Internet Engineering Task Force (IETF) R. Zhang
Request for Comments: 8350 China Telecom
Category: Experimental R. Pazhyannur
ISSN: 2070-1721 S. Gundavelli
Cisco
Z. Cao
H. Deng
Z. Du
Huawei
April 2018
Internet Engineering Task Force (IETF) R. Zhang
Request for Comments: 8350 China Telecom
Category: Experimental R. Pazhyannur
ISSN: 2070-1721 S. Gundavelli
Cisco
Z. Cao
H. Deng
Z. Du
Huawei
April 2018
Alternate Tunnel Encapsulation for Data Frames in Control and Provisioning of Wireless Access Points (CAPWAP)
无线接入点控制和供应（CAPWAP）中数据帧的备用隧道封装
Abstract
摘要
Control and Provisioning of Wireless Access Points (CAPWAP) is a protocol for encapsulating a station's data frames between the Wireless Transmission Point (WTP) and Access Controller (AC). Specifically, the station's IEEE 802.11 data frames can be either locally bridged or tunneled to the AC. When tunneled, a CAPWAP Data Channel is used for tunneling. In many deployments, encapsulating data frames to an entity other than the AC (for example, to an Access Router (AR)) is desirable. Furthermore, it may also be desirable to use different tunnel encapsulation modes between the WTP and the Access Router. This document defines an extension to the CAPWAP protocol that supports this capability and refers to it as alternate tunnel encapsulation. The alternate tunnel encapsulation allows 1) the WTP to tunnel non-management data frames to an endpoint different from the AC and 2) the WTP to tunnel using one of many known encapsulation types, such as IP-IP, IP-GRE, or CAPWAP. The WTP may advertise support for alternate tunnel encapsulation during the discovery and join process, and the AC may select one of the supported alternate tunnel encapsulation types while configuring the WTP.
无线接入点的控制和供应（CAPWAP）是一种用于在无线传输点（WTP）和接入控制器（AC）之间封装站点数据帧的协议。具体而言，站点的IEEE 802.11数据帧可以本地桥接或通过隧道传输到AC。当通过隧道传输时，CAPWAP数据信道用于隧道传输。在许多部署中，将数据帧封装到AC以外的实体（例如，到接入路由器（AR））是可取的。此外，还可能希望在WTP和接入路由器之间使用不同的隧道封装模式。本文档定义了支持此功能的CAPWAP协议的扩展，并将其称为备用隧道封装。备用隧道封装允许1）WTP通过隧道将非管理数据帧传输到不同于AC的端点，2）使用许多已知封装类型（如IP-IP、IP-GRE或CAPWAP）中的一种，将WTP通过隧道传输。WTP可以在发现和加入过程期间公布对备用隧道封装的支持，并且AC可以在配置WTP时选择受支持的备用隧道封装类型之一。
Status of This Memo
关于下段备忘
This document is not an Internet Standards Track specification; it is published for examination, experimental implementation, and evaluation.
本文件不是互联网标准跟踪规范；它是为检查、实验实施和评估而发布的。
This document defines an Experimental Protocol for the Internet community. This document is a product of the Internet Engineering Task Force (IETF). It represents the consensus of the IETF community. It has received public review and has been approved for publication by the Internet Engineering Steering Group (IESG). Not all documents approved by the IESG are candidates for any level of Internet Standard; see Section 2 of RFC 7841.
本文档为互联网社区定义了一个实验协议。本文件是互联网工程任务组（IETF）的产品。它代表了IETF社区的共识。它已经接受了公众审查，并已被互联网工程指导小组（IESG）批准出版。并非IESG批准的所有文件都适用于任何级别的互联网标准；见RFC 7841第2节。
Information about the current status of this document, any errata, and how to provide feedback on it may be obtained at https://www.rfc-editor.org/info/rfc8350.
有关本文件当前状态、任何勘误表以及如何提供反馈的信息，请访问https://www.rfc-editor.org/info/rfc8350.
Copyright Notice
版权公告
Copyright (c) 2018 IETF Trust and the persons identified as the document authors. All rights reserved.
版权所有（c）2018 IETF信托基金和确定为文件作者的人员。版权所有。
This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (https://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License.
本文件受BCP 78和IETF信托有关IETF文件的法律规定的约束(https://trustee.ietf.org/license-info)自本文件出版之日起生效。请仔细阅读这些文件，因为它们描述了您对本文件的权利和限制。从本文件中提取的代码组件必须包括信托法律条款第4.e节中所述的简化BSD许可证文本，并提供简化BSD许可证中所述的无担保。
Table of Contents
目录
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Conventions Used in This Document . . . . . . . . . . . . 7
1.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 7
1.3. History of the Document . . . . . . . . . . . . . . . . . 8
2. Alternate Tunnel Encapsulation Overview . . . . . . . . . . . 9
3. Extensions for CAPWAP Protocol Message Elements . . . . . . . 11
3.1. Supported Alternate Tunnel Encapsulations . . . . . . . . 11
3.2. Alternate Tunnel Encapsulations Type . . . . . . . . . . 11
3.3. IEEE 802.11 WTP Alternate Tunnel Failure Indication . . . 12
4. Alternate Tunnel Types . . . . . . . . . . . . . . . . . . . 13
4.1. CAPWAP-Based Alternate Tunnel . . . . . . . . . . . . . . 13
4.2. PMIPv6-Based Alternate Tunnel . . . . . . . . . . . . . . 14
4.3. GRE-Based Alternate Tunnel . . . . . . . . . . . . . . . 15
5. Alternate Tunnel Information Elements . . . . . . . . . . . . 16
5.1. Access Router Information Elements . . . . . . . . . . . 16
5.1.1. AR IPv4 List Element . . . . . . . . . . . . . . . . 16
5.1.2. AR IPv6 List Element . . . . . . . . . . . . . . . . 17
5.2. Tunnel DTLS Policy Element . . . . . . . . . . . . . . . 17
5.3. IEEE 802.11 Tagging Mode Policy Element . . . . . . . . . 19
5.4. CAPWAP Transport Protocol Element . . . . . . . . . . . . 20
5.5. GRE Key Element . . . . . . . . . . . . . . . . . . . . . 22
5.6. IPv6 MTU Element . . . . . . . . . . . . . . . . . . . . 23
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 24
7. Security Considerations . . . . . . . . . . . . . . . . . . . 25
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 25
8.1. Normative References . . . . . . . . . . . . . . . . . . 25
8.2. Informative References . . . . . . . . . . . . . . . . . 27
Contributors . . . . . . . . . . . . . . . . . . . . . . . . . . 28
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 28
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Conventions Used in This Document . . . . . . . . . . . . 7
1.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 7
1.3. History of the Document . . . . . . . . . . . . . . . . . 8
2. Alternate Tunnel Encapsulation Overview . . . . . . . . . . . 9
3. Extensions for CAPWAP Protocol Message Elements . . . . . . . 11
3.1. Supported Alternate Tunnel Encapsulations . . . . . . . . 11
3.2. Alternate Tunnel Encapsulations Type . . . . . . . . . . 11
3.3. IEEE 802.11 WTP Alternate Tunnel Failure Indication . . . 12
4. Alternate Tunnel Types . . . . . . . . . . . . . . . . . . . 13
4.1. CAPWAP-Based Alternate Tunnel . . . . . . . . . . . . . . 13
4.2. PMIPv6-Based Alternate Tunnel . . . . . . . . . . . . . . 14
4.3. GRE-Based Alternate Tunnel . . . . . . . . . . . . . . . 15
5. Alternate Tunnel Information Elements . . . . . . . . . . . . 16
5.1. Access Router Information Elements . . . . . . . . . . . 16
5.1.1. AR IPv4 List Element . . . . . . . . . . . . . . . . 16
5.1.2. AR IPv6 List Element . . . . . . . . . . . . . . . . 17
5.2. Tunnel DTLS Policy Element . . . . . . . . . . . . . . . 17
5.3. IEEE 802.11 Tagging Mode Policy Element . . . . . . . . . 19
5.4. CAPWAP Transport Protocol Element . . . . . . . . . . . . 20
5.5. GRE Key Element . . . . . . . . . . . . . . . . . . . . . 22
5.6. IPv6 MTU Element . . . . . . . . . . . . . . . . . . . . 23
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 24
7. Security Considerations . . . . . . . . . . . . . . . . . . . 25
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 25
8.1. Normative References . . . . . . . . . . . . . . . . . . 25
8.2. Informative References . . . . . . . . . . . . . . . . . 27
Contributors . . . . . . . . . . . . . . . . . . . . . . . . . . 28
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 28
Service Providers are deploying very large Wi-Fi networks containing hundreds of thousands of Access Points (APs), which are referred to as Wireless Transmission Points (WTPs) in Control and Provisioning of Wireless Access Points (CAPWAP) terminology [RFC5415]. These networks are designed to carry traffic generated from mobile users. The volume in mobile user traffic is already very large and expected to continue growing rapidly. As a result, operators are looking for scalable solutions that can meet the increasing demand. The scalability requirement can be met by splitting the control/ management plane from the data plane. This enables the data plane to scale independent of the control/management plane. This specification provides a way to enable such separation.
