10.3 Protocol Architecture

This section illustrates the end-to-end protocol architecture for the mobile IP and simple IP services. There are some enhancements in the protocol messages between MSC and BSC for IP services, but the protocol stack between them is the same as in the CS network (i.e., A1/A2 over SS7), and is not shown for simplicity. All the control messages at PPP and above layers are user plane data for the radio link layers.

10.3.1 Simple IP

The control plane for simple IP is illustrated in the Figure 10-2. PPP is used for establishing link layer connection between MS and PDSN. A11 is a modified version of simple IPv4 and is used for providing mobility management, charging data collection, and GRE tunnel management between PDSN and PCF. A11 is transported over UDP as specified for simple IPv4. A9 is defined to provide mobility management and GRE tunnel management between PCF and BS. Link access control (LAC) is used between BS and MS for processing cdma2000 layer 3 signaling messages.

Figure 10-2. Simple IP protocol architecture control plane.

Figure 10-3 shows the user plane for simple IP protocol architecture. The PPP layer encapsulates and transfers IP packets between MS and PDSN. A10 and A8 use GRE tunnels to transfer packets.

Figure 10-3. Simple IP protocol architecture user plane.

10.3.2 Mobile IP

The control plane for mobile IP is shown in Figure 10-4. In the stack shown, IKE is assumed as a key distribution mechanism between PDSN/FA and HA. Also, IPsec is assumed for both control and user plane between PDSN/FA and HA. All the protocol layers underneath the PPP layer stay the same as in simple IP. The main difference from simple IP is a layer of mobile IP signaling, which is transported over UDP. The mobile IP layer provides mobility across PDSNs.

Figure 10-4. Mobile IP protocol architecture (control plane).

The user plane protocol for mobile IP is illustrated in Figure 10-5. The end host (or correspondent node) sends packets to the MS. The packets arrive at HA and are tunneled to the PDSN/FA using IP tunnels. The stack under PPP is similar to simple IP, where packets are carried using GRE tunnels from PDSN to BS.

Figure 10-5. Mobile IP protocol architecture (user plane).