ARPANET 1822L Host Access Protocol
RFC 851

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Request for Comments: 851
     Obsoletes RFC: 802

                  The ARPANET 1822L Host Access Protocol

                                  RFC 851

                              Andrew G. Malis
                       ARPANET Mail: malis@bbn-unix

                       Bolt Beranek and Newman Inc.
                              50 Moulton St.
                           Cambridge, MA  02238

                                April 1983

     This RFC specifies the ARPANET 1822L Host Access Protocol,  which
     is  a successor to the existing 1822 Host Access Protocol.  1822L
     allows ARPANET hosts to use  logical  names  as  well  as  1822's
     physical  port  locations to address each other.  The RFC is also
     being  presented  as  a  solicitation  of  comments   on   1822L,
     especially   from   host   network   software   implementers  and
     maintainers.




     1822L Host Access Protocol                             April 1983
     RFC 851

                             Table of Contents

     1   INTRODUCTION.......................................... 1
     2   THE ARPANET 1822L HOST ACCESS PROTOCOL................ 4
     2.1   Addresses and Names................................. 6
     2.2   Name Translations................................... 8
     2.2.1   Authorization and Effectiveness................... 8
     2.2.2   Translation Policies............................. 11
     2.2.3   Reporting Destination Host Downs................. 13
     2.2.4   1822L and 1822 Interoperability.................. 16
     2.3   Uncontrolled Packets............................... 18
     2.4   Establishing Host-IMP Communications............... 20
     2.5   Counting RFMS When Using 1822L..................... 22
     2.6   1822L Name Server.................................. 24
     3   1822L LEADER FORMATS................................. 27
     3.1   Host-to-IMP 1822L Leader Format.................... 28
     3.2   IMP-to-Host 1822L Leader Format.................... 35
     4   REFERENCES........................................... 43

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     1822L Host Access Protocol                             April 1983
     RFC 851

                                  FIGURES

     1822 Address Format....................................... 6
     1822L Name Format......................................... 7
     1822L Address Format...................................... 7
     Communications between different host types.............. 17
     Host-to-IMP 1822L Leader Format.......................... 28
     NDM Message Format....................................... 31
     IMP-to-Host 1822L Leader Format.......................... 35
     Name Server Reply Format................................. 39

                                  - ii -




     1822L Host Access Protocol                             April 1983
     RFC 851

     1  INTRODUCTION

     This RFC specifies the ARPANET 1822L Host Access Protocol,  which

     will allow hosts to use logical addressing (i.e., host names that

     are independent of their physical location  on  the  ARPANET)  to

     communicate  with  each  other.  This new host access protocol is

     known as the ARPANET 1822L (for Logical)  Host  Access  Protocol,

     and  is  a  successor  to  the  current  ARPANET 1822 Host Access

     Protocol, which is described in  sections  3.3  and  3.4  of  BBN

     Report  1822  [1].   Although  the  1822L protocol uses different

     Host-IMP leaders than the 1822 protocol, the IMPs  will  continue

     to support the 1822 protocol, and hosts using either protocol can

     readily communicate with each other (the  IMPs  will  handle  the

     translation automatically).

     There is one major restriction to the  new  1822L  protocol:   it

     will be implemented in C/30 IMPs only, and will therefore only be

     usable by hosts connected to C/30 IMPs, as Honeywell and Pluribus

     IMPs  do  not have sufficient memory to hold the new programs and

     tables.  This restriction  also  means  that  logical  addressing

     cannot  be used to identify a host on a non-C/30 IMP.  While this

     is not a problem on the ARPANET, which only has  C/30  IMPs,  the

     restriction  will  apply  if  logical  addressing  is used on any

     network that mixes C/30 and non-C/30 IMPs.

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     1822L Host Access Protocol                             April 1983
     RFC 851

     The RFC's terminology is consistent  with  that  used  in  Report

     1822, and any new terms will be defined when they are first used.

     Familiarity  with  Report  1822  (section  3  in  particular)  is

     assumed.   As could be expected, the RFC makes many references to

     Report 1822.  As a result, it uses, as a convenient abbreviation,

     "see 1822(x)" instead of "please refer to Report 1822, section x,