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Received: FROM SRI-NIC BY USC-ISIF.ARPA WITH TCP ; 14 Jul 83 18:55:48 PDT
Date: 14 Jul 1983 1750-PDT
From: NIC at SRI-NIC
Subject: DDN Newsletter No. 28
To: DDN-NEWS-LIST4: ;
cc: nic at SRI-NIC
=======================================================================
DDN-NEWS 28 NETWORK INFO CENTER for
14 July 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 ON THE MILNET/ARPANET SPLIT
Section II. UNOFFICIAL
Topic: - QUESTION AND ANSWER ABOUT ICMP
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SECTION I
FURTHER DETAILS ON THE MILNET/ARPANET SPLIT
Introduction
This newsletter continues the discussion of the upcoming
ARPANET/MILNET split started in DDN Newsletter 26 and continued in DDN
Newsletter 27. If you have not yet read these, you are encouraged to
do so. Most hosts keep a publicly accessible local copy, and they can
also be found at SRI-NIC [10.0.0.73] in the file
<DDN-NEWS>DDN-NEWS-X.TXT, where "x" is the newsletter number. SRI-NIC
allows FTP login with the username "anonymous" and password "guest".
Testing the Logical Split
The logical split of the existing ARPANET into the Experimental
ARPANET and the MILNET is a major change which requires substantual
testing to insure it will be accomplished as an orderly process.
ALL HOSTS AND USERS will be impacted. The ARPANET will change from one
network into two, and communications with hosts on the other net will
require a knowledge of internet procedures. MILNET hosts will use a
new network number (Network 26). (Details of procuring updated host
tables from the Network Information Center will be covered in a forth-
coming newsletter.)
The MILNET and the ARPANET will remain connected via five mail bridges
(internet gateways augmented with a load-splitting mechanism and an
access control filter). The load-splitting mechanism works as follows.
Each bridge will contain a table assigning the "default" bridge for
each host to use in sending traffic to the other network. If a host
sends a message via the wrong bridge and its default bridge is
operational, the host will receive an ICMP redirect message telling it
which alternate gateway (i.e., default bridge) to use. This mechanism
allows the five gateways to balance the internet traffic. After the
initial default assignment, if one of the bridges is found to be
carrying a disproportionate share of the load, then the host
assignment table will be modified. No changes to host software are
required. As long as a host supports ICMP, the host-to-gateway
protocol, it can make full use of the bridges without knowing its
default bridge assignment in advance.
A schedule has been developed for testing prior to the actual split.
The goals of this testing are to:
o Verify the mail bridge load-splitting mechanism and
access control filter.
o Test host TCP/IP and ICMP implementations.
o Test the entire system networkwide.
Initial testing will use the testbed environment already available at
BBN. BBN has a local ARPANET-clone network, the BBNNET (Network 8),
which is connected to the ARPANET via a gateway. During daytime hours
the BBNNET passes about 50% as much traffic as does the ARPANET, with
the existing gateway passing about 1,000,000 packets during an average
day, with about 80,000 packets per hour passing through it during peak
hours. This represents a significantly heavier load than will pass
through any of the five mail bridges, therefore the BBNNET will
provide a realistic test environment.
The testing schedule is:
15 June: Two additional gateways between the ARPANET and the BBNNET
are installed.
30 June: The gateway load-splitting mechanism is operational.
15 June to 15 August: Gateway load-splitting and routing between
the ARPANET and the BBNNET are verified.
To aid users in verifying their capabilities to communicate with the
MILNET, the first MILNET host to receive net number 26 will be a
public news host implemented on a C/70, which will allow anonymous
logins and will contain information of general interest to the
ARPANET/MILNET community.
In addition, to assist TAC users, a TACNEWS service will be provided.
By typing "@n" to the TAC, a TAC user will automatically be connected
to the public news host wherever it may exist without having to know
its actual internet address.
Following are some of the major milestones of the Split.
1 July - 1 September: The mail bridges between ARPANET and MILNET
are installed.
15 July: The C70 public news host is installed as the first host in
the MILNET COI. Also, a second MILNET interface will be
added to SRI-NIC. Host managers and technical personnel
should now try to connect to the C/70 news host via the
mail bridges in order to test their ICMP implementations.
28 July - 2 August: Network technical liaison meetings in:
Los Angeles and San Francisco, Cambridge and Washington DC
1 September - 1 October: The NIC maintains the old (ARPANET-only)
and the new (ARPANET/MILNET) host tables in parallel.
During this period MILNET hosts may voluntarily change
to Network No. 26 provided their changeover is coordinated
with the NIC to permit timely update of the official host
tables. Two full day tests will occur, during which the
network will enforce the split, and hosts must use the new
host tables.
4 October: The logical split occurs. Network IMPs will enforce the
proper COI for each host, and network addressing will be
updated to reflect the split.
1 Febuary 1984: Access control filters are implemented in the mail
bridges. Although this capability has existed for some
time, its implementation is deferred to reduce the problems
associated with the logical split on 4 October.
____________________________________________________________________
Section II.
QUESTION:
From: Brian McCune <mccune@aids-unix>
To: nic@nic
Subject: ICMP
Your latest newsletter seemed to imply that without ICMP running
in our machine (AIDS-UNIX), we couldn't send mail to a host on
MILNET (e.g., RADC-TOPS20). Is this so, or couldn't we
send a message to another ARPANET host that knows how to
relay the message on in the right format? (This other host might not
be an actual gateway, just an intermediate translator.)
Brian McCune
-------
ANSWER:
From: Andrew Malis <malis@bbns>
Subject: Re: ICMP
To: mccune@aids-unix
Cc: nic@sri-nic, malis@bbns
Brian,
It is true that you could send mail through such a forwarding
host, but using such a scheme has many problems, including:
- you couldn't receive any return mail without including in all
of your mail a return path back through the forwarding host.
- You would need the official permission from the administators
of your forwarding host before using it in this manner.
- You would be unable to participate in any TELNET or FTP
transactions with hosts on the other net (or on ANY other
network besides your own). This is going to become
increasingly important as many current ARPANET hosts are being
moved to local networks at their sites, and then communicating
with the ARPANET via gateways. Here at BBN, for instance, we
have about 30 hosts on various local networks that access the
ARPANET via gateways - the host that I am typing on at this
moment falls into this category. We are able to save many
thousands of dollars a month that we would otherwise have to
pay to provide each of these hosts with a direct ARPANET host
port. I understand the ISI has even more local hosts behind
gateways.
- In the future, DCA may "cut off" hosts that do not fully
support TCP/IP, including ICMP, in the same manner that
NCP-only hosts have been removed from the net. Any
implementation of IP that does not include ICMP is incomplete
(read the IP spec if you don't believe me).
In the end, you will be saving yourself much long-term grief by
bringing up ICMP. You are a UNIX site; there are at least 10
different UNIX implementations of IP that include ICMP. I'm sure
that you could do a lot of copying of existing code, if you
couldn't just install one of these outright.
Regards,
Andy Malis
For the Network Operations Center, BBN
_________________________________________________________________
The next newsletter in this series will describe how network users
and host software maintainers may prepare for the split.
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