Nortel BCM50e, Configuration

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Appendix E PPTP 229
BCM50e Integrated Router Configuration - Advanced
PAC must have IP connectivity; however, the PAC must also have dial-up
capability. The phone call is between the user and the PAC and the PAC tunnels
the PPP frames to the PNS. The PPTP user is unaware of the tunnel between the
PAC and the PNS.
Figure 139 PPTP protocol overview
Microsoft includes PPTP as a part of the Windows OS. In Microsoft’s
implementation, the PC, and hence the Business Secure Router, is the PNS that
requests the PAC (the ANT) to place an outgoing call over AAL5 to an RFC 2364
server.
Control and PPP connections
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.
Note that a tunnel control connection supports multiple call sessions.
Figure 140 depicts the message exchange of a successful call setup between a PC
and an ANT.