 






     Software
     Product
     Description

     ________________________________________________________________

     PRODUCT NAME:  DECserver 200 for VMS, Version 3.1   SPD 27.53.05

     DESCRIPTION

     The DECserver 200 Terminal Server is a network terminal switch
     for Ethernet Local Area Networks. The DECserver 200 provides
     a convenient method to logically connect up to eight Digital
     asynchronous terminals to one or more service nodes (hosts) on
     an Ethernet. Once the terminal is connected, a user can utilize
     application programs and utilities as though the terminal were
     directly connected to a host via a DZ11, DMF32, or DHU11 device,
     with a few exceptions. Thus, it may be possible to utilize the
     DECserver 200 to connect all terminals to service nodes in place
     of traditional interfaces, except for host console terminals.
     Remote connection via dial-in modems is fully supported.

     The DECserver 200 also allows for VMS host-initiated connections
     to serial printers. A special print symbiont on VMS service
     nodes can initiate connections to serial printers connected to
     DECserver 200 ports. This allows the printers to be distributed
     throughout a facility and accessed transparently by service node
     users. Incoming host-initiated connect requests may be queued
     FIFO (first in/first out) at the server.

     The DECserver 200 also provides the capability to connect host
     systems that do not support the LAT (Local Area Transport) pro-
     tocol, Digital personal computers, and dial-out modems directly
     to ports on the server. Interactive server users can issue com-
     mands to connect to services which are offered on such ports.
     Port-to-port connections on the same server are also supported.



                                  DIGITAL                  March 1991

                                                          AE-JC42F-TE

 


     DECserver 200 for VMS, Version 3.1                  SPD 27.53.05



     The DECserver 200 implements the Local Area Transport protocol
     for communication with service nodes that implement this pro-
     tocol on the same Ethernet. This interface has been optimized
     for high terminal I/O performance over an Ethernet, while reduc-
     ing host CPU cycles required to handle interrupts. Hence, under
     most I/O loading conditions, a significant performance gain may
     be realized by using the DECserver 200 versus direct terminal
     connections via DZ11s.

     The DECserver 200 also implements and supports the Terminal De-
     vice/Session Management Protocol (TD/SMP) to manage multiple
     sessions at the device level. The DECserver 200 provides the
     ability to communicate with devices which also implement this
     protocol, and assists in the management of multiple sessions for
     these devices. By implementing this protocol, the DECserver 200
     can permit attached devices to maintain screen and keyboard con-
     text for multiple LAT sessions, as well as allow these devices
     to run multiple LAT sessions concurrently.

     The DECserver 200 implements the ODL (On Demand Loading) font
     loading protocol which allows Asian terminals that implement
     the ODL protocol to communicate with a VMS host via a termi-
     nal server. The Asian terminals will be able to request font
     definitions from a VMS host when connected to a DECserver 200.

     Software that runs on the DECserver 200 is downline loaded over
     the network from a Phase IV DECnet load host. Terminal access
     using the DECserver 200 does not require DECnet running in the
     same service node; LAT uses the Ethernet addressing mechanism to
     transport terminal messages. The DECserver 200 server software
     will operate with all Digital service nodes which support the
     LAT protocol.

     Features such as login load balancing, multiple terminal ses-
     sions, automatic failover, and remote printer support can lead
     to greater user productivity.



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     DECserver 200 for VMS, Version 3.1                  SPD 27.53.05



     For wide area network communications, terminal users can con-
     nect to a local service node running DECnet, where they can
     "SET HOST" to a remote system via the DECnet network terminal
     protocol. If this system has the requisite X.25 or SNA 3270 ac-
     cess routines, a terminal user could communicate to a remote
     SNA or X.25 host through the appropriate gateway and this inter-
     vening host. A DECserver 200 terminal user cannot communicate
     directly to remote hosts through DECnet Routers or X.25/SNA
     Gateways. Wide area network traffic will not provide the same
     high level of performance as local terminal connections, due to
     the additional DECnet and Internet protocol overhead.




























