9.1 PDP状态的定义

爱卫生

9.1.0 通用的
   A GPRS subscription contains the subscription of one or more PDP addresses. Each PDP address is an element of a PDP context. The same PDP address may appear in one or more PDP contexts in the MS, the SGSN, the S GW, the P GW and the GGSN. Each PDP context may be associated with a TFT. At most one PDP context associated with the same PDP address may exist at any time with no TFT assigned to it. Every PDP context exists independently in one of two PDP states. The PDP state indicates whether data transfer is enabled for that PDP address and TFT or not. In case all PDP contexts associated with the same PDP address are deactivated, data transfer for that PDP address is disabled. Activation and deactivation are described in clause "PDP Context Activation, Modification, Deactivation, and Preservation Functions". All PDP contexts of a subscriber are associated with the same MM context for the IMSI of that subscriber.
   一个GPRS的签约包含了对一个或多个PDP地址的签约使用。每个PDP地址都是PDP上下文的一个元素。相同的PDP地址可以在MS/SGSN/SGW/PGW/GGSN的一个或多个PDP上下文中出现。每个PDP上下文可以和一个TFT关联。最多，在任意时刻只能有一个使用相同PDP地址的PDP上下文没有TFT的分配（隐含的就是说，如果MS有二次激活，则一定要有关联的TFT）。所有的PDP上下文的状态都是两种PDP状态的其中一种。PDP状态指示针对这个PDP地址和TFT是否有数据传递。一旦具有相同PDP地址的所有PDP上下文去激活了，针对这个PDP地址的数据传输将被禁止。激活和去激活将在章节“PDP Context Activation, Modification, Deactivation, and Preservation Functions“描述。一个签约用户的所有PDP上下文和这个签约用户的IMSI对应的相同的MM上下文进行关联。

9.1.1 INACTIVE State
   The INACTIVE state characterises the data service for a certain PDP address of the subscriber as not activated. The PDP context contains no routeing or mapping information to process PDP PDUs related to that PDP address. No data can be transferred. A changing location of a subscriber causes no update for the PDP context in INACTIVE state even if the subscriber is GPRS-attached.
   Mobile-terminated PDP PDUs received in INACTIVE state by the GGSN may initiate the Network-Requested PDP Context Activation procedure if the GGSN is allowed to initiate the activation of the PDP context for that PDP address. Otherwise, mobile-terminated PDP PDUs received in INACTIVE state invoke error procedures in the P GW or GGSN relevant to the packet data network protocol, for example, an IP packet is discarded and an ICMP (see RFC 792 [41]) packet (error notification) is returned to the source of the received packet. Other error procedures may be introduced on the application level, but this is outside the scope of the present document.
   The MS initiates the movement from INACTIVE to ACTIVE state by initiating the PDP Context Activation procedure.
   INACTIVE状态说明针对某个特定签约用户的PDP地址的数据业务未激活。PDP上下文没有路由和映射信息来处理和这个PDP地址对应的PDP PDU。没有数据被传递。签约用户的位置移动不会使INACTIVE状态的PDP上下文有任何的更新，即使这个签约用户是已经GPRS附着了。
   如果GGSN上收到了要发给INACTIVE状态的手机的PDP PDUs，GGSN可以发起Network-Requested PDP Context Activation流程（现网都不支持）----如果GGSN允许为这个PDP地址发起PDP上下文的激活的话。否则，将在PGW或GGSN上调用相应的协议来执行错误处理流程。例如，一个IP包将被丢弃，并且一个ICMP报文将被返回给源节点。其他的错误处理流程可以在应用层引入，但已经超出本规范的讨论范围了。
   MS可以通过发起PDP上下文激活流程将状态从INACTIVE切换到ACTIVE状态。

9.1.2 Active状态
   In ACTIVE state, the PDP context for the PDP address in use is activated in the MS, SGSN and GGSN when using Gn/Gp, or in the MS, SGSN, S GW and P GW when using S4. The PDP context contains mapping and routeing information for transferring PDP PDUs for that particular PDP address between the MS and the P GW or GGSN. The PDP state ACTIVE is permitted only when the mobility management state of the subscriber is STANDBY, READY, PMM IDLE, or PMM CONNECTED. The Iu interface radio access bearer may or may not be established for an active PDP context.
   An active PDP context for an MS is moved to INACTIVE state when the deactivation procedure is initiated.
All active PDP contexts for an MS are moved to INACTIVE state when the MM state changes to IDLE or PMM DETACHED.
   在Active状态，针对这个PDP地址的PDP上下文将在MS中激活，当使用Gn/Gp接口时，在SGSN和GGSN中激活。或者当使用S4接口时，在MS、SGSN、SGW、PGW中激活。PDP上下文包含了在MS和PGW或GGSN之间的特定PDP地址所对应需要传递的PDP PDUs的路由和映射信息。PDP状态Active仅在移动性管理状态时Standby,Ready,PMM-Idle,PMM-Connected下才有效。Iu接口的无线接入承载（RAB)可能或者不一定会为一个active的PDP上下文建立。
   一个MS的active PDP上下文将通过去激活流程切换到INACTIVE状态。当MS中所有active的PDP上下文都迁移到INACTIVE状态后，则对应的MM状态将切换到IDLE或PMM-DETACHED。

Figure 61: Functional PDP State Model