Details On Multilink Ppp - Siemens INSYS Pocket ISDN-TA Operating Manual

Configuring the POCKET ISDN-TA
To enable Multilink PPP handling within the POCKET ISDN-TA please enable the B
channel protocol ML-PPP: atb31 rsp. prot = 31.
ML-PPP may be used with different authentification procedures during the call up
of the line. One of these is CHAP. You may enable ML-PPP CHAP by the following
steps:
• Enter "at**chappwd=<password>" to input your password in the POCKET
ISDN-TA.
• Enter "AT&W" to store the setting in the POCKET ISDN-TA.
Afterwards a ML-PPP connection is initially made using CHAP authentification. If
the server does not handle CHAP an automatic fallback to PAP is performed.
You may control the settings by typing "AT&V1".
Warning: Since the password is shown in plain text it may be disclosed by
unauthorized persons.

4.5.1 Details on Multilink PPP

Currently on INSYS TAs running Multilink PPP (ML-PPP) the following authentication
protocols (AP) are supported:
• Password Authentication Protocol (PAP)
• Challenge Handshake Authentication Protocol (CHAP) with the variants
• MD5 according to RFC 1321
• Microsoft Chap according to RFC 2433
PAP exchanges the password in clear text format in the B-channel, whereas CHAP
encrypts the password according to the algorithms described in the RFCs
mentioned above. For CHAP the password has to be stored in the POCKET ISDN-TA
in addition to the setting in the Dial-up Network under Windows 95. Under Windows
98/ME/2000 this is not necessary.
The following basic rules apply when the POCKET ISDN-TA is configured to run ML-
PPP:
1. If the remote side requests (in the Link Control Protocol LCP ConfigRequest) an
AP that the POCKET ISDN-TA can handle, the request is forwarded to local side.
2. If the remote side requests an AP that the POCKET ISDN-TA cannot handle, the
POCKET ISDN-TA proposes the safest protocol depending on its capabilities:
• PAP if no password chappwd is locally stored,
• CHAP/MS-CHAP MD5 if a password chappwd is locally stored.
This step may be repeated a limited number of times only, if this number
exceeds, the POCKET ISDN-TA falls back to single link operation until the next
connection is tried.
27