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     DECserver 200 for VMS, Version 3.1                  SPD 27.53.05



     Features

     Terminal Connection Management

     Through the use of a simple command, users can establish a
     logical connection, called a session, to any service node that
     implements the LAT protocol on the same Ethernet LAN. This
     connection makes the terminal appear as if it were physically
     connected to the service node, and the terminal user can use
     standard system utilities and applications supported by that
     node. Each terminal connected to the server can connect to the
     same or a different service node on the Ethernet. Furthermore,
     several servers can be used to connect many terminals to one or
     more service nodes.

     A service node can have one or more services that are offered to
     DECserver 200 users. Services and nodes are identified by name.
     Users always connect to services, not to nodes, although often
     one of the service names will be the node name.

     In a VAXcluster environment, the DECserver 200 sees each VAX-
     cluster on the Ethernet as a collection of service nodes of-
     fering a common service. Each cluster node may also offer a
     service whose name is equivalent to its node name. In this case,
     a terminal user can connect either to the cluster service or a
     service associated with a particular cluster node.

     Non-LAT Host Support

     The DECserver 200 can be used to provide logical terminal con-
     nections to hosts that do not implement the LAT protocol. In
     this type of configuration, the server becomes the Ethernet
     connection and protocol support for these hosts. This expands
     the LAT network accessibility to the terminal user to include
     LAT hosts directly connected to the same Ethernet and hosts
     connected to the LAT network via the DECserver 200.



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     DECserver 200 for VMS, Version 3.1                  SPD 27.53.05



     A host that supports XON/XOFF, ASCII standards and EIA RS-232-
     C/CCITT V.24/V.28 interfaces can be connected to the DECserver
     200. This provides the terminal user with a transparent connec-
     tion to the non-LAT host. It is strongly recommended that server
     port and the host side port utilize modem control signals to
     automatically signal the host upon session disconnection.

     In this configuration, there is a one-to-one correspondence
     between the port on a DECserver 200 and the connection on the
     host. The server manager assigns service names to individual
     ports or groups of ports that connect the host interface to the
     server.

     Load Balancing

     When a connection is made to a service, the actual node for the
     connection is determined by load balancing. Load balancing is a
     process the server uses when more than one node offers the same
     service. Service nodes do not have to be configured in a cluster
     in order for load balancing to be used. Service nodes with the
     same names may be running different operating systems. Using the
     load balancing process, the server connects to the node with the
     highest rating for the service desired. This rating is based on
     the current loading on the nodes that offer the service.

     Multiple Sessions

     The DECserver 200 allows each user to establish and maintain up
     to 8 sessions to one or more service nodes, up to a maximum of
     64 per DECserver 200. Only one session per user can be active at
     a time. Through simple switching commands, the user can access
     the different sessions without repeating a login dialog each
     time. Some operating systems may impose limits on the number of
     LAT sessions such a host will support.

     Multiple Session Management



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     DECserver 200 for VMS, Version 3.1                  SPD 27.53.05



     The DECserver 200 server allows direct communication with de-
     vices which support the TD/SMP protocol. This protocol provides
     the ability for the attached device to maintain screen and key-
     board context for the multiple LAT sessions which the DECserver
     200 provides. By implementing the ability to directly communi-
     cate with this protocol to the attached device, the DECserver
     200 can now assist in the management of context of these mul-
     tiple sessions, as well as allow for simultaneous output to
     multiple LAT sessions being maintained by the device.

     Outbound Connection Queues

     If a terminal user requests a connection to a server, and the
     requested service is currently in use, the terminal server users
     may opt to have the connection requested queued to the remote
     service. This feature will happen automatically whenever a
     connection fails for this reason if the user's port has been
     appropriately configured. The connection request is queued
     at the service node end and is processed first-in/first-out
     (FIFO) until such time as the user's connection request can
     be completed. This feature assists in the fair management of
     limited network resources. Once queued for connection, the user
     also has the option to cancel the queue entry and proceed with
     other sessions.















                                     6

 


     DECserver 200 for VMS, Version 3.1                  SPD 27.53.05



     Welcome Identification

     The DECserver 200 server standard welcome banner, which includes
     terminal server type, version number, internal baselevel, and
     protocol version number, is issued whenever a user successfully
     logs in to the server. The server will also print a server
     manager settable identification string. This can be useful for
     automatic server identification, or for small daily messages
     used for communication with the terminal server users.

