Technical Spec´s X.25 Mini-Gateway to TCP/IP Migration*

© Farsite Communication Ltd. • 2012


The FarLinX Mini Gateway is the smallest member of the FarLinX Gateway range - it can handle your smaller scale single X.25 line to TCP/IP migration requirements. It offers many of the same features as in the larger FarLinX X25 Gateway range but at a lower price and in a more compact enclosure. The Gateway supports XOT to X.25 switching, X.25 to TCP data translation and connection routing, TCP to XOT, a Triple-X PAD, and a Host PAD. All this is easily managed from your browser. There are also daily activity logs with a selectable level of detail, automatically archived on a daily basis. The SNMP support provides alerts for a numerous different conditions including critical events such as line down and line up.

The more powerful FarLinX X25 Gateway range is more suitable where multiple and faster X.25 lines are used.

Key Features

        • TCP to X.25 data translation with a very wide variety of modes including: character streaming,
          RFC1006, Cisco RBP, APACS, ISO 8583, header stripping and parity conversion and many more
        • TCP ↔ X.25 and TCP ↔ XOT routing including: fixed routes, dynamic routing and PAD routing
        • Call routing between XOT (X.25 over TCP/IP) and the X.25 line
        • X.28 PAD option supporting Telnet and an async connection
        • X.25 Host PAD emulation support
        • LAN accessible X.25 line as a sharable remotely manageable resource
        • Choice of X.25 network interface connections: RS232 (V.24), V.35, RS422, RS530, X.21
        • 400 messages per second and up to 50 simultaneous connections (PVC, SVC)
        • Line Monitor (local or remote) to view X.25 traffic for easy network problem diagnosis
        • Optional support for TCP/IP authentication and data security using IPSEC
        • Browser graphical configuration, SNMP alerts for critical events and activity logging
        • Real time display of current connections, line performance, errors, connections and much more
          Small rugged low profile all metal case, low power consumption

Typical Applications

        • Reduce line costs by replacing expensive X.25 lines with a TCP/IP connection and conversion to X.25 at each terminating node
        • Conversion of legacy X.25 connections and data for transfer over a TCP/IP network
        • POS Gateway to allow TCP/IP and X.25 based Point of Sale systems to interoperate
        • Replacing an X.28 PAD over X.25 with an X.28 PAD over XOT
        • FTAM or X.400 operation between TCP/IP and X.25
        • Conversation from TCP to XOT eliminating the need for X.25 at that location
        • LAN accessible and sharable X.25 port resource

Functional Overview - XOT and X.25 Switching

The FarLinX Mini Gateway provides a reliable means of routing connections between X.25 and XOT (X.25 over TCP/ IP). Connections can be routed between X.25/X.28 and XOT which is treated as another connection path. The connection routing module supports default routes, hunt groups, X.25 address translation, and routing commands with NUA wildcards for maximum flexibility.

Up to 50 SVC or PVC sessions can be handled simultaneously over XOT and the X.25 line.


This configuration shows a complete X.25 network simulated by FarLinX Mini Gateway's
running XOT over an IP network (4 X.25 lines in this example but could be hundreds or thousands).
This allows complete X.25 networks to be replaced while leaving hosts connected by X.25 to that network undisturbed.

Functional Overview - data packetization and routing between TCP and X.25 or XOT

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 or XOT connected hosts. The Gateway provides routing facilities to select the appropriate Host from those available and maintains X.25 or XOT sessions to the Host as required.

Up to 50 SVC or PVC sessions can be handled simultaneously between TCP/IP and X.25 or XOT.


