9.2 PDP上下文激活、修改、去激活以及保持功能（9.2.0---9.2.1）

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9.2.0 General通用的部分
    This clause describes the procedures to enable a GPRS-attached MS to initiate the activation, modification, and deactivation functions for a PDP context in the MS, the SGSN, the S GW and the P GW or GGSN. In addition procedures to enable a P GW or GGSN to request the activation, modification and deactivation of a PDP context to a GPRS-attached subscriber are described.
    NOTE 1: If the MS is in PMM IDLE state, it needs to perform a service request procedure to enter the PMM CONNECTED state before initiating these procedures.
    NOTE 2: There are two procedures specified for GGSN initiated PDP Context Activation; the Network Requested PDP Context Activation Procedure and the Network Requested Secondary PDP Context Activation Procedure. P GWs support only the Network Requested Secondary PDP Context Activation Procedure. The network requested bearer control makes use of the Network Requested Secondary PDP Context Activation Procedure only.
    本章节描述了一个GPRS附着的MS来发起针对在MS/SGSN/SGW/PGW/GGSN中的PDP上下文进行激活、修改以及去激活流程的功能。另外，还介绍了由PGW或GGGSN来请求发起针对一个GPRS附着的MS的PDP上下文的激活、修改和去激活流程。
    注释1：如果MS是在PMM-IDLE状态，它需要执行service request流程来进入到PMM-CONNECTED状态才能发起这些流程。
    注释2：有两个流程是关于GGSN发起的PDP上下文激活；一个是网络侧发起的PDP上下文激活流程以及网络侧发起的二次PDP激活流程。PGW仅支持网络侧发起的网络侧二次激活流程。网络侧请求的承载控制仅使用网络侧请求的二次激活流程。

    Upon receiving an Activate PDP Context Request message or an Activate Secondary PDP Context Request message, the SGSN shall initiate procedures to set up PDP contexts. The first procedure includes subscription checking, APN selection, and host configuration, while the latter procedure excludes these functions and reuses PDP context parameters including the PDP address but except the QoS parameters. Once activated, all PDP contexts that share the same PDP address and APN shall be managed equally. At least one PDP context shall be activated for a PDP address before a Secondary PDP Context Activation procedure may be initiated. When the MS performs an RA update procedure to change from a release 99 to a release 97 or 98 system, only one active PDP context per PDP address and APN shall be preserved. This PDP context is selected taking the QoS profile and NSAPI value into account.
    When the SGSN is using the S4 interface to an S GW for a PDP Context, EPS Bearer procedures will be used.
    The EPS subscription context includes a mandatory default bearer QoS profile for each subscribed APN. If the S4 SGSN has received a default bearer QoS profile and the first PDP context to a given APN is activated, the S4 SGSN disregards the QoS requested by the MS and sends the default bearer QoS for this APN to the S GW. For MSs, for which the S4 SGSN has not received a default bearer QoS per APN, the S4 SGSN treats MS originated QoS requests the same as the Gn/Gp SGSN. For MSs, for which the S4 SGSN has not received a subscribed APN-AMBR per APN, the S4 SGSN provides APN-AMBR to the Serving GW and PDN GW. Details on mapping MBR to APN-AMBR are specified in Annex E of TS 23.401 [89].
The E-UTRAN capable MS shall not deactivate the PDP context created by the PDP Context Activation Procedure unless all PDP contexts for the same PDN connection are to be deactivated. The MS shall not modify the QoS of the PDP context created by the PDP Context Activation Procedure.
    The non E-UTRAN capable MS should not deactivate the PDP context created by the PDP Context Activation Procedure unless all PDP contexts for the same PDN connection are to be deactivated. The MS should not modify the QoS of the PDP context created by the PDP Context Activation Procedure.
    一旦接收到一个Activate PDP Context Request或一个Activate Secondary PDP Context Request消息，SGSN应发起相应的流程来建立PDP上下文。第一个流程包含签约数据检查、APN的选择、以及主机配置，在后面的流程中不包括这些功能，以及重复使用PDP上下文的参数包括PDP地址但不包括QOS参数。一旦激活，所有共享相同PDP地址和APN信息的PDP上下文应被同等的管理。在二次PDP上下文激活之前至少要有一个PDP上下文被激活。当MS执行了RAU流程从之前R99版本切换到了一个R97或98版本（3GPP版本号）的系统，仅每个PDP地址和APN的一个active的PDP上下文将被保持下来。这个PDP上下文将根据Qos profile和NSAPI的值来决定。
    当SGSN使用S4接口连接到一个SGW的PDP上下文，将引入EPS承载相关流程。
    EPS签约上下文包括一个强制的针对每个签约APN的缺省承载Qos profile。如果S4-SGSN收到了一个缺省的承载Qos profile并且对这个给定的APN的第一个PDP上下文已经激活，S4-SGSN将忽视MS请求的QOS，并且发送针对这个APN的缺省承载QOS给SGW。对MS来说，如果S4-SGSN没有收到这个每个APN的缺省承载QOS，S4-SGSN将把MS请求的Qos和基于Gn/Gp SGSN进行相同对待。对于MS来说，如果S4-SGSN没有收到每个APN的签约的APN-AMBR，则S4-SGSN将为SGW和PGW提供APN-AMBR。关于MBR和APN-AMBR的映射细节在TS23.401附录E中描述。具有E-UTRAN能力的MS不应将通过PDP上下文激活流程创建的PDP上下文去激活，除非到相同PDN连接的所有PDP上下文要都要被去激活。MS不应修改由PDP上下文激活流程创建的PDP上下文的QOS。
   不具备E-UTRAN能力的MS不应将通过PDP上下文激活流程创建的PDP上下文去激活，除非到相同PDN连接的所有PDP上下文要都要被去激活。MS不应修改由PDP上下文激活流程创建的PDP上下文的QOS。