服务提供商正在部署包含数十万个接入点（AP）的超大Wi-Fi网络，这些接入点在无线接入点（CAPWAP）的控制和供应术语[RFC5415]中称为无线传输点（WTP）。这些网络旨在承载移动用户产生的流量。移动用户流量已经非常大，预计将继续快速增长。因此，运营商正在寻找能够满足不断增长的需求的可扩展解决方案。通过将控制/管理平面与数据平面分离，可以满足可伸缩性要求。这使数据平面能够独立于控制/管理平面进行缩放。本规范提供了实现这种分离的方法。
CAPWAP [RFC5415] [RFC5416] defines a tunnel mode that describes how the WTP handles the data plane (user traffic). The following types are defined:
CAPWAP[RFC5415][RFC5416]定义了一种隧道模式，用于描述WTP如何处理数据平面（用户流量）。定义了以下类型：
o Local Bridging: All data frames are locally bridged.
o 本地桥接：所有数据帧都是本地桥接的。
o IEEE 802.3 Tunnel: All data frames are tunneled to the Access Controller (AC) in IEEE 802.3 format.
o IEEE 802.3隧道：所有数据帧都以IEEE 802.3格式通过隧道传输到访问控制器（AC）。
o IEEE 802.11 Tunnel: All data frames are tunneled to the AC in IEEE 802.11 format.
o IEEE 802.11隧道：所有数据帧都以IEEE 802.11格式通过隧道传输到AC。
Figure 1 describes a system with Local Bridging. The AC is in a centralized location. The data plane is locally bridged by the WTPs; this leads to a system with a centralized control plane and a distributed data plane. This system has two benefits: 1) it reduces the scale requirement on the data traffic handling capability of the AC, and 2) it leads to more efficient/optimal routing of data traffic while maintaining centralized control/management.
图1描述了一个具有本地桥接的系统。空调位于集中位置。数据平面由WTPs本地桥接；这就形成了一个具有集中控制平面和分布式数据平面的系统。该系统有两个优点：1）降低了对AC数据流量处理能力的规模要求；2）在保持集中控制/管理的同时，提高了数据流量的效率/优化路由。
Locally Bridged
+-----+ Data Frames +----------------+
| WTP |===============| Access Router |
+-----+ +----------------+
\\
\\ CAPWAP Control Channel +----------+
++=========================| AC |
// CAPWAP Data Channel: | |
// IEEE 802.11 Mgmt Traffic +----------+
//
+-----+ +----------------+
| WTP |============== | Access Router |
+-----+ +----------------+
Locally Bridged
Data Frames
Locally Bridged
+-----+ Data Frames +----------------+
| WTP |===============| Access Router |
+-----+ +----------------+
\\
\\ CAPWAP Control Channel +----------+
++=========================| AC |
// CAPWAP Data Channel: | |
// IEEE 802.11 Mgmt Traffic +----------+
//
+-----+ +----------------+
| WTP |============== | Access Router |
+-----+ +----------------+
Locally Bridged
Data Frames
Figure 1: Centralized Control with Distributed Data
图1：分布式数据的集中控制
The AC handles control of WTPs. In addition, the AC also handles the IEEE 802.11 management traffic to/from the stations. There is a CAPWAP Control and Data Channel between the WTP and the AC. Note that even though there is no user traffic transported between the WTP and AC, there is still a CAPWAP Data Channel. The CAPWAP Data Channel carries the IEEE 802.11 management traffic (like IEEE 802.11 Action Frames).
AC处理WTP的控制。此外，AC还处理进出站点的IEEE 802.11管理流量。WTP和AC之间有一个CAPWAP控制和数据通道。请注意，尽管WTP和AC之间没有传输任何用户流量，但仍有一个CAPWAP数据通道。CAPWAP数据通道承载IEEE 802.11管理流量（如IEEE 802.11动作帧）。
Figure 2 shows a system where the tunnel mode is configured to tunnel data frames between the WTP and the AC using either the IEEE 802.3 Tunnel or 802.11 Tunnel configurations. Operators deploy this configuration when they need to tunnel the user traffic. The tunneling requirement may be driven by the need to apply policy at the AC. This requirement could be met in the locally bridged system (Figure 1) if the Access Router (AR) implemented the required policy. However, in many deployments, the operator managing the WTP is different than the operator managing the Access Router. When the operators are different, the policy has to be enforced in a tunnel termination point in the WTP operator's network.
图2显示了一个系统，其中隧道模式配置为使用IEEE 802.3隧道或802.11隧道配置在WTP和AC之间隧道数据帧。运营商在需要隧道用户流量时部署此配置。隧道要求可能是由在AC应用策略的需要驱动的。如果接入路由器（AR）实现了所需的策略，则在本地桥接系统（图1）中可以满足该要求。但是，在许多部署中，管理WTP的运营商与管理接入路由器的运营商不同。当运营商不同时，必须在WTP运营商网络中的隧道终止点实施该策略。
+-----+
| WTP |
+-----+
\\
\\ CAPWAP Control Channel +----------+
++=========================| AC |
// CAPWAP Data Channel: | |
// IEEE 802.11 Mgmt Traffic | |
// Data Frames +----------+
//
+-----+
| WTP |
+-----+
+-----+
| WTP |
+-----+
\\
\\ CAPWAP Control Channel +----------+
++=========================| AC |
// CAPWAP Data Channel: | |
// IEEE 802.11 Mgmt Traffic | |
// Data Frames +----------+
//
+-----+
| WTP |
+-----+
Figure 2: Centralized Control and Centralized Data
图2：集中控制和集中数据
The key difference with the locally bridged system is that the data frames are tunneled to the AC instead of being locally bridged. There are two shortcomings with the system in Figure 2: 1) it does not allow the WTP to tunnel data frames to an endpoint different from the AC, and 2) it does not allow the WTP to tunnel data frames using any encapsulation other than CAPWAP (as specified in Section 4.4.2 of [RFC5415]).
与本地桥接系统的关键区别在于，数据帧通过隧道传输到AC，而不是本地桥接。图2中的系统有两个缺点：1）它不允许WTP将数据帧隧道到与AC不同的端点，2）它不允许WTP使用CAPWAP以外的任何封装（如[RFC5415]第4.4.2节所规定）将数据帧隧道到端点。
Figure 3 shows a system where the WTP tunnels data frames to an alternate entity different from the AC. The WTP also uses an alternate tunnel encapsulation such as Layer 2 Tunneling Protocol (L2TP), L2TPv3, IP-in-IP, IP/GRE, etc. This enables 1) independent scaling of data plane and 2) leveraging of commonly used tunnel encapsulations such as L2TP, GRE, etc.
图3显示了一个系统，其中WTP将数据帧隧道到与AC不同的备用实体。WTP还使用备用隧道封装，如第2层隧道协议（L2TP）、L2TPv3、IP中的IP、IP/GRE等。这使得1）能够独立扩展数据平面，2）利用常用的隧道封装，如L2TP，GRE等。
Alternate Tunnel to AR (L2TPv3, IP-IP, CAPWAP, etc.)
