Manual

Cisco Packet Data Serving Node (PDSN) Release 2.0
System Overview
6
12.3(11)T
Figure 4 CDMA Network —Simple IP with VPDN Scenario
A VPDN connection is established in the following order:
1. A PPP peer (mobile station) connects with the local NAS (the Cisco PDSN).
2. The NAS begins authentication when the client dials in. The NAS determines that the PPP link
should be forwarded to a tunnel server for the client. The location of the tunnel server is provided
as part of the authentication by the Remote Authentication Dial-in User Service (RADIUS) server.
3. The tunnel server performs its own authentication of the user and starts the PPP negotiation. It
performs authentication for both the tunnel setup and the client.
The PPP client is forwarded through a Layer 2 Tunneling Protocol (L2TP) tunnel over User
Datagram Protocol (UDP).
4. The PPP setup is completed and all frames exchanged between the client and tunnel server are sent
through the NAS. The protocols running within PPP are transparent to the NAS.
Cisco PDSN Mobile IP
With Mobile IP, the mobile station can roam beyond the coverage area of a given PDSN and still maintain
the same IP address and application-level connections.
Figure 5 shows the placement of the Cisco PDSN in a Mobile IP scenario.
Ho
me
B
rok
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RAN
Visited Access
Provider Network
R-P
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IP
network
RADIUS
PDSN
Network
Access
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(NAS)
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obile station