ISDN and ISP's

[tekboy]

This is a stupid question but I now just about nothing when it comes to ISDN. Can you connect to any ISP over an ISDN line using the same number that a regular analog modem would dial, or does the ISP need to support ISDN?

[desmocat]

No, an ISDN connection is a digital loop whereas dial up is analog. You have a SPID,(service profile identification number)for each B channel on an ISDN loop. The basic loop is a BRI, (basic rate interface)which consists of 2 B channels@64Kbps(data)and 1 D channel @ 16kbps for call setup and signaling.
The switch at your telco's CO has to be ISDN capable (most are) and that is what you connect to.
Call setup is much faster with ISDN, along the lines of 1 to 2 seconds, quite a bit faster than dial up, because the switch and your ISDN t/a don't have to do all the handshaking and negotiation that modems do, because by entering some configuration info when you set up your T/A(terminal adapter, the ISDN "modem")the switch already knows who it is and where its going so it doesn't have to do a lot of work to put the call through.
And yes,the ISP has to support ISDN on their end also.


[This message has been edited by desmocat (edited 08-29-2001).]