    During the PDP Context Activation Procedure the bearer control mode, applicable to all PDP Contexts within the activated PDP Address/APN pair, is negotiated. The Bearer Control Mode (BCM) is one of 'MS_only' or 'MS/NW':
- When 'MS_only' the MS shall request any additional PDP contexts for the PDP Address/APN pair through the Secondary PDP Context Activation Procedure. Session Management procedures described in 9.2 apply with the following restrictions:
- The P GW or GGSN shall not initiate any Network Requested Secondary PDP Context Activation;
- The P GW or GGSN shall not modify or delete the TFT.
- When 'MS/NW' both the MS and the P GW or GGSN may request additional PDP contexts for the PDP Address/APN pair. The MS shall use the Secondary PDP Context Activation Procedure.The P GW or GGSN shall use the Network Requested Secondary PDP Context Activation Procedure. The MS shall, when modifying the QoS of a PDP context, include a TFT with at least packet filter identifiers to indicate which packet filters in the TFT that is associated with the QoS change.   
   在PDP上下文激活流程期间的承载控制模式，适用于所有带有激活的PDP地址/APN对的PDP上下文，是采用的协商机制。承载控制模式可以是'MS_only"或者'MS/NW':
1 当'MS_only'时，MS应通过二次PDP上下文激活流程来为PDP地址/APN对来请求额外的PDP上下文。在9.2中描述的会话管理流程有以下的限制：
- PGW或GGSN不应发起网络侧请求的二次PDP上下文激活。
- PGW或GGSN不应修改或删除TFT。
2 当'MS/NW'时，MS和PGW或GGSN可以为PDP地址/APN对来请求额外的PDP上下文。MS应使用二次PDP激活流程。PGW或GGSN应使用网络侧请求的二次PDP上下文激活流程.MS应，在修改PDP上下文的QOS时，包含一个至少带有一个包过滤ID的TFT来指示在这个TFT中是哪个包过滤需要涉及到QOS的变更。

    NOTE 3: The MS indicates the packet filters in the TFT so that the network can perform the appropriate authorization.
    Session Management procedures described in clause 9.2 apply with the following restrictions:
- The MS shall not upgrade the QoS of a PDP context until a TFT has been sent by the MS for this PDP context;
- If a PDP context is associated with a TFT containing packet filters set by the MS and P GW/GGSN, the MS is only allowed to modify the bit rate parameters in the QoS profile of that PDP Context;
- The MS shall not initiate any Secondary PDP Context Activation without sending a TFT;
    NOTE 4: After a deactivation of the PDP context without TFT, the P GW or GGSN initiates the re-establishment of this PDP context using the Network Requested Secondary PDP Context Activation Procedure without sending a TFT to the MS.
- The MS shall not add a TFT to a PDP context that was established without a TFT.
- Only the entity that sets a packet filter in the TFT (either MS or P GW/GGSN) is allowed to modify or delete this packet filter.
    注释3：MS在TFT中指明包过滤符，因为网络侧可以执行合适的授权。
    在9.2章节中提到的会话管理流程有如下限制：
- MS在发送这个PDP上下文的TFT之前都不应为这个PDP上下文升级QOS。
- 如果带有包过滤的TFT和一个PDP上下文关联，并且在MS和PGW/GGSN中设置了，则MS仅允许修改PDP上下文的Qos Profile中的比特率参数；
- MS在发起任何二次PDP上下文激活流程时都不应不带TFT。
    注释4：在对一个没有TFT的PDP上下文去激活后，PGW或GGSN使用网络侧请求的二次PDP上下文激活流程来发起这个PDP上下文的重建，并不发送TFT给MS。
- MS不应为一个已经建立的并且没有TFT的PDP上下文尝试去加入一个TFT。
- 仅是在TFT中设置了包过滤的实体（或者是MS或者是PGW/GGSN）才允许来修改或删除这个包过滤。

