[attach]436[/attach]
Figure 63- PDP Context Activation Procedure for A_Gb mode
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Figure 64- PDP Context Activation Procedure for Iu mode
NOTE 1: All steps in figures 63 and 64, except steps 4 and 8, are common for architecture variants using Gn/Gp based interaction with GGSN and using S4 based interaction with S GW and P GW. For an S4-based interaction with S GW and P GW, procedure steps (A) and (B) are defined in clause 9.2.2.1A.
If Emergency Service is required and an emergency PDP Context is not already active the MS shall request a PDP Context for emergency services via emergency indication in the Activate PDP Context Request message when initiating the PDP Context Request Procedure. An emergency attached MS shall initiate the PDP Context Request procedure directly after the Attach procedure is completed. Any additional emergency PDP Context Activation by an MS shall be rejected by the SGSN if there is already an emergency PDP context activated.
注释1：所有在图例63和64描述的步骤，除了步骤4和8，对于使用Gn/Gp接口和GGSN交互，还是使用S4接口和SGW/PGW交互都是公共的流程。对于使用S4接口和SGW/PGW的交互，步骤A和B在9.2.2.1A中定义。
如果需要紧急服务但又没有一个紧急的PDP上下文是active的，则MS应在发起PDP激活流程时，在Activate PDP Context Request消息中携带紧急指示来请求一个用于紧急业务的PDP上下文。一个已经紧急附着的MS应在附着流程完成之后发起PDP上下文激活流程。如果已经有一个紧急PDP上下文激活的话，则任意额外的PDP上下文激活请求都将被SGSN拒绝。
1) The MS sends an Activate PDP Context Request (NSAPI, TI, PDP Type, PDP Address, Access Point Name, QoS Requested, Protocol Configuration Options, Request Type) message to the SGSN. In this version of the protocol, the MS shall leave PDP Address empty. The MS may use Access Point Name to select a reference point to a certain packet data network and/or to select a service. Access Point Name is a logical name referring to the packet data network and/or to a service that the subscriber wishes to connect to. QoS Requested indicates the desired QoS profile. For an E-UTRAN capable UE, the QoS requested shall include interactive or background traffic class in this message. If the UE is not E-UTRAN capable, in this release the QoS requested should include interactive or background traffic class in this message. If the request is as a result of a Network-Requested PDP context activation procedure, the MS shall not set the PDP Type to IPv4v6, but to the value received in the Request PDP Context Activation message: see clause 9.2.2.2.1.
1）MS发送一个Activate PDP Context Request(NSAPI、TI、PDP Type、PDP Address、APN、Qos Requested、PCO、Request Type）消息给SGSN。在这个版本的协议中,MS应将PDP地址留为空。MS可以使用APN来选择到一个特定PDN网络的参考点并且/或者选择某项服务。APN是一个逻辑的名字，对应到一个PDN网络并且/或者一个签约用户期望连接的服务。"Qos Requested"指示了Qos profile。对于一个具有LTE能力的UE，则请求的QOS应指示交互式或背景类的流量类别。如果UE没有LTE的能力，在这个规范版本中，请求的Qos应指示交互式或背景类的流量类别。如果这个请求消息是作为一个"Network Requested PDP Context Activation"流程的结果，MS则不应将PDP类型设置为IPv4v6，但是应在请求的PDP上下文激活消息中设置，参考9.2.2.2.1。
NOTE 2: In case an S4-SGSN is used in the network the QoS Requested information element shall be ignored in the network.
Protocol Configuration Options is used to transfer the NRSU and Address Allocation Preference to the GGSN and may be used to transfer the BCM as well as optional PDP parameters and/or request to the GGSN (see TS 29.060 [26] and TS 24.229 [75]). Protocol Configuration Options is sent transparently through the SGSN. NRSU indicates MS support of the network requested bearer control. The Protocol Configuration Options may include the Address Allocation Preference indicating that the MS prefers to obtain an IPv4 address only after the PDP Context Accept by means of DHCPv4 as defined in RFC 2131 [47].
注释2：如果场景中是一个S4-SGSN，则Qos Requested IE应被网络侧忽略。
PCO用于传递NRSU和地址分配期望给GGSN并且可用来传递BCM以及可选的PDP参数以及/或者请求给GGSN（参考TS29.060以及TS24.229)。PCO通过SGSN进行透明的传递。NRSU指示了MS对网络侧请求的承载控制的支持能力。PCO也可以包含MS的地址分配期望来指示GGSN，MS是仅期望在PDP上下文接受后通过DHCPV4的方法来获取一个IPv4的地址。
If the SGSN has stored a value for the Maximum APN restriction and the value indicates the most restrictive type, then the SGSN shall reject any Activate PDP Context requests to a different APN, using the PDP Context Activation Reject message including an appropriate error cause.
