Technical Reference for ZyXEL omni.net series
7-2
Data will be transmitted only when the link is in the open phase. Negotiation details are described in
RFC1661.
Feature List
Async to Sync Conversion
PPP uses HDLC-like framing as encapsulation, which can be bit-oriented or character-oriented.
Most ISDN routers use bit-oriented HDLC framing, also known as synchronous transmission.
However, serial transmission in most personal computers is still character-oriented, also known as
asynchronous transmission. In order for an ISDN router and PC to communicate, it is necessary to
do asynchronous to synchronous conversion. The omni.net can be used as a bridge. Any data from
a PC to a ZyXEL Omni TA will be converted from asynchronous to synchronous form and vice
versa.
PPP HDLC framing is described in
RFC1662.
PPP over ISDN is described in
RFC1618.
Related AT Command
Description
ATB40
Async to Sync PPP Conversion
Table 35. Related AT Command for Async to Sync Conversion
Authentication Conversion
After a link is established, it is necessary to authenticate the peer for security reasons. There are two
popular authentication methods. One is Password Authentication Protocol (PAP) and the other is
Challenge Handshake Authentication Protocol (CHAP). PAP is less secure because it transmits the
username/password in plain text form. Unlike PAP, CHAP transmits the username/password in
coded form. Some ISPs may support CHAP as the only method for authentication.
For those applications that do not support CHAP, the omni.net converts PAP into CHAP. By
default, the PAP/CHAP conversion is always activated, so the authentication from the ISDN TA to
PC is always PAP. That means you must configure your software to accept plain text as password
authentication. Do not worry about password leakage, the omni.net TA will send the password out
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