ADSL- comes under circuit or packet switching?

[swaminathan]

Hi

I found that ADSL is packet switching type of communictaion. Definition for circuit switching is
"A type of communications in which a dedicated (http://www.webopedia.com/TERM/D/dedicated.html) channel (http://www.webopedia.com/TERM/C/channel.html) (or circuit) is established for the duration of a transmission."

In practical, telco line connects to the ADSL modem/router through which we are communicating to internet.In this context I have some doubt.The telco line which is connected to our ADSL modem is not shared with any other device ,connects only to the CO of the telco where we get the internet connection.That means the line which connects to the modem is dedicated upto CO.then it becomes circuit switching or not upto the CO .

Anybody please explain?

[Big Evil]

Quotes from two of the best engineer out there in the world.


DSL is a technology based on the fact that copper cable can carry high frequencies a few miles. These frequencies are broken it 4K ranges. These 4K ranges are collected together to form a UP and a DOWN. The copper starts at a common point and radiates out. They discovered they had cross over at the common point so they could send a large bandwidth of data but only receive a small amount. Furthermore the odd 4K block would be unusable due to the physically nature of the copper. They found they could get about 10Mb down the copper. I must admit I could not see much use for it and I was more focused on downloading videos over ISDN-2. to my retail estate. Then one day a thing called the Internet became popular which required little upload and large download. In the UK the ADSL line connects to a router and at the other end a DSL Access Module (DSLAM). Basically you run ATM from you router to the DSLAM and that ATM is carried back to the ISP. ATM has the concept of virtual circuit and virtual path. Many circuits can take one path. ATM consists of 53 byte cells which are switched through an ATM network but the virtual circuit has to be established first so it similar to the normal telephone network. So theoretically your router could have many virtual circuits connecting to many ISPs. Time moves on and ADSL2+ can get rates upto 24Mb. Furthermore Telco use DSL to provide E1 or 2Mb series in Europe. So yes it is circuit based and it does use a copper pair. I hope that helps rather than confuses.




To expand a little on top of what Conwyn outlines there... The ATM portion would tend to be more a circuit-switched approach, but many vendors have a PPPoA or PPPoE implementation, which eventually makes it more like packet switching with some underlying circuit switching stuff in the middle.


Confused enough? Yeah, well, sometimes things can't be simply explained by one particular title!