If the SGSN decides to establish Direct Tunnel between RNC and GGSN, the SGSN provides to the RNC the Direct Tunnel specific parameters in step 5 "RAB Assignment Procedure" and shall initiate PDP Context Update procedure in step 8 to update IP Address and TEID for Downlink data.
Request Type indicates "Handover" when the MS has already an activated PDN GW/HA due to mobility with non-3GPP accesses, and is only interpreted by SGSNs using S4.
如果存储了一个最大APN限制的值并且这个值指示了限制类型，SGSN应拒绝任意到另一个不同APN的PDP上下文激活请求，使用PDP Context Activation Reject消息并包含一个合适的错误代码。
如果决定在RNC和GGSN之间建立直接隧道，则SGSN在步骤5"RAB Assignment流程"中给RNC提供直接隧道相关的参数并且应在第8步发起PDP Context Update流程来更新下行数据的IP地址和TEID。
Request Type在MS因为非3GPP接入的移动已经有一个激活的PDN GW/HA，指示为"Handover"。并仅仅由使用S4接口的SGSN来解释。
The PDP context activation for emergency services shall be exempted from the Maximum APN restriction control. If there is already an emergency bearer activated, the SGSN shall reject any PDP context activation request for normal services if the mobility and access restrictions do not allow the MS to access normal services.
If the message is being sent via a HNB which has a collocated L-GW, it includes the L-GW address in the Direct Transfer message to the SGSN.
对于紧急业务的PDP上下文激活不受最大APN限制的控制。如果已经有紧急承载激活了，并且移动和接入限制不允许MS来接入正常业务的话，则SGSN应拒绝任何正常业务的PDP上下文激活请求。
如果消息是通过带有捆绑LGW的HNB（家庭基站）发送，它将在直传消息中包含L-GW地址给SGSN。
2) In A/Gb mode, security functions may be executed. These procedures are defined in clause "Security Function".
3) In A/Gb mode and if BSS trace is activated, the SGSN shall send an Invoke Trace (Trace Reference, Trace Type, Trigger Id, OMC Identity) message to the BSS. Trace Reference, and Trace Type are copied from the trace information received from the HLR or OMC.
4) The SGSN validates the Activate PDP Context Request using PDP Type (optional), PDP Address (optional), and Access Point Name (optional) provided by the MS and the PDP context subscription records. The SGSN shall use the CSG Subscription Data to authorize the LIPA connection to the APN provided by the MS. A PDP Address may only be sent by an MS implemented according to an earlier protocol release. The validation criteria, the APN selection criteria, and the mapping from APN to a GGSN are described in annex A.
2）对A/Gb模式，可以执行安全功能。这些流程请参考章节“安全功能”。
3）对于A/Gb模式并且BSS的trace功能激活了，SGSN应发送Invoke Trace(Trace Reference, Trace Type, Trigger Id,OMC Identity)消息给BSS。Trace Reference，以及Trace Type是从HLR或OMC收到的trace信息中复制过来的。
4）SGSN使用PDP上下文的签约数据来对MS的Activate PDP Context Request消息中的PDP Type（可选），PDP地址（可选）以及APN（可选）来进行验证。SGSN应使用CSG签约信息来为提供了APN的MS的LIPA连接进行授权。PDP地址仅可以是由一个早期协议版本实现MS发送。验证的原则，APN选择的原则，APN和GGSN的映射请参考附录A。
For an emergency PDP Context Activation the SGSN applies the parameters from SGSN Emergency Configuration Data for the emergency bearer establishment performed in this step and any potentially stored IMSI related subscription data are ignored by the SGSN.
If no GGSN address can be derived or if the SGSN has determined that the Activate PDP Context Request is not valid according to the rules described in annex A, the SGSN rejects the PDP context activation request.
If a GGSN address can be derived, the SGSN creates a TEID for the requested PDP context. If the MS requests a dynamic address, the SGSN lets a GGSN allocate the dynamic address. The SGSN may restrict the requested QoS attributes given its capabilities and the current load, and it shall restrict the requested QoS attributes according to the subscribed QoS profile.
