ISDN Framing Info [closed]

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I learned that ISDN Basic Rate Interface has

• 1 D-Channel à 16kbit/s for connection and config
• 2 B-Channels à 64kbit/s for Data
• 1 YY à 48kbit/s for Framing Info

Summarized that are 192kbit/s. But in Wikipedia I read about 144kbit/s without YY. What is YY? I can't possibly imagine that this is overhead for framing/transportation of ISDN...

Answer 1

It seems that the transmission protocol actually needs 48kbit/s.

"Two B channels at 64 Kbps plus one D channel at 16 Kbps equals 144K bps. The ISDN Basic Rate transmission protocol uses an additional 48 Kbps of bandwidth for maintenance and synchronization, so an ISDN Basic Rate Access actually uses 192 Kbps." [testfest.com]