BACKBONE NETWORKS

Table of Contents  INTRODUCTION  ATM BACKBONE*  SDH BACKBONE  IP BACKBONE*

* to be released

• INTRODUCTION

 

A backbone network is the focal point where all the traffic carried in the access networks converges to be switched and routed to the proper destination.

It is a vital link in the networking chain that requires

• Reliability and Availability: essential feature since all the communications would break down if the backbone fails. This implies usually a mesh network with redundant paths and to some extent redundant equipments
• Performance and Scalibility: the backbone must have a much greater bandwidth than the access networks feeders. It means higher speed transmission channels but also low latency backbone equipments. It must also be easily scalable to provide increasing bandwidth as traffic grows.
• Connectivity: Any user shall be able to communicate with any other one, with its own protocol and media communication particularities
• Network Cost Optimization to structure and combine the traffic flows (with different quality of Service requirements) in order to minimize the backbone costs and still provide a satisfactory service quality to the different users (an ever-lasting challenge)
• Monitoring and Control of the network (Network Management) to detect and rapidly correct failures, but also to anticipate traffic bottlenecks and reoptimize the network
• Privacy and Safety: the backbone must be safe and be protected against malicious attacks
The above requirements usually will lead to different backbone networks with different architectures. The critical network design parameters are:
• The size of the network, in terms of number of users and their required bandwidth
• The geographical dispersion: LAN, MAN, WAN
• The communication media: data, voice, video and multimedia
• The dependence of the network in the user business ("on line" Trade exchange)
 

Nevertheless those different customized networks resort more or less to the same basic backbone technologies that will be presented in this chapter. They can be ordered in a multilayered architecture represented below for the LAN et the WAN (similarities are obvious) with :

• transmission at the Physical layer
• switching at the layers 2 & 3


THE "NETBURGER"

Figure notes:
- The dotted lines represent progressively obsolete connections, the full ones the currently used connections, the multi lines the future.
- The arrow lines represent the LAN & WAN interconnections

Focus will be on the most promising technologies for the future. Will be reviewed:

• The digital SDH or SONET transmission Backbone that provides the transmission digital links used to interconnect the Service backbones
• The Service switching backbones providing specific communication services to the user:
• X25 and Frame Relay for data services mainly, voice over data with Frame Relay
• ATM for high-speed data and multimedia services
• IP for TCP/IP ("Client-Server") and Internet services.
So take the thread and start with the SDH Backbone