Internet Connectivity

Working with partner ISP Mistral, ITD can provide you with ADSL, SDSL or Leased Line internet connections. We will work out what sort of connection is best for you and provide it at an affordable and competitive price.

Contention Ratios

When choosing an ADSL or SDSL line, it is important to check what contention ratio there may be on this line. Although the line may ostensibly facilitate 8Mb download speed, if it has a contention ratio of 50:1, this means that up to 50 other users could use that line at the same time, reducing the speed from 8Mb to 160kb!

Which line to choose?

ADSL lines are not guaranteed and do not have Service Level Agreements (SLAs), they are also contended at either 50:1 or 20:1 ratios. Depending on your location, you may be able to access download speeds of up to 8Mb, however, due to infrastructure limitations, this is often as low as 3Mb before taking into account contention. Upload speeds tend to be limited to 256kb.

SDSL lines may be contended but can be un-contended. They are also subject to SLAs which mean that they are less likely to fail and if they do, their service will generally be brought back much quicker than with ADSL – as one might expect there is a price premium to pay for this. SDSL lines may have the same download as upload speeds and this can be important if a significant amount of two-way traffic is required.

Leased Lines offer the fasted line speeds and are un-contended. Download speeds are the same as upload. They have the most demanding SLAs and are least likely to fail. They are generally required where a significant amount of traffic is required such as where video conferencing or VOIP is used or where it is considered that the extra cost of such a line is worth the improved quality of service.

An ADSL line is often used in tandem with a Leased Line as a Failover, so that if the Leased Line fails, the traffic is automatically transferred to the ADSL line without any noticeable interruption and then when the original service is resumed, the ADSL fails back to the Leased Line automatically.