对于一个紧急的PDP上下文激活，SGSN将应用SGSN中关于紧急配置数据中的参数来建立紧急承载，其他的可能存储的和IMSI相关的签约数据在SGSN中将被忽略。
如果获取不到GGSN的地址，或者如果SGSN认为这个请求的Activate PDP Context Request消息经过对照附录A的规则进行检查发现是invalid,则SGSN拒绝这个PDP上下文的激活请求。
如果可以获取到GGSN的地址，则SGSN为请求的PDP上下文创建一个TEID。如果MS请求一个动态地址，SGSN将让GGSN来分配动态地址。SGSN可以根据它的能力以及当前的负荷状况来限制MS请求的Qos，并且也应根据用户签约的Qos profile里的数据来限制用户请求的Qos属性。
The SGSN sends a Create PDP Context Request (PDP Type, PDP Address, Access Point Name, QoS Negotiated, Negotiated Evolved ARP, TEID, NSAPI, MSISDN, Selection Mode, Charging Characteristics, Trace Reference, Trace Type, Trigger Id, OMC Identity, Protocol Configuration Options, serving network identity, Maximum APN Restriction IMEISV, CGI/SAI, User CSG Information, RAT type, S-CDR CAMEL information, MS Info Change Reporting support indication, NRSN, Dual Address Bearer Flag, APN-AMBR) message to the affected GGSN. The Negotiated Evolved ARP IE shall contain the Subscribed Evolved ARP value. If the SGSN did not receive a Subscribed Evolved ARP value in subscription data from the HLR the SGSN shall derive this value from the Allocation/Retention Priority of the QoS profile negotiated according to Annex E in TS 23.401 [89]. The inclusion of the Negotiated Evolved ARP IE indicates that the SGSN supports the Evolved ARP feature. The SGSN shall send the serving network identity to the GGSN. Access Point Name shall be the APN Network Identifier of the APN selected according to the procedure described in Annex A. PDP Address shall be empty if a dynamic address is requested. The GGSN may use Access Point Name to find a packet data network and optionally to activate a service for this APN. Selection Mode indicates whether a subscribed APN was selected, or whether a non-subscribed APN sent by an MS or a non-subscribed APN chosen by the SGSN was selected. Selection Mode is set according to Annex A. The GGSN may use Selection Mode when deciding whether to accept or reject the PDP context activation. For example, if an APN requires subscription, the GGSN is configured to accept only the PDP context activation that requests a subscribed APN as indicated by the SGSN with Selection Mode. Charging Characteristics indicates which kind of charging the PDP context is liable for. The charging characteristics on the subscription and individually subscribed APNs as well as the way the SGSN handles Charging Characteristics and chooses to send them or not to the GGSN is defined in TS 32.251 [70]. The SGSN shall include Trace Reference, Trace Type, Trigger Id, and OMC Identity if GGSN trace is activated. The SGSN shall copy Trace Reference, Trace Type, and OMC Identity from the trace information received from the HLR or OMC. The Maximum APN Restriction denotes the most stringent restriction as required by any already active PDP contexts. If there are no already active PDP contexts, this value is set to the least restrictive type (see clause 15.4). If the GGSN receives the Maximum APN Restriction, then the GGSN shall check if the Maximum APN Restriction value does not conflict with the APN Restriction value associated with this PDP context request. If there is no conflict the request shall be allowed, otherwise the request shall be rejected with the SGSN sending a PDP Context Activation Reject Message to the MS including an appropriate error cause. NRSN indicates SGSN support of the network requested bearer control. The Dual Address Bearer Flag shall be set when the MS requests PDN type IPv4v6 and all SGSNs, which the MS may be handed over to, are Release 8 or above supporting dual addressing, which is determined based on node pre configuration by the operator.
SGSN发送一个Create PDP Context Request(PDP Type, PDP Address, Access Point Name, QoS Negotiated, Negotiated Evolved ARP, TEID, NSAPI, MSISDN, Selection Mode, Charging Characteristics, Trace Reference, Trace Type, Trigger Id, OMC Identity, Protocol Configuration Options, serving network identity, Maximum APN Restriction IMEISV, CGI/SAI, User CSG Information, RAT type, S-CDR CAMEL information, MS Info Change Reporting support indication, NRSN, Dual Address Bearer Flag, APN-AMBR)消息给相应的GGSN。协商的演进ARP IE应包含签约的演进ARP的值。如果SGSN没有从HLR的签约数据中获取这个值，那SGSN应按照TS23.401附录E的规则，从协商的Qos profile里面的ARP值来获取对应的演进ARP。协商的演进ARP IE指示了SGSN是否支持这个特性。SGSN应发送服务网络ID给GGSN。APN应该是根据附录A的规则选择的APN的Network ID部分。如果请求的是动态地址，则PDP地址 IE应留为空。GGSN可以使用APN来找到对应的PDN网络以及可选的来为这个APN激活某项业务。选择模式指示了是否选择的是一个签约的APN，或者是由MS发送的未签约的APN，或者是由SGSN选择未签约的APN。选择模式根据附录A进行设置。GGSN可以使用选择模式来决定是接受还是拒绝这个PDP上下文的就好哦。例如：如果是一个请求签约的APN，GGSN上配置了可以接受由SGSN通过选择模式指示请求一个签约APN。计费特征CC指示了PDP上下文适用于什么类型的计费。签约数据中的CC以及个别签约的APN以及SGSN处理CC的方法以及选择它们来发送或不发送给GGSN，在TS32.251中定义。如果GGSN trace激活了，SGSN则应在消息中包含Trace Reference, Trace Type, Trigger Id, 和OMC Identity。上述这些和trace有关的信息是从HLR或OMC中收到，并复制过来的。最大APN限制指示了针对任意已经激活的PDP上下文的最严厉的限制。如果没有已经激活的PDP上下文，这个值将设置为最少限制类型（参考章节15.4）。如果GGSN收到了这个最大APN限制，那么GGSN应检查最大APN限制的值和这个PDP上下文请求关联的APN限制的值不冲突。如果没有冲突，则请求被允许，否则请求应被拒绝，并带上合适的原因代码。NRSN指示了SGSN是否支持网络侧请求的承载控制。Dual Address Bearer Flag是在MS请求PDN类型为IPv4v6的时候设置。
For emergency attached UEs IMSI is included if available and if the IMSI cannot be authenticated the IMSI is included and marked as unauthenticated.