     Local Mode and Service Mode

     For the most part, the environment provided by the DECserver
     200 is identical to that the user would experience if attached
     directly to the service node. When operating in this mode, the
     user is said to be in Service Mode. Occasionally, such as during
     connection establishment, the user interacts directly with the
     DECserver 200. When operating in this mode, the user is in Local
     Mode.

     In Local Mode, the terminal input is interpreted directly by
     DECserver 200 as commands to be performed by the server. The
     local mode prompt can be modified by a privileged command and
     can be changed from LOCAL> to any printable characters (up to 16
     characters).

     Additional commands and displays to support the features avail-
     able with the TD/SMP protocol are usable in Local Mode. These
     commands will be used to enable or disable server recognition of
     the TD/SMP commands.

     Local Mode has three different levels of privilege: privileged,
     nonprivileged and secure. Privileged mode is provided for the
     Server Manager to control the environment of the server and
     the terminal users. Access to this mode is password protected.
     Nonprivileged commands allow the terminal user to control their
     service sessions, set their terminal characteristics and show
     server information. The Server Manager can set the server to
     secure mode on a per-terminal basis which further limits the
     commands and displays of services and nodes that users can

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     DECserver 200 for VMS, Version 3.1                  SPD 27.53.05



     enter, to only those which directly relate to the user's own
     terminal.

     The Server Manager environment is a logical extension of the
     user environment. The Server Manager is treated as a server user
     with a privileged status. The Server Manager sets a terminal
     to this status using a command which requires a password. This
     privileged status allows the Server Manager to enter commands
     not normally available to server users. These commands set
     server characteristics, provide control over server port usage,
     and provide the ability to control the user's access to the
     server and network services.

     In Service Mode, the terminal input is passed directly to the
     connected service node with several exceptions. One exception,
     called the local switch character, allows the user to enter Lo-
     cal Mode from Service Mode. The <BREAK> key may also be used for
     this function. Other exceptions, called the forward and backward
     switch characters, allow the user to switch between sessions
     without the need to enter local mode. The switch characters are
     disabled by default but may be enabled by command. Both CTRL/S
     and CTRL/Q are normally interpreted locally but flow control
     using these characters can be disabled.

     Autoconnection

     Autoconnection is a function that automatically connects a
     user terminal to a service node when connection failures occur
     or upon user login to the server. In conjunction with this
     function, a dedicated or preferred service can be specified
     for each terminal user.

     If a dedicated service is specified, the DECserver 200 will
     attempt to connect to that service when a character is typed on
     the terminal keyboard or when an existing connection fails. In
     dedicated service mode, only one session is available. As this
     mode is designed to simulate a direct terminal connection, no
     local mode commands or messages are available to the terminal

                                     8

 


     DECserver 200 for VMS, Version 3.1                  SPD 27.53.05



     user. Ports with dedicated service can be automatically logged
     out of the server when the user logs out of the service node.

     If a preferred service is specified, the DECserver 200 will
     attempt to connect to that service as with the dedicated service
     mode of operation. However, the terminal user can enter local
     mode and establish other sessions.

     Automatic Session Failover

     If a service is available on two or more service nodes and
     a connection to a service fails, the server will attempt to
     connect the user to another service node offering the same
     service. The user does not have to be already connected to
     that service node. Furthermore, the user's context at the time
     of failure is not automatically restored and login to the new
     service is required.

     Groups

     Every terminal and service node in a LAT network is a member
     of one or more groups, which are specified by a list of numbers
     from 0 - 255. Groups allow an easy means of subdividing the net-
     work into what appears to be many smaller networks. A terminal
     user is only aware of the services that are offered by nodes in
     the same group(s).

     The Server Manager can specify the authorized group(s) in which
     a terminal is a member. The authorized groups define the set of
     services that the user is allowed to access. In addition, a user
     can further restrict access to services by disabling some of
     the authorized groups using a non-privileged group command. The
     user-settable group codes are a subset of the authorized groups.

     Groups provide a restrictive view of the network. This re-
     stricted view is mainly for user convenience and, although it
     also provides a form of security, it is not intended to be the
     primary form of access authorization or system security for a
     node.

