Software
           Product
           Description

           _________________________________________________________

           PRODUCT NAME:  DECbridge 500 Software Microcode,    SPD 32.28.04
                          Version 3.0

           DESCRIPTION

           DECbridge 500 Software Microcode is dedicated microcode which
           runs in the DECbridge 500 FDDI to 802.3/Ethernet hardware
           bridge platform. The DECbridge 500 is an ISO model Level 2
           protocol-independent bridge that allows users to connect an
           existing 802.3/Ethernet LAN to a high speed FDDI network.

           DECbridge 500 hardware is shipped from the factory with the
           DECbridge 500 Software Microcode preloaded. The microcode
           resides in the bridge's electronically alterable memory, thus
           allowing subsequent versions of the microcode to be down-
           line loaded. DECbridge 500 Software Microcode is maintained
           in the hardware base even during power-off states.

           Local area network bridges are the building blocks of the
           extended LAN. An extended LAN is a collection of LANs that
           are interconnected to logically appear as one large local
           area network. The bridge interconnects an 802.3/Ethernet LAN
           to an FDDI LAN allowing only data destined for an adjacent
           LAN to pass through the device. By performing this traffic
           control and direction, network bandwidth is maximized since
           only traffic required on the extended LAN is allowed to tra-
           verse the bridge. Additionally, the DECbridge 500 device per-
           forms all the necessary data packet conversions to allow FDDI
           and 802.3/Ethernet to interoperate on the extended LAN.

           The general characteristics of DECbridge 500 are:

           o  Performs initialization and bootstrapping.

                                    DIGITAL                June 1991

                                                         AE-PBPYE-TE

 



           DECbridge 500 Software Microcode, Version 3.0    SPD 32.28.04


           o  Provides a simple network management protocol (SNMP) agent
              allowing "show" function requests when made from SNMP man-
              agement systems.[*]

           o  Performs Diagnostic Selftest automatically at power-up
              and also when it is initiated by network management soft-
              ware.

           o  Performs filter and forward decisions on incoming data
              packets.

           o  Performs bi-directional standard-based translation be-
              tween FDDI and 802.3/Ethernet data formats, providing di-
              rect transparent communications between 802.3/Ethernet
              and FDDI LANs.

           o  Performs specialized translation of certain protocols to
              provide transparent communication between 802.3/Ethernet
              and FDDI LANS as specified by IEEE802/Ethernet LANs.

           o  Performs IP (TCP, UDP, ICMP, and EGP) data packet frag-
              mentation per RFC 791. Allows transparent forwarding of
              large FDDI IP packets to 802.3/Ethernet LANs.

           o  Performs Spanning Tree loop detection in both the IEEE
              802.1d implementation as well as in Digital's LAN Bridge
              implementation mode; automatically configures to Digi-
              tal LAN Bridge and 802.1d Spanning Tree implementations
              for backwards compatibility with the installed base of
              Digital LAN Bridge users.

           o  Provides flexible filtering (destination, address, pro-
              tocol) and password access protection for greater net-
              work control, increased security and bandwidth utiliza-
              tion, and reduced propagation of network problems.*

           o  Performs FDDI station management as specified by the ANSI
              X3T9 SMT V6.2 standard.

           o  Performs Ring Map functions as per SMT V6.2.*

           _________________

         [*] Requires Network Management Software to access this feature.

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           DECbridge 500 Software Microcode, Version 3.0    SPD 32.28.04


           o  Updates all the DECbridge 500 counters and settable pa-
              rameters.

           o  Performs failure detection of DECbridge's cooling fans
              and alerts users through management software.*

           o  Performs operating system support scheduling, maintains
              timers and receive requests.

           HARDWARE REQUIREMENTS

           DECbridge 500 hardware is required to run DECbridge 500 Soft-
           ware Microcode.

           SOFTWARE LICENSE

           The software license required to run DECbridge 500 Software
           Microcode is included with the hardware.

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

           SOFTWARE WARRANTY

           Warranty of this software microcode 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, and DECbridge are trademarks of
               Digital Equipment Corporation.









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