ISDN v ADSL
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Joined: Aug 2000
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From: UK
ISDN v ADSL
Call me Mr Thicko, but I am not sure I understand the differences between ISDN and ADSL. I use ADSL at home, but at work we are trying to get onto a fast line for the web and linking several remote sites. I'm told that ISDN may be the way to go...
Any expert out there give me a simple run-down in lay terms?
Thanks guys.
Any expert out there give me a simple run-down in lay terms?
Thanks guys.
Ecce Homo! Loquitur...
Joined: Jul 2000
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From: Peripatetic
ADSL is asynchronous - the down link is much higher than the uplink. In an ADSL implementation, the bandwidth is divided into 255 subcarriers, each of which is nominally 4 kHz wide.
The first subcarrier channel is used for voice in native analog format. The upstream data generally runs in channels 7-32 and the downstream data in channels 33-250. Telephone companies restrict the bandwidth by restricting the channels. The maximum bandwidth is 1.536Mb downstream.
Normal BT transfer rates are upstream 256Kb and downstream 500Kbs, 1Mbs and 2Mbs depending on area availablility and price.
ISDN works in channels of 64k. It is synchronous with the same bandwidth each way. A standard home installation is one channel. For business use, additional channels can be added up to totals of 24 (T1 line - 1.544Mb); 96 (T2 line - 6.312 Mbps) or 672 (T3 line - 44.736Mb). T1 is known in Europe as E1 etc. You can go faster with T4, but that requires an optical connection.
T1/2/3 Lines are dedicated permanently on connections Each 64K channel can be configured to carry voice or data traffic.
Hence, if you get a T1 line you get a much higher uplink speed and the ability to run up to 24 separate data channels or to combine them as required.
ADSL is also limited to where it is available due to restrictions on the distance from the exchange, as you move further from the exchange the data rate falls till the service is not available at all. T1/2/3 transfer rates are not dependant on your physical location. This means that you always have the bandwidth you purchase no matter where your office is in relation to the exchange.
The first subcarrier channel is used for voice in native analog format. The upstream data generally runs in channels 7-32 and the downstream data in channels 33-250. Telephone companies restrict the bandwidth by restricting the channels. The maximum bandwidth is 1.536Mb downstream.
Normal BT transfer rates are upstream 256Kb and downstream 500Kbs, 1Mbs and 2Mbs depending on area availablility and price.
ISDN works in channels of 64k. It is synchronous with the same bandwidth each way. A standard home installation is one channel. For business use, additional channels can be added up to totals of 24 (T1 line - 1.544Mb); 96 (T2 line - 6.312 Mbps) or 672 (T3 line - 44.736Mb). T1 is known in Europe as E1 etc. You can go faster with T4, but that requires an optical connection.
T1/2/3 Lines are dedicated permanently on connections Each 64K channel can be configured to carry voice or data traffic.
Hence, if you get a T1 line you get a much higher uplink speed and the ability to run up to 24 separate data channels or to combine them as required.
ADSL is also limited to where it is available due to restrictions on the distance from the exchange, as you move further from the exchange the data rate falls till the service is not available at all. T1/2/3 transfer rates are not dependant on your physical location. This means that you always have the bandwidth you purchase no matter where your office is in relation to the exchange.
Last edited by ORAC; 9th July 2002 at 19:18.