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     DECserver 200 for VMS, Version 3.1                  SPD 27.53.05



     Security

     The DECserver 200 provides functions which enhance security
     features already available in the service nodes. DECserver 200
     security includes the ability to lock a terminal's keyboard from
     other users, optional login protection, and nonprivileged local
     mode of operation as a default.

     A user may lock the terminal using a lock password. This allows
     the user to leave sessions running at the terminal without fear
     of security violations. When a terminal is locked, all input
     from the terminal is ignored until the lock password is re-
     entered. The lock feature may be disabled by the Server Manager.

     Each terminal port can be set to operate in a secure mode which
     causes all commands that relate to other users to be disabled
     for that port.

     Login passwords can be enabled on a per-line basis by the server
     manager. If enabled, the terminal user must enter a login pass-
     word to access server functions.

     DECserver 200 users normally have access to the nonprivileged
     local mode. In this mode, users may only issue commands that af-
     fect their own terminal environment. The server has a privileged
     mode for server manager's use. The mode is password protected.

     Online HELP Facility

     A full online reference HELP facility is available. The server's
     HELP command provides information on the correct syntax and
     details about each command. In addition, a tutorial HELP feature
     allows new users to quickly learn the basics of DECserver 200
     operation. Tutorial HELP may be entered upon logging into the
     server.

     Directory Service

     Any DECserver 200 user can obtain a directory of services avail-
     able to that user with a SHOW SERVICES command. Services for
     which the user is not authorized will not be displayed.

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     DECserver 200 for VMS, Version 3.1                  SPD 27.53.05



     Permanent Characteristics

     The DECserver 200 maintains permanent characteristics in non-
     volatile memory which is retained even when the power is dis-
     connected. Permanent characteristics are maintained for service
     and server parameters as well as per-port parameters. Permanent
     characteristics can be reset to factory defaults by pressing the
     software reset button on the hardware unit while plugging in the
     power cord.

     Port Characteristics Configuration

     Characteristics governing the operation of an individual port
     can be displayed by a nonprivileged terminal user interactively
     from their terminal. Many of the characteristics may be set-up
     by the user, but certain characteristics are privileged and may
     only be changed by the Server Manager.

     Port parameters that can be set and displayed include: speed,
     character size, group codes, parity, terminal type, access,
     autobaud, modem and password protection.

     Port Access

     A port on a DECserverB 200 may be set up in different ways de-
     pending on the device attached to the port and its intended use.
     DECserver 200 supports EIA-RS-232-C and DECconnect asynchronous
     devices operating at speeds up to 19.2K bps.

     Port access is the characteristic which determines how a port
     may access or be accessed by interactive users and service
     nodes.

     o  Access Local - Designed for interactive terminals. This al-
        lows the device (typically an interactive terminal) attached
        to the port to CONNECT to LAT services. This type of access
        is also used for dial-in modems.


                                    11

 


     DECserver 200 for VMS, Version 3.1                  SPD 27.53.05



     o  Access Remote - Designed for applications-driven devices such
        as asynchronous printers which are allocated by a service
        node process. This allows the implementation of certain
        shared printers by multiple service nodes. This type of
        access is also used for connections to dial-out modems, and
        non-LAT host systems.

     o  Access Dynamic - Designed for devices (such as personal
        computers or printers with keyboards) which require both
        Local and Remote access.

     o  Access None - Designed to allow the server manager to disable
        the use of a port.

     With printer support capabilities, the setup procedure of remote
     printers needs to be done once and is automatically reconfigured
     on system startup. The particular server port must be config-
     ured for remote access and set up to match the characteristics
     of the printer. The system startup command file must be mod-
     ified to call the two command files provided with the service
     node software. Finally, the command files themselves must be
     customized to reflect the environment of their node. The server
     can optionally queue remote connects if these connects cannot be
     satisfied immediately. This queue management can be enabled for
     the server by the server manager. Note that this is a connection
     queue only.

