清热化湿PDPContextManagement：：Chapter7：
7.2 PDP Context Management
A PDP context contains routing information for packet transfer between an MS and a GGSN to have access to an external packet-switching network. It is identified by an exclusive MS PDP address (mobile's IP address). This means that the MS will have as many PDP address as activated PDP contexts.
A concept of condary PDP context has been introduced in order to have veral PDP contexts sharing the same PDP address and the same access to the external packet-switching network. This concept was introduced for multimedia applications where each medium type requires specific transport characteristics and is mapped into a specific PDP context. It is bad on the traffic flow template, which is a filtering mechanism ud by the GGSN to route downlink IP packets toward the appropriate medium within the MS.
A given PDP context is in the active state when this PDP address is activated for data transf
er. Before transferring data between an MS and a GGSN, it is necessary that a PDP context be activated.
皮日休PDP context procedures have been defined in order to create, modify, and delete PDP contexts within the MS, SGSN, and GGSN entities. The SM protocol is ud between the MS and the SGSN and the GTP protocol is ud in the controlling plane between the SGSN and the GGSN for PDP context procedures.
7.2.1 PDP Context Definition
A PDP context provides access to an external packet-switching network through the PLMN network. The data associated with the PDP context is as follows:
大黄的功效与作用及禁忌
∙Access point name (APN). This is the reference to a GGSN.
∙Network rvice access point identifier (NSAPI). This is an index of the PDP context that us the rvices provided by the SNDCP layer for GPRS data transfer. Up to 11 applications over the SNDCP layer may be identified by the NSAPI parameter. The NSAP
I parameter is prent in the SNDCP header.
∙LLC rvice access point identifier (LLC SAPI). This identifies the SAP ud for GPRS data transfer at the LLC layer.
磁带存储
∙PDP address. This identifies the MS address related to a particular PDP context. This field consists of veral fields including the PDP type (IP or PPP), PDP address type (IPv4 or IPv6), and address information containing the IP address.
∙QoS. This defines the quality of rvice related to a particular PDP context. Parameters related to QoS are described in Section 2.4.
复得返自然∙Radio priority. This specifies the priority level ud by the MS at the lower layers for transmission of data related to a PDP context.
∙Protocol configuration options. This defines external network protocol options associated with a PDP context. It may contain information about protocols such as the link control protocol (LCP), the PPP authentication protocol (PAP), the challenge handshake authenti
cation protocol (CHAP), and the Internet Protocol Control Protocol (IPCP).
Several PDP contexts can be activated at the same time in the MS. This means that the MS is able to transfer or receive data at the same time for veral applications. Each PDP context is identified at the MS level, at the SGSN level, and at the GGSN level by the NSAPI. This identifier will be ud to identify the logical link within the MS between the SNDCP entity and the application layer. An NSAPI is associated with an individual PDP address. When the SGSN receives a packet from the GGSN addresd to an MS identified by its PDP address, the SGSN inrts the associated NSAPI in the SNDCP header. Thus when the MS receives a packet from the SGSN, it identifies the appropriate application layer from the NSAPI parameter included in the SNDCP header.
7.2.2 PDP Address
A mobile's PDP address (IP address) can be assigned statically at the time of subscription or dynamically when the context is activated, depending on the operator's choice. A PDP address assigned permanently is called a static PDP address while a PDP
address assigned during a PDP context activation is called a dynamic PDP address. The dynamic PDP address assignment is provided either by the GGSN, which creates a new entry in its PDP context table, or by the PDN operator.
7.2.3 酵素的功效Traffic Flow Template
In the GPRS Relea 99 recommendations, veral activated PDP contexts may share the same PDP address and the same APN. This is not the ca in the earlier releas.
金枪不倒药Some applications should require at the same time veral activated PDP contexts with different QoS profiles while reusing the same PDP address and other PDP context information from an existing active PDP context. For example, multimedia applications involve veral flows (e.g., voice and video that request different QoS but the same PDP address and the same APN). As a result of veral PDP contexts activated at the same time with the same PDP address and the same APN, the different multimedia application flows can be routed between the MS and the GGSN via different GTP tunnels and possibly different LLC links.哈利波特作者简介
