Hi
N-ISDN (narrowband isdn) defines 2 interfaces for the user to access
the network. One is the BRI, whis is defined as 2 B channels (64K for
user data) plus 1 D channel (for signaling, 16K). BRIs where designed
to work on "most" of the current available phone cables running
from the central offices to the customer house. There are more details,
like reference points, (S/T, u, etc), there is some bandwidth for
framing, DC balancing, etc (48K) so the total bandwidth for the BRI
is 192 Kb.
The PRI is the other interface, it uses the electrical "well known"
interfaces of T1 and E1, to access the ISDN network. In T1 you have
23 channels for user data (B) plus 1 channel for disgnaling (D), plus 1
bit in every frame for frame sync plus other functions. In
E1 is 30 B, 1 D, plus 1 channel (channel 0) for frame sync, CRC-4, etc.
So a PRI is a E1 or T1 used to access a ISDN network. Do not make
the common error to confuse the electrical interface (e1, t1) with the
use of if (PRI for ISDN, DS1 for telephone systems, old PBX)
PRI uses the same protocols as BRI (q.921, q.931), and the B channels
can be used as data or voice like in BRI (this if the bearer capality
of the call)
A good book would be the ISDN book from William Stalling the one from
Ullises Black.
Other info:
http://ns0.comfort.hu/katalogus/patton/t1e1_reva/index.htm
http://www.ralphb.net/ISDN/
Regards!
Chris Wornell wrote:
>
> Hello,
>
> For some reason, PRI has racked my brain ever since I learned about it.
> From what I understand, its basically a line with 23 64kb B channels and 1
> 64kb D channel. The thing I'm confused about is I always see it mentioned
> with ISDN. Is it really just an ISDN line with a bigger pipe? Is there
any
> sort of dialing required when using it? Does it use the same protocols as
> ISDN? Can you use each channel for either voice or data dynamically like
> BRI? Any information would be helpful.
>
> Thank you,
>
> Chris Wornell
> CCNA, CCDA
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