     Terminal Operation

     The DECserver 200 software supports the simultaneous operation
     of up to eight asynchronous devices at speeds from 75 bps to
     19.2K bps. The software also supports:

     o  Full modem control support (DECserver 200/MC only)

     o  Data leads only support

     o  XON/XOFF flow control

     o  CTS/RTS and DSR/DTR flow control (DECserver 200/MC only)

     o  Split speed (transmit and receive) terminal operation

                                    12

 


     DECserver 200 for VMS, Version 3.1                  SPD 27.53.05



     o  Modem fallback features (DECserver 200/MC only)

     o  Block Mode transfers

     o  Automatic line speed detection

     o  Digital personal computer file transfer

     o  Data transparency mode

     o  Ability to pass break character and error notification

     o  Ability to assist in multiple session management via TD/SMP.

     Server Management

     Several facilities exist for managing and troubleshooting server
     operation. The Server Manager in privileged mode can set up
     server identification information, change port characteristics,
     or fine tune the operating characteristics of the server. The
     Server Manager can also assign service names to groups of one
     or more ports which are connected to non-LAT hosts or modems.
     Troubleshooting facilities include diagnostic tests, a remote
     console feature, and online statistics.

     A privileged user can diagnose Ethernet communications prob-
     lems by looping messages to an Ethernet host and through the
     Ethernet hardware interface at the server. To diagnose terminal
     problems, users can execute a command to transmit test data to
     their terminal, or the server manager can send test data to any
     terminal.

     The capability also exists for the server manager to test a
     service connection by sending data from the initiating port to
     the service node and back again. The data is then compared and
     any discrepancies reported. At the service node, the data can be
     looped back by the LAT protocol, or internally or externally at
     the service port. This feature is supported only by DECserver
     200 service nodes; VMS service nodes do not support this service
     loopback capability.

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     DECserver 200 for VMS, Version 3.1                  SPD 27.53.05



     The server maintains a variety of statistics and counters. These
     include the following: Ethernet data link statistics, LAT pro-
     tocol statistics, and port error statistics. These data can
     be displayed and zeroed by the Server Manager. Server param-
     eters that can be modified and displayed include the server
     identification, circuit timer, session limits, and login limits.

     Remote Server Management

     The DECserver 200 implements the console carrier feature which
     enables access to the DECserver 200 local mode from a Phase IV
     DECnet host on the same LAN. With the exception of remote con-
     sole port configuration, the entire local mode user interface is
     accessible to the remote console carrier user. This includes the
     privileged commands, if the user knows the server's privileged
     password. This capability allows centralized server management
     and remote server diagnosis.

     Communications

     DECserver 200 software is designed to run on DECserver 200
     hardware exclusively which includes an Ethernet interface for
     connection to an Ethernet transceiver cable.

     The DECserver 200/MC has eight EIA RS-232-C/CCITT V.24 asyn-
     chronous line interfaces for connecting terminals to the unit.

     The DECserver 200/DL has a single 36 pin DECconnect connector
     for eight ports.

     On the DECserver 200/MC, each port on the server can be set
     up by the Server Manager to operate using full-duplex modem
     control. The DECserver 200/MC is compatible with Digital's
     family of modems and with Bell 100 and 200 series modems and
     their equivalents. A BREAK feature is available and can be set
     on a per-port basis. This allows the DECserver 200/MC to force
     a break condition on connections to host interfaces. BREAK can
     also be passed through from a terminal connected on the server
     to the non-LAT host connected on the server.

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     DECserver 200 for VMS, Version 3.1                  SPD 27.53.05



     DECserver 200 Operation

     The DECserver 200 ROM-based firmware provides the necessary
     maintenance operation protocols for downline loading DECserver
     200 software from a Phase IV DECnet load host over the Eth-
     ernet into server memory. All self-test diagnostics are in
     DECserver ROM, so downline loading is not a precondition for
     DECserver self-test. In the event of a bugcheck caused by a fa-
     tal error, the unit will normally attempt to upline dump server
     memory to a DECnet Phase IV host. Following this, the unit will
     automatically initialize itself and invoke a downline load.