The GGSN creates a new entry in its PDP context table and generates a Charging Id. The new entry allows the GGSN to route PDP PDUs between the SGSN and the packet data network, and to start charging. The way the GGSN handles Charging Characteristics that it may have received from the SGSN is defined in TS 32.251 [70]. The GGSN may restrict QoS Negotiated given its capabilities and the current load or increase the QoS Negotiated based on any external input (e.g. policy control). The GGSN then returns a Create PDP Context Response (TEID, PDP Type, PDP Address, Protocol Configuration Options, QoS Negotiated, Negotiated Evolved ARP, Charging Id, Prohibit Payload Compression, APN Restriction, Cause, MS Info Change Reporting Action, CSG Information Reporting Action, BCM, APN-AMBR) message to the SGSN. The GGSN sets the Negotiated Evolved ARP based on local policy or PCC. The Allocation/Retention Priority of the QoS Profile Negotiated is derived from the Evolved ARP according to the mapping principles of TS 23.401 [89], Annex E. The Prohibit Payload Compression indicates that the SGSN should negotiate no data compression for this PDP context. The SGSN shall apply the Negotiated Evolved ARP if received from the GGSN. If the MS has requested PDP type IPv4v6 and both IPv4 and IPv6 addressing is possible in the PDN but the Dual Address Bearer Flag is not set, or only single IP version addressing is possible in the PDN, the GGSN selects a single IP version (either IPv4 or IPv6). If the MS has requested PDP type IPv4 or IPv6, the GGSN uses the PDP type supplied by the MS in case it is supported in the PDN, otherwise an appropriate error cause will be returned. The GGSN allocates a PDP Address according to the selected PDP type. If the GGSN has selected a PDN type different from the one sent by the MS, the GGSN indicates, together with the PDP type IE, a reason cause to the MS why the PDP type has been modified as described in clause 9.2.1. PDP Address is included if the GGSN allocated a PDP address. If the GGSN has been configured by the operator to use External PDN Address Allocation for the requested APN, PDP Address shall be set to 0.0.0.0, indicating that the PDP address shall be negotiated by the MS with the external PDN after completion of the PDP Context Activation procedure. The GGSN shall relay, modify and monitor these negotiations as long as the PDP context is in ACTIVE state, and use the GGSN-Initiated PDP Context Modification procedure to transfer the currently used PDP address to the SGSN and the MS. However, the MS cannot rely on always getting a session management level update of the IP address, which it has negotiated with the external PDN. This is because the P-GW does not update the IP address within the EPS bearer modification procedure, see clause 9.2.3.2A. Protocol Configuration Options contains the BCM as well as optional PDP parameters that the GGSN may transfer to the MS. BCM shall also be sent as a separate IE to the SGSN. These optional PDP parameters may be requested by the MS in the Activate PDP Context Request message, or may be sent unsolicited by the GGSN. Protocol Configuration Options is sent transparently through the SGSN.The Create PDP Context messages are sent over the backbone network. The BCM is used by the SGSN to handle unexpected session management signalling.
