DARPA Internet gateway
RFC 823
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RFC - Historic
(September 1982; No errata)
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2013-03-02
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Request for Comments: 823
Obsoletes IEN-30 and IEN-109
THE DARPA INTERNET GATEWAY
RFC 823
Robert Hinden
Alan Sheltzer
Bolt Beranek and Newman Inc.
10 Moulton St.
Cambridge, Massachusetts 02238
September 1982
Prepared for
Defense Advanced Research Projects Agency
Information Processing Techniques Office
1400 Wilson Boulevard
Arlington, Virginia 22209
This RFC is a status report on the Internet Gateway developed by BBN. It
describes the Internet Gateway as of September 1982. This memo presents
detailed descriptions of message formats and gateway procedures, however
this is not an implementation specification, and such details are
subject to change.
DARPA Internet Gateway September 1982
RFC 823
Table of Contents
1 INTRODUCTION.......................................... 1
2 BACKGROUND............................................ 2
3 FORWARDING INTERNET DATAGRAMS......................... 5
3.1 Input............................................... 5
3.2 IP Header Checks.................................... 6
3.3 Routing............................................. 7
3.4 Redirects........................................... 9
3.5 Fragmentation....................................... 9
3.6 Header Rebuild..................................... 10
3.7 Output............................................. 10
4 PROTOCOLS SUPPORTED BY THE GATEWAY................... 12
4.1 Cross-Net Debugging Protocol....................... 12
4.2 Host Monitoring Protocol........................... 12
4.3 ICMP............................................... 14
4.4 Gateway-to-Gateway Protocol........................ 14
4.4.1 Determining Connectivity to Networks............. 14
4.4.2 Determining Connectivity to Neighbors............ 16
4.4.3 Exchanging Routing Information................... 17
4.4.4 Computing Routes................................. 19
4.4.5 Non-Routing Gateways............................. 22
4.4.6 Adding New Neighbors and Networks................ 23
4.5 Exterior Gateway Protocol.......................... 24
5 GATEWAY SOFTWARE..................................... 26
5.1 Software Structure................................. 26
5.1.1 Device Drivers................................... 27
5.1.2 Network Software................................. 27
5.1.3 Shared Gateway Software.......................... 29
5.2 Gateway Processes.................................. 29
5.2.1 Network Processes................................ 29
5.2.2 GGP Process...................................... 30
5.2.3 HMP Process...................................... 31
APPENDIX A. GGP Message Formats.......................... 32
APPENDIX B. Information Maintained by Gateways........... 39
APPENDIX C. GGP Events and Responses..................... 41
REFERENCES............................................... 43
-i-
DARPA Internet Gateway September 1982
RFC 823
1 INTRODUCTION
This document explains the design of the Internet gateway
used in the Defense Advanced Research Project Agency (DARPA)
Internet program. The gateway design was originally documented
in IEN-30, "Gateway Routing: An Implementation Specification"
[2], and was later updated in IEN-109, "How to Build a Gateway"
[3]. This document reflects changes made both in the internet
protocols and in the gateway design since these documents were
released. It supersedes both IEN-30 and IEN-109.
The Internet gateway described in this document is based on
the work of many people; in particular, special credit is given
to V. Strazisar, M. Brescia, E. Rosen, and J. Haverty.
The gateway's primary purpose is to route internet datagrams
to their destination networks. These datagrams are generated and
processed as described in RFC 791, "Internet Protocol - DARPA
Internet Program Protocol Specification" [1]. This document
describes how the gateway forwards datagrams, the routing
algorithm and protocol used to route them, and the software
structure of the current gateway. The current gateway
implementation is written in macro-11 assembly language and runs
in the DEC PDP-11 or LSI-11 16-bit processor.
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