There are a couple Cisco documents that talk about 192-kbps for ISDN BRI,
but I think the authors of these documents confused the specifics of Layer
1 signalling on the S-Bus with overall BRI ISDN.
Here's what I found by doing some quick research outside Cisco's site. I
hope it's from reputable sources:
In the case where S and T are coincident, NT1 is connected to a TE1 or TA
by means of a passive bus called the S-Bus. The Layer 1 protocol on this
bus uses frames that comprise 16 bits from the B1 channel (transmitted at a
rate of 64 kbps), 16 bits from the B2 channel (transmitted at a rate of 64
kbps), 4 bits from the D channel, (transmitted at a rate of 16 kbps) and 12
framing bits (transmitted at a rate of 48 kbps). This is equivalent to a
total throughput of 192 kbps.
In the US, we use the U interface, not the S/T interface. Once again, if
the sources I found are reputable, then the transfer rate when the U
interface is used is 160 kbps.
Anyway, if you get a question with both the 192 and 144 answers, you're
screwed, but I don't think you will. I think the tests are written such
that the right answer for the transmission rate of BRI is 144 kbps.
Priscilla
>>To: [EMAIL PROTECTED]
>>Path: not-for-mail
>>From: "Patrick Bass" <[EMAIL PROTECTED]>
>>
>>
>>In Cisco internetworking Technology Overview it states...
>>
>> "BRI also provides for framing control and other overhead, brining its
>>total bit rate to 192 kbps."
>>
>>In Cisco Internetwork Design it states...
>>
>>"The D channel signaling protocol comprises Layers 1 through 3 of the OSI
>>reference model, brining its total bit rate to 144 kbps."
>>
>>If I'm taking a Cisco certification exam and the question is "What is the
>>total bit rate of a BRI" and the answers are a) 128 b) 144 c) 192 d)
>>whatever.......what's the correct answer? Is it 144 kbps or 192 kbps?
>>
>>I realize that it is 192 kbps when you take the 48 kbps for framing into
>>account.... but considering the fact that two Cisco sources give different
>>totals for "total bit rate" what am I to answer if I wish to get the answer
>>correct?
>>
>>
>>_________________________________
>>FAQ, list archives, and subscription info:
>>http://www.groupstudy.com/list/cisco.html
>>Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
________________________
Priscilla Oppenheimer
http://www.priscilla.com
_________________________________
FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html
Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
