X.25 Packet Switching Networks

Course Overview

X.25 is one of the most stable and mature IT Wide Area Nework technologies. Offering potential savings over long diastance dial up modem, or ISDN connections, yet offering the same addressable flexibility, X.25 is one of the most widely proliferated connection oriented global WAN systems.

X.25 is widely used in sectors such as the tavel and finance industries, and finds widespread use in both public data networks and corporate networks.

This course provides an essential coverage of X.25 networking technology markets, systems, and operation. It also covers X.25 network troubleshooting techniques, and provides an objective discussion of the applications that are typically served by X.25, and its future uses.

Audience

This course is essential for all staff who will install, configure, administrate, support, sell, or market X.25 networking products services, or solutions.

Prerequisites

Delegates must have a good understanding of data communications principles, prior to attending. Course 301: Introduction To Data Communications and Networking, is recommended.

Course Outline

Introduction

• Development of the OSI concept and the OSI 7 Layer Model
• Structure of the 7 Layer model
• Positioning X.25 within the model

X.25 Layer 1 scope and operation

• X.21, X.21 bis V.24, X.21 bis V.35, RS232, RS 449

X.25 Layer 2 scope, features and facilities and operation

• Requirements of a link level protocol
• LAPB frame format
• Link initialisation and shut down procedures
• Errored frame detection
• Errored frame recovery
• Link assurance facilities
• Link level timers

X.25 Layer 3 scope, features, facilities and operation

• Function of layer 3 protocols
• Packet Assembly/Disassembly
• Packet encapsulation
• The packet header
• Logical channels and virtual circuits
• Network user addresses
• Call set up and clear packet types
• Cause and diagnostic codes
• Data and supervisory packets
• Delivery confirmation
• The D BIT
• Layer 3 flow control
• Extended mode numbering

Advanced Layer 3 facilities

• Call facilities: reverse charging, fast select types, throughput class, packet and window size negotiation, closed user groups, source rotatry hunting and call diversion
• Packet segmentation
• The M BIT
• Level 3 timers

Associated PAD protocols

• X.3, X.28, and X.29 operation

Packet Switched Network Management

• OSI network management model
• X.25 key indicators
• X.25 troubleshooting techniques and protocol analysers

X.25 Network sizing and design

• Assessing user throughput requirements
• Switch and trunk sizing
• Building in resilience
• Diverse routing
• Internetworking with other X.25 networks
• Requirements of gateway switches
• Providing address translation with the user data field
• Internetworking with non X.25 networks: TCP/IP, Ethernet, ISDN, Frame Relay, and ATM

X.25 Case Study

X.25 The future

• The future of X.25 as a global technology, and how it compares with systems such as Frame Relay, ISDN, ATM and the Internet.