==Phrack Inc.==

                     Volume Two, Issue 18, Phile #4 of 11

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   -           PRIMOS:                                                     -
   -                       NETWORK  COMMUNICATIONS                         -
   -                                                                       -
   -                       PRIMENET, RJE, DPTX                             -
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   -                                                                       -
   - Presented by Magic Hasan                                   June 1988  -
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   PRIME's uniform operating system, PRIMOS, supports a wide range of
communications products to suit any distributed processing need.  The PRIMENET
distributed networking facility provides complete local and remote network
communication services for all PRIME systems.  PRIME's Remote Job Entry (RJE)
products enable multi-user PRIME systems to emulate IBM, CDC, Univac,
Honeywell and ICL remote job entry terminals over synchronous communication
lines. PRIME's Distributed Processing Terminal Executive (DPTX) allows users
to construct communication networks with PRIME and IBM-compatible equipment.

                                   PRIMENET
                                   --------

   PRIMENET provides complete local and remote network communication services
for all PRIME systems.  PRIMENET networking software lets a user or process on
one PRIME system communicate with any other PRIME system in the network
without concern for any protocol details.  A user can log in to any computer
in the network from any terminal in the network.  With PRIMENET, networking
software processes running concurrently on different systems can communicate
interactively.  PRIMENET allows transparent access to any system in the
network without burdening the user with extra commands.

   PRIMENET has been designed and implemented so that user interface is simple
and transparent.  Running on a remote system from a local node of the network
or accessing remote files requires no reprogramming of user applications or
extensive user training.  All the intricacies and communication protocols of
the network are handled by the PRIMENET software.  For both the local and
remote networks, PRIMENET will allow users to share documents, files, and
programs and use any disk or printer configured in the network.

   For a local network between physically adjacent systems, PRIME offers the
high-performance microprocessor, the PRIMENET Node Controller (PNC).  The
controller users direct memory access for low overhead and allows loosely
coupled nodes to share resources in an efficient manner.  The PNCs for each
system are connected to each other with a coaxial cable to form a high-speed
ring network, with up to 750 feet (230 meters) between any two systems.

   Any system in the PNC ring can establish virtual circuits with any other
system, making PNC-based networks "fully connected" with a direct path between
each pair of systems.  The ring has sufficient bandwidth (1 MB per second) and
addressing capability to accommodate over 200 systems in a ring structure;
however, PRIMENET currently supports up to sixteen systems on a ring to
operate as a single local network.

   The PRIMENET Node Controller is designed to assure continuity of operation
in the event that one of the systems fails.  One system can be removed from
the network or restored to on-line status without disturbing the operations of
the other system.  An active node is unaware of messages destined for other
nodes in the network, and the CPU is notified only when a message for that
node has been correctly received.

   Synchronous communications over dedicated leased lines or dial-up lines is
provided through the Multiple Data Link Controller (MDLC).  This controller
handles certain protocol formatting and data transfer functions normally
performed by the operating system in other computers.  The controller's
microprogrammed architecture increases throughput by eliminating many tasks
from central processor overhead.

   The communications controller also supports multiple protocols for
packet-switched communications with Public Data Networks such as the United
States' TELENET and TYMNET, the Canadian DATAPAC, Great Britain's
International Packet Switching Service (IPSS), France's TRANSPAC, and the
European Packet Switching Network, EURONET.  Most Public Data Networks require
computers to use the CCITT X.25 protocol to deal with the management of
virtual circuits between a system and others in the network.  The synchronous
communications controller supports this protocol.  PRIME can provide the X.25
protocol for use with the PRIMENET networking software without modification to
the existing hardware configuration.

   PRIMENET software offers three distinct sets of services.  The
Inter-Program Communication Facility (IPCF) lets programs running under the
PRIMOS operating system establish communications paths (Virtual circuits) to
programs in the same or another PRIME system, or in other vendors' systems
supporting the CCITT X.25 standard for packet switching networks.  The
Interactive Terminal Support (ITS) facility permits terminals attached to a
packet switching network, or to another PRIME system, to log-in to a PRIME
system with the same capabilities they would have if they were directly
attached to the system.  The File Access Manager (FAM) allows terminal users
or programs running under the PRIMOS operating system to utilize files
physically stored on other PRIME systems in a network.  Remote file operations
are logically transparent to the application program.  This means no new
applications and commands need  to be learned for network operation.

   The IPCF facility allows programs in a PRIME computer to exchange data with
programs in the same computer, another PRIME computer, or another vendor's
computer, assuming that that vendor supports X.25.  This feature is the most
flexible and powerful one that any network software package can provide.  It
basically allows an applications programmer to split up a program, so that
different pieces of the program execute on different machines a network.  Each
program component can be located close to the resource (terminals, data,
special peripherals, etc.) it must handle, decode the various pieces and
exchange data as needed, using whatever message formats the application
designer deems appropriate.  The programmer sees PRIMENET's IPCF as a series
of pipes through which data can flow.  The mechanics of how the data flows are
invisible; it just "happens" when the appropriate services are requested.  If
the two programs happen to end up on the same machine, the IPCF mechanism
still works.  The IPCF offers the following advantages:

        1)  The User does not need to understand the detailed
            mechanisms of communications software in order to
            communicate.
        2)  Calls are device-independent.  The same program will
            work over physical links implemented by the local node
            controller (local network), leased lines, or a packet
            network.
        3)  Programs on one system can concurrently communicate
            with programs on other systems using a single
            communications controller.  PRIMENET handles all
            multiplexing of communications facilities.
        4)  A single program can establish multiple virtual
            circuits to other programs in the network.