    The MS indicates support of the network requested bearer control through the Network Request Support UE (NRSU) parameter, which is applicable to all PDP contexts within the same PDP address / APN pair. The SGSN indicates support of the network requested bearer control through the Network Request Support Network (NRSN) parameter.
    If the NRSN is not included in the Update PDP Context Request message from the SGSN, or the SGSN does not indicate support of the network requested bearer control, the GGSN or P GW shall, following a SGSN-Initiated PDP Context  Modification (triggered by SGSN change), perform a GGSN or P GW-Initiated PDP Context Modification to change the BCM to 'MS-Only' for all PDP-Address/APN-pairs for which the current BCM is 'MS/NW'.
   Upon receiving a Deactivate PDP Context Request message, the SGSN shall initiate procedures to deactivate the PDP context. When the last PDP context associated with a PDP address is deactivated, N PDU transfer for this PDP address is disabled.
   An MS does not have to receive the (De ) Activate PDP Context Accept message before issuing another (De )Activate PDP Context Request. However, only one request can be outstanding for every TI.
   MS通过NRSU（网络请求支持之UE）参数来指示对网络侧请求的承载控制的支持，并适用于在相同PDP地址/APN对中的所有PDP上下文（即一个Primary+n个Secondary PDP上下文）。SGSN通过NRSN（网络侧请求之网络）这个参数来指示对网络侧请求的承载控制功能的支持。
   如果NRSN在SGSN发送的Update PDP Context Request消息中没有包含，或者SGSN指示了不支持网络侧请求的承载控制，GGSN或PGW，应该，在完成这个SGSN发起的PDP上下文修改（由SGSN变化触发）之后，执行一个GGSN或PGW发起的PDP上下文修改流程将对所有PDP地址/APN对的BCM从/MS/NW'切换到'MS_Only"。
   一旦接收到一个PDP上下文去激活请求消息，SGSN应执行流程来去激活这个PDP上下文。当最后一个和这个PDP地址关联的PDP上下文本去激活后，到这个PDP地址的N-PDU的传递功能也将被禁止。
   一个MS在发起另一个激活/去激活PDP上下文请求之前，不需要等待接收到当前的激活/去激活PDP上下文接受消息。然而，对所有TI（Transcation ID)来说,只有一个请求可以是未完成的。(也就是隐含的说明了，MS在收到一个PDP激活accept消息之前，不能发起另一个PDP上下文的激活请求）。

   By sending a RAB Release Request or Iu Release Request message to the SGSN, the RAN initiates the release of one or more RABs. The preservation function allows the active PDP contexts associated with the released RABs to be preserved in the CN, and the RABs can then be re-established at a later stage.
   An S4-based SGSN shall for all active PDN Connections for a certain MS use either S4 or Gn/Gp. This is achieved by the SGSN rejecting a PDP Context activation violating this:
- If an MS is sending an Activate PDP Context Request for an APN using Gn, the activation will be rejected by the SGSN if a PDP Context using S4 already exists for this MS;
- If an MS is sending an Activate PDP Context Request for an APN using S4, the activation will be rejected by the SGSN if a PDP Context using Gn already exists for this MS.
   If case S4 is selected for a certain MS the SGSN shall not modify the EPS bearer level QoS parameters received from the PDN GW during establishment or modification of a dedicated bearer. The SGSN may, however, reject the establishment or modification of a dedicated bearer (e.g. in case of roaming when the bearer level QoS parameter values do not comply with a roaming agreement).
   通过发送一个RAB Release Request或Iu Release Request消息给SGSN,RAN将释放一个或多个RABs。保持功能将允许这些已经被释放了RAB的active PDP上下文仍然在核心网中被保持下来，而RABs可以在后续阶段被重新建立。
   一个S4-SGSN应为对应某个特定MS的所有active的PDN连接使用S4或Gn/Gp接口。这是如下实现的---当一个PDP上下文的激活违反了下面的规则，则SGSN将拒绝进行激活：
- 如果一个MS使用Gn接口来发送一个Activate PDP Context Request，且有一个PDP上下文已经通过S4接口为这个MS创建了，则SGSN将拒绝这个激活。
- 如果一个MS使用S4接口来发送一个Activate PDP Context Request，且有一个PDP上下文已经通过Gn接口为这个MS创建了，则SGSN将拒绝这个激活。
   万一为一个特定的MS选择了S4接口，则SGSN不应修改在建立期间从PGW收到的EPS承载级别Qos参数，也不应去修改一个专有承载的修改。但SGSN可以，拒绝一个专有承载的建立或修改（例如：如果在漫游的场景中，承载级别Qos参数和运营商之间的漫游协定不一致的情况下）。