_________
+-----+ ( ) +-----------------+
| WTP |======+Internet +==============|Access Router(AR)|
+-----+ (_________) +-----------------+
\\ ________ CAPWAP Control
\\ ( ) Channel +--------+
++=+Internet+========================| AC |
// (________)CAPWAP Data Channel: +--------+
// IEEE 802.11 Mgmt Traffic
// _________
+-----+ ( ) +----------------+
| WTP |====+Internet +================| Access Router |
+-----+ (_________) +----------------+
Alternate Tunnel to AR (L2TPv3, IP-in-IP, CAPWAP, etc.)
Alternate Tunnel to AR (L2TPv3, IP-IP, CAPWAP, etc.)
_________
+-----+ ( ) +-----------------+
| WTP |======+Internet +==============|Access Router(AR)|
+-----+ (_________) +-----------------+
\\ ________ CAPWAP Control
\\ ( ) Channel +--------+
++=+Internet+========================| AC |
// (________)CAPWAP Data Channel: +--------+
// IEEE 802.11 Mgmt Traffic
// _________
+-----+ ( ) +----------------+
| WTP |====+Internet +================| Access Router |
+-----+ (_________) +----------------+
Alternate Tunnel to AR (L2TPv3, IP-in-IP, CAPWAP, etc.)
Figure 3: Centralized Control with an Alternate Tunnel for Data
图3：具有备用数据通道的集中控制
The WTP may support widely used encapsulation types such as L2TP, L2TPv3, IP-in-IP, IP/GRE, etc. The WTP advertises the different alternate tunnel encapsulation types it can support. The AC configures one of the advertised types. As is shown in Figure 3, there is a CAPWAP Control and Data Channel between the WTP and AC. The CAPWAP Data Channel carries the stations' management traffic, as in the case of the locally bridged system. The main reason to maintain a CAPWAP Data Channel is to maintain similarity with the locally bridged system. The WTP maintains three tunnels: CAPWAP Control, CAPWAP Data, and another alternate tunnel for the data frames. The data frames are transported by an alternate tunnel between the WTP and a tunnel termination point, such as an Access Router. This specification describes how the alternate tunnel can be established. The specification defines message elements for the WTP to advertise support for alternate tunnel encapsulation, for the AC to configure alternate tunnel encapsulation, and for the WTP to report failure of the alternate tunnel.
WTP可支持广泛使用的封装类型，如L2TP、L2TPv3、IP中的IP、IP/GRE等。WTP宣传其可支持的不同备选隧道封装类型。AC配置其中一种播发类型。如图3所示，WTP和AC之间有一个CAPWAP控制和数据通道。CAPWAP数据通道承载站点的管理流量，如本地桥接系统的情况。维护CAPWAP数据通道的主要原因是保持与本地桥接系统的相似性。WTP维护三个隧道：CAPWAP控制、CAPWAP数据和数据帧的另一个备用隧道。数据帧由WTP和隧道终端点（例如接入路由器）之间的备用隧道传输。本规范描述了如何建立备用隧道。该规范为WTP定义了消息元素，以公布对备用隧道封装的支持，为AC定义了配置备用隧道封装的消息元素，为WTP定义了报告备用隧道故障的消息元素。
The alternate tunnel encapsulation also supports the third-party WLAN service provider scenario (i.e., Virtual Network Operator (VNO)). Under this scenario, the WLAN provider owns the WTP and AC resources while the VNOs can rent the WTP resources from the WLAN provider for network access. The AC belonging to the WLAN service provider manages the WTPs in the centralized mode.
备用隧道封装还支持第三方WLAN服务提供商场景（即虚拟网络运营商（VNO））。在这种情况下，WLAN提供商拥有WTP和AC资源，而VNO可以从WLAN提供商租用WTP资源进行网络访问。属于WLAN服务提供商的AC以集中模式管理WTP。
As shown in Figure 4, VNO 1 and VNO 2 don't possess the network access resources; however, they provide services by acquiring resources from the WLAN provider. Since a WTP is capable of supporting up to 16 Service Set Identifiers (SSIDs), the WLAN provider may provide network access service for different providers
如图4所示，VNO 1和VNO 2不具备网络接入资源；但是，它们通过从WLAN提供商处获取资源来提供服务。由于WTP能够支持多达16个服务集标识符（ssid），因此WLAN提供商可以为不同的提供商提供网络接入服务
with different SSIDs. For example, SSID1 is advertised by the WTP for VNO 1 while SSID2 is advertised by the WTP for VNO 2. Therefore, the data traffic from the user can be directly steered to the corresponding Access Router of the VNO who owns that user. As is shown in Figure 4, AC can notify multiple AR addresses for load balancing or redundancy.
使用不同的ssid。例如，SSID1由WTP为VNO 1播发，而SSID2由WTP为VNO 2播发。因此，来自用户的数据流量可以直接引导到拥有该用户的VNO的相应接入路由器。如图4所示，AC可以通知多个AR地址进行负载平衡或冗余。
+----+
| AC |
+--+-+
CAPWAP-CTL |
+-----------------+
| CAPWAP-DATA: IEEE 802.11 Mgmt Traffic
|
WLAN Provider| VNO 1
+-----+ CAPWAP-DATA (SSID1) +---------------+
SSID1 | WTP +--------------------------|Access Router 1|
SSID2 +--+-++ +---------------+
| |
| | VNO 1
| | GRE-DATA (SSID1) +---------------+
| +---------------------------|Access Router 2|
| +---------------+
|
| VNO 2
| CAPWAP-DATA (SSID2) +---------------+
+-----------------------------|Access Router 3|
+---------------+
+----+
| AC |
+--+-+
CAPWAP-CTL |
+-----------------+
| CAPWAP-DATA: IEEE 802.11 Mgmt Traffic
|
WLAN Provider| VNO 1
+-----+ CAPWAP-DATA (SSID1) +---------------+
SSID1 | WTP +--------------------------|Access Router 1|
SSID2 +--+-++ +---------------+
| |
| | VNO 1
| | GRE-DATA (SSID1) +---------------+
| +---------------------------|Access Router 2|
| +---------------+
|
| VNO 2
| CAPWAP-DATA (SSID2) +---------------+
+-----------------------------|Access Router 3|
+---------------+
Figure 4: Third-Party WLAN Service Provider
图4：第三方WLAN服务提供商
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all capitals, as shown here.
本文件中的关键词“必须”、“不得”、“必需”、“应”、“不应”、“建议”、“不建议”、“可”和“可选”在所有大写字母出现时（如图所示）应按照BCP 14[RFC2119][RFC8174]所述进行解释。
Station (STA): A device that contains an IEEE 802.11-conformant Medium Access Control (MAC) and Physical layer (PHY) interface to the Wireless Medium (WM).
站点（STA）：包含符合IEEE 802.11的媒体访问控制（MAC）和无线媒体（WM）的物理层（PHY）接口的设备。
Access Controller (AC): The network entity that provides WTP access to the network infrastructure in the data plane, control plane, management plane, or a combination therein.
访问控制器（AC）：提供WTP访问数据平面、控制平面、管理平面或其中组合中网络基础设施的网络实体。
Access Router (AR): A specialized router usually residing at the edge or boundary of a network. This router ensures the connectivity of its network with external networks, a wide area network, or the Internet.
接入路由器（AR）：通常位于网络边缘或边界的专用路由器。此路由器确保其网络与外部网络、广域网或Internet的连接。
Wireless Termination Point (WTP): The physical or network entity that contains a Radio Frequency (RF) antenna and wireless Physical layer (PHY) to transmit and receive station traffic for wireless access networks.
无线终端点（WTP）：包含射频（RF）天线和无线物理层（PHY）的物理或网络实体，用于为无线接入网络发送和接收站点流量。
CAPWAP Control Channel: A bidirectional flow defined by the AC IP Address, WTP IP Address, AC control port, WTP control port, and the transport-layer protocol (UDP or UDP-Lite) over which CAPWAP Control packets are sent and received.
