ZyXEL Communications Intelligent Broadband Sharing Gateway P-324 - Manual (Page 250)

Prestige 324 Intelligent Broadband Sharing Gateway
6 PPTP
Each PPTP session has distinct control connection and PPP data connection.
Call Connection
The control connection runs over TCP. Similar to L2TP, a tunnel control connection is first established
before call control messages can be exchanged. Please note that a tunnel control connection supports
multiple call sessions.
The following diagram depicts the message exchange of a successful call setup between a PC and an ANT.
Diagram 5 Example Message Exchange between PC and an ANT
PPP Data Connection
The PPP frames are tunneled between the PNS and PAC over GRE (General Routing Encapsulation, RFC
1701, 1702). The individual calls within a tunnel are distinguished using the Call ID field in the GRE
header.