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  The following text describes the general principles used by an SGSN using S4 when mapping between PDP Contexts and EPS Bearers.
  The MS is using PDP Context Activation, Modification and Deactivation functions, and PDP Contexts are therefore used between MS and SGSN. An SGSN using Gn/Gp only will use these procedures towards GGSNs as well. An SGSN using S4 will for a specific PDP Context towards an MS map these procedures into equivalent procedures using EPS Bearer towards S GW and P GW. EPS Bearer procedures will not be used between MS and SGSN.
  以下文字描述了一个S4-SGSN在PDP上下文和EPS承载之间进行映射时应遵循的通用的原则。
  MS使用PDP上下文激活、修改和去激活功能后，一个PDP上下文将在MS和SGSN之间使用。一个仅基于Gn/Gp接口的SGSN将只使用上述这些流程和GGSN进行交互。但一个基于S4接口的SGSN则需要将和MS交互的上述流程进行映射，变成和EPC（下一代的PS核心网）等价的流程，从而使用EPS（演进的包交换系统）承载和SGW/PGW进行交互。EPS承载流程不在MS和SGSN之间使用。

  The following principles are to be used:
- 1:1 mapping between one PDP context and one EPS Bearer;
- 1:1 mapping between NSAPI and EPS Bearer ID;
- The P GW treats an MS-initiated request, e.g. a Secondary PDP Context Activation Request, according to the UE-initiated Resource Request procedures in TS 23.401 [89];
- PDN GW and Serving GW need to be RAT aware to allow for 2G/3G specific handling of EPS bearers, e.g. MS initiated secondary PDP Context activation must make the P GW to activate a new EPS bearer.
- The QoS profiles of the PDP context and EPS bearer are mapped as specified in TS 23.401 [89].
- If the S4 SGSN receives default bearer QoS information per subscribed APN from the HSS, the S4 SGSN enforces this QoS for the first PDP context which is activated to the given APN. Otherwise the S4 SGSN restricts requested QoS according to the maximum QoS per subscribed APN.
  因此，将使用下面的原则进行映射：
- 一个PDP上下文和一个EPS承载进行1对1映射。
- NSAPI和EPS Bearer ID进行1对1映射。
- PGW上，将把MS发起的请求，例如二次PDP上下文激活请求等，根据TS23.401中规定的UE发起的资源请求流程来进行对待。
- PGW和SGW需要了解RAT类型，来允许针对2G/3G关于EPS承载的特定处理，例如MS发起的二次激活流程一定要使得PGW来激活一个新的EPS承载。
- PDP上下文和EPS承载中的Qos profile将根据TS23.401的规定来进行映射。
- 如果一个S4-SGSN从HSS接收到每个签约APN的缺省承载QOS信息，那S4-SGSN将为使用这个APN的第一个激活的PDP上下文强制使用这个缺省的Qos信息。另外，S4-SGSN还将根据每个签约APN的最大Qos来对请求的Qos进行限制。

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   PDP addresses can be allocated to an MS in four different ways:
- the HPLMN operator assigns a PDP address permanently to the MS (static PDP address);
- the HPLMN operator assigns a PDP address to the MS when a PDP context is activated (dynamic HPLMN PDP address);
- the VPLMN operator assigns a PDP address to the MS when a PDP context is activated (dynamic VPLMN PDP address); or
- the PDN operator or administrator assigns a permanent or dynamic IP address to the MS (External PDN Address Allocation).
   PDP地址可以通过以下四种不同方式分配给MS：
- HPLMN运营商为MS分配一个永久的PDP地址（静态PDP地址）；
- HPLMN运营商在一个PDP上下文激活时为MS分配一个PDP地址；（动态HPLMN PDP地址）；
- VPLMN运营商在一个PDP上下文激活时为MS分配一个PDP地址；（动态HPLMN PDP地址）；
- PDN运营商或者管理员为MS分配一个永久或动态IP地址（外部PDN地址分配）。

  It is the HPLMN operator that defines in the subscription whether a dynamic HPLMN or VPLMN PDP address can be used. The HPLMN operator may assign a static PDP address in the PDP context subscription record. An MS implemented according to this version of the protocol does not support static PDP addresses, which are permanently configured in the MS and sent by the MS within the PDP context activation request. The handling of static addresses, which are sent by the MS, is retained in the SGSN in order to ensure backwards compatibility for MSs implemented according to earlier protocol releases.
  For every IMSI, zero, one, or more dynamic PDP addresses per PDP type can be assigned. For every IMSI, zero, one, or more static PDP addresses per PDP type can be subscribed to.
  HPLMN运营商可以在签约数据中定义，是否可以使用一个动态的HPLMN或一个VPLMN PDP地址。HPLMN运营商可以在PDP上下文签约记录中分配一个静态PDP地址。一个按照这个版本的协议实现的MS，如果协议不支持静态PDP地址，但在MS中预配置了静态PDP地址，并在PDP上下文请求中发送给网络侧。对于这种由MS发过来的静态地址的处理，在SGSN中仍保持着，这是为了保持和MS中这个协议早期版本的向后兼容性。
  对于所有的IMSI，每个PDP类型可以有0个、1个或多个动态PDP地址分配。对于所有的IMSI，每个PDP类型可以签约0个、1个或多个静态PDP地址。

