In March 1976, Study Group VII of the CCITT adopted Recommendation X.25. Since that time, X.25 has become the cornerstone for achieving interoperability over wide-area networks.

UconX Corporation's X.25 product, UconX.25, is designed for execution in a client-server environment. With UconX.25, the entire X.25 protocol stack runs on the UconX family of LAN-based, multi-protocol communication servers. The UconX server attaches to your local area network to provide wide-area connectivity for all clients on the LAN.

UconX also supports UconX.25 on a variety of high-speed SBus, VMEbus and PCI intelligent communication controllers.

A single server or controller can support X.25 operation on multiple serial links. Or, you can run other UconX protocols, such as HDLC ABM or Asynchronous Data Transfer, on some links and X.25 on others.

Features.

• Adapted from and compatible with SpiderX.25 from Spider Systems Limited. SpiderX.25 has been certified on twenty public data networks worldwide.
• CCITT X.25 ('80), X.25 ('84) and X.25 ('88) Level III.
• CCITT X.25 ('80), X.25 ('84) and X.25 ('88) Level II.
• ISO 8208 support for DTE-DTE operation.
• ISO 7776 support for X.25 LAPB compatible data link procedures.
• Supports reverse charging, RPOA selection, flow control parameter negotiation, CUG selection, throughput class negotiation and fast select on a per call basis.
• Supports extended packet sequence numbering, non-standard default window sizes and non-standard packet sizes.
• Supports multiple serial lines (subnetworks) which are independently configurable for baud rate, clock source, frame size, timeouts and more.
• Other UconX protocols can run on the same platform, simultaneously with X.25.
• Client software in source form includes an Application Programming Interface (API), network library routines, databases and utilities to facilitate startup, configuration, tuning, testing, monitoring and operation of X.25.
• For embedded communication controllers, a host device driver is included, in source form.
• Line monitor diagnostic feature can be used to display all frames transmitted and received on any serial line.l

Client API.

UconX.25 includes a simple, easy-to-use API to protocol software running on a LAN-based server or communication controller. The API provides a standard interface to the TCP/IP software or host driver. This makes application programs easily portable among client operating systems as well as the various UconX server and embedded controller platforms.

X.25 Packet Layer Protocol.

The UconX.25 Level III Packet Layer Protocol (PLP) provides reliable packet-switching connections for client applications. It is compliant with CCITT 1980, 1984 and 1988 X.25 Recommendations. Basic (modulo 8) and extended (modulo 128) packet sequence numbering are supported. UconX.25 provides Connection-oriented Network Service (CONS) as described in ISO 8348 and 8878; and DTE-DTE operation according to ISO 8208. Both Virtual Call (VC) and Permanent Virtual Circuit (PVC) services are supported while facility handling is provided on a per-call basis. Comprehensive mechanisms are supplied for X.25 configuration and tuning.

UconX.25 supports the Spider Systems proprietary Network Layer Interface (NLI) for use by applications when accessing the PLP. The NLI is a set of structures that specify requests and associated parameters to be acted on by the PLP. NLI messages are sent to and received from the PLP using the UconX API.

Link Layer Protocol.

The UconX.25 Level II interface (HDLC LAPB) conforms to CCITT LAPB 1980, 1984 and 1988 recommendations. The X.25 LAPB-compatible DTE data link procedures are supported in accordance with ISO 7776. UconX.25 provides both modulo 8 and modulo 128 frame sequence numbering.

Client Configuration Utilities.

Client utilities are included to allow easy configuration of your X.25 network. You create ASCII text files containing parameter values for each level of the protocol, and you can have separate files for each subnetwork if you need to configure them differently. One central configuration utility directs the entire initialization procedure, automatically calling the other utilities as needed.

The following parameters can be configured:

• Network protocol type X.25 version ('80, '84, '88).
• DCE/DTE/DXE.
• Range of PVCs.
• Ranges of two-way, one-way incoming, two-way incoming and one-way outgoing logical channels.
• Modulo 8 or 128 sequence numbering.
• Default and maximum negotiable packet sizes.
• Default and maximum negotiable X.25 window sizes.
• Maximum concatenation of received data packets with "more data" flag set.
• Maximum acknowledgement delay.
• Values for T20 - T26, R20, R22 and R23.
• Throughput class Quality of Service parameter ranges.
• Subscription to Closed User Groups, extended call packets, fast select, local charging prevention, reverse charging, TOA/NPI Address Format, NUI override, Diagnostic packet support.
• Bar window- and packet-size negotiation, incoming or outgoing calls, calls with TOA/NPI Address Format.
• Values for N2 and T1.
• Expected time to receive a response with F-bit set.
• Expected time to receive a reply to REJ.
• Time to wait for a busy condition to clear.
• Time to wait for a PDU.
• Time to wait before transmitting a delayed RR.
• Maximum number of I PDUs received before sending RR.
• Maximum number of unacknowledged I PDUs to send.
• Window position at which to send PDU with P-bit set.
• Maximum size of LAPB I frame.
• Ignore UA frames in ERROR state.
• Retransmit frame reject on receipt of frame reject in ERROR state.
• Transmit frame reject when invalid frame response received in ERROR state.
• Send frame reject if S-frame received without P-bit set.
• Send DM on entry to ADM state after N2 expiration.
• Maximum frame size.
• Line speed or external clocking.
• Address translation for interface class.

Client Statistical Utility.

UconX.25 includes a statistical utility that displays, in easy-to-read format, various level II and level III protocol statistics for a particular subnetwork. (For example, calls established, SABMs received, good frames sent and received.)

Client Databases.

A group of client databases can be set up to make accessing your X.25 network easier. These databases contain such information as calling addresses for each subnetwork, host names and aliases, and network user identifiers. A network subroutine library is also included to provide access to the databases as well as other useful functions.

Line Monitor.

The UconX.25 product includes a unique Line Monitor feature that can be used at any time for diagnostic purposes. To use this feature, an application program on a client system opens a special connection to X.25 and specifies a serial link to be monitored. The protocol software records each frame as it is transmitted and received on the link, and sends the information to the client application. UconX supplies a sample monitor application which displays the received information in an easy-to-read format.

The information supplied for each X.25 frame includes direction (transmit or receive), frame type, address, and state of the Poll/Final bit. Depending on the frame type, sequence numbers and size of information field may also be displayed.

The first time you attempt to establish a connection to a remote site, or any time you need to analyze problems with a particular connection, you can use this feature--instead of an expensive protocol analyzer.

Ordering Information: For more information or to place an order, please contact Joseph Dohn at (619) 627-1700 or email us at sales@uconx.com . For technical questions about our products, please email us at tech@uconx.com .