Thursday, May 15, 2008

What is DSL?

Time to Focus on some Telecommunications

Sure, we have all heard the term "DSL" thrown around and know that in some shape or form connects a user to the internet, but what does is stand for? What does it do? How does it work? In this entry, we are going over the very basics of DSL and how it provides businesses (and homes too) with internet connectivity.

Drum Roll please.... DSL stands for "Digital Subscriber Line"

Why Do You Need It?

Well, if you did not have it (or cable for that matter) you could not read this post or navigate anywhere on the internet. Thus, DSL is used to foster:

  • Connectivity for business networks
  • Transferring of files
  • Data gathering / Researching information
  • Connecting with the millions upon millions of other users all logged into the net

How it Works:
DSL is provisioned over the same copper pair (twisted pair) wire your voice line uses and provides continuous connectivity. Copper wire uses analog signaling (ie voice conversations) and initially when the idea was thought up to run data over the lines, a modem was born.

A modem transmits the analog signal from the line into a digital transmission, carries it over the network, and translates it back into an analog signal. As a result, this only allowed bandwidth of up to 56kbps (kilo-bits per second). Now, as we are all well aware, 56kbps in this world is slower than watching a rock move. Cell phones have faster connectivity now. Thus, emerged DSL technology.

With Digital Subscriber Lines, there is no need to convert analog transmissions into digital signals and then back to analog. The information starts off as digital, which boasts a tremendous increase in bandwidth capabilities. In the Southeast, for example, DSL is available up to 6.0Mbps (mega bits per second). That is a HUGE boost!

Also, in the age of 56k modems, either you were on the internet or on the phone. They could not occur simultaneously. With DSL, both voice and internet connectivity occur on the same line, thus reducing costs.

Types of DSL
There is one main type of DSL. I am going to leave the others alone because the majority of users do not use them.

Asymmetrical Digital Subscriber Lines (ADSL) is geared towards homes and small businesses because of the bandwidth breakdowns. Since most users download information from the internet more than upload (i.e. every time you go to a website, you download rich graphics, text, etc etc or download music/movies) you require bandwidth. As a result, engineers were able to design DSL to give you more download speed. This is because typical users upload a lot less (i.e. send emails, upload files etc).

However, if your business demands a lot of upload bandwidth, you would need a symmetrical DSL (SDSL), but if that is the case, an internet T-1 circuit would be the best option and we will discuss T-1s at a later date.

Things to Consider

  • DSL is distance sensitive, so the further away the business is away from the Telecom. Provider's Central Office , the slower the connection. Thus, the users closest to the COs benefit from the fastest speeds.
  • DSL has its own line. A business does not share it with anyone except those on the network. Whereas with cable, everyone in a "neighborhood" shares one big pipe. So, come 3:00pm when the kids come home, the cable network will slow down.

Why DSL may not be for You

  • Like I mentioned above, distance plays a factor. As a result, if a business requires a lot of bandwidth and is not ready for the investment in a T-1, they will be out of luck.
  • It's not available everywhere. Some central offices are not capable or, once again, distance plays a factor
  • Faster receiving than sending of information
  • Copper Line Quality. If the copper wires are really old, quality may suffer.

Why DSL is for You
  • Always On. DSL is always on and always ready to surf. A business never has to log-on or off.
  • Voice calls come in on the same line, so you do not have to buy a line just for internet connectivity.
  • Most of the time, there is no need for additional wiring
  • Service Providers usually supply the modem/router.

Overall, the creation of DSL allowed a lot of business to have internet connectivity and not have to buy all new equipment or wiring. All that really has to occur is the purchase of a router and informing your service provider you need connectivity. While there are some downsides to DSL and of course the great debate of cable vs. DSL (another time, I don't have the strength), DSL is a sound investment that provides businesses with basic reliable internet connectivity.

Side Notes:
I want to leave you with some general terms.
DSLAM: Digital Subscriber Line Access Multiplier - This device inter-connects all the individual DSL lines in an area and transports them into one big pipe to the high speed backbone which provides gigs upon gigs of bandwidth which keeps the network flowing. Whereas cable providers give "sectors" one big pipe and everyone shares it.
Filters: Filters block signals above certain frequencies so the voice and data transmissions are not interfered with and cause problems. So, if you hear static on the lines, sometimes it is because the filter needs to be replaced.

~the GURU

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