GGSN在它的PDP上下文中创建一个新的条目并且生成一个Charging Id.这个新的条目允许GGSN在SGSN和PDN网络之间为PDP PDUs进行路由，并且开始计费。GGSN上处理计费特征码的方法（可能从SGSN上获取）在TS32.251定义。GGSN可以根据它自己的能力以及当前的负荷情况对协商的Qos进行限制，或者根据任何外部输入（例如来自PCRF的策略控制）来增加协商的Qos。GGSN然后将返回一个Create PDP Context Response(TEID、PDP Type、PDP Address、PCO、Qos Negitiated、Negotiated Evolved ARP, Charging Id, Prohibit Payload Compression, APN Restriction, Cause, MS Info Change Reporting Action, CSG Information Reporting Action, BCM, APN-AMBR)消息给SGSN。GGSN根据本地策略或PCC来设置协商的演进ARP。协商的Qos Profile里的ARP是根据TS23.401的映射规则从演进的ARP里提取出来的。"禁止Payload压缩"指示了SGSN应为这个PDP上下文来协商无数据压缩。SGSN如果从GGSN收到协商的演进ARP的话，将应用这个值。如果MS请求的PDP Type IPv4v6并且IPv4和IPv6的地址在PDN网络中都可用的情况下则可为MS提供IPv4或IPv6，但是如果Dual Address Bearer Flag没有设置，或在PDN中仅支持一种单一的IP版本，GGSN将选择这个单一的IP版本（IPv4或IPv6）。如果MS请求的PDP类型是IPv4或IPv6，GGSN则使用MS提供的PDP类型---如果这在PDN网络中支持的话，否则将返回一个合适的原因代码。GGSN根据选择的PDP类型分配一个PDP地址。如果GGSN为MS选择了之前不一样的PDP类型，GGSN则和PDP类型 IE一起，给MS一个指示，告诉MS为什么PDP类型被修改，在9.2.1章节描述。如果GGSN分配了一个PDP地址则要包含这个PDP地址。如果GGSN配置了使用外部PDN地址分配机制（例如DHCP），则PDP地址应设置为0.0.0.0，指示MS应在完成PDP上下文激活流程之后和外部PDN网络协商来获取PDP地址。只要这个PDP上下文一直保持在Active状态，则GGSN应能为这种地址协商提供透传、修改和监控机制，并且能使用GGSN发起的PDP上下文修改流程来传递当前使用的PDP地址给SGSN和MS。然而，MS不能总是依赖于得到一个IP地址的会话管理级别的更新（如果这个IP地址是和外部PDN协商获取的）。这是因为P-GW不能在EPS承载修改流程中更新IP地址，参考9.2.3.2A章节。PCO包含了BCM以及可选的由GGSN传递给MS的PDP参数。BCM应该作为一个单独的IE来发给SGSN。可选的PDP参数可以由MS在Activate PDP Context Request消息中请求，或者由GGSN主动发送。PCO是由SGSN进行透明传递的。Create PDP Context消息通过骨干网络进行发送。BCM被SGSN用于处理不期望的会话管理信令。
If QoS Negotiated received from the SGSN is incompatible with the PDP context being activated, the GGSN rejects the Create PDP Context Request message. The GGSN operator configures the compatible QoS profiles.
If an APN Restriction is received from the GGSN for this PDP Context, then the SGSN shall store this value for the PDP Context and the SGSN shall check this received value with the stored value for the Maximum APN Restriction to ensure there are no conflicts between values. If the consequence of this check results in the PDP context being rejected, the SGSN shall initiate a PDP Context Deactivation and return an appropriate error cause. If the PDP Context is accepted, it shall determine a (new) value for the Maximum APN Restriction. If there is no previously stored value for Maximum APN Restriction, then the Maximum APN Restriction shall be set to the value of the received APN Restriction.
The emergency PDP context activation shall be exempted from the Maximum APN restriction control.
If the MS Info Change Reporting Action and/or the CSG Information Reporting Action are received from the GGSN for this PDP context, then the SGSN shall store this for the PDP context and the SGSN shall report to that GGSN whenever a CGI/SAI/RAI or user CSG information change occurs that meets the GGSN request, as described in clause 15.1.1a.
The GGSN derives the BCM based on NRSU, NRSN and operator policy if previously received in the Create PDP Context Request message. The derived BCM is sent to the MS indicating the Bearer Control Mode applicable to all PDP Contexts within the activated PDP Address/APN pair.
The SGSN shall re-verify and may restrict the QoS Negotiated received in the response from the GGSN against the subscribed QoS profile and additionally restrict the QoS negotiated based on its capabilities and current load. The SGSN shall use this updated QoS Negotiated for the subsequent steps.
The SGSN shall apply a Negotiated Evolved ARP even if it is different from the Subscribed Evolved ARP.
The SGSN determines the UE AMBR to be used by the RAN based on the subscribed UE-AMBR and the APN AMBR for active APNs, see clause 15.2.2.
[attach]901[/attach]
Figure 65 Secondary PDP Context Activation Procedure for A_Gb mode
[attach]902[/attach]
Figure 66 Secondary PDP Context Activation Procedure for Iu mode
1）The MS sends an Activate Secondary PDP Context Request (Linked TI, NSAPI, TI, QoS Requested, TFT, Protocol Configuration Options) message to the SGSN. Linked TI indicates the TI value assigned to any one of the already activated PDP contexts for this PDP address and APN. QoS Requested indicates the desired QoS profile. TFT is sent transparently through the SGSN to the GGSN to enable packet classification for downlink data transfer. TI and NSAPI contain values not used by any other activated PDP context. Protocol Configuration Options may be used to transfer optional PDP parameters and/or requests to the GGSN (see GSM 29.060 [26] and 24.229 [75]). Protocol Configuration Options is sent transparently through the SGSN.
If the SGSN decides to establish Direct Tunnel between RNC and GGSN, the SGSN provides to the RNC the Direct Tunnel specific parameters in step 4 "RAB Assignment Procedure" and shall initiate PDP Context Update procedure in step 6 to update IP Address and TEID for Downlink data.
