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 (external)

PPPuses 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’s necessary to do asynchronous to synchronous conversion. The omni can be used as a bridge. Any data from a PC to a ZyXEL 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 command:

ATB40 - Async to Sync PPP 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 which do not support CHAP, the omni converts PAP into CHAP. By default, the PAP/CHAP conversion is always activated, so the authentication from the 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 TA will send the password out in hashed form

Point-to-Point Protocol (PPP) 45

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ZyXEL Communications omni series user manual Feature list, Async to Sync Conversion external