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Network Working Group                                         E. HarslemRequest for Comments: 80                                      J. HeafnerNIC: 5608                                                           RAND                                                         1 December 1970PROTOCOLS AND DATA FORMATS   Because of recent discussions of protocols and data formats we issue   this note to highlight our current attitudes and investigations in   those regards.  We first discuss some specific sequences, and then   offer some thoughts on two general implementation approaches that   will handle these and other specifics.  We wish to place emphasis on   the _general solutions_ and not on the specifics.INITIAL CONNECTION PROTOCOLS   We wish to make two points concerning specific Initial Connection   Protocols (IPCs).  Firstly, the IPC described in NEW/RFC #66--its   generality and a restatement of that ICP.  Secondly, a proposal for a   variant ICP using basically the same logic as NWG/RFC #66.I. NWG/RFC #66   The only technical error in this IPC is that as diagrammed both the   Server and User send ALL messages before the connections are   established which is inconsistent with Network Document No. 1.  This   can easily be remedied as will be shown in the restatement below.   In terms of generality, any ICP that is adopted as a standard should   apply to more situations than a process calling a logger.  That is,   some Network service processes that hook directly to a user process,   independent of logger action, could perhaps use a standard ICP.   Thus, as is shown below, the process name field of the server socket   should be a parameter with a value of zero being a special case for   loggers.   Restatement of NWG/RFC #66 (using the same wording where appropriate)      1. To initiate contact, the using process attaches a receive         socket (US) and requests connection to process SERV socket #1         in the serving HOST.  (SERV = 0 for ICP to the logger.)  As a         result the using NCP sends:Harslem, et. al.                                                [Page 1]

RFC 80                 Protocols and Data Formats        1 December 1970            1              4                 3          1     1         +-----+---------------------+---------------+-----+-----+         | RTS |          US         |      SERV     |  1  |  P  |         +-----+---------------------+---------------+-----+-----+         over link 1, where P is the receive link.      2. The serving process (SERV) may decide to refuse to the call, in         which case it closes the connection.  If it accepts the call,         the serving process completes the connection (via an INIT         system call, hence an STR).            1           3          1            4         +-----+----------------+-----+--------------------+         | STR |      SERV      |  1  |         US         |         +-----+----------------+-----+--------------------+      3. When the connection is completed, the user process allocates a         nominal amount of space to the connection, resulting in the NCP         sending:            1     1            4         +-----+-----+--------------------+         | ALL |  P  |       SPACE        |         +-----+-----+--------------------+         where SPACE is the amount.      4. The serving process then selects the socket pair it wishes to         assign this user.  It sends exactly an even 32 bit number over         the connection.  This even 32 bit number (SS) is the receive         socket in the serving HOST.  This socket and the next higher         numbered socket are reserved for the using process.      5. It then closes the connection.  The serving NCP sends (step 4):                    4         +---------------------+         |         SS          |         +---------------------+         on link P, and (step 5):Harslem, et. al.                                                [Page 2]

RFC 80                 Protocols and Data Formats        1 December 1970            1            3         1             4         +-----+----------------+-----+--------------------+         | CLS |       SERV     |  1  |         US         |         +-----+----------------+-----+--------------------+         on the control link (which is echoed by the using NCP).      6. Now that both server and user are aware of the remote socket         pair for the duplex connection, <STR, RTS>s can be exchanged.         _Sever sends User_            1            4                     4         +-----+--------------------+--------------------+         | STR |      SS + 1        |          US        |         +-----+--------------------+--------------------+---+         | RTS |         SS         |        SS + 1      | Q |         +-----+--------------------+--------------------+---+         where Q is the Server's receive link.         _User sends Server_            1             4                    4         +-----+--------------------+--------------------+         | STR |       US + 1       |         SS         |         +-----+--------------------+--------------------+---+         | RTS |          US        |       SS + 1       | R |         +-----+--------------------+--------------------+---+         where R is the User's receive link.         ALLocates may then be sent and transmission begun.II.  A Variation of NWG/RFC #66   This variation reduces Network messages and eliminates duplication of   information transfer.   Steps 3 and 4 above are deleted.  The user process is not notified   directly which of the Server's sockets it will be assigned.  The user   process, however, will listen on sockets US and US + 1 for calls from   SERV after step 5 above.  It can reject any spurious calls.  In   accepting the calls from SERV, the connection is established.   The following sample sequence illustrates this ICP.  (The notation is   as above).Harslem, et. al.                                                [Page 3]