Example network configuration using the FarLinX Mini Gateway to interlink the TCP/IP and X.25 networks

TCP to X.25 or XOT data translation functions

The Gateway supports a wide range of TCP to X.25 or XOT 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 / XOT connection
        • POS protocols APACS, ISO 8583, HGEPOS plus CTL (Card Tech Ltd) - Requires the POS Firmware Option

Connection Routing and Address Mapping

The FarLinX Mini Gateway can support routes to hundreds of different X.25 / XOT hosts. Similarly, when using the called X.25 address as the routing key, incoming X.25 / XOT calls can be routed to hundreds of different TCP/IP hosts.
When making connections to the X.25 network or XOT, the Gateway has the capability of mapping the source IP address to a calling X.25 address, thus allowing the destination X.25 / XOT host to identify the connection source uniquely.
The Dynamic routing options allow the X.25 address (NUA) and call parameters to be set by the remote application at the time each X.25 / XOT connection is established. These modes allow X.25 packetisation information to be passed to the application. Linux and Windows sample applications provided.
The main modes supported include:

        • Statically defined routing
        • XDRPD (eXtended Dynamic Routing Packetized Data) and DRPD - these formats allow TCP connected applications to dynamically setup and control the X.25 or XOT 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

Functional Overview - PAD Features

X.28 Host Pad

The FarLinX Mini Gateway can be configured to act as an X.28 host PAD for a remote terminals or applications connecting over X.25 and expecting a host that supports X.28. The host PAD sends X.28 PAD configuration commands over X.25 to the connecting terminals. The host PAD profile is configurable.

X.28 Triple-X PAD

Triple-X PAD (X.28, X.3 and X.29) support is included with the Gateway, accessible over TCP/IP via Telnet or using the single permanent async port. The connecting terminal is presented with a Triple-X PAD service and can be used to make X.25 connections over the physical X.25 line(s) or via XOT connections to remote hosts. The initial PAD profiles for each async port and for the Telnet access are fully configurable.

Encryption over TCP/IP (IPSEC)

Available as an option at the time of ordering, the FarLinX Mini Gateway can be supplied with an IPSEC capability that can provide communications security in IP networks. It can be especially important when public Internet connections are used for part of the communications path.

IPSEC operates between a pair of devices. Each must know details of the remote device in order to authenticate communications and successfully encrypt/decrypt data being sent and received. In the FarLinX Mini Gateway, the details of multiple partner Gateways can be configured. The pre-shared key used to authenticate is unique for each remote partner. Once authentication has completed an exchange of encryption keys takes place under the pre-shared key. The session key is used only for a single session.

FarLinX Gateway models without IPSEC can be supplied to any country. Models with IPSEC capability can be exported without a special export licence to some countries. Where IPSEC is required and the destination country is not on the pre-approved list, FarSite will apply for an export license for that customer.

Statistics, Event Logging and SNMP


The gateway maintains a comprehensive set of statistics and activity counts. This information can be used to indicate the total loads on the Gateway and also to give early warning of line performance problems and even misconfigured systems elsewhere in the network.


All connections setup through the Gateway can be logged. The logs are automatically saved on a daily basis, old logs can be displayed as required. Log events can also be routed to syslog to allow logging centrally.

The connection status of active connections / most recent connections / disconnections are displayed in a browser window.


The Gateway supports SNMP alerts with 3 configurable levels. Alerts can be issued for SVCs connecting and disconnecting, PVC errors, connection routing errors, line up and line down events and many more events.

Built in X.25 Line Monitor

The Gateway includes on the CD Line Monitor software installable on a PC that allow the X.25 traffic to be recorded and displayed in real time. Multiple Gateways can be monitored simultaneously. Support to allow the popular Wireshark line monitor to record and display the X.25, TCP/IP and XOT line traffic is also included.

Line Monitor showing a trace of an X.25 line

This very useful feature allows Network Managers and System Installers to locally or remotely analyse and rapidly diagnose problems that may occur on the X.25 lines without the need for expensive external line monitors.

The line traces can be saved and viewed later, for example in a customer support situation.


The Gateway is configured from a Browser, IE, Firefox and Chrome are all supported. Access to the configuration is secured through a user name and password.

