In a general packet radio system (GPRS) network, the following
procedures require domain name resolution: Packet Data Protocol (PDP)
context activation procedures, inter-SGSN routing area update (RAU)
procedures, and inter-SGSN serving RNC (SRNC) relocation procedures.

PDP Context Activation Procedure

Figure 1 shows the PDP context activation procedure.

Figure 1 PDP context activation procedure


http://localhost:7904/pages/31185199/02/31185199/02/resources/figure/ch/SGSN/fig_60_129.png

The PDP context activation procedure is as follows:

1. The mobile station (MS) sends the serving GPRS support node (SGSN)
   a PDP context activation request message that carries an access point
   name (APN), such as CMNET.
2. After receiving the PDP context activation request, the SGSN sends
   a domain name resolution request to the domain name server (DNS).
   The domain name to be resolved is a complete APN, such as CMNET.MNC000.MCC460.GPRS.
3. The DNS server returns the result of the SGSN resolution request,
   the IP address of the gateway GPRS support node (GGSN) signaling plane,
   such as 10.161.234.254.
4. Based on the resolution result, the SGSN sends the target GGSN
   an activation request message that carries the APN.
5. After receiving the activation request, the GGSN allocates an
   IP address for the MS based on the APN and returns the IP address
   to the SGSN.
6. The SGSN sends the IP address allocated by the GGSN to the MS
   and activation succeeds.
7. After activation has been completed, the MS can communicate with
   an external network by using the allocated IP address.

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