tailieunhanh - IP-Based Next-Generation Wireless Networks phần 3

Ví dụ, GGSN cần biết IMSI của điện thoại di động để truy vấn HLR để xác định mà SGSN hiện đang phục vụ các điểm đến điện thoại di động. Tĩnh thông tin để lưu trữ cho một địa chỉ PDP, nơi lưu trữ chúng, và làm thế nào một GGSN lấy các thông tin tĩnh được coi là vấn đề thực hiện và do đó không được chuẩn hóa bởi 3GPP. | 64 WIRELESS IP NETWORK ARCHITECTURES To support Network-requested PDP Context Activation for a PDP address the GGSN must have static information about the PDP address. For example the GGSN needs to know the mobile s IMSI in order to query the HLR to determine which SGSN is currently serving the destination mobile. What static information to store for a PDP address where to store them and how a GGSN retrieves such static information are regarded as implementation issues and therefore not standardized by 3GPP. As illustrated in Figure the GGSN starts Network-Requested PDP Context Activation by sending a Send-Routing-Information-for-GPRS message to the HLR to retrieve the address of the destination mobile s serving SGSN. This message carries the mobile s IMSI which will be used by the HLR to determine whether the request can be granted and to search the HLR database for the requested information regarding this mobile. The HLR replies with Send-Routing-Information-for-GPRS-ACK message. This message will carry the address of the mobile s serving SGSN if the HLR determines to grant the Send-Routing-Information-for-GPRS received from the GGSN or an error cause if the HLR cannot grant the Send-Routing-Information-for-GPRS message. The GGSN will then send a PDU Notification Request message to the mobile s serving SGSN to ask the SGSN to instruct the mobile to initiate PDP context activation. The PDU Notification Request message will carry the mobile s IMSI the PDP Type the PDP Address for which a PDP context should be activated and the APN that the SGSN and the mobile should use to determine which GGSN to use. Upon receiving the PDU Notification Request the SGSN will first inform the GGSN that it will honor the GGSN s request by returning a PDU Notification Response message to the GGSN. Then the SGSN will send a Request PDP Context Activation message to the mobile to instruct the mobile to start the Mobile-initiated PDP Context Activation procedure described in Figure