Ole,
Both you and Priscilla are correct. The TEI and SAPI are part
of the layer two addressing for LAPD. This means that for question
14 (Chapter 7, page 247) the correct answer is B. Good catch on your
part. Sorry to have taken you off track.
I had just recently identified this error as part of the corrections
for the second printing of the book. I am working to get a list of
errata ready for publication on the ccprep website. When the information
goes up, I will post the URL to GroupStudy.
I appreciate the discussion and feedback here and welcome any other
comments or questions you have as you work your way through.
Glad the book is working out for you despite the error. Hope it continues
to prove helpful.
AQ
At 06:21 PM 7/27/00, Priscilla Oppenheimer wrote:
>Layer 3 is not the same as the OSI network layer, though. ISDN has a
>different protocol stack. It sounds like the writer of the study guide
>question might have been confused by this gotcha.
>
>Your answer of "a unique datalink layer address" is better than the answer
>in the book of "a unique network layer address."
>
>TEI is a device identifier. SAPI is like an LLC SAP and identifies the
>point where Q.921's Layer 2 provides a service to Q.921's Layer 3. For
>example, SAPI 0 = call control, etc. We're still at the OSI datalink
>layer, though.
>
>Cisco Press's CIT book has all sorts of details. It might be a good place
>to check.
>
>Priscilla
>
>
>At 05:12 PM 7/27/00, Taylor, Don wrote:
>>Your post made me wonder, so I went a-searchin'. The only thing I was able
>>to find on it that might be somewhat authoritative is the following URL:
>>http://www.cisco.com/univercd/cc/td/doc/product/software/ios120/12cgcr/dial_
>>r/drprt1/drbri.htm
>>
>>Scroll to the bottom of the page and look at the table (or just do a search
>>for "sapi" - it only shows up once). Note that SAPI doesn't enter the
>>equation until layer 3.
>>
>>- Don
>>
>>-----Original Message-----
>>From: Ole Drews Jensen [mailto:[EMAIL PROTECTED]]
>>Sent: Thursday, July 27, 2000 1:16 PM
>>To: '[EMAIL PROTECTED]'
>>Subject: TEI & SAPI
>>
>>
>>I had a question in my study guide about what the combination of TEI & SAPI
>>gives you.
>>
>>My answer was 'A unique datalink layer address', but the answer in the book
>>said 'A unique network layer address'.
>>
>>I had the understanding that this was info in the address field of the LAPD
>>protocol (Q.921) which is operating on the ISDN D-channel in the Datalink
>>layer.
>>
>>Who's right, and if I'm wrong - could someone please explain why?
>>
>>I hope this is a typo in the book, because just when you think you know what
>>the .... it's all about, you get thrown a "No, you're wrong" in the face...
>>
>>Thanks in advance,
>>
>>Ole
>>
>>P.S. Besides the few typo's I've seen, so far this BCRAN book (from McGraw
>>Hill) is excellent!!!!
>>
>>~~~~~~~~~~~~~~~~~~~~~~~~
>> Ole Drews Jensen
>> Systems Network Manager
>> CCNA, MCSE, MCP+I
>> RWR Enterprises, Inc.
>> [EMAIL PROTECTED]
>>~~~~~~~~~~~~~~~~~~~~~~~~
>
>
>________________________
>
>Priscilla Oppenheimer
>http://www.priscilla.com
>
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Adam Quiggle
Senior Network Engineer
MCI Worldcom/BP Amoco
CCNA, MCNE, MCSE
[EMAIL PROTECTED]
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