   PRIMENET's ITS facility allows an interactive terminal to have access to
any machine in the network.  This means that terminals can be connected into
an X.25 packet network along with PRIME computers.  Terminal traffic between
two systems is multiplexed over the same physical facilities as inter-program
data, so no additional hardware is needed to share terminals between systems.

   This feature is ordinarily invisible to user programs, which cannot
distinguish data entering via a packet network from data coming in over AMLC
lines.  A variant of the IPCF facility allows users to include the terminal
handling protocol code in their own virtual space, thus enabling them to
control multiple terminals on the packet network within one program.
Terminals entering PRIMOS in this fashion do not pass through the usual log-in
facility, but are immediately connected to the application program they
request. (The application program provides whatever security checking is
required.)

   The result is the most effective available means to provide multi-system
access to a single terminal, with much lower costs for data communications and
a network which is truly available to all users without the expense of
building a complicated private network of multiplexors and concentrators.

   By utilizing PRIMENET's File Access Manager (FAM), programs running under
PRIMOS can access files on other PRIME systems using the same mechanisms used
to access local files.  This feature allows users to move from a single-system
environment to a multiple-system one without difficulty.  When a program and
the files it uses are separated into two (or more) systems the File Access
Management (FAM)is automatically called upon whenever the program attempts to
use the file.  Remote file operations are logically  transparent to the user
or program.

   When a request to locate a file or directory cannot be satisfied locally,
the File Access Manager is invoked to find the data elsewhere in the network.
PRIMOS initiates a remote procedure call to the remote system and suspends the
user.  This procedure call is received by an answering slave process on the
remote system, which performs the requested operation and returns data via
subroutine parameters.  The slave process on the remote system is dedicated to
its calling master process (user) on the local system until released.  A
master process (user) can have a slave process on each of several remote
systems simultaneously.  This means that each user has a dedicated connection
for the duration of the remote access activity so many requests  can be
handled in parallel.

   FAM operation is independent of the specific network hardware connecting
the nodes.  There is no need to rewrite programs or learn new commands when
moving to the network environment.  Furthermore, the user need only be
logged-in to one system in the network, regardless of the location of the
file.  Files on the local system or remote systems can be accessed dynamically
by file name within a program, using the language-specific open and close
statements.  No external job control language statements are needed for the
program to access files. Inter-host file transfers and editing can be
performed using the same PRIMOS utilities within the local system by
referencing the remote files with their actual file names.

                                REMOTE JOB ENTRY
                                ----------------

   PRIME's Remote Job Entry (RJE) software enables a PRIME system to emulate
IBM, CDC, Univac, Honeywell and ICL remote job entry terminals over
synchronous communication lines.  PRIME's RJE provides the same communications
and peripheral support as the RJE terminals they emulate, appearing to the
host processor to be those terminals.  All PRIME  RJE products provide three
unique benefits:

        * PRIME RJE is designed to communicate with multiple
          remote sites simultaneously.

        * PRIME RJE enables any terminal connected to a PRIME system to
          submit jobs for transmission to remote processors, eliminating the
          requirement for dedicated terminals or RJE stations at each
          location.

        * PRIME's mainframe capabilities permit concurrent running of RJE
          emulators, program development and production work.

   PRIME's RJE supports half-duplex, point-to-point, synchronous
communications and operates over dial-up and dedicated lines.  It is fully
supported by the PRIMOS operating system.


                 DISTRIBUTED PROCESSING TERMINAL EXECUTIVE (DPTX)
                 ------------------------------------------------

   PRIME's Distributed Processing Terminal Executive (DPTX) allows users to
construct communication networks with PRIME and IBM-compatible equipment.
DPTX conforms to IBM 3271/3277 Display System protocols, and can be integrated
into networks containing IBM mainframes, terminals and printers without
changing application code or access methods and operates under the PRIMOS
operating system.

   DPTX is compatible with all IBM 370 systems and a variety of access methods
and teleprocessing monitors:  BTAM, TCAM, VTAM, IMS/VS, CIC/VS, and TSO.  They
provide transmission speeds up to 9600 bps using IBM's Binary Synchronous
Communications (BSC) protocol.

   DPTX is comprised of three software modules that allow PRIME systems to
emulate and support IBM or IBM compatible 3271/3277 Display Systems.  One
module, Data Stream Compatibility (DPTX/DSC), allows the PRIME system to
emulate the operation of a 3271 on the IBM system.  This enables both terminal
user and application programs (interactive or batch) on the PRIME System to
reach application programs on an IBM mainframe.  A second module, Terminal
Support Facility (DPTX/TSF), allows a PRIME system to control a network of IBM
3271/3277 devices.  This enables terminal users to reach application programs
on a PRIME computer.  The third module, Transparent Connect Facility
(DPTX/TCF), combines the functions of modules one and two with additional
software allowing 3277 terminal users to to reach programs on a IBM mainframe,
even though the terminal subsystem is physically connected to a PRIME system,
which is connected to an IBM system.

   PRIMOS offers a variety of different Communication applications.  Being
able to utilize these applications to their fullest extent can make life easy
for a Primos "enthusiast."  If you're a beginner with Primos, the best way to
learn more, as with any other system, is to get some "hands-on" experience.
Look forward to seeing some beginner PRIMOS files in the near future.  -MH
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Special thanks to PRIME INC. for unwittingly providing the text for this
article.
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