Ref: 99980058
Title: Bridge X.25 Product Line
Date: 2/1/86

Copyright 3Com Corporation, 1991.  All rights reserved.

Bridge Communications offers a family of X.25 services allowing
terminals and computers to efficiently communicate over packet
switching networks.  These software services are described below.
The software runs on the same hardware base.  The software for
the GS/1 is called SW/2-CS/ICS; the software for the CS/1-X.25 is
called SW/1-X.25.

Bridge's X.25 products provide three services, any combination of
which can coexist on a single GS/1:

1.  Interconnection Service (ICS)

When using the Interconnection Service, the GS/1 line is
configured as a Data Terminal Equipment (DTE) to a PDN.
Xerox Network Systems (XNS) packets are encapsulated across
X.25 Virtual Circuits to interconnect two or more Ethernets.

2.  Connection Service (CS)

When using the Connection Service, the GS/1 line is also
configured as a DTE to a PDN.  Terminals on the LAN can
access hosts on the PDN using logical names.  Terminals on a
PDN PAD can call up the GS/1 via a user interface to access
host resources.  This User Interface can also be disabled and
terminals can be passed through to a specific host based on
the X.25 address used.

3.  CS/1-X.25

When using the SW/1-X.25 software, the line is configured as
a Data Communication Equipment (DCE)  and connected to an
X.25 host.  This software provides the following services:

*   Terminal-to-host access using X.29.

*   Host-to-host access using X.25 packet level protocols.


Features

Following is a list of the common features of the Bridge X.25
products.  The distinctive features of each product are described
in more detail in the next section.

1.  Supports up to eight communications ports with four ports
operating at speeds up to 64K b/sec.  Each pair of ports has
an aggregate data transfer capacity of 76K b/sec between each
Ethernet segment.  RS-232, RS-422, and V.35 interfaces are
available.

2.  Compatible with Ethernet version 1.0, 2.0, or IEEE 802.3.

3.  Configurable X.25 packet size from 128 to 512 bytes for
optimal performance in a given application (e.g., terminal
traffic, file transfer).

4.  Allows incoming and outgoing calls to be barred.  This
feature allows unauthorized incoming and outgoing calls to be
screened for security purposes.

5.  Multiple 68000 architecture provides high performance
Ethernet controller, protocol processing, and device Input/
Output.


.h1;Gateway Server/1 Interconnection Service

Overview

The GS/1 with Interconnection Service is a high-performance
communications processor that provides Interconnection and
routing services to physically isolated Ethernet segments over an
X.25 private or public data network.  The GS/1 is designed to
facilitate the physical extension or distribution of Ethernet
networks.

The GS/1 Interconnection Service is a network layers router that
uses the XNS Internetwork Datagram Protocol (IDP) to route
packets of information across an X.25 PDN.  Internal and inter-
network routing tables are dynamically updated using the XNS
Routing Information Protocol (RIP).

The GS/1 gathers statistics to assist the network manager in
monitoring utilization, throughput, error rates, packet delay,
and other important network measurements.  Configuration
utilities provide a fast, simple method of customizing the GS/1
for a specific internetwork configuration or for tuning to
achieve optimum performance.

Features

*   Uses XNS Internetwork Datagram Protocols (IDP) and Routing
Information Protocols (RIP) for routing and dynamic network
addressing functions.  In addition, the RIP broadcast timer
can be disabled or enabled via a system generation program in
the GS/1 software to limit excessive X.25 usage.

*   Provides automatic rerouting over alternative communication
links ensuring high data transfer and reliable transmission.

*   Allows simultaneous interconnection to as many as 48 remote
Ethernets.

.h1;Gateway Server/1 Connection Service

Overview

The GS/1 with Connection Service enables devices on a Bridge
Local Area Network (LAN) to communicate with hosts on an X.25
PDN.  In addition, remote devices can access the Bridge LAN by
establishing a virtual circuit from the PDN's PAD to the GS/1.
In effect, the GS/1 enables the LAN to which it is connected to
appear as a distributed PAD to the X.25 network, allowing all
systems attached to the Ethernet LAN to share a connection with
the PDN and access attached resources.

The Xerox Network Systems (XNS) protocols are used at the network
and transport layers.  In addition to the X.25 protocol, which
has been certified by several PDN, the CCITT X.3/X.28/X.29
protocols have been implemented to support terminal-to-host
parameter selection.

Features

*   User transparent connections can be configured to logically
named X.25 resources or Ethernet attached devices.

*   The LAN acts as an expandable, distributed PAD to X.25 based
networks.

*   Configurable port, system, and network parameters.

*   Network access control to X.25 ports (16 access groups) and
to local resources accessed from PDN.

*   Bridge Communications user interface with simplified command
menus, help facilities, and user definable command files.

*   Network management facilities for performance monitoring,
routine error logging, hierarchical configuration control,
fully distributed logical naming service.

*   Connection from an Ethernet attached device to an X.25
resource established through a single command.

*   Connection pass-through that allows a PAD user to access a
host on the Ethernet network in one simple step depending on
the X.25 address used.  Refer to the "Bridge Implementation
of X.25" section for an example of this feature.

*   Supports up to 48 simultaneous virtual circuits.


.h1;Communications Server/1 with X.25

Overview

The CS/1-X.25 is a high performance front-end processor that
connects minicomputers, mainframes, and workstations supporting
an X.25 interface to a Bridge Communications' Ethernet Local Area
Network (LAN).  The CS/1-X.25 uses the industry-standard X.25
protocol between the CS/1-X.25 and the hosts, providing an
efficient high-speed link without requiring modification of the
host software.

The CS/1-X.25 can be used in terminal-to-host data switch
applications as well as for host-to-host file-transfer.  Thus,
standard file transfer packages can be used on the LAN.  In both
cases, the CS/1-X.25 makes the LAN appear to be a PDN to the X.25
host software.

Features

*   Configurable port, system, and network parameters.

*   Network management facilties for performance monitoring,
routine error logging, hierarchical configuration control,
fully distributed logial naming service.

*   Eliminates requirement for additional serial Input/Output
ports on hosts.

*   Supports X.3/X.28/X.29 interface and protocol standards for
terminal to host communications.

*   Xerox Network Systems (XNS) high-level protocols provide end-
to-end reliability, routing, sequencing, flow control,
session multiplexing, and compatibilty with other members of
Bridge Communications Product Line.

*   Supports up to 48 virtual circuits.

*   Supports packet level interface for host-to-host file
transfer and X.29 protocols for terminal access.

*   Host-to-host file transfer across the LAN and a PDN supported
via call user data field extensions.