RFC 80                 Protocols and Data Formats        1 December 1970   1. User --> Server         1            4                    3         1     1      +-----+--------------------+----------------+-----+-----+      | RTS |         US         |       SERV     |  1  |  P  |      +-----+--------------------+----------------+-----+-----+   2. Server --> User      If accepted:         1           3          1             4      +-----+----------------+-----+---------------------+      | STR |      SERV      |  1  |         US          |      +-----+----------------+-----+---------------------+      | CLS |      SERV      |  1  |         US          |      +-----+----------------+-----+---------------------+      If rejected:         1           3          1             4      +-----+----------------+-----+---------------------+      | CLS |      SERV      |  1  |         US          |      +-----+----------------+-----+---------------------+   3. If accepted, user listens on US and US + 1.   4. Server --> User         1             4                     4      +-----+--------------------+---------------------+      | STR |       SS + 1       |          US         |      +-----+--------------------+---------------------+---+      | RTS |         SS         |        US + 1       | Q |      +-----+--------------------+---------------------+---+   5. User accepts the calls, hence:      User --> Sender         1              4                     4      +-----+---------------------+--------------------+      | STR |        US + 1       |        SS + 1      |      +-----+---------------------+--------------------+---+      | RTS |        US + 1       |          SS        | R |      +-----+---------------------+--------------------+---+      and the connection is established.Harslem, et. al.                                                [Page 4]

RFC 80                 Protocols and Data Formats        1 December 1970   This reduces the number of network messages by two and only passes   the information regarding the Server's sockets once via RTS and STR.   PRE-SPECIFIED DATA FORMATS   We would like to adopt those suggestions for data formats in NWG/RFC   #42 and #63.  We subscribe to multiple standards as solutions to   particular problem classes.   AN ADAPTABLE MECHANISM      We would like to adapt to Network use, problem programs that were      not planned with the Network in mind, and which, no doubt, will      not easily succumb to Network standards existing at the time of      their inclusion.  This incompatibility problem is just as      fundamental a part of the research underlying the Network as is      different Host hardware.  To require extensive front-ends on each      such program is not a reasonable goal.  We view the Network as an      amalgamation of a) Hosts that provide services; b) parasite Hosts      that interface terminals to the services, and c) a spectrum of      Hosts that behave as both users and providers of services.  To      require that each parasite Host handle different protocols and      data formats for all services that its users need is not a      reasonable goal.  The result is programs and terminals that wish      to communicate but do not speak the same language.      One approach to the protocol and data format problems is to      provide an adaptable mechanism that programs and terminals can use      to easily access Network resources.  ARPA is sponsoring the      Adaptive Communicator Project at Rand which is a research effort      to investigate a teachable front-end process to interface man to      program.  The variety of terminal devices being explored include      voice, tablets, sophisticated graphics terminals, etc.      The Adaptive Communicator looks very encouraging but it will not      be ready for some time.  The Network Project at Rand chose to take      the adaptable approach (_not_ adaptive, i.e., no heuristics, no      self-learning).  Our problem is to get Rand researchers onto the      Network easily, assuming that they have different simultaneous      applications calling for different program protocols and data      configurations.      Protocols and data formats will be described separately to      illustrate what we mean by adaptation.  Protocols are sequences of      "system calls" that correspond to (and result in NCP's issuance      of) NCP commands.  Data formats are the descriptions of regular      message contents and are not meaningful to an NCP.Harslem, et. al.                                                [Page 5]

