Cisco ASR 5000 Series - Page 693

Serving GPRS Support Node (SGSN) Overview
How the SGSN Works ▀
Cisco ASR 5000 Series Product Overview ▄
OL-22938-02
Figure 170. Call Flow for PDP Context Activation
6
7
4
1
MS/UE SGSN GGSN
DNS
Server
DHCP
Server
AAA
Server
2
2
3
5
The following table provides detailed explanations for each step indicated in the figure above.
Table 88. PDP Context Activation Procedure
Step
Description
1
The MS/UE sends a PDP Activation Request message to the SGSN containing an Access Point Name (APN).
2
The SGSN sends a DNS query to resolve the APN provided by the MS/UE to a GGSN address.
The DNS server provides a response containing the IP address of a GGSN.
3
The SGSN sends a Create PDP Context Request message to the GGSN containing the information needed to authenticate
the subscriber and establish a PDP context.
4
If required, the GGSN performs authentication of the subscriber.
5
If the MS/UE requires an IP address, the GGSN may allocate one dynamically via DHCP.
6
The GGSN sends a Create PDP Context Response message back to the SGSN containing the IP Address assigned to the
MS/UE.
7
The SGSN sends a Activate PDP Context Accept message to the MS/UE along with the IP Address.
Upon PDP Context Activation, the SGSN begins generating S-CDRs. The S-CDRs are updated periodically based on
Charging Characteristics and trigger conditions.
A GTP-U tunnel is now established and the MS/UE can send and receive data.