ISDN and DDR

This Tutorial attempts to cover all ISDN/DDR material likely to be on the CCNA exam. As a result of your ISDN studies, you should be able to answer any test questions about ISDN, PPP, and DDR. In addition to helping you pass the exam, learning ISDN well will give you a very important foundation for further progress in your internetworking knowledge and career. It's worth remembering that ATM, ISDN, and Frame Relay were all developed as part of the same standards process, a process that followed and drew from the OSI model development.

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