1 MS发送Activate Secondary PDP Context Request (Linked TI, NSAPI, TI, QoS Requested, TFT, Protocol Configuration Options)消息给SGSN.Linked TI指示的TI值表明了这个PDP上下文是和一个已经建立的具有这个PDP地址和APN的PDP上下文进行关联。 QoS Requested 指明了期望的Qos profile。TFT通过SGSN透明传递给GGSN用于下行方向数据传递的包的分类。TI和NSAPI包含的值不用于任何其他的已经激活的PDP上下文。PCO用于传递可选的PDP参数和/或请求给GGSN（参考GSM 29060和24229)。PCO是通过SGSN透明传递的。
如果SGSN决定要建立一个RNC和GGSN之间的直接隧道，SGSN给RNC提供建立直接隧道相关的参数（在步骤4的RAB分配流程中指明）并且应发起PDP上下文更新流程（在步骤6中）来更新下行方向用户面的IP地址和TEID。
2) In A/Gb mode, security functions may be executed. These procedures are defined in clause "Security Function".
2 在A/Gb模式，安全功能可以执行。这个流程在"安全功能"章节定义。
3) The SGSN validates the Activate Secondary PDP Context Request using the TI indicated by Linked TI. The same GGSN address is used by the SGSN as for the already-activated PDP context(s) for that TI and PDP address.
The SGSN may restrict the requested QoS attributes given its capabilities and the current load, and it shall restrict the requested QoS attributes according to the subscribed QoS profile, which represents the maximum QoS per PDP context to the associated APN. The GGSN may restrict or increase, and negotiate the requested QoS as specified in clause "PDP Context Activation Procedure". The SGSN sends a Create PDP Context Request (QoS Negotiated, TEID, NSAPI, Primary NSAPI, TFT, Protocol Configuration Options, serving network identity, IMEISV, CGI/SAI, RAT type, S-CDR CAMEL information, CGI/SAI/RAI change support indication, Correlation-ID) message to the affected GGSN. The SGSN shall send the serving network identity to the GGSN. Primary NSAPI indicates the NSAPI value assigned to any one of the already activated PDP contexts for this PDP address and APN. TFT is included only if received in the Activate Secondary PDP Context Request message. Protocol Configuration Options is sent transparently through the SGSN if received in the Activate secondary PDP Context Request message. The Correlation-ID shall only be included if the Secondary PDP Context Activation is performed as part of the Network Requested Secondary PDP Context Activation Procedure (clause 9.2.2.3), and shall be linked to the TI as described in clause 9.2.2.3.
The GGSN uses the same packet data network as used by the already-activated PDP context(s) for that PDP address, generates a new entry in its PDP context table, and stores the TFT. The new entry will allow the GGSN to route PDP PDUs via different GTP tunnels between the SGSN and the packet data network. The GGSN returns a Create PDP Context Response (TEID, QoS Negotiated, Cause, Protocol Configuration Options, Prohibit Payload Compression, APN Restriction, CGI/SAI/RAI change report required) message to the SGSN. Protocol Configuration Options may be used to transfer optional PDP parameters to the UE (see GSM 29.060 [26] and 24.229 [75]). The Prohibit Payload Compression indicates that the SGSN should negotiate no data compression for this PDP context. If an APN Restriction is received from the GGSN for this PDP Context, then the SGSN shall store this value for the PDP Context.
If the CGI/SAI/RAI report required is received from the GGSN for this PDP context, then the SGSN shall store this for the PDP context and the SGSN shall report to that GGSN whenever a CGI/SAI/RAI change occurs that meets the GGSN request.
The SGSN shall re-verify and may restrict the QoS Negotiated received from the GGSN against the subscribed QoS profile and additionally restrict the QoS negotiated based on its capabilities and current load. The SGSN shall use this updated QoS Negotiated for the subsequent steps.
3)SGSN使用Linked TI里面指明的TI值来验证Activate Secondary PDP Context Request。SGSN将使用和关联的PDP上下文相同的GGSN地址来进行二次PDP上下文的激活。
SGSN可以根据自己的能力和当前的负荷来限制请求的Qos属性，它应根据签约的Qos profile所描述的和相关APN关联的每个PDP上下文的最大Qos来对请求的Qos进行限制。SGSN发送Create PDP Context Request (QoS Negotiated, TEID, NSAPI, Primary NSAPI, TFT, Protocol Configuration Options, serving network identity, IMEISV, CGI/SAI, RAT type, S-CDR CAMEL information, CGI/SAI/RAI change support indication, Correlation-ID) 消息给相应的GGSN。SGSN应发送serving network identity给GGSN。Primary NSAPI指示了关联的已经激活的PDP上下文的NSAPI值。TFT只有从Activate secondary PDP Context Request消息里收到了以后才会携带。Correlation-ID仅当是网络侧发起的二次PDP激活请求时才被携带，参考9.2.2.3.