  When dynamic addressing from the HPLMN or the VPLMN is used, it is the responsibility of the GGSN or P GW to allocate and release the dynamic PDP address.
  When External PDN Address Allocation is used, the following applies for GGSN:
- the PLMN may obtain a PDP address from the PDN and provide it to the MS during PDP context activation, or the MS may directly negotiate a PDP address with the PDN after the PDP context activation procedure is executed. If the PLMN provides the address during PDP context activation in case of External PDN Address Allocation, then it is the responsibility of the GGSN and PDN to allocate and release the dynamic PDP address by means of protocols such as DHCP or RADIUS. If DHCP is used, the GGSN provides the function of a DHCP Client. If RADIUS is used, the GGSN provides the function of a RADIUS Client. If the MS negotiates a PDP address with the PDN after PDP context activation in case of External PDN Address Allocation, it is the responsibility of the MS and the PDN to allocate and release the PDP address by means of protocols such as DHCP or MIP. In case of DHCP, the GGSN provides the function of a DHCP Relay Agent as defined in RFC 2131 [47] and RFC 1542 [45]. In case of MIP, the GGSN provides the function of a Foreign Agent as defined in RFC 3344 [46].
  当在HPLMN或VPLMN需要使用动态地址，这将是GGSN或PGW的职责来分配和释放这些动态PDP地址。
  当外部PDN地址分配需要用到时，下面的规则将应用到GGSN上：
- PLMN可以从PDN获取一个PDP地址并且在PDP上下文激活流程中提供给MS，或MS可以在PDP上下文激活流程执行后，直接和PDN去协商一个PDP地址。如果PLMN在PDP上下文激活期间使用外部PDN地址来为MS提供动态地址，那这将是GGSN和PDN的职责来分配和释放这些动态PDP地址，可以通过DHCP或RADIUS等方法来实现。如果使用的是DHCP，GGSN就将作为DHCP的客户端。如果使用的是RADIUS，那GGSN也应提供RADIUS客户端的功能。如果MS在PDP上下文激活流程之后和PDN协商了一个外部的PDN地址的分配，那这将是MS和PDN的职责来分配和释放这些PDP地址，可以使用DHCP或MIP的方法。如果使用的是DHCP，GGSN就将作为DHCP消息的中继代理，在RFC2131和RFC1542中定义。如果使用的是MIP，GGSN将提供外部代理的功能，这在RFC3344中定义。

  External PDN Address Allocation (including DHCP functionality) in P GW is specified in TS 23.401 [89].
Only static PDP addressing is applicable in the network-requested PDP context activation case.
  When SGSN is using S4 is PDP type IPv4v6 supported:
  PDP types IPv4, IPv6 and IPv4v6 are supported. A PDP Context of PDP type IPv4v6 may be associated with one IPv6 address/prefix only or with both one IPv4 and one IPv6 address/prefix. PDP types IPv4 and IPv6 are utilised in case the MS and/or the GGSN or P GW support IPv4 addressing only or IPv6 addressing only; or operator preferences dictate the use of a single IP version type only, or the subscription is limited to IPv4 only or IPv6 only. In addition, PDP types IPv4 and IPv6 are utilised for interworking with nodes of earlier releases.
  PGW上的外部PDN地址分配（包括DHCP功能）在TS23.401中定义。在网络侧请求的PDP上下文激活场景中只适用静态PDP地址。
  当SGSN使用S4接口并且支持PDP类型IPV4V6的情况下：
  PDP类型IPV4，IPV6以及IPV4V6都支持。一个PDP类型IPV4V6的PDP上下文仅和一个IPV6地址/前缀关联，或者和一个IPV4和一个IPV6地址/前缀关联。PDP类型IPV4和IPV6将在MS和/或GGSN或PGW仅支持IPV4地址或仅支持IPV6地址的情况下使用；或者运营商期望仅使用单一的一种IP版本，或者签约数据限制了只能使用IPV4或IPV6.另外，PDP类型IPV和IPV6也可以在节点间早期版本之间的互操作场景中使用。