CAPWAP控制通道：由AC IP地址、WTP IP地址、AC控制端口、WTP控制端口和传输层协议（UDP或UDP Lite）定义的双向流，通过该协议发送和接收CAPWAP控制数据包。
CAPWAP Data Channel: A bidirectional flow defined by the AC IP Address, WTP IP Address, AC data port, WTP data port, and the transport-layer protocol (UDP or UDP-Lite) over which CAPWAP Data packets are sent and received. In certain WTP modes, the CAPWAP Data Channel only transports IEEE 802.11 management frames and not the data plane (user traffic).
CAPWAP数据通道：由AC IP地址、WTP IP地址、AC数据端口、WTP数据端口和传输层协议（UDP或UDP Lite）定义的双向流，通过该协议发送和接收CAPWAP数据包。在某些WTP模式下，CAPWAP数据通道仅传输IEEE 802.11管理帧，而不传输数据平面（用户流量）。
This document was started to accommodate Service Providers' need of a more flexible deployment mode with alternative tunnels [RFC7494]. Experiments and tests have been done for this alternate tunnel network infrastructure. However important, the deployment of relevant technology is yet to be completed. This Experimental document is intended to serve as an archival record for any future work on the operational and deployment requirements.
本文档的开始是为了满足服务提供商对更灵活的部署模式和备用隧道的需求[RFC7494]。已经对这种备用隧道网络基础设施进行了实验和测试。然而，重要的是，相关技术的部署尚未完成。本实验性文件旨在作为未来关于作战和部署需求的任何工作的档案记录。
+-+-+-+-+-+-+ +-+-+-+-+-+-+
| WTP | | AC |
+-+-+-+-+-+-+ +-+-+-+-+-+-+
|Join Request [ Supported Alternate |
| Tunnel Encapsulations ] |
|---------------------------------------->|
| |
|Join Response |
|<----------------------------------------|
| |
|IEEE 802.11 WLAN Configuration Request [ |
| IEEE 802.11 Add WLAN, |
| Alternate Tunnel Encapsulation ( |
| Tunnel Type, Tunnel Info Element) |
| ] |
|<----------------------------------------|
| |
| |
+-+-+-+-+-+-+ |
| Setup | |
| Alternate | |
| Tunnel | |
+-+-+-+-+-+-+ |
|IEEE 802.11 WLAN Configuration Response |
|[ Alternate Tunnel Encapsulation ( |
| Tunnel Type, Tunnel Info Element) ] |
|---------------------------------------->|
| |
+-+-+-+-+-+-+ |
| Tunnel | |
| Failure | |
+-+-+-+-+-+-+ |
|WTP Alternate Tunnel Failure Indication |
|(Report Failure (AR Address(es))) |
|---------------------------------------->|
| |
+-+-+-+-+-+-+-+ |
| Tunnel | |
| Established | |
+-+-+-+-+-+-+-+ |
|WTP Alternate Tunnel Failure Indication |
|(Report Clearing Failure) |
|---------------------------------------->|
| |
+-+-+-+-+-+-+ +-+-+-+-+-+-+
| WTP | | AC |
+-+-+-+-+-+-+ +-+-+-+-+-+-+
|Join Request [ Supported Alternate |
| Tunnel Encapsulations ] |
|---------------------------------------->|
| |
|Join Response |
|<----------------------------------------|
| |
|IEEE 802.11 WLAN Configuration Request [ |
| IEEE 802.11 Add WLAN, |
| Alternate Tunnel Encapsulation ( |
| Tunnel Type, Tunnel Info Element) |
| ] |
|<----------------------------------------|
| |
| |
+-+-+-+-+-+-+ |
| Setup | |
| Alternate | |
| Tunnel | |
+-+-+-+-+-+-+ |
|IEEE 802.11 WLAN Configuration Response |
|[ Alternate Tunnel Encapsulation ( |
| Tunnel Type, Tunnel Info Element) ] |
|---------------------------------------->|
| |
+-+-+-+-+-+-+ |
| Tunnel | |
| Failure | |
+-+-+-+-+-+-+ |
|WTP Alternate Tunnel Failure Indication |
|(Report Failure (AR Address(es))) |
|---------------------------------------->|
| |
+-+-+-+-+-+-+-+ |
| Tunnel | |
| Established | |
+-+-+-+-+-+-+-+ |
|WTP Alternate Tunnel Failure Indication |
|(Report Clearing Failure) |
|---------------------------------------->|
| |
Figure 5: Setup of an Alternate Tunnel
图5：备用隧道的设置
The above example describes how the alternate tunnel encapsulation may be established. When the WTP joins the AC, it should indicate its alternate tunnel encapsulation capability. The AC determines whether an alternate tunnel configuration is required. If an appropriate alternate tunnel type is selected, then the AC provides the Alternate Tunnel Encapsulations Type message element containing the tunnel type and a tunnel-specific information element. The tunnel-specific information element, for example, may contain information like the IP address of the tunnel termination point. The WTP sets up the alternate tunnel using the Alternate Tunnel Encapsulations Type message element.
上述示例描述了如何建立备用隧道封装。当WTP加入AC时，它应指示其备用隧道封装能力。AC确定是否需要备用通道配置。如果选择了适当的备用隧道类型，则AC将提供包含隧道类型和隧道特定信息元素的备用隧道封装类型消息元素。例如，隧道特定信息元素可以包含诸如隧道终端点的IP地址之类的信息。WTP使用备用隧道封装类型消息元素设置备用隧道。
Since an AC can configure a WTP with more than one AR available for the WTP to establish the data tunnel(s) for user traffic, it may be useful for the WTP to communicate the selected AR. To enable this, the IEEE 802.11 WLAN Configuration Response may carry the Alternate Tunnel Encapsulations Type message element containing the AR list element corresponding to the selected AR as shown in Figure 5.
由于AC可以为WTP配置具有多个可用AR的WTP，以建立用于用户流量的数据隧道，因此WTP可以与所选AR进行通信。为此，IEEE 802.11 WLAN配置响应可携带备用隧道封装类型消息元素，该消息元素包含与所选AR相对应的AR列表元素，如图5所示。
On detecting a tunnel failure, the WTP SHALL forward data frames to the AC and discard the frames. In addition, the WTP may dissociate existing clients and refuse association requests from new clients. Depending on the implementation and deployment scenario, the AC may choose to reconfigure the WLAN (on the WTP) to a Local Bridging mode or to tunnel frames to the AC. When the WTP detects an alternate tunnel failure, the WTP informs the AC using a message element, IEEE 802.11 WTP Alternate Tunnel Failure Indication (defined in Section 3.3). It MAY be carried in the WTP Event Request message, which is defined in [RFC5415].
在检测到隧道故障时，WTP应将数据帧转发给AC并丢弃帧。此外，WTP可以分离现有客户端并拒绝来自新客户端的关联请求。根据实施和部署场景，AC可选择将WLAN（在WTP上）重新配置为本地桥接模式或将帧隧道至AC。当WTP检测到备用隧道故障时，WTP使用消息元素IEEE 802.11 WTP备用隧道故障指示（在第3.3节中定义）通知AC。它可以在[RFC5415]中定义的WTP事件请求消息中携带。
The WTP also needs to notify the AC of which AR(s) are unavailable. Particularly, in the VNO scenario, the AC of the WLAN service provider needs to maintain the association of the AR addresses of the VNOs and SSIDs and provide this information to the WTP for the purpose of load balancing or master-slave mode.
WTP还需要通知AC哪些AR不可用。特别地，在VNO场景中，WLAN服务提供商的AC需要维护VNO和ssid的AR地址的关联，并为了负载平衡或主从模式的目的将该信息提供给WTP。
The message element has a Status field that indicates whether the message is reporting a failure or clearing the previously reported failure.
消息元素有一个状态字段，指示消息是报告故障还是清除以前报告的故障。
For the case where an AC is unreachable but the tunnel endpoint is still reachable, the WTP behavior is up to the implementation. For example, the WTP could choose to either tear down the alternate tunnel or let the existing user's traffic continue to be tunneled.
