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What you need to know about ADSL

When shopping around for connectivity services, price is often a major concern. “How can we best maximise the potential of our service while minimising any costs?” Under this line of reasoning, services such as ADSL (Asymmetrical Digital Subscriber Line) may seem very attractive, with speeds up to 24Mb download and a 1Mb upload. However, it is important to understand that lower end prices often mean lower end services, and the limitations of these services is something to consider before committing to any network solutions for your business.

How ADSL works

ADSL is usually sold by a carrier, such as Telstra or AAPT as a service. This service is usually provisioned on a public switched telephone network number or PSTN. PSTNs are essentially the physical copper based phone lines that are ubiquitous worldwide as the widest and most basic method for long distance communication. Like the basic dial-up services that came before it, ADSL allows for the user to run a connection to either the Internet or other network over the PSTN. Where the ADSL has its advantage lies in the fact that it can run simultaneously with a normal phone service, unlike dial up services.

Sounds like a pretty amazing alternative to a more expensive service, doesn’t it? Not only can you reuse a phone line that is likely already present and available at the location, but it’s low cost and ubiquity guarantees that it will be available in most locations. These are all very good points which reflect just how important ADSL is as a technology.

It is important that any IT manager carefully considers their own requirements before committing to any decision. ADSL offers many advantages that are immediately apparent to the prospective user, but hides a few very severe disadvantages that are not apparent until after the service has been qualified, ordered and provisioned.

Speed not guaranteed

Most standard ADSL services (essentially the cheapest ones you can find) are often advertised as being “up to” a certain speed. This use of language is very deliberate, and is meant to indicate that while many ADSL services are indeed capable of reaching the maximum speed they are available to (24Mbps download, 1Mbps upload), various conditions like distance from the local exchange, quality of local telecommunications infrastructure and many others can adversely affect the service’s speed. The provider will only guarantee that an ADSL service will perform up to a certain (and much lower than the maximum) speed. If this can be considered a major problem, than it is recommended you look into more premium ADSL services with included PSTNs and guaranteed speeds from the provider.

Not All PSTNs are made the same

As noted before, ADSL services can be, and often are run simultaneously over a PSTN with a standard phone service. However, the quality of the phone service requires much less in terms of good infrastructure/short distance from the exchange than any ADSL services. While most providers are happy to check ADSL services to ensure that they are functioning properly according to their individual Service Level Agreements, they often do not guarantee the PSTN will be capable of supporting a good, or even decent, ADSL service. This is a common issue when it comes to telecommunications. Often a network solution is a combination of many different services, and not all of them can be considered “premium” or attract the additional level of quality that the name provides.

Downtime and SLAs

ADSL services are ubiquitous within the residential market. As the cheapest and most available broadband connectivity option, it can be found in households across Australia. Unfortunately, this means that ADSL services often suffer from a myriad of issues that do not affect other, more premium service types such as Ethernet over Fibre or Ethernet over Copper. ADSL is often a contended service, which means that the busier the neighbourhood becomes, the more adversely the speed and performance of the ADSL connection will become. ADSL services are also some of the least supported in the industry when it comes to Service Level Agreements (SLAs) and responses to downtime. What you don’t end up paying for as part of the bill, you will pay for in potentially slow or negatively impacted performance, downtime, and lack of support responsiveness in relation to more premium service types. These issues can be mitigated by purchasing premium ADSL services or Ethernet over Copper services which are more expensive but include dedicated SLAs and their own dedicated copper lines.

What to take home from this article

Essentially, it is the job of any good IT manager to ensure that they get the best bang for their buck when it comes to IT services. Budget can be and often is a major focus during all steps of designing and provision a new network connectivity solution. But the key is to know the limitations of the technology you seek to implement. While cheap, ubiquitous and often at times appropriate for remote sites with few staff, ADSL will not provide a complete best-practice business solution. It is often employed for remote teleworkers and as  a cost effective failover for more premium services, ensuring that in the event that an unexpected outage limit or disable connectivity there will be an inexpensive backup service prepared to take over.