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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。
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