对于AC不可到达但隧道端点仍然可到达的情况，WTP行为取决于实现。例如，WTP可以选择拆除备用隧道，或者让现有用户的流量继续通过隧道传输。
This message element is sent by a WTP to communicate its capability to support alternate tunnel encapsulations. The message element contains the following fields:
此消息元素由WTP发送，以传达其支持备用隧道封装的能力。message元素包含以下字段：
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Tunnel-Type 1 | Tunnel-Type 2 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ... | Tunnel-Type N |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Tunnel-Type 1 | Tunnel-Type 2 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ... | Tunnel-Type N |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 6: Supported Alternate Tunnel Encapsulations
图6：支持的备用隧道封装
o Type: 54 for Supported Alternate Tunnel Encapsulations Type
o 类型：54用于支持的备用隧道封装类型
o Length: The length in bytes; two bytes for each Alternative Tunnel-Type that is included
o 长度：以字节为单位的长度；包含的每个备选隧道类型两个字节
o Tunnel-Type: This is identified by the value defined in Section 3.2. There may be one or more Tunnel-Types, as is shown in Figure 6.
o 隧道类型：由第3.2节中定义的值确定。可能有一种或多种隧道类型，如图6所示。
This message element can be sent by the AC, allows the AC to select the alternate tunnel encapsulation, and may be provided along with the IEEE 802.11 Add WLAN message element. When the message element is present, the following fields of the IEEE 802.11 Add WLAN element SHALL be set as follows: MAC mode is set to 0 (Local MAC), and Tunnel Mode is set to 0 (Local Bridging). Besides, the message element can also be sent by the WTP to communicate the selected AR(s).
该消息元素可由AC发送，允许AC选择备用隧道封装，并可与IEEE 802.11添加WLAN消息元素一起提供。当消息元素存在时，IEEE 802.11添加WLAN元素的以下字段应设置如下：MAC模式设置为0（本地MAC），隧道模式设置为0（本地桥接）。此外，WTP还可以发送消息元素以与所选AR通信。
The message element contains the following fields:
message元素包含以下字段：
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Tunnel-Type | Info Element Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Info Element
+-+-+-+-+-+-+-+-+-+
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Tunnel-Type | Info Element Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Info Element
+-+-+-+-+-+-+-+-+-+
Figure 7: Alternate Tunnel Encapsulations Type
图7：备用隧道封装类型
o Type: 55 for Alternate Tunnel Encapsulations Type
o 类型：55用于备用隧道封装类型
o Length: > 4
o 长度：>4
o Tunnel-Type: The Tunnel-Type is specified by a 2-byte value. This specification defines the values from 0 to 6 as given below. The remaining values are reserved for future use.
o 隧道类型：隧道类型由2字节的值指定。本规范定义了0到6之间的值，如下所示。其余值保留供将来使用。
* 0: CAPWAP. This refers to a CAPWAP Data Channel described in [RFC5415] and [RFC5416].
* 0:CAPWAP。这是指[RFC5415]和[RFC5416]中描述的CAPWAP数据信道。
* 1: L2TP. This refers to tunnel encapsulation described in [RFC2661].
* 1:L2TP。这是指[RFC2661]中描述的隧道封装。
* 2: L2TPv3. This refers to tunnel encapsulation described in [RFC3931].
* 2:L2TPv3。这是指[RFC3931]中描述的隧道封装。
* 3: IP-in-IP. This refers to tunnel encapsulation described in [RFC2003].
* 3:IP中的IP。这是指[RFC2003]中描述的隧道封装。
* 4: PMIPv6-UDP. This refers to the UDP encapsulation mode for Proxy Mobile IPv6 (PMIPv6) described in [RFC5844]. This encapsulation mode is the basic encapsulation mode and does not include the TLV header specified in Section 7.2 of [RFC5845].
* 4:PMIPv6-UDP。这是指[RFC5844]中描述的代理移动IPv6（PMIPv6）的UDP封装模式。该封装模式是基本封装模式，不包括[RFC5845]第7.2节中规定的TLV标头。
* 5: GRE. This refers to GRE tunnel encapsulation as described in [RFC2784].
* 5:GRE。这是指[RFC2784]中所述的GRE隧道封装。
* 6: GTPv1-U. This refers to the GPRS Tunnelling Protocol (GTP) User Plane mode as described in [TS.3GPP.29.281].
* 6:GTPv1-U。这是指[TS.3GPP.29.281]中所述的GPRS隧道协议（GTP）用户平面模式。
o Info Element: This field contains tunnel-specific configuration parameters to enable the WTP to set up the alternate tunnel. This specification provides details for this element for CAPWAP, PMIPv6, and GRE. This specification reserves the tunnel type values for the key tunnel types and defines the most common message elements. It is anticipated that message elements for the other protocols (like L2TPv3) will be defined in other specifications in the future.
o 信息元素：此字段包含特定于隧道的配置参数，以使WTP能够设置备用隧道。本规范提供了CAPWAP、PMIPv6和GRE的此元素的详细信息。本规范保留关键隧道类型的隧道类型值，并定义最常见的消息元素。预计其他协议（如L2TPv3）的消息元素将在将来的其他规范中定义。
The WTP MAY include the Alternate Tunnel Failure Indication message in a WTP Event Request message to inform the AC about the status of the alternate tunnel. For the case where the WTP establishes data tunnels with multiple ARs (e.g., under a VNO scenario), the WTP needs to notify the AC of which AR(s) are unavailable. The message element contains the following fields:
WTP可以在WTP事件请求消息中包括备用隧道故障指示消息，以通知AC备用隧道的状态。对于WTP使用多个AR建立数据隧道的情况（例如，在VNO场景下），WTP需要通知AC哪些AR不可用。message元素包含以下字段：
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| WLAN ID | Status | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. Access Router Information Element .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| WLAN ID | Status | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. Access Router Information Element .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 8: IEEE 802.11 WTP Alternate Tunnel Failure Indication
图8:IEEE 802.11 WTP备用隧道故障指示
o Type: 1062 for IEEE 802.11 WTP Alternate Tunnel Failure Indication
o 类型：1062，用于IEEE 802.11 WTP备用隧道故障指示
o Length: > 4
o 长度：>4
o WLAN ID: An 8-bit value specifying the WLAN Identifier. The value MUST be between 1 and 16.
o WLAN ID：指定WLAN标识符的8位值。该值必须介于1和16之间。
o Status: An 8-bit boolean indicating whether the radio failure is being reported or cleared. A value of 0 is used to clear the event, while a value of 1 is used to report the event.
o 状态：一个8位布尔值，指示是否正在报告或清除无线电故障。值0用于清除事件，而值1用于报告事件。
o Reserved: MUST be set to a value of 0 and MUST be ignored by the receiver.
o 保留：必须设置为0的值，并且必须被接收器忽略。
o Access Router Information Element: The IPv4 or IPv6 address of the Access Router that terminates the alternate tunnel. The Access Router Information Elements allow the WTP to notify the AC of which AR(s) are unavailable.
o 访问路由器信息元素：终止备用隧道的访问路由器的IPv4或IPv6地址。接入路由器信息元素允许WTP通知AC哪些AR不可用。
If the CAPWAP encapsulation is selected by the AC and configured by the AC to the WTP, the Info Element field defined in Section 3.2 SHOULD contain the following information:
如果AC选择CAPWAP封装并将其配置到WTP，则第3.2节中定义的信息元素字段应包含以下信息：
o Access Router Information: The IPv4 or IPv6 address of the Access Router for the alternate tunnel.
o 访问路由器信息：备用隧道的访问路由器的IPv4或IPv6地址。
o Tunnel DTLS Policy: The CAPWAP protocol allows optional protection of data packets using DTLS. Use of data packet protection on a WTP is not mandatory but is determined by the associated AC policy. (This is consistent with the WTP behavior described in [RFC5415].)