GGSN将为这个PDP上下文使用相同的PDN网络和相同的PDP地址，并在它的PDP上下文表中生成一个新条目，并存储TFT。这个新条目将允许GGSN通过不同的GTP隧道来在SGSN和PDN网络之间路由PDP PDUs。GGSN返回一个Create PDP Context Response (TEID, QoS Negotiated, Cause, Protocol Configuration Options, Prohibit Payload Compression, APN Restriction, CGI/SAI/RAI change report required)消息给SGSN。PCO可用于传输一些可选的PDP参数给UE（参考GSM29060和24229）。Prohibit Payload Compression指示SGSN不应为这个PDP上下文来协商进行数据压缩。如果从GGSN那里收到了关于这个PDP上下文的APN限制，那SGSN应存储用于这个PDP上下文的这个值。
如果从GGSN收到了，要求对这个PDP上下文进行CGI/SAI/RAI报告，那SGSN应存储起来并在CGI/SAI/RAI发生变化的情况下报告给GGSN来满足GGSN的请求。
SGSN应重新验证并且限制从GGSN收到的协商的Qos，可以根据签约的Qos profile和它当前的能力和负荷情况。SGSN将应用这个更新后的Qos协商值在后续的步骤中。
4) In Iu mode, RAB setup is done by the RAB Assignment procedure.
5) In A/Gb mode, BSS packet flow context procedures may be executed. These procedures are defined in clause "BSS Context".
6) The SGSN sends an Update PDP Context Request message to the GGSN, including the QoS attributes that have been accepted by the RAN. In case the QoS attributes have been downgraded in step 5 for A/Gb mode or in step 4 for Iu mode, the SGSN may inform the GGSN about the downgraded QoS. The GGSN shall not attempt to renegotiate the QoS attributes. A RAN Procedures Ready flag is included in the Update PDP Context Request. A GGSN that receives an Update PDP Context Request with a RAN Procedures Ready flag set, should start to route downlink PDP PDUs immediately. The No QoS negotiation indication is set in Update PDP Context Request to indicate to the GGSN that the SGSN does not upgrade the previously negotiated QoS attributes and that the GGSN shall accept the provided QoS attributes without negotiation. The GGSN confirms the reception of the message and the potentially downgraded QoS attributes by sending an Update PDP Context Response to the SGSN. If the SGSN established Direct Tunnel in step 4 it shall send Update PDP Context Request and include the RNC's Address for User Plane and downlink TEID for data, the No QoS negotiation indication and DTI. DTI is used to instruct the GGSN to apply Direct Tunnel specific error handling as described in clause 13.8.
4 在Iu模式，RAB建立通过RAB Assignment流程来完成。
5 在A/Gb模式，BSS packet flow context流程可以被执行。请参考章节"BSS Context"。
6 SGSN发送Update PDP Context Request消息给GGSN，包括被RAN接受的Qos属性。一旦在A/Gb模式的步骤5或Iu模式的步骤4中的Qos被降级，SGSN应通知GGSN关于这个降级的Qos。GGSN不应尝试来重新协商Qos属性。在Update PDP Context Request会携带RAN Procedures Ready flag。当GGSN收到的请求中带有这个flag，就应立即开始发送下行的PDP PDUs。No QoS negotiation也在Update PDP Context Request消息中被指示，用来告诉GGSN，说名SGSN不能升级到之前协商好的Qos属性，GGSN应使用在这个请求消息里提供的Qos属性，并且不能再协商。GGSN发送Update PDP Context Response给SGSN来确认，并且潜在的降低Qos。如果SGSN在步骤4中建立了直接隧道，它应发送Update PDP Context Request并且包含RNC的用户面地址和TEID已经No QoS negotiation指示和DTI。DTI用于指示GGSN要应用直接隧道，在13.8章节中列出的特别错误处理事件除外。
7) The SGSN selects Radio Priority and Packet Flow Id based on QoS Negotiated, and returns an Activate Secondary PDP Context Accept (TI, QoS Negotiated, Radio Priority, Packet Flow Id, Protocol Configuration Options) message to the MS. If the MS indicated in the MS Network Capability it does not support BSS packet flow procedures, then the SGSN shall not include the Packet Flow Id. In A/Gb mode, the QoS Negotiated shall take into account the Aggregate BSS QoS Profile, if any, returned from the BSS. Protocol Configuration Options is sent transparently through the SGSN if received in the Create PDP Context Response message. The SGSN is now able to route PDP PDUs between the GGSN and the MS via different GTP tunnels and possibly different LLC links.
If the MS is incapable of accepting the new QoS Negotiated, the MS should initiate application level signalling to lower the QoS requirements for the concerned application(s). If this is not possible then the MS shall instead de-activate the PDP context with the PDP Context Deactivation Initiated by the MS procedure.
