ISDN Protocols and Standards

Having looked at the various codes used to describe ISDN equipment and references, now is a good time to get the remaining codes out of the way – those associated with ISDN protocols and standards. Different codes are used by the ITU-T to differentiate between standards and protocols that relate to the ISDN network, ISDN concepts, and ISDN switching and signaling. These include:

E-series. E-series ISDN standards relate to the telephone network. For example, standard E.164 describes international ISDN addressing.

I-series. I-series ISDN standards deal with ISDN concepts and interfaces. For example, standard I.112 outlines vocabulary terms of ISDN.

Q-series. Q-series ISDN standards relate to ISDN switching and signaling. For example, standard Q.921 describes the details of the Link Access Procedure on the ISDN D channel, LAPD.

Author: Dan DiNicolo

Dan DiNicolo is a freelance author, consultant, trainer, and the managing editor of He is the author of the CCNA Study Guide found on this site, as well as many books including the PC Magazine titles Windows XP Security Solutions and Windows Vista Security Solutions. Click here to contact Dan.