o 隧道DTLS策略：CAPWAP协议允许使用DTLS对数据包进行可选保护。在WTP上使用数据包保护不是强制性的，但由相关AC策略决定。（这与[RFC5415]中描述的WTP行为一致。）
o IEEE 802.11 Tagging Mode Policy: It is used to specify how the CAPWAP Data Channel packets are to be tagged for QoS purposes (see [RFC5416] for more details).
o IEEE 802.11标记模式策略：用于指定如何标记CAPWAP数据通道数据包以实现QoS（有关更多详细信息，请参阅[RFC5416]）。
o CAPWAP Transport Protocol: The CAPWAP protocol supports both UDP and UDP-Lite (see [RFC3828]). When run over IPv4, UDP is used for the CAPWAP Data Channels. When run over IPv6, the CAPWAP Data Channel may use either UDP or UDP-Lite.
o CAPWAP传输协议：CAPWAP协议支持UDP和UDP Lite（请参阅[RFC3828]）。在IPv4上运行时，UDP用于CAPWAP数据通道。在IPv6上运行时，CAPWAP数据通道可以使用UDP或UDP Lite。
The message element structure for CAPWAP encapsulation is shown in Figure 9:
CAPWAP封装的消息元素结构如图9所示：
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Tunnel-Type=0 | Info Element Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. Access Router Information Element .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. Tunnel DTLS Policy Element .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. IEEE 802.11 Tagging Mode Policy Element .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. CAPWAP Transport Protocol Element .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Tunnel-Type=0 | Info Element Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. Access Router Information Element .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. Tunnel DTLS Policy Element .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. IEEE 802.11 Tagging Mode Policy Element .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. CAPWAP Transport Protocol Element .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 9: Alternate Tunnel Encapsulation - CAPWAP
图9：备用隧道封装-CAPWAP
A user plane based on PMIPv6 (defined in [RFC5213]) can also be used as an alternate tunnel encapsulation between the WTP and the AR. In this scenario, a WTP acts as the Mobile Access Gateway (MAG) function that manages the mobility-related signaling for a station that is attached to the WTP IEEE 802.11 radio access. The Local Mobility Anchor (LMA) function is at the AR. If PMIPv6 UDP encapsulation is selected by the AC and configured by the AC to a WTP, the Info Element field defined in Section 3.2 SHOULD contain the following information:
基于PMIPv6（在[RFC5213]中定义）的用户平面也可以用作WTP和AR之间的备用隧道封装。在这种情况下，WTP充当移动接入网关（MAG）功能，用于管理连接到WTP IEEE 802.11无线接入的站点的移动性相关信令。本地移动锚（LMA）功能位于AR。如果AC选择PMIPv6 UDP封装并将其配置为WTP，则第3.2节中定义的信息元素字段应包含以下信息：
o Access Router (acting as LMA) Information: IPv4 or IPv6 address for the alternate tunnel endpoint.
o 访问路由器（充当LMA）信息：备用隧道端点的IPv4或IPv6地址。
The message element structure for PMIPv6 encapsulation is shown in Figure 10:
PMIPv6封装的消息元素结构如图10所示：
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Tunnel-Type=4 | Info Element Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. Access Router Information Element .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Tunnel-Type=4 | Info Element Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. Access Router Information Element .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 10: Alternate Tunnel Encapsulation - PMIPv6
图10：备用隧道封装-PMIPv6
A user plane based on Generic Routing Encapsulation (defined in [RFC2784]) can also be used as an alternate tunnel encapsulation between the WTP and the AR. In this scenario, a WTP and the Access Router represent the two endpoints of the GRE tunnel. If GRE is selected by the AC and configured by the AC to a WTP, the Info Element field defined in Section 3.2 SHOULD contain the following information:
基于通用路由封装（在[RFC2784]中定义）的用户平面也可以用作WTP和AR之间的备用隧道封装。在这种情况下，WTP和接入路由器代表GRE隧道的两个端点。如果AC选择GRE并将其配置为WTP，则第3.2节中定义的信息元素字段应包含以下信息：
o Access Router Information: The IPv4 or IPv6 address for the alternate tunnel endpoint.
o 访问路由器信息：备用隧道端点的IPv4或IPv6地址。
o GRE Key Information: The Key field is intended to be used for identifying an individual traffic flow within a tunnel [RFC2890].
o GRE密钥信息：密钥字段用于识别隧道内的单个交通流[RFC2890]。
The message element structure for GRE is shown in Figure 11:
GRE的消息元素结构如图11所示：
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Tunnel-Type=5 | Info Element Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. Access Router Information Element .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. GRE Key Element .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Tunnel-Type=5 | Info Element Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. Access Router Information Element .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. GRE Key Element .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 11: Alternate Tunnel Encapsulation - GRE
图11：备用隧道封装-GRE
This section defines the various elements described in Sections 4.1, 4.2, and 4.3.
本节定义了第4.1、4.2和4.3节中描述的各种要素。
These information elements can only be included in the Alternate Tunnel Encapsulations Type message element and the IEEE 802.11 WTP Alternate Tunnel Failure Indication message element as their sub-elements.
这些信息元素只能作为其子元素包含在备用隧道封装类型消息元素和IEEE 802.11 WTP备用隧道故障指示消息元素中。
The Access Router Information Elements allow the AC to notify a WTP of which AR(s) are available for establishing a data tunnel. The AR information may be an IPv4 or IPv6 address. For any Tunnel-Type, this information element SHOULD be included in the Alternate Tunnel Encapsulations Type message element.
接入路由器信息元素允许AC通知WTP哪些AR可用于建立数据隧道。AR信息可以是IPv4或IPv6地址。对于任何隧道类型，此信息元素应包含在备用隧道封装类型消息元素中。
If the Alternate Tunnel Encapsulations Type message element is sent by the WTP to communicate the selected AR(s), this Access Router Information Element SHOULD be included in it.
如果WTP发送备用隧道封装类型消息元素以与所选AR通信，则该访问路由器信息元素应包含在其中。
The following are the Access Router Information Elements defined in this specification. The AC can use one of them to notify the WTP about the destination information of the data tunnel. The Elements containing the AR IPv4 address MUST NOT be used if an IPv6 Data Channel with IPv6 transport is used.
以下是本规范中定义的访问路由器信息元素。AC可以使用其中一个来通知WTP数据隧道的目的地信息。如果使用具有IPv6传输的IPv6数据通道，则不得使用包含AR IPv4地址的元素。
This element (see Figure 12) is used by the AC to configure a WTP with the AR IPv4 address available for the WTP to establish the data tunnel for user traffic.
AC使用此元素（见图12）配置WTP，使其具有可用于WTP的AR IPv4地址，以建立用户流量的数据隧道。
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| AR IPv4 Element Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. AR IPv4 Address-1 .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. AR IPv4 Address-2 .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. AR IPv4 Address-N .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| AR IPv4 Element Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. AR IPv4 Address-1 .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. AR IPv4 Address-2 .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. AR IPv4 Address-N .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 12: AR IPv4 List Element
图12:AR IPv4列表元素
Type: 0
类型：0
Length: This refers to the total length in octets of the element, excluding the Type and Length fields.
长度：指元素的总长度（以八位字节为单位），不包括类型和长度字段。
AR IPv4 Address: The IPv4 address of the AR. At least one IPv4 address SHALL be present. Multiple addresses may be provided for load balancing or redundancy.
AR IPv4地址：AR的IPv4地址。至少应存在一个IPv4地址。可以为负载平衡或冗余提供多个地址。
This element (see Figure 13) is used by the AC to configure a WTP with the AR IPv6 address available for the WTP to establish the data tunnel for user traffic.
AC使用此元素（见图13）配置WTP，使其具有可用于WTP的AR IPv6地址，以建立用户流量的数据隧道。
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| AR IPv6 Element Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. AR IPv6 Address-1 .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. AR IPv6 Address-2 .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. AR IPv6 Address-N .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| AR IPv6 Element Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. AR IPv6 Address-1 .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. AR IPv6 Address-2 .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. AR IPv6 Address-N .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 13: AR IPv6 List Element
图13:AR IPv6列表元素
Type: 1
类型：1
Length: This refers to the total length in octets of the element excluding the Type and Length fields.