  PDP types are set by the MS as follows:
- An MS, which is IPv6 and IPv4 capable, shall request for PDP type IPv4v6.
- An MS, which supports IPv4 addressing only, shall request for PDP type IPv4.
- An MS, which supports IPv6 addressing, shall request for PDP type IPv6.
- When the IP addressing capability of the MS is not known in the MS (as in the case when the MT and TE are separated and the capability of the TE is not known in the MT), the MS shall request for PDP type IPv4v6.
  During the PDP Context Activation procedure the S4 SGSN compares the requested PDP type to the PDP type in the subscription records for the given APN and sets the PDP type as follows:
- If the requested PDP type is allowed by subscription, the S4 SGSN sets the PDP type as requested.
- If the requested PDP type is IPv4v6 and subscription data only allows PDP type IPv4 or only allows PDP type IPv6, the S4 SGSN sets the PDP type according to the subscribed value. A reason cause shall be returned to the UE indicating that only the assigned PDP type is allowed. In this case the UE shall not request for another PDP context to the same APN for the other IP version.
- If the requested PDP type is IPv4 or IPv6, and neither the requested PDP type nor PDP type IPv4v6 are subscribed, the PDP context activation request is rejected.
- If the requested PDP type is IPv4v6, and both IPv4 and IPv6 PDP types are allowed by subscription but not IPv4v6, the S4 SGSN shall set the PDP type to IPv4 or IPv6 where the selection between IPv4 and IPv6 is implementation specific. The MS may then initiate another PDP Context Activation procedure to this APN in order to activate a second PDP context with the other single address PDP type which was not allocated by the network.
  PDP类型将根据以下规则在MS中设置：
- 一个MS，支持IPV4和IPV6，应请求PDP类型IPV4V6/
- 一个MS，只支持IPV4，应请求PDP类型IPV4。
- 一个MS,只支持IPV6，应请求PDP类型IPV6/
- 当在MS中的IP地址能力信息未知时（比如MT和TE分离的情况，MT就不知道TE的地址能力），MS应请求PDP类型IPv4v6.
  在PDP上下文激活流程中，S4-SGSN对比针对某个给定的APN中，请求的PDP类型和签约数据中的PDP类型，根据以下原则来决定：
- 如果请求的PDP类型在签约数据中允许，S4-SGSN将按请求的PDP类型进行设置。
- 如果请求的PDP类型是IPV4V6并且签约数据仅允许PDP类型IPV4或仅允许PDP类型IPV6,S4-SGSN将根据签约数据的值来设置PDP类型。并且将给UE返回一个原因代码，来指示仅允许分配的PDP类型。在这里，UE不应为相同APN的其他PDP上下文请求不同的IP版本。
- 如果请求的PDP类型是IPV4或IPV6，并且签约数据中既不允许IPV4也不允许IPV6，则激活将被拒绝。
- 如果请求的PDP类型是IPV4V6，并且签约数据允许IPV4也允许IPV6，但不允许IPV4V6，那S4-SGSN应设置PDP类型为IPV4或IPV6，具体的选择取决于厂家的实现。MS可以发起到这个APN的另一个PDP上下文激活流程来激活第二个PDP上下文，并带有不由网络侧分配的其他PDP地址类型。
  
  The PDN GW may restrict the usage of PDP type IPv4v6 as follows:
- If the MS requests PDP type IPv4v6, but the operator preferences dictate the use of a single IP version only, the PDP type shall be changed to a single address PDP type (IPv4 or IPv6) and a reason cause shall be returned to the MS indicating that only the assigned PDP type is allowed. In this case, the MS should not request another PDP context for the other PDP type.
- If the MS requests PDP type IPv4v6, but the operator uses single addressing per PDP context due to interworking with nodes of earlier releases, the PDP type shall be changed to a single address PDP type and a reason cause of "single address bearers only" shall be returned to the MS. In this case the MS may request another PDP context for the other PDP type to the same APN with a single address PDP type (IPv4 or IPv6) other than the one already activated.
  The mechanism used to allocate an IPv4 address to an MS depends on the MS and the network capabilities. The MS may indicate to the network within the Protocol Configuration Options element that the MS wants to obtain the IPv4 address with DHCPv4 as defined in RFC 2131 [47]:
- the MS may indicate that it prefers to obtain an IPv4 address as part of the PDP context activation procedure. In such a case, the MS relies on the network to provide an IPv4 address to the MS as part of the PDP context activation procedure.
- the MS may indicate that it prefers to obtain the IPv4 address after the PDP Context Activation by DHCPv4. That is, the network does not provide the IPv4 address for the MS as part of the PDP context activation procedures but sets the PDP address as 0.0.0.0. After the PDP Context establishment procedure is completed, the MS initiates the IPv4 address allocation by using DHCPv4 (see details in TS 29.061 [27] and RFC 2131 [47]).
  If the MS does not send such an indication of address allocation preference, the network selects the IPv4 address allocation method based on per APN configuration.
  PGW可以按以下规则限制PDP类型IPV4V6的使用：
- 如果MS请求的PDP类型是IPV4V6，但是运营商期望仅使用一个单一的IP版本，PDP类型应被变更为一个单一的地址PDP类型（IPV4或IPV6）并且给MS返回一个原因代码来指示仅允许使用分配的PDP类型。在这里，ME不应为另一个PDP上下文请求另一个PDP类型。
- 如果MS请求的PDP类型是IPV4V6，但运营商因为和早期版本的节点互操作的问题使用了每个PDP上下文的单一地址类型，那PDP类型应被变更为一个单一的地址PDP类型（IPV4或IPV6)并返回一个原因代码“single address bearers only"给MS。在这里，MS可以为属于相同APN的其他PDP上下文请求一个除了激活分配到的PDP类型以外的其他PDP类型。
  这个分配IPV4地址给MS的机制，依赖于MS和网络侧的能力。MS可以通过网络侧PCO元素（即NAS消息中的一个字段）来指示网络侧MS希望通过DHCPV4的方法来获取IPV4地址，在RFC2131中定义：
- MS可以指示它期望获取一个IPV4地址，这将作为PDP激活流程的一部分。在这里，MS依赖网络侧来提供一个IPV4地址，也是作为PDP激活流程的一部分。
- MS可以指示在PDP激活流程完成之后使用DHCPV4来获取一个IPV4地址。那就是，网络侧在PDP激活流程过程中不为MS提供IPV4地址，但会设置PDP地址为0.0.0.0。在完成PDP上下文建立后，MS使用DHCPV4来获取IPV4地址。（参考TS29.061和RFC2131)。
  如果MS没有在PDP激活时说明自己的一个期望，那网络侧将根据每个APN的配置来完成IPV4地址的选择。

