Study Question

[jesseeu]

Here is a question about ISDN from the Sybex book I'm studying. Can anyone give their opinion on which three are the correct answers? I am certain that the book is wrong here. And it is not listed in the errata on sybex's site.

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Whith regard to ISDN, which of the following are ture? (Choose three.)

A. Each ISDN channel has transmission speeds of up to 64kbps.
B. The ISDN B channel can carry video, voice, or data.
C. The ISDN B channel transmission rate varies depending on the service used.
D. The ISDN D channel transmits control information.
E. The ISDN B channels can be configured with different subnets and encapsulation types when dialer profiles are configured.
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I chose B,D, and E. The book said it is A, B, and D. Now I don't think the book specifically talked about configuring different subnets and encapsulation types on the B channels, but I know it said "there are 3 ISDN channels, two "B" and one "D". The Bs having 64k each and the D having 16k (which is used for signaling and other low bandwidth services such as an alarm line.)

What do you guys think?

Thanks,
Jesse

 

[lgarner]

A" is confusing. The answers seem to indicate that they're talking about BRI, but in a PRI "A" is correct, and the question doesn't specify which type.

 

[Cluebird]

A, B, D are correct.

C is not correct because 64kbps is the DS1 channel and isn't further limited. ISDN doesn't use RBS and you don't have 32kbps B channels or 48 kbps channels for example. Everything with the TDM circuits is based on one voice channel of 64kbps and multiples of the DS1 which then are used for carrying data.

E is incorrect because it tests concepts about dialer profiles rather than ISDN. Since the question asks specifically about ISDN, dialer profiles are a distractor.

 

[hessaacd]

technically A is correct because it says "speeds UP TO 64kbps"
The speed cannot exceed 64 kpbs for any one channel.