DSL
Digital Subscriber Line (DSL) technology enables existing copper exchange lines to be used for high-speed data connectivity. There are two main types of DSL services currently available; both can be used for either public Internet access or virtual private network (VPN) access.
Asymmetrical Digital Subscriber Line (ADSL)
This provides up to 8128kb download speed with an upload speed of up to 448kb (a premium product can provide an upstream rate of up to 832kb). This service is ideal for home users or small offices primarily browsing the web, or small/remote offices in the corporate network that will download more information than they upload.
Synchronous Digital Subscriber Line (SDSL)
This provides a full-duplex link of up to 2Mb, primarily for business users who have a lot of traffic in both directions. Applications such as IP Video conferencing or VoIP will sometimes require this type of link.
In each case the user's connection to the local exchange will be guaranteed bandwidth at the specified rate. After this, traffic will be subject to contention with other user's traffic (although still logically separate and secure). Different services are available with varying levels of contention, including fully guaranteed (or 'uncontended') bandwidth.
Typically, when traffic levels are 'bursty', with many peaks and troughs throughout the day, contended services are acceptable because different customers peak at different times. These types of traffic profiles also tend to be highly asymmetric, so ideally suited to ADSL connections. Every customer is different and there is no hard and fast rule.
Highly sensitive real-time applications such as VoIP and IP video conferencing, on the other hand, tend to require services with lower contention or no contention at all. Given that these applications also usually require the same speed in both directions, lower contention ratios tend to be more commonly supplied with
SDSL connections.
Claranet sources DSL connectivity from a wide variety of wholesale suppliers, using both BT wholesale and other LLU (Local Loop Unbundling) partners. This enables us to provide a wide variety of speeds and contention ratios.