爱卫生

  IPv6 address allocation is somewhat different from the IPv4 address allocation procedure. The address of an IPv6 node is allocated by stateless autoconfiguration. The stateless autoconfiguration procedure does not need any external entity involved in the address autoconfiguration.
  The GGSN informs the MS that it shall perform stateless address autoconfiguration by means of the Router Advertisements, as defined in RFC 4861 [98]. For this purpose, the GGSN shall automatically and periodically send Router Advertisement messages towards the MS after a PDP context of type IPv6 is activated.
  In order to support the standard IPv6 stateless address autoconfiguration mechanism, as defined by the IETF, within the particular context of UMTS (point-to-point connections, radio resource efficiency, etc), the GGSN shall assign a prefix that is unique within its scope to each PDP context applying IPv6 stateless address autoconfiguration. The size of the prefix is according to the maximum prefix length for a global IPv6 address. This avoids the necessity to perform duplicate address detection at the network level for every address built by the MS. The GGSN shall not use the prefix advertised to the MS to configure an address on any of its interfaces.
  GGSN使用路由通告RA消息来通知MS应执行无状态地址自动配置，在RFC4861定义。因为这个原因，GGSN应在一个类型为IPV6的PDP上下文激活后，自动并且是周期性的发送RA消息给MS。
  为了支持标准的无状态IPV6地址自动配置机制，在IETF的定义中，对于某个特定的UMTS的上下文(点到点连接，无线资源效率等），GGSN应分配一个IPV6前缀并保证它在每个应用IPV6无状态地址自动配置的PDP上下文范围内唯一。前缀的长度将根据一个全局IPV6地址的最大前缀长度来决定。这将保证在网络级为所有MS分配的地址进行重复地址检测。GGSN不应将通告给MS的前缀配置到它的任何一个自己的接口上。

  To ensure that the link-local address generated by the MS does not collide with the link-local address of the GGSN, the GGSN shall provide an interface identifier (see RFC 4862 [99]) to the MS and the MS shall use this interface identifier to configure its link-local address. For stateless address autoconfiguration however, the MS can choose any interface identifier to generate addresses other than link-local, without involving the network. In particular, the SGSN and the GGSN are not updated with the actual address used by the MS, as the prefix alone identifies the PDP context.
  Figure 62 illustrates the IPv6 stateless autoconfiguration procedure The figure and its description show only the messages and actions specific to the IPv6 stateless address autoconfiguration procedure. For a complete description of the PDP Context Activation Procedure, refer to the corresponding clause.
  为了确保MS生成的链路本地地址和GGSN的链路本地地址不冲突，GGSN应给MS提供一个接口ID，MS应使用这个接口ID来配置它的链路本地地址。然而对于无状态地址自动配置，MS可以选择除了链路本地之外的任何接口ID来生成地址，不需要网络侧的参与。特别的，SGSN和GGSN没有更新MS实际使用的地址，因为仅前缀就可以识别出PDP上下文。
  图例62描述了IPv6无状态自动配置流程，对于完整的关于PDP上下文激活流程的描述，可参考相应的章节。

Figure 62: IPv6 Stateless Address Autoconfiguration Procedure

  NOTE 1: All steps in Figure 62 except step 2 are common for architecture variants using Gn/Gp based interaction with Gn/Gp-based interaction with a GGSN and using S4-based interaction with an S GW and a P GW. For a S4-based interaction with a S GW and P GW, procedure step (A) is defined in clause 9.2.2.1A.
1) The MS sends an Activate PDP Context Request message to the SGSN as defined in clause "PDP Context Activation Procedure". The MS shall leave PDP Address empty and set PDP Type to IPv6 or IPv4v6.
2) Upon reception of the Create PDP Context Request, the GGSN creates an IPv6 address composed of the prefix allocated to the PDP context and an interface identifier generated by the GGSN. This address is then returned in the PDP Address information element in the Create PDP Context Response message. The processing of the Create PDP Context Request and Create PDP Context Response, in both the SGSN and the GGSN, is otherwise as specified in clause "PDP Context Activation Procedure".

