Impact of broadband standards

Date: 2015-10-07; view: 404.

As an ISO layer 1 transport standard, intended for building the PTO's backbone transmission networks, SDH currently has no real rivals. The nearest thing to a competitor that has emerged so far is Asynchronous Transfer Mode (ATM), and its adoption was strongly favoured by several European PTOs. However, ATM, as with most of the other popular broadband standards comes under the heading of 'Fast Packet' technologies. As with all packet transfer techniques, it tends to be better at transporting bursts of traffic, rather than the largely constant traffic load presented by the PSTN. On top of this, ATM is a standard that is really aimed at the problem of rationalising the switching machines required for the complete range of telecom services, rather than producing a bedrock transport network. In theory, it is capable of doing this, but at present, commercial implementations of ATM switches are thought to be at least five years away. In the meantime, SDH equipment will be deployed to such an extent that it will be impossible to dislodge it from its position as the workhorse of all PTO transport networks. ATM switches, when they are introduced, will appear to the SDH network as yet one more client service which needs SDH transmission bandwidth allocated to it. As the operational problems of running a cell based service are progressively overcome, we can expect an increasingly proportion of the SDH transmission network capacity to be routed to these ATM switches.

Besides ATM, there are several other Fast Packet techniques that have been proposed, which are either already available, or promised soon. They are all aimed at satisfying the business communities requirements for wide area data transmission, and, in particular, the burgeoning requirement for LAN interconnect. In view of what was said in Section 42.1 about the needs of business customers driving PTOs to install SDH networks, it is essential to determine whether the introduction of these other techniques will render SDH super­fluous