Summary
ISDN refers to a set of communication protocols proposed by telephone companies to permit telephone networks to carry integrated voice, video, and data services. ISDN permits communication over high-quality, high-speed, digital communication channels.

DDR is used in order to save the costs of a dedicated WAN line for organizations and companies that do not need a permanent connection. It can also be used as a backup by organizations that use the dedicated line for critical applications.

An understanding of the following key points should have been achieved:

  • ISDN carries data, voice, and video
  • ISDN uses standards for addressing, concepts, and signaling
  • ISDN uses the physical and data-link layers
  • Interfaces and reference points for ISDN
  • Router configuration for ISDN
  • Which traffic is allowed when configuring DDR
  • Static routes for DDR
  • The correct encapsulation type for DDR
  • Access lists affecting DDR traffic
  • Dialer interfaces