ARPANET AHIP-E Host Access Protocol (enhanced AHIP)
RFC 1005

Document Type RFC - Unknown (May 1987; No errata)
Last updated 2013-03-02
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Network Working Group                            Atul Khanna, Andy Malis
Request for Comments: 1005                      BBN Communications Corp.
                                                                May 1987

        The ARPANET AHIP-E Host Access Protocol (Enhanced AHIP)

1. Status of this Memo

   This RFC is a proposed specification for the encoding of Class A
   IP addresses for use on ARPANET-style networks such as the Milnet
   and Arpanet, and for enhancements to the ARPANET AHIP Host Access
   Protocol (AHIP; formerly known as 1822).  These enhancements
   increase the size of the PSN field, allow ARPANET hosts to use
   logical names to address each other, allow for the communication
   of type-of-service information from the host to the PSN and
   enable the PSN to provide congestion feedback to the host on a
   connection basis. Distribution of this memo is unlimited.
   Comments on this RFC should be sent to the netmail address
   "ahipe@bbn.com".

Khanna & Malis                                                  [Page 1]
RFC 1005                                                        May 1987

                             Table of Contents

        1   INTRODUCTION.......................................... 4

        2   IP ISSUES............................................. 6
        2.1   Current Interpretation of Class A IP Address
              Fields
               ................................................... 6
        2.2   Requirements and Constraints Affecting New
              Class A Mapping
               ................................................... 7
        2.3   New Interpretation of IP Address Fields............. 8
        2.4   Discussion of the New Mapping.......................10
        2.5   Interoperability between Current AHIP and
              AHIP-E
               ...................................................11

        3   LOGICAL ADDRESSING................................... 13
        3.1   Addresses and Names................................ 13
        3.2   Name Translations.................................. 14
        3.2.1   Authorization and Effectiveness.................. 15
        3.2.2   Translation Policies............................. 16
        3.2.3   Reporting Destination Host Downs................. 17
        3.3   Establishing Host-PSN Communications............... 18
        3.4   Name Server........................................ 19

        4   OTHER CHANGES........................................ 20
        4.1   Type-of-Service Specification...................... 20
        4.2   Subnet Congestion Feedback......................... 21
        4.3   Precedence Level Information....................... 21

        5   FORMATS FOR NEW AHIP-E MESSAGES...................... 23
        5.1   Host-to-PSN AHIP-E Leader Format................... 23
        5.2   PSN-to-Host AHIP-E Leader Format................... 27

        6   AHIP-E VERSIONS...................................... 33

        7   REFERENCES........................................... 34

Khanna & Malis                                                  [Page 2]
RFC 1005                                                        May 1987

                                  FIGURES

        2.1  IP Class A Mapping................................... 6
        2.2  New Class A IP Address Interpretation................ 8
        2.3  AHIP-E Address and Name.............................. 9
        3.1  Current AHIP Address Format......................... 13
        3.2  AHIP-E Address Format............................... 14
        3.3  Logical Name Format................................. 14
        5.1  Host-to-PSN AHIP-E Leader Format.................... 23
        5.2  NDM Message Format.................................. 25
        5.3  PSN-to-Host AHIP-E Leader Format.................... 27
        5.4  Name Server Reply Format............................ 30

Khanna & Malis                                                  [Page 3]
RFC 1005                                                        May 1987

1  INTRODUCTION

This RFC is a proposed specification for the encoding of Class A
IP addresses for use on ARPANET-style networks such as the Milnet
and Arpanet, and for enhancements to the AHIP Protocol (AHIP is the
preferred term for what has previously been known as the 1822
protocol).  These enhancements and modifications are partially
motivated by a need to overcome the current address limitation
of 256 PSNs per network and by a desire to allow hosts to take
advantage of logical addressing with minimal change to their AHIP
software. This enhanced AHIP protocol will be referred to as
"AHIP-E".  These enhancements will:

    1.   Increase the size of the PSN field to 10 bits.

    2.   Allow hosts to use logical names (i.e., host names that are
         independent of physical location on the network) in addition to
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