     DECserver 200 Configuration and Performance

     The process of configuring the DECserver 200 is based primarily
     on tradeoffs of cost and performance within the realm of satis-
     fying user application requirements. Network applications will
     range from low-speed, low-cost situations (e.g. connecting re-
     mote terminals through low-speed modems) to those of relatively
     high performance (e.g., connecting high-speed local terminals to
     local hosts within a local area network or connecting to non-LAT
     systems). The performance of a given server is a function of the
     expected network traffic, the load on hosts to which terminals
     are connected, and resultant processing pursuant to the dedi-
     cated function of the unit. Thus performance depends on several
     factors:

     o  Number of terminals

     o  Number of host systems with active connections to the server

     o  Number of active connections to non-LAT hosts

     o  Terminal speeds

     o  Terminal user applications

     o  Number and size of host buffers

     o  Terminal workload

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     DECserver 200 for VMS, Version 3.1                  SPD 27.53.05



     The DECserver can sustain an aggregate character throughput of
     over 11520 characters per second. This is equivalent to running
     four ports at 19200 bits per second, and four at 9600 bps.

     In order to achieve a viable configuration, the user and/or a
     Digital software specialist should perform a level of appli-
     cation analysis which addresses the factors above. The actual
     maximum data throughput cannot be calculated by multiplying the
     number of lines by the line speed, since many factors already
     discussed in this section may reduce the actual throughput.

     Restrictions on DECserver 200 Usage

     While terminal connections using the DECserver 200 have been
     designed to simulate direct terminal connections as much as pos-
     sible, a few differences necessarily exist because of the nature
     of the product. Under most circumstances, these differences are
     not noticed by terminal users or service node application pro-
     grams. However, applications which are directly dependent on the
     following functions may not operate as with a direct connection:

     o  Applications that depend on reading or setting the terminal
        speed, character size and parity by manipulating system data
        structures

     o  Applications that depend on an extremely fast response time
        (typically less than 200 ms) to operate

     o  Applications that utilize an alternate terminal driver in the
        service node

     o  Applications that expect incoming connections to have fixed
        device names

     HARDWARE REQUIREMENTS

     VAX, MicroVAX or VAXstation configuration as specified in the
     System Support Addendum (SSA 27.53.05-x).

     SOFTWARE REQUIREMENTS *

                                    16

 


     DECserver 200 for VMS, Version 3.1                  SPD 27.53.05



     VMS Operating System
     DECnet-VAX

     *  Refer to the System Support Addendum for availability and
        required versions of prerequisite/optional software (SSA
        26.53.05-x).

     Refer to the following SPDs for information on other supported
     DECserver 200 systems:

     DECserver 200 for RSX-11M-PLUS and Micro/RSX (SPD 15.72.xx)

     DECserver 200 for ULTRIX-32 (SPD 27.54.xx)

     ORDERING INFORMATION

     Software Licenses: QL-VCBA*-**
     Software Media: QA-VCBA*-H*
     Software Documentation: QA-VCBAA-GZ
     Software Product Services: QT-VCBA*-**
     LAT Networks Concept Guide: AA-LD84B-TK

     *  Denotes variant fields. For additional information on avail-
        able licenses, services and media refer to the appropriate
        price book.














                                    17

 


     DECserver 200 for VMS, Version 3.1                  SPD 27.53.05



     SOFTWARE LICENSING

     This software is furnished under the licensing provisions of
     Digital's Standard Terms and Conditions. For more information
     about Digital's licensing terms and policies, contact your local
     Digital office.

     The DECserver 200 software license applies to the DECserver 200
     on which the server software runs, not to service host node CPUs
     in the network.

     This product does not provide support for the VMS License Man-
     agement Facility. A Product Authorization Key (PAK) is not
     required for installation or use of this version of the product.

     SOFTWARE PRODUCT SERVICES

     A variety of service options are available from Digital. For
     more information contact your local Digital office.

     SOFTWARE WARRANTY

     Warranty for this software product is provided by Digital with
     the purchase of a license for the product as defined in the
     Software Warranty Addendum of this SPD.

     [R]   IBM is a registered trademark of International Business
           Machines Corporation.

     [TM]  The DIGITAL Logo, VAX, MicroVAX, VAXstation, VMS, DECmate,
           DECnet and DECserver are trademarks of Digital Equipment
           Corporation.







                                    18