The Configuration Application allows all the features of the Gateway to be managed. The majority of configuration changes to the Gateway are made dynamically so continuous operation of the Gateway can be maintained.

Configurations can be saved for later use.

System Upgrades

Upgrades to the firmware can be remotely and securely uploaded to the device to allow the latest revision firmware to be used. Rollback to a previous version is supported.

Technical Specifications

XOT <-> X.25   connection routing

PVCs and SVCs; SVC routing is flexible with support for wild-cards and address translation

TCP/IP <-> XOT connection routing

PVCs and SVCs; SVC routing is flexible with support for wild-cards and address translation

TCP <-> X.25 / XOT call routing modes

Statically defined routing, Dynamically configured routing, PAD Routing, X.25 data switching

Data packetization

Includes Customisable Message Header Conversion, Cisco RBP, RFC-1006 and packetisation of messages terminated by specific characters (ETX, Carriage Return etc), X.25 parity conversion

POS Protocols

Optional software upgrade to support Point of Sale protocols APACS, ISO 8583, HGEPOS and CTL (Card Tech Ltd)

X.28 PAD

X.28 Host PAD and X.28   PAD terminal support. PAD support is available through Telnet and the built in async port.

Secure connections over TCP/IP

IPSEC option selectable for support of authenticated and encrypted data connectivity over TCP/IP

Data packets per second

Up to 400 messages per second

Maximum connections

Up to 50, can be any mix of SVCs and PVCs

Logging key events

Events log maintained for events such as the connections and disconnections, X.25 call failures, X.25 line down, and X.25 line up. Log auto archived daily. The most recent events are displayed in real time on a scrolling display in the Browser. Can be routed to syslog for remote logging

Line Monitor

Line monitor application included for display of frames and packets on X.25 connections, can be run locally or remotely. Wireshark supported.


Securely configured by a Browser and Java applets using XML, login required. Configurations can be saved.

SNMP Alerts

Configurable levels, generated for events such as X.25 line down, X.25 line up, connections established and disconnections and gateway failures (when in dual operation).


Statistics provided for line activity, line errors, protocol problem, Gateway activity. Resetable on demand.

X.25 network connectors

Connections for RS232   (V.24), X.21, V.35 and, RS530 (RS422) available.
  Line speeds up to 64Kbits/s; internal and external generated line clocks.
  X.25 network cables are ordered separately.

Types of X.25 connection

X.25 network, leased   (fixed) line

Types of PAD connection

Async lines, Telnet

X.25 feature summary

Data packet size up to 4096 bytes
SVC and PVC logical connections
X.25 CCITT Compliance 1980, 84 and 88
DCE and DTE operation
Reverse charging, Closed User Groups (CUG), Network User Identification (NUI), Fast Select, Throughput Class Negotiation
Hunt groups, backup lines
Compatible with all known public and private X.25 networks

XOT Specification

Complies with RFC 1613 - X.25 over TCP (XOT)


10/100 BaseT LAN port, RJ45.


CE:   EN55022:2006+A1:2007, EN55024:1998+A1:2001+A2:2003, EN61000-3-2:2006, EN61000-3-3:1995+A1:2001:A2:2005. FCC part 15. UL. Safety: EN 60950-1: 2006. RoHS compliant.

Power Requirements

100vac to 240vac, 50/60 Hz, 6 Watts.


Solid state design, all metal case, software selectable power down. Reset to factory defaults switch.
Dimensions: metric - 170(W) x 158(D) x 34(H) mm, imperial - 6.7”(W) x 6.2”(D)   x 1.4"(H)
Weight: 0.57 kg (1.25 lbs).
Operating Temperature range: 5 to 40°C (41 to 104°F), Humidity: 20% to 95% RH   (non-condensing)
Storage Temperature range: 0 to 70°C (32 to 158°F), Humidity: 5% to 95% RH   (non-condensing)

Warranty period

2 years

* All specifications are subject to change