RFC 80                 Protocols and Data Formats        1 December 1970   The Form Machine (adapting to data formats)      To put the reader in context, the Form Machine is of the class of      finite state machines that recognize a form of _regular_      expressions_ which, in our case, describe data formats.  The      notation, however, is aimed at particular descriptions and      therefore can be more succinct, for our purposes, than the      language of regular expressions.      The Form Machine is an experimental software package that couples      a variety of programs and terminals whose data format requirements      are different.  We envision Form Machines located (to reduce      Network traffic) at various service providing Hosts.      To test the Form Machine idea, we are implementing two IBM OS-      callable subroutines; a compiler that compiles statements which      describe forms of data formats; and an executor that executes a      compiled form on a data stream.      To describe the Form Machine test, it is necessary to mention      another program at Rand--the Network Services Program (NSP), which      is a multi-access program that interfaces the Network Control      Program both to arbitrary programs and to Video Graphics Consoles.      (We view a terminal as just another program with a different      interface, i.e., # characters/line, # lines/page, unique hardware      features, the application to which it is put, etc.)  The Form      Machine subroutines are callable from NSP upon consoles or program      direction.      Operationally, a console user names and specifies the data forms      that he will use.  The forms are compiled and stored for later      use.  At some future time when the user wishes to establish      Network connections and transmit data, he dynamically associates      named forms with each side of a port--a symbolically named Network      full duplex connection.  Data streams incoming or outgoing are      executed according to the compiled form and the transformed data      stream is then passed along to the console/program or to the      Network, respectively.      The details of the syntax of our Form Machine notation are      unimportant to the collective Network community.  However, the      provisions of the notation are of interest.  It will eventually      encompass the description of high performance CRT displays, TTY,      and arbitrary file structures.  To test its viability, a subset of      such features is being implemented.Harslem, et. al.                                                [Page 6]

RFC 80                 Protocols and Data Formats        1 December 1970      The current version is characterized by the following features:         1)    Character code translation (viz., decimal, octal,               hexidecimal, 8 bit ASCII, 7 bit ASCII, EBCDIC, and               binary).         2)    Multiple break strings (many terminals have multiple               termination signals).         3)    Insertion of literals (used primarily for display               information presentation).         4)    Skip or delete arbitrary strings (used to remove record               sequence numbers, etc., that are not to be displayed).         5)    Record sequence number generation.         6)    String-length computation and insertion.         7)    _Arbitrary_ data string length specifications, e.g., "a               hex literal string followed by an _arbitrary_ number of               EBCDIC characters, followed by a break string, .....".         8)    Concatenation of Network messages, i.e., the execution of               compiled forms on incomplete data strings.         9)    Data field transposition.         10)   Both explicit and indefinite multiplicative factors for               both single and multi-line messages.      Features that are not being implemented but will be added, if      successful, include:         1)    Graphics oriented descriptions.         2)    General number translations.         3)    Conditional statements.         4)    A pointer capability.   The Protocol Manager (adapting to NCP command sequences)      The NSP allows terminal users and programs to work at the NCP      protocol level; i.e., LISTEN, INIT, et al.  It also allows them to      transmit and massage information meaningful only to themselves.      This "hands-on" approach is desirable from the systemsHarslem, et. al.                                                [Page 7]

RFC 80                 Protocols and Data Formats        1 December 1970      programmer's, or exploratory point of view.  However, it is      desirable to eliminate the laborious "handshaking" for the      researcher who repeatedly uses a given remote program by allowing      him to define, store, retrieve, and execute "canned" protocol      sequences.      We are currently specifying a Protocol Manager as a module of NSP      that will allow the above operations on NCP command sequences.      Features of the module are:         1) The sequences may contain "break points" to permit the            console user to dynamically inject any contextually needed            information.         2) The parameters of a command may contain tokens whose values            are supplied by the remote party during the protocol dialog.            For example, in Note #66 the socket number provided by the            server is to be used by the user in subsequent RTS, STR            commands.   REQUEST      We would like to hear from anyone concerning the notion of      adaptation to data formats and protocol.  Is this a reasonable      approach?  What should it encompass?      JFH:EFH:hsHarslem, et. al.                                                [Page 8]

RFC 80                 Protocols and Data Formats        1 December 1970   Distribution      Albert Vezza, MIT      Alfred Cocanower, MERIT      Gerry Cole, SDC      Bill English, SRI      Bob Flegel, Utah      James Forgie, LL      Peggy Karp, MITRE      Nico Haberman, Carnegie-Mellon      John Heafner, RAND      Bob Kahn, BB&N      Margie Lannon, Harvard      James Madden, Univ. of Ill.      Thomas O'Sullivan, Raytheon      Larry Roberts, ARPA      Robert Sproull, Stanford      Ron Stoughton, UCSB      Chuck Rose, Case University      Benita Kirstel, UCLA           [This RFC was put into machine readable form for entry]            [into the online RFC archives by Lorrie Shiota, 10/01]Harslem, et. al.                                                [Page 9]