 






     Software
     Product
     Description

     ________________________________________________________________

     PRODUCT NAME:  DECserver 250 for VMS, Version 2.0   SPD 25.J5.01

     DESCRIPTION

     The DECserver 250 is a network server for printers for Ethernet
     Local Area Networks. The DECserver 250 provides a convenient
     method to connect logically the following:

     o  Two Digital asynchronous parallel printers (using Dataprod-
        ucts parallel interface standard)

     o  Three Digital asynchronous serial printers

     o  A Digital asynchronous serial printer or terminal with modem
        control to one or more service nodes (hosts) on an Ethernet

     The DECserver 250 implements the Local Area Transport (LAT)
     protocol for communication with service nodes that implement
     this protocol on the same Ethernet.

     Software that runs on the DECserver 250 is down-line loaded over
     the network from a Phase IV DECnet load host.

     DECserver 250 Option

     The DECserver 250 hardware consists of a single box that pro-
     vides the following:

     o  Two Digital Parallel printer ports, each of which uses a male
        37 pin connector

     o  Four EIA RS-232-C/CCITT V.24 asynchronous line interfaces for
        connecting three serial printers and one serial printer or
        terminal

                                  DIGITAL               November 1990

                                                          AE-NH91B-TE

 


     DECserver 250 for VMS, Version 2.0                  SPD 25.J5.01



     o  Ethernet interface transceiver port

     Features

     Connection Management

     A print symbiont on VMS service nodes initiates connections to
     asynchronous printers connected to DECserver 250 ports.

     Users can establish a logical connection from any service node
     that implements the LAT protocol on the same Ethernet LAN. The
     terminal connected to the server can be used to make multiple
     connections to the same or to different service nodes on the
     Ethernet. Only one connection per asynchronous printer can be
     made.

     Load Balancing

     The DECserver 250 offers load balancing, which is a function
     that dynamically spreads the user load evenly among service
     nodes that offer the same service.

     The LAT Control Program (LATCP) is used by the System Manager to
     establish service definitions.

     On-line HELP Facility

     A full on-line reference HELP facility, with tutorial HELP fea-
     ture, is available on the printer/terminal port. The remaining
     ports do not have access to the HELP facilities.

     Permanent Characteristics

     The DECserver 250 maintains permanent characteristics in non-
     volatile memory, which is retained even when the power is dis-
     connected.

     Port Characteristics Configuration

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     DECserver 250 for VMS, Version 2.0                  SPD 25.J5.01



     Characteristics governing the operation of the DECserver 250
     ports can be displayed interactively from the printer/terminal
     port when connected to a terminal. Characteristics other than
     permanent may be setup by the user or Server Manager.

     Port Access

     Port access is the characteristic which determines how a port
     may access or be accessed by interactive users and service
     nodes. The printer/terminal port of the DECserver 250 is the
     only asynchronous port with modem control. This port is the only
     one available for terminal connection and the only one which
     offers these access modes:

     o  Local - Designed for the interactive terminal to allow the
        device attached to the port to communicate directly with the
        server.

     o  Service - Service Mode is used for communications between the
        server and service nodes.

     All other ports use remote access, which is designed for ap-
     plications driven devices such as asynchronous printers, which
     are allocated by a service node process. This allows the im-
     plementation of certain shared printers by multiple service
     nodes.

     Refer to the System Support Addendum (SSA 25.J5.01-x) for the
     list of printers, terminals, and modems supported.

     DECserver 250 Operation

     The DECserver 250 ROM-based firmware provides the necessary
     maintenance operation protocols for down-line loading DECserver
     250 software from a Phase IV DECnet load host over the Ethernet
     into server memory. All self-test diagnostics are DECserver 250
     ROM-based and are executed prior to a Load request.

     DECserver 250 Configuration and Performance

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     DECserver 250 for VMS, Version 2.0                  SPD 25.J5.01



     The performance of a given server is a function of the expected
     network traffic, the load on hosts to which ports are connected,
     and resultant processing pursuant to the dedicated function of
     the unit. Thus performance depends on several factors:

     o  Number of ports in use

     o  Number of host systems with active connections to the server

     o  Printer speeds

     o  Terminal connection/speed on the printer/terminal port

     o  User applications

     o  Number and size of host buffers

     o  Server workload

     o  Network and host loading

     In terms of throughput to the printer ports, the DECserver 250
     supports the equivalent of two 1200 LPM printers, or one 2000
     LPM printer running at full speed, or aggregate transfer rates
     of 19,200 baud on two of the serial ports and 9600 baud on the
     remaining two serial ports.

     HARDWARE REQUIREMENTS

     VAX, MicroVAX, or VAXstation configuration as specified in the
     System Support Addendum (SSA 25.J5.01-x).

     SOFTWARE REQUIREMENTS *

     VMS Operating System

     DECnet-VAX

     *  Refer to the System Support Addendum (SSA 25.J5.01-x) for the
        availability and required versions for prerequisite/optional
        software.

     ORDERING INFORMATION

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     DECserver 250 for VMS, Version 2.0                  SPD 25.J5.01



     Software Licenses: QL-VTMA*-**
     Software Media: QA-VTMA*-**
     Software Documentation: QA-VTMA*-GZ
     Software Product Services: QT-VTMA*-**

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

     SOFTWARE LICENSING

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

     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.

     [TM]  The DIGITAL Logo, DECserver, DECnet, VMS, MicroVAX, VAXs-
           tation, VAXserver and VMS are trademarks of Digital Equip-
           ment Corporation.









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