长度：指元素的总长度（以八位字节为单位），不包括类型和长度字段。
AR IPv6 Address: The IPv6 address of the AR. At least one IPv6 address SHALL be present. Multiple addresses may be provided for load balancing or redundancy.
AR IPv6地址：AR的IPv6地址。至少应存在一个IPv6地址。可以为负载平衡或冗余提供多个地址。
The AC distributes its Datagram Transport Layer Security (DTLS) usage policy for the CAPWAP data tunnel between a WTP and the AR. There are multiple supported options, which are represented by the bit fields below as defined in AC Descriptor message elements. The WTP MUST abide by one of the options for tunneling user traffic with AR. The Tunnel DTLS Policy Element obeys the definition in [RFC5415]. If, for reliability reasons, the AC has provided more than one AR address in the Access Router Information Element, the same Tunnel
AC为WTP和AR之间的CAPWAP数据隧道分发其数据报传输层安全（DTLS）使用策略。有多个受支持的选项，由AC描述符消息元素中定义的以下位字段表示。WTP必须遵守AR隧道用户流量的选项之一。隧道DTLS策略元素遵守[RFC5415]中的定义。如果出于可靠性原因，AC在接入路由器信息元素中提供了多个AR地址，则相同的隧道
DTLS Policy (the last one in Figure 14) is generally applied for all tunnels associated with those ARs. Otherwise, Tunnel DTLS Policy MUST be bonded together with each of the Access Router Information Elements, and the WTP will enforce the independent tunnel DTLS policy for each tunnel with a specific AR.
DTLS策略（图14中的最后一个）通常适用于与这些ARs相关的所有隧道。否则，隧道DTLS策略必须与每个接入路由器信息元素绑定在一起，并且WTP将针对具有特定AR的每个隧道强制执行独立的隧道DTLS策略。
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Tunnel DTLS Policy Element Type| Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved |D|C|R|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. AR Information .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved |D|C|R|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. AR Information .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. ...... .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved |D|C|R|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Tunnel DTLS Policy Element Type| Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved |D|C|R|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. AR Information .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved |D|C|R|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. AR Information .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. ...... .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved |D|C|R|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 14: Tunnel DTLS Policy Element
图14：隧道DTLS策略元素
Type: 2
类型：2
Length: This refers to the total length in octets of the element excluding the Type and Length fields.
长度：指元素的总长度（以八位字节为单位），不包括类型和长度字段。
Reserved: A set of reserved bits for future use. All implementations complying with this protocol MUST set to 0 any bits that are reserved in the version of the protocol supported by that implementation. Receivers MUST ignore all bits not defined for the version of the protocol they support.
保留：一组保留位，供将来使用。符合此协议的所有实现必须将该实现支持的协议版本中保留的任何位设置为0。接收器必须忽略所有未为其支持的协议版本定义的位。
D: DTLS-Enabled Data Channel Supported (see [RFC5415]).
D：支持DTLS启用的数据通道（请参阅[RFC5415]）。
C: Clear Text Data Channel Supported (see [RFC5415]).
C：支持明文数据通道（参见[RFC5415]）。
R: A reserved bit for future use (see [RFC5415]).
R：为将来使用而保留的位（参见[RFC5415]）。
AR Information: This means Access Router Information Element. In this context, each address in AR Information MUST be one of previously specified AR addresses.
AR信息：这意味着访问路由器信息元素。在此上下文中，AR信息中的每个地址必须是先前指定的AR地址之一。
In Figure 14, the last element that has no AR Information is the default tunnel DTLS policy, which provides options for any address not previously mentioned. Therefore, the AR Information field here is optional. In this element, if all ARs share the same tunnel DTLS policy, there won't be an AR Information field or its specific tunnel DTLS policy.
在图14中，没有AR信息的最后一个元素是默认的隧道DTLS策略，它为前面未提到的任何地址提供选项。因此，此处的AR信息字段是可选的。在此元素中，如果所有AR共享相同的隧道DTLS策略，则不会有AR信息字段或其特定的隧道DTLS策略。
In IEEE 802.11 networks, the IEEE 802.11 Tagging Mode Policy Element is used to specify how the WTP applies the QoS tagging policy when receiving the packets from stations on a particular radio. When the WTP sends out the packet to data channel to the AR(s), the packets have to be tagged for QoS purposes (see [RFC5416]).
在IEEE 802.11网络中，IEEE 802.11标记模式策略元素用于指定WTP在从特定无线电上的电台接收数据包时如何应用QoS标记策略。当WTP将数据包发送到AR的数据通道时，必须为QoS目的对数据包进行标记（参见[RFC5416]）。
The IEEE 802.11 Tagging Mode Policy abides by the IEEE 802.11 WTP Quality of Service defined in Section 6.22 of [RFC5416].
IEEE 802.11标记模式策略遵守[RFC5416]第6.22节中定义的IEEE 802.11 WTP服务质量。
If, for reliability reasons, the AC has provided more than one AR address in the Access Router Information Element, the same IEEE 802.11 Tagging Mode Policy (the last one in Figure 15) is generally applied for all tunnels associated with those ARs. Otherwise, IEEE 802.11 Tagging Mode Policy MUST be bonded together with each of the Access Router Information Elements, and the WTP will enforce the independent IEEE 802.11 Tagging Mode Policy for each tunnel with a specific AR.
如果出于可靠性原因，AC在接入路由器信息元素中提供了多个AR地址，则相同的IEEE 802.11标记模式策略（图15中的最后一个）通常适用于与这些AR相关联的所有隧道。否则，IEEE 802.11标记模式策略必须与每个接入路由器信息元素结合在一起，并且WTP将对具有特定AR的每个隧道强制执行独立的IEEE 802.11标记模式策略。
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Tagging Mode Policy Ele. Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved |P|Q|D|O|I|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. AR Information .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved |P|Q|D|O|I|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. AR Information .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. ...... .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved |P|Q|D|O|I|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Tagging Mode Policy Ele. Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved |P|Q|D|O|I|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. AR Information .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved |P|Q|D|O|I|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. AR Information .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. ...... .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved |P|Q|D|O|I|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 15: IEEE 802.11 Tagging Mode Policy Element
图15:IEEE 802.11标记模式策略元素
Type: 3
类型：3
Length: This refers to the total length in octets of the element excluding the Type and Length fields.
长度：指元素的总长度（以八位字节为单位），不包括类型和长度字段。
Reserved: A set of reserved bits for future use.
保留：一组保留位，供将来使用。
P: When set, the WTP is to employ the IEEE 802.1p QoS mechanism (see [RFC5416]).
P：设置时，WTP将采用IEEE 802.1p QoS机制（请参见[RFC5416]）。
Q: When the 'P' bit is set, the 'Q' bit is used by the AC to communicate to the WTP how IEEE 802.1p QoS is to be enforced (see [RFC5416]).
Q：设置“P”位时，AC使用“Q”位与WTP通信如何实施IEEE 802.1p QoS（参见[RFC5416]）。
D: When set, the WTP is to employ the DSCP QoS mechanism (see [RFC5416]).
D：设置时，WTP将采用DSCP QoS机制（请参见[RFC5416]）。
O: When the 'D' bit is set, the 'O' bit is used by the AC to communicate to the WTP how Differentiated Services Code Point (DSCP) QoS is to be enforced on the outer (tunneled) header (see [RFC5416]).
O：设置“D”位时，AC使用“O”位与WTP通信如何在外部（隧道）报头上强制实施区分服务代码点（DSCP）QoS（请参阅[RFC5416]）。
I: When the 'D' bit is set, the 'I' bit is used by the AC to communicate to the WTP how DSCP QoS is to be enforced on the station's packet (inner) header (see [RFC5416]).
I：设置“D”位时，AC使用“I”位与WTP通信，说明如何在站点的数据包（内部）报头上实施DSCP QoS（参见[RFC5416]）。
AR Information: This means Access Router Information Element. In this context, each address in AR information MUST be one of the previously specified AR addresses.
