ZyWALL 10 Internet Security Gateway
Access Concentrator) and the PPTP user. The PNS is the box that hosts both the PPP and the PPTP stacks and forms one end of the PPTP tunnel. The PAC is the box that dials/answers the phone calls and relays the
PPPframes to the PNS. The PPTP user is not necessarily a PPP client (can be a PPP server too). Both the PNS and the PAC must have IP connectivity; however, the PAC must in addition have
Microsoft includes PPTP as a part of the Windows OS. In Microsoft’s implementation, the PC, and hence the ZyWALL, is the PNS that requests the PAC (the ANT) to place an outgoing call over AAL5 to an RFC 2364 server.
Control & PPP connectionsEach 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 ANTPPP 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.
D | PPTP |