For each additionally activated PDP context a QoS profile and TFT may be requested.
If the secondary PDP context activation procedure fails or if the SGSN returns an Activate Secondary PDP Context Reject (Cause, Protocol Configuration Options) message, the MS may attempt another activation with a different TFT, depending on the cause.
7 SGSN根据协商的Qos来选择无线优先级和Packet Flow Id，并且返回一个Activate Secondary PDP Context Accept (TI, QoS Negotiated, Radio Priority, Packet Flow Id, Protocol Configuration Options)消息给MS。如果MS在MS Network Capability中曾经指示过它不支持BSS packet flow流程，那么SGSN不应包含Packet Flow Id。在A/Gb模式，协商的Qos应用于考虑Aggregate BSS QoS Profile。PCO是在Create PDP Context Response消息里收到透明传递给手机的。SGSN现在可以通过不同的GTP隧道和可能不同的LLC链路来在MS和GGSN之间路由PDP PDUs了。
如果MS没有能力接受新的协商的Qos，MS应发起应用层的信令（例如HTTP层）来降低Qos要求。如果不行的话，那么MS将发起PDP Context Deactivation来将这个PDP上下文去激活。对每个额外的激活的PDP上下文，都可能需要提供一个Qos profile和TFT。
如果PDP上下文二次激活流程失败或者SGSN返回了一个Activate Secondary PDP Context Reject (Cause, Protocol Configuration Options)消息，那MS根据cause code的不同，可以尝试用另一个不同的TFT来进行激活。
很好的问题，也很难的问题感觉。找了好久，才找到一个勉强能说服自己的答案。仅供参考。不一定对。
关于Iu模式，如果MS要发送一个Activate PDP Context Request给网络侧，那他只能在PMM-IDLE或PMM-CONNETED状态发，如果是后者，则已经在附着阶段做过鉴权，因此PDP激活不需要重复做。关键是前者，如果用户在PMM-IDLE状态下如果要做PDP上下文的激活，那这时候Iu信令连接已经释放了，所以UE在发送PDP激活请求之前，首先要发送一个Service Request流程重建Iu连接，而针对Service Request流程，协议在6.12.1章节规定：“The SGSN shall perform the security functions if the MS in PMM-IDLE state initiated the service request.“。也就是说，在这个业务请求流程中，SGSN会对MS做一个鉴权。这样Iu连接建立好后，MS的PDP激活请求就可以发送了，就没必要重新鉴权了。
但A/Gb模式不一样，如果MS在standby状态下发PDP激活请求的话，不需要重建信令连接（没这个概念），并且MS从standby到idle状态的切换时间可能是很长的，要经过T3312、可达计时器、隐式去附着计时器查不过1个多小时的时间，SGSN才将用户的状态从standby切换到idle。因此，从安全性角度出发，SGSN当然有权利要求对用户重新做鉴权。
我的理解和你的还是有一些分歧。主要体现在
1 你提到的“当MS/UE发出Activate PDP Context Request之时，其前提应该是该MS/UE已经处于Ready或者PMM-Connected状态了。”这个感觉不一定。首先，从流程上来讲。MS/UE在Standby和PMM-IDLE状态下都是可以触发PDP激活流程的。特别是Standby状态可以直接发，而PMM-IDLE要发的话，会首先发起一个Service Request流程将PMM状态切换到PMM-CONNECTED，然后再发PDP激活流程。这个在规范里是这么说的：“The PDP state ACTIVE is permitted only when the mobility management state of the subscriber is STANDBY, READY, PMM IDLE, or PMM CONNECTED. ”，以及在6.9章PDP激活流程中提到“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.”。所以，Iu模式下，正如你所说，发出PDP激活请求时的UE，移动是在PMM-CONNECTED状态了，已经经过鉴权了，所以在Iu模式下的PDP激活不需要鉴权。这点我们的观点应该是一致的。 而2G下不一样，也是我们的分歧所在，我认为MS在Standby状态下是可以直接发起PDP激活请求的，而不用先将MM状态切换到Ready。这和3G是不一样的。因为根据23060中6.1.1.4的MM状态切换图说明：Standby到Ready状态的切换条件是上行PDU的传递，而PDP激活请求就是一个PDU消息的传递。因此在MS发出PDP激活请求的那时刻，可能是Ready也可能是Standby状态。而正像我前面提到的，由于MS停留在Standby的时间很长，可能1个多小时。网络侧当然可能要求MS进行重新鉴权。
2 规范中提到的都是"Security Function"，在后续的信令流程中也都用Security Function替代。Security Function包括鉴权和加密两个方面。但实际上在应用时是有偏向的。规范里提到的Security Function应该更关注的是鉴权的功能，而加密的功能是可选的。因为首先要防止的是用户假冒，而安全性从来都是一个可选功能，不应该以此来作为判断规范信令流程中是必选还是可选流程的依据。
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