SDSL

SDSL (Synchronous Digital Subscriber Line) offers symmetric services at 0.5, 1 and 2Mb. Like ADSL it runs on a copper bearer circuit so speed degrades with distance from the exchange. This degradation is limited by restricting the maximum reach to about half that of ADSL. Installation lead times are typically 3-4 weeks and include the bearer circuit.

There are three distinctly different services on offer.

BT SDSL

Back in 2005, when 2Mb circuits were considered fast, BT committed to rollout the service to 1300 exchanges. High prices led to low market take-up so BT capped the rollout at 729 exchanges and that is still the extent of the service. It remains the most expensive and is only offered with 10:1 contention. BT have also indicated the service will be withdrawn by 2016.

LLU SDSL

Both Easynet and C&W offer uncontended (1:1) SDSL at a lower price point than BT so these are popular services. Easynet has enabled a little over 1000 exchanges and C&W a couple of hundred less. Not surprisingly many exchanges are served by both players so the total coverage will be around 1500 exchanges.

TTB SDSL(M)

Here we are into smoke ’n’ mirrors territory. TalkTalk Business have taken their ADSL2+ Annex M service with an up channel speed <2.5Mb and throttled the down channel speed to the same value thus creating a notionally 2Mb symmetrical service. This highly innovative service is offered uncontended (1:1) at a very reasonable £99 per month.