LAPD is used on the ISDN D channel. PPP (or HDLC or whatever) is used on
the B channels. SO neither is encapsulated in the other.
The Paquet book for BCRAN has a useful table covering what protocols are
used at which layers on which channels, which I have attempted to reproduce
below...
D channel B channel
Layer 3 DSS1 (Q.931) IP/IPX
Layer 2 LAPD (Q.921) HDLC/PPP/FR/LAPB
Layer 1 I.430/I.431/ANSI T1.601
Hope that helps,
JMcL
---------------------- Forwarded by Jenny Mcleod/NSO/CSDA on 03/01/2001
09:27 am ---------------------------
"Pierre-Alex" <[EMAIL PROTECTED]>@groupstudy.com on 30/12/2000
10:45:47 am
Please respond to "Pierre-Alex" <[EMAIL PROTECTED]>
Sent by: [EMAIL PROTECTED]
To: "Jim Dixon" <[EMAIL PROTECTED]>
"Cisco" <[EMAIL PROTECTED]>
cc:
Subject: RE: ISDN LAPD versus PPP
Reading between the lines (see bellow) it seems that PPP is NOT
encapsulated
in LAPD. It looks like PPP starts encapsulating network traffic on its own
as soon as LAPD has set up the ISDN call. Please correct me if I am wrong.
Thank You.
"3.3. Link Dead (physical-layer not ready)
The link necessarily begins and ends with this phase. When an
external event (such as carrier detection or network administrator
configuration) indicates that the physical-layer is ready to be used,
PPP will proceed to the Link Establishment phase.
During this phase, the LCP automaton (described later) will be in the
Initial or Starting states. The transition to the Link Establishment
phase will signal an Up event to the LCP automaton."
Pierre-Alex
-----Original Message-----
From: Jim Dixon [mailto:[EMAIL PROTECTED]]
Sent: Friday, December 29, 2000 3:42 PM
To: Pierre-Alex
Subject: RE: ISDN LAPD versus PPP
Here are some RFC's that you might read that might help.
http://www.isi.edu/in-notes/rfc1661.txt
http://www.isi.edu/in-notes/rfc2516.txt
http://www.isi.edu/in-notes/rfc2878.txt
Jim
-----Original Message-----
From: Pierre-Alex [mailto:[EMAIL PROTECTED]]
Sent: Friday, December 29, 2000 3:11 PM
To: Cisco
Subject: ISDN LAPD versus PPP
Is it a true statement to say that if your using ppp encapsulation on your
interface, the ppp packets are encapsulated in the LAPD packets. If not,
where else would ppp packets be encapsulated?
I have found no document showing the relationship of ppp and LAPD if you
have some reference I would greatly appreciate.
Pierer-Alex
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