For the Network+ and the CCNA exams, it is required to know the basics of ISDN.
ISDN resides at the Physical, Data link, and Network layers, and uses existing telephone lines.
ISDN BRI Basic Rate Service
- 2 B channels at 64 Kbps each for data, and 1 D channel at 16 Kbps for signaling.
- Total throughput is 128 Kbps.
ISDN PRI Primary Rate Service
- 23 B channels at 64 Kbps each for data and 1 D channel at 64 Kbps for signaling.
- Total throughput is 1.544 MBps.
European ISDN has 30 B channels for a total throughput of 2.05 MBps.
Benefits offered with ISDN
- Modem dial up time is very fast compared to an analog modem, (approx. 11 seconds).
- May be used with voice, data, and video.
- ISDN is a good backup for an office leased line.
- 24/7 connectivity is not required.
- ISDN uses existing telephone lines.
B-ISDN (Broadband ISDN) is available in some areas, and offers speeds above 1.544 MBps.
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