Implementation of the Host - Host Software Procedures in GORDO
RFC 11

Document Type RFC - Unknown (August 1969; No errata)
Obsoleted by RFC 33
Last updated 2014-05-06
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Network Working Group                                         G. Deloche
Request for Comments: 11                                            UCLA
                                                             August 1969

                   Implementation of the Host - Host
                      Software Procedures in GORDO

TABLE OF CONTENTS

   Chapter                                                        Page
   -------                                                        ----
   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . .   1
   2.  HOST - HOST Procedures . . . . . . . . . . . . . . . . . .   2
       2.1  Generalities  . . . . . . . . . . . . . . . . . . . .   2
       2.2  Connections and Links . . . . . . . . . . . . . . . .   2
            2.2.1  Definitions  . . . . . . . . . . . . . . . . .   2
            2.2.2  Connection types . . . . . . . . . . . . . . .   3
       2.3  Message Structure . . . . . . . . . . . . . . . . . .   5
       2.4  User Transactions . . . . . . . . . . . . . . . . . .   6
            2.4.1  List of transactions   . . . . . . . . . . . .   7
            2.4.2  HOST-HOST protocol and control messages  . . .   8
   3.  Implementation in GORDO  . . . . . . . . . . . . . . . . .  11
       3.1  Introduction to GORDO . . . . . . . . . . . . . . . .  11
            3.1.1  GORDO file system  . . . . . . . . . . . . . .  11
            3.1.2  GORDO process  . . . . . . . . . . . . . . . .  12
       3.2  Software Organization Overview  . . . . . . . . . . .  12
       3.3  Software Description  . . . . . . . . . . . . . . . .  13
            3.3.1  Data structures  . . . . . . . . . . . . . . .  13
                   3.3.1.1  Allocation tables . . . . . . . . . .  13
                   3.3.1.2  Buffer pages  . . . . . . . . . . . .  16
            3.3.2  Programs . . . . . . . . . . . . . . . . . . .  18
                   3.3.2.1  Handler . . . . . . . . . . . . . . .  18
                   3.3.2.2  Network . . . . . . . . . . . . . . .  19
       3.4  Software Procedures . . . . . . . . . . . . . . . . .  20
            3.4.1  Description of some typical sequences  . . . .  20

   Appendix A:  Flowcharts  . . . . . . . . . . . . . . . . . . .  23

   [[RFC Editor Note: [s] represents subscript s]]

1.  INTRODUCTION

   This technical note concentrates upon (1) the HOST-HOST procedures
   and (2) the implementation of the corresponding programs in GORDO
   (Operating System of the UCLA HOST).

Deloche                                                         [Page 1]
RFC 11          Host - Host Software Procedures in GORDO     August 1969

   The first section is closely related to the BBN reports No. 1822 and
   1763[1] and specifies the HOST functions for exchanging messages.  It
   mostly deals with links and connections, message structure,
   transactions, and control messages.

   The second section is software oriented; it explains how the HOST
   functions are implemented and integrated into GORDO.  It is involved
   with data structures, programs, buffers, interrupt processing, etc.

   [1]  Parts of this section are taken from or referred to those
   reports.

2.  HOST-HOST PROCEDURES

2.1  Generalities

   The basic idea is that several users, at a given HOST, should
   simultaneously be able to utilize the network by time-sharing its
   physical facilities.

   This implies that within each HOST operating system, there must exist
   a special program that multiplexes outgoing messages from the users
   into the network and distributes incoming messages to the appropriate
   users.  We will call this special program the Network program.

2.2  Links and Connections  (See figure 1)

   2.2.1  Definitions

   It is convenient to consider the Network as a black box - a system
   whose behavior is known but whose mechanisms are not - for
   communicating messages between remote users rather than between pairs
   of HOST computers.

      (a)  Logical connections

         We define a logical connection as being a communication path
         linking two users at remote HOST[s].

         With that concept, a user (user program) in a HOST computer can
         (1) establish several logical connections to any remote HOST
         users, and (2) send or receive messages over those connections.

         Connections appear to users as full duplex.

         One of the purposes of the Network program is to serve the
         users in establishing, identifying, and maintaining these
         connections.

Deloche                                                         [Page 2]
RFC 11          Host - Host Software Procedures in GORDO     August 1969

      (b)  Logical links

         Each logical connection is made of a pair of directional links:
         one for transmitting, the other for receiving.

         Those links, called logical links, are established by the
         Network programs and used by them.

         Note here that users are only interested in connections and are
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