  注释1：在图例62中的所有步骤除了步骤2对于采用Gn/Gp或S4接口的SGSN来说都是公共的流程。针对基于S4接口和SGW/PGW的交互，步骤A在章节9.2.2.1A中描述。

1）MS发送Activate PDP Context Request消息给SGSN。MS应将PDP地址字段设为空，并将PDP Type字段设为IPV6或IPV4V6.

2）一旦接收到Create PDP Context Request,GGSN创建一个由分配给这个PDP上下文的前缀再加上一个接口ID组成的IPv6地址。这个地址将在Create PDP Context Response消息的PDP地址信息元素中返回给SGSN。

  NOTE 2: Since the MS is considered to be alone on its link towards the GGSN, the interface identifier does not need to be unique across all PDP contexts on any APN.
3) The MS receives the IPv6 address produced by the GGSN in the Activate PDP Context Accept. The MS extracts the interface identifier from the address received and stores it. The MS shall use this interface identifier to build its link-local address and may also use it for building its full IPv6 address, as describe in step 5. The MS shall ignore the prefix contained in the address received in the Activate PDP Context Accept. The processing of the Activate PDP Context Accept is otherwise as specified in clause "PDP Context Activation Procedure".
4) The MS may send a Router Solicitation message to the GGSN to activate the sending of the Router Advertisement message.
  注释2：因为MS被认为在它的链路上和GGSN是独立的，那接口ID不需要在任意APN的所有PDP上下文中唯一。

3）MS在Activate PDP Context Accept消息中接收到IPv6地址。MS从收到的地址中提取出接口ID部分并且保存起来。MS应使用这个接口ID来构建它的链路本地地址，并且也可以使用它来构建自己的完整IPV6地址，在步骤5描述。MS应忽略在Activate PDP Context Accept消息中接收到的地址的前缀部分。

4）MS可以发送一条RS消息给GGSN来激活RA消息的发送。

5) The GGSN sends a Router Advertisement message. The Router Advertisement messages shall contain the same prefix as the one provided in step 2. A given prefix shall not be advertised on more than one PDP context on a given APN, or set of APNs, within the same addressing scope. The GGSN shall be configured to advertise only one prefix per PDP context.
   After the MS has received the Router Advertisement message, it constructs its full IPv6 address by concatenating the interface identifier received in step 3, or a locally generated interface identifier, and the prefix received in the Router Advertisement. If the Router Advertisement contains more than one prefix option, the MS shall only consider the first one and silently discard the others.
   NOTE 3: The MS can at any time change the interface identifier used to generate full IPv6 addresses, without involving the network, i.e. without updating the PDP context in the SGSN and the GGSN.
   Because any prefix that the GGSN advertises in a PDP context is unique within the scope of the prefix (i.e. site-local or global), there is no need for the MS to perform Duplicate Address Detection for this IPv6 address. Therefore, the GGSN shall silently discard Neighbor Solicitation messages that the MS may send to perform Duplicate Address Detection. It is possible for the MS to perform Neighbor Unreachability Detection towards the GGSN, as defined in RFC 4861 [98]; therefore if the GGSN receives a Neighbor Solicitation as part of this procedure, the GGSN shall provide a Neighbor Advertisement as described in RFC 4862 [99].
5）GGSN发送一个RA消息。这个消息包含了在步骤2中相同的前缀。一个给定的前缀不应在具有相同地址范围的一个APN或一组APN的多个PDP上下文中通告。GGSN应在配置时注意这一点，仅为每个PDP上下文配置通告一个前缀。

   在MS收到RA消息之后，它将步骤3中收到的接口ID或一个本地产生的接口ID和RA消息的前缀连接在一起，构建自己的完整的IPV6地址。如果RA中包含了多个前缀选项，MS应只考虑第一个并将剩下的丢弃。

   注释3：MS可以在任何时候改变自己的接口ID来生成完整的IPV6地址，而不需要网络侧的参与，也就是在SGSN和GGSN上没有PDP上下文的更新消息。

   因为在GGSN通告的一个PDP上下文的任意前缀在前缀范围内都是唯一的（也就是站点-本地或全局地址），因此没有必要为MS来执行IPV6地址的重复检测。因此，GGSN应默默地丢弃掉可能用于执行重复地址检测的NS消息。也可以让MS来执行到GGSN的邻居不可达检测（NUD），在RFC4861中定义；因此如果GGSN收到了作为这个流程一部分的NS消息，GGSN应提供一个NA响应，这在RFC 4862中描述。

yinxueai

新的版本啦，改变了好多呀

ligq1812

太好了，，学习学习