TCP to X.25 general purpose Gateway software for the transfer and routing of data between X.25 and TCP/IP networks

FarSync TCP-X25 GP Gateway providing the bridge between an X.25 and an IP network

The FarSync TCP-X25 GP Gateway is a high speed TCP/IP to X.25 gateway providing connection routing, session control, data mapping and packetisation


The FarSync TCP-X25 GP Gateway provides a flexible and reliable means of efficiently transferring data between TCP/IP and X.25 networks. The Gateway runs as a software application on Servers supporting Windows XP, 2000 and Server 2003. The X.25 connections are handled by using FarSync X25 cards.

Key Features

  • General Purpose TCP to X.25 data translation with a very wide variety of modes including: fixed routes, dynamic routing, RFC1006, Cisco RBP compatibility, header stripping and parity correction
  • High performance, non stop operation - more than 1000 messages per second
  • Up to 16 lines and up to 4000 SVC and PVC connections, 2048 on any one X.25 line
  • Multiple Gateways providing Resilience with Load Balancing
  • Simple configuration with a Web accessible Configuration Application

The product can support protocols when the X.25 Host system treats the incoming X.25 data as a character stream. It can also convert the data when a header is used to describe the message payload within the TCP connections and remove this header on the X.25 virtual circuits. Data types supported include: RFC1006, Cisco RBP and special character delimiting. Dynamic routing is supported where the Client TCP application determines the X.25 address and call parameters used at the time the connection is established. The Gateway can provide connectivity to several different Host systems at the same time with each can have different data conversion configurations.

The Gateway also support X.25 Data Switching over TCP this allows X.25 devices to be interconnected via an IP network without the layer 3 overheads associated with XOT.

Two or more Gateways can be used in a load balanced, resilient configuration that has no single point of failure when run on Windows Server 2003.

There are complete appliance versions of this Gateway available, see FarLinX TCP-X25 GP Gateway plus also special purpose POS (Point of Sale) TCP to X.25 Gateways and a TCP to X.25 SMS Message Router.

Typical Applications

The FarSync TCP-X25 GP Gateway can be used in a whole host of different applications, the common factor being the requirement to transfer data between TCP and X.25. Such uses include:

  • Conversion of legacy X.25 connections and data to a TCP/IP network
  • X.25 to TCP/IP resilient Hub
  • Reproduction of X.25 connections mapped over an IP network
  • TCP/IP network sockets access to X.25
  • 4 port X.25 switch with selective routing of data over TCP/IP (Requires the FarSync X.25 Switch)

GP Gateway Operation

The Gateway provides connection establishment and data packetization services for general protocols to allow applications sending data over TCP/IP to interface to X.25 connected hosts. The Gateway provides routing facilities to select the appropriate Host from those available and maintains X.25 sessions to the Host as required.

The Gateway listens on a number of TCP ports – one port per configured X.25 Host. When a client establishes a TCP connection to the Gateway, the Gateway sets up an X.25 virtual circuit to the appropriate Host. Once the end-to-end connection is complete, the messages can be transferred.

At the end of the transaction, if the terminal disconnects, the Gateway will clear the X.25 virtual circuit. Alternatively, if the Host clears the X.25 virtual circuit first, the Gateway will disconnect the TCP connection to the terminal.

The Gateway can be used in conjunction with the FarSync X.25 Switch to provide routing of X.25 calls between X.25 lines and permit selective filtering of calls to the FarSync TCP-X25 GP Gateway.

TCP to X.25 Data Translation Functions

The Gateway supports a wide range of TCP to X.25 data translation and connection functions, these include:

  • Character stream
  • ETX terminated messages
  • Special character terminated messages (customisable)
  • Message header conversion - types available 2 or 4 byte ASCII or Binary length representation
  • Custom message header conversion
  • RFC1006 - ISO Transport Class 0 protocol data units, using the RFC-1006 encapsulation on the TCP connection
  • Cisco RBP - Record Boundary Preservation
  • X.25 Parity conversion - the Gateway performs any required parity adjustments and removal on the x.25 connection

Many of the functions can be configured for the same connection for maximum flexibility.

Connection Routing and Address Mapping

The FarSync TCP-X25 GP Gateway can support routes to 2,000 different X.25 hosts. Similarly, when using the called X.25 address as the routing key, incoming X.25 calls can be routed to thousands of different TCP/IP hosts.

When making connections to the X.25 network, the Gateway has the capability of mapping the source IP address to a calling X.25 address, thus allowing the destination X.25 host to identify the connection source uniquely.

The Dynamic routing option allows the X.25 address (NUA) and call parameters to be set by the remote application at the time each X.25 connection is established. X.25 packetisation information is passed to the application.

