of this or previous newsletters,
- Invoke FTP at your local host
- Connect to SRI-NIC (the NIC host, 10.0.0.73)
- Login as 'anonymous', password = 'guest'
- Do a 'get' on files with pathnames
<DDN-NEWS>DDN-NEWS-27.TXT
<DDN-NEWS>DDN-MGT-BULLETIN-3.TXT
or
<DDN-NEWS>DDN-NEWS-n.TXT
<DDN-NEWS>DDN-MGT-BULLETIN-n.TXT
where 'n' = the number of the newsletter or bulletin desired
NOTE: Only those newsletters since issue 20 pertain to the network
after the cutover to the TCP/IP protocols, or to the new Defense Data
Network and the MILNET/ARPANET split. Most readers will no longer
need the information contained in issues 1-19.
A list outlining which IMPs and hosts will be on MILNET and which will
be on ARPANET may be FTPed as outlined above using the pathname
<NETINFO>MILNET-ARPANET.LIST
A list of network liaison for each host may be FTPed with pathname
<NETINFO>LIAISON.TXT
The Network Information Center (NIC) at SRI International will be the
primary repository for information concerning MILNET/ARPANET and the
upcoming split. For further information contact
NIC@SRI-NIC or (415) 859-3695
Network Information Center
SRI International
Room EJ232
333 Ravenswood Avenue
Menlo Park, CA 94025
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