24-Aug-83 14:18:26-PDT,9615;000000000001 Return-Path: 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 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 ---------------------------------------------------------------------- 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-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 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 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. -------