The main modes supported include:

  • Statically defined routing
  • DRPD - the Dynamic Routing Packetized Data format allows TCP connected applications to dynamically setup the X.25 connection
  • X.25 Data Switching - allows X.25 devices to be interconnected via an IP network without the overheads associated with XOT
  • PAD Routing - PAD or Dynamic routing may be employed to allow the TCP client application to specify the X.25 call parameters

Performance and Expandability

The FarSync TCP-X25 GP Gateway easily handles very high message loads. Support for large numbers of X.25 lines and multiple Gateways provides enormous scalable expansion capability and resiliency. The main performance and expansion features of the Gateway are:

  • more than 1000 messages (packets of data) per second on each Gateway
  • Up to 4000 simultaneous connections (recommended maximum) with up to 2048 on a X.25 line
  • Multiple load balancing Gateways with up to 32 sharing a single IP address
  • X.25 line speeds up to 8 Mbits/s
  • From 1 to 16 X.25 lines per Gateway
  • X.25 Networks, Leased Lines and X.25 Dialup connections supported

Overview of Resilient Operation

The FarSync TCP-X25 GP Gateway can be deployed in a wide variety of ways to achieve the level of resilience required by the application. The level will depend on the value of the data traffic and the acceptable degree of user intervention required to rectify any problem. The aim with resilience is to remove single points of failure. Resilient configurations using more than one Gateway also allow improved performance by sharing the traffic load between several machines.

Network Line Redundancy

To achieve network line redundancy, a single FarSync TCP-X25 GP Gateway may operate with two or more X.25 lines. It can route data over any active line connected to the Gateway so that if one line goes out of operation then the other lines continue to be used automatically.

Gateway Redundancy and Load Balancing

For fully resilient operation, two (or more) FarSync TCP-X25 GP Gateways may be deployed. They can be either configured for simple failover from a primary to a backup machine or for full load balanced operation. In Network Load Balancing (NLB) mode both failover and load balancing of the connections are provided thus ensuring there is no single point of failure and that there is no performance bottleneck.

The Gateway Supervisor application supplied with the Gateway checks the state of the X.25 network lines and as these change state between fully operational and faulty it automatically enables/disables the unit from the pool of FarSync TCP-X25 GP Gateway's, thus managing the availability of that particular Gateway machine. Key events such as the loss of an X.25 line are recorded on a daily rotating event log.

Configuration Application

Sample screen shot of the  general configuration screen of the GP Gateway

The Configuration Application for the Gateway allows the TCP interface, X.25 connection, data translation configuration and the event log levels to be selected. Almost all changes to the configuration are made dynamically so continuous operation of the Gateway can be maintained.

On line help is provided for the parameters.

X.25 connections

The FarSync TCP-X25 GP Gateway uses the FarSync X25 T-Series or M-Series cards to provide the X.25 connection. One or more of these high performance PCI-X / PCI / PCMCIA cards are required to connect to the physical X.25 line/s that allow access to the X.25 attached Hosts. For further information, see FarSync X.25 cards.

Maintenance Contract

FarSite recognises that this product is often used as a key component in systems and as such a guaranteed response to unexpected problems is required. A maintenance contract is available for the FarSync TCP-X25 GP Gateway and FarSync X.25 cards for priority service and rapid problem resolution.

Technical Specifications
Product Name FarSync TCP-X25 GP Gateway
Product Code FS9001
Product Features
TCP to X.25 translation Modes Character stream, ETX terminated messages, CR terminated messages,
Message header conversion (types available Conv Hdr 2-bin, Conv Hdr 2-ascii, Conv Hdr 4-bin, Conv Hdr 4-ascii), Customisable message header conversion
RFC1006, Cisco RBP, X.25 Parity conversion
TCP to X.25 Call Routing Modes Statically defined routing, DRPD, X.25 Data Switching, PAD Routing
Maximum Simultaneous Connections 4,000 (recommended maximum per Gateway)
Messages per second More than 1000 Messages (packets of data) per second
TCP multiple ports Yes, configurable
TCP/IP connections to the Gateway Standard PC LAN cards
FarSync WAN cards for leased line / internet / intranet connections using T1, E1, G.SHDSL, X.21 and V.35 network connectors
Resilience and load balancing Yes, from 2 to 32 Gateways
Logging key events Events such as the connections being established and dropped, X.25 call fails, X.25 line down, and X.25 lineup are logged on a daily rotating log file
Non-stop operation Yes, most configuration changes applied dynamically
Operating Systems support Windows XP Professional, Windows Server 2003,
Windows 2000 Professional, Windows 2000 Server,
Windows 2000 Advanced Server, Windows 2000 Datacenter Server
X.25 Card Specifications
X.25 cards supported See FarSync X25 Cards (PCI, PCI-X, PCIe, USB, PCMCIA)
Maximum X.25 lines 16 lines (4 x 4 port FarSync X.25 cards)
FarSync X.25 Feature Summary

Speeds up to 8 Mbits/s
Network Connectors: V.35, X.21, RS530, RS232C (V.24)
SVC and PVC logical connections
X.25 CCITT Compliance 1980, 84 and 88
Data packet size up to 4096 bytes
Reverse charging, Closed User Groups (CUG), Network User Identification (NUI), Fast Select, Throughput Class Negotiation
Built in remotely accessible Line Monitor
Compatible with all known X.25 networks including for example: Datex-P, BT X.25 Direct, Eirpac, Austpac, Transpac, Iberpac and Itapac

Information in this document is subject to change without notice.

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