AR信息：这意味着访问路由器信息元素。在此上下文中，AR信息中的每个地址必须是先前指定的AR地址之一。
In Figure 15, the last element that has no AR information is the default IEEE 802.11 Tagging Mode Policy, which provides options for any address not previously mentioned. Therefore, the AR Information field here is optional. If all ARs share the same IEEE 802.11 Tagging Mode Policy, in this element, there will not be an AR Information field and its specific IEEE 802.11 Tagging Mode Policy.
在图15中，没有AR信息的最后一个元素是默认的IEEE 802.11标记模式策略，它为之前未提及的任何地址提供选项。因此，此处的AR信息字段是可选的。如果所有AR共享相同的IEEE 802.11标记模式策略，则在此元素中，将不存在AR信息字段及其特定的IEEE 802.11标记模式策略。
The CAPWAP data tunnel supports both UDP and UDP-Lite (see [RFC3828]). When run over IPv4, UDP is used for the CAPWAP Data Channels. When run over IPv6, the CAPWAP Data Channel may use either UDP or UDP-Lite. The AC specifies and configures the WTP for which the transport protocol is to be used for the CAPWAP data tunnel.
CAPWAP数据隧道同时支持UDP和UDP Lite（请参阅[RFC3828]）。在IPv4上运行时，UDP用于CAPWAP数据通道。在IPv6上运行时，CAPWAP数据通道可以使用UDP或UDP Lite。AC指定并配置将传输协议用于CAPWAP数据隧道的WTP。
The CAPWAP Transport Protocol Element abides by the definition in Section 4.6.14 of [RFC5415].
CAPWAP传输协议元素符合[RFC5415]第4.6.14节中的定义。
If, for reliability reasons, the AC has provided more than one AR address in the Access Router Information Element, the same CAPWAP Transport Protocol (the last one in Figure 16) is generally applied for all tunnels associated with those ARs. Otherwise, CAPWAP Transport Protocol MUST be bonded together with each of the Access Router Information Elements, and the WTP will enforce the independent CAPWAP Transport Protocol for each tunnel with a specific AR.
如果出于可靠性原因，AC在接入路由器信息元素中提供了多个AR地址，则同一CAPWAP传输协议（图16中的最后一个）通常适用于与这些AR相关的所有隧道。否则，CAPWAP传输协议必须与每个接入路由器信息元素结合在一起，WTP将为每个具有特定AR的隧道强制执行独立的CAPWAP传输协议。
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type=4 | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Transport | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. AR Information .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Transport | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. AR Information .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. ...... .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Transport | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type=4 | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Transport | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. AR Information .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Transport | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. AR Information .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. ...... .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Transport | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 16: CAPWAP Transport Protocol Element
图16:CAPWAP传输协议元素
Type: 4
类型：4
Length: 1
长度：1
Transport: The transport to use for the CAPWAP Data Channel. The following enumerated values are supported:
传输：用于CAPWAP数据通道的传输。支持以下枚举值：
1 - UDP-Lite: The UDP-Lite transport protocol is to be used for the CAPWAP Data Channel. Note that this option MUST NOT be used if the CAPWAP Control Channel is being used over IPv4 and if the AR address contained in the AR Information Element is an IPv4 address.
1-UDP Lite：UDP Lite传输协议将用于CAPWAP数据通道。请注意，如果CAPWAP控制通道通过IPv4使用，并且AR信息元素中包含的AR地址是IPv4地址，则不得使用此选项。
2 - UDP: The UDP transport protocol is to be used for the CAPWAP Data Channel.
2-UDP：UDP传输协议将用于CAPWAP数据通道。
AR Information: This means Access Router Information Element. In this context, each address in AR information MUST be one of the previously specified AR addresses.
AR信息：这意味着访问路由器信息元素。在此上下文中，AR信息中的每个地址必须是先前指定的AR地址之一。
In Figure 16, the last element that has no AR information is the default CAPWAP Transport Protocol, which provides options for any address not previously mentioned. Therefore, the AR Information field here is optional. If all ARs share the same CAPWAP Transport Protocol, in this element, there will not be an AR Information field and its specific CAPWAP Transport Protocol.
在图16中，没有AR信息的最后一个元素是默认的CAPWAP传输协议，它为前面未提到的任何地址提供选项。因此，此处的AR信息字段是可选的。如果所有AR共享相同的CAPWAP传输协议，则在此元素中，将不存在AR信息字段及其特定的CAPWAP传输协议。
If a WTP receives the GRE Key Element in the Alternate Tunnel Encapsulations Type message element for GRE selection, the WTP MUST insert the GRE Key to the encapsulation packet (see [RFC2890]). An AR acting as a decapsulating tunnel endpoint identifies packets belonging to a traffic flow based on the Key value.
如果WTP在用于GRE选择的备用隧道封装类型消息元素中接收到GRE密钥元素，则WTP必须将GRE密钥插入封装数据包（请参见[RFC2890]）。充当解封装隧道端点的AR基于键值识别属于业务流的分组。
The GRE Key Element field contains a 4-octet number defined in [RFC2890].
GRE Key Element字段包含[RFC2890]中定义的4位八位组编号。
If, for reliability reasons, the AC has provided more than one AR address in the Access Router Information Element, a GRE Key Element MAY be bonded together with each of the Access Router Information Elements, and the WTP will enforce the independent GRE Key for each tunnel with a specific AR.
如果出于可靠性原因，AC在接入路由器信息元素中提供了多个AR地址，则GRE密钥元素可以与每个接入路由器信息元素结合在一起，并且WTP将针对具有特定AR的每个隧道强制执行独立的GRE密钥。
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| GRE Key Element Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| GRE Key |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. AR Information .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| GRE Key |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. AR Information .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. ...... .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| GRE Key Element Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| GRE Key |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. AR Information .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| GRE Key |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. AR Information .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. ...... .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 17: GRE Key Element
图17:GRE关键要素
Type: 5
类型：5
Length: This refers to the total length in octets of the element excluding the Type and Length fields.
长度：指元素的总长度（以八位字节为单位），不包括类型和长度字段。
GRE Key: The Key field contains a 4-octet number that is inserted by the WTP according to [RFC2890].
GRE密钥：密钥字段包含由WTP根据[RFC2890]插入的4位八位组编号。
AR Information: This means Access Router Information Element. In this context, it SHOULD be restricted to a single address and MUST be the address of one of previously specified AR addresses.
AR信息：这意味着访问路由器信息元素。在此上下文中，它应限制为单个地址，并且必须是先前指定的AR地址之一的地址。
Any address not explicitly mentioned here does not have a GRE key.
此处未明确提及的任何地址都没有GRE密钥。
If AC has chosen a tunneling mechanism based on IPv6, it SHOULD support the minimum IPv6 MTU requirements [RFC8200]. This issue is described in [ARCH-TUNNELS]. AC SHOULD inform the WTP about the IPv6 MTU information in the Tunnel Info Element field.
如果AC选择了基于IPv6的隧道机制，它应该支持最低IPv6 MTU要求[RFC8200]。该问题在[ARCH-TUNNELS]中进行了描述。AC应在隧道信息元素字段中将IPv6 MTU信息告知WTP。
If, for reliability reasons, the AC has provided more than one AR address in the Access Router Information Element, an IPv6 MTU Element MAY be bonded together with each of the Access Router Information Elements, and the WTP will enforce the independent IPv6 MTU for each tunnel with a specific AR.
如果出于可靠性原因，AC在接入路由器信息元素中提供了多个AR地址，则IPv6 MTU元素可以与每个接入路由器信息元素结合在一起，并且WTP将针对具有特定AR的每个隧道强制执行独立的IPv6 MTU。
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv6 MTU Element Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Minimum IPv6 MTU | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. AR Information .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Minimum IPv6 MTU | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. AR Information .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ...... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv6 MTU Element Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Minimum IPv6 MTU | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. AR Information .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Minimum IPv6 MTU | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. AR Information .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ...... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 18: IPv6 MTU Element
图18:IPv6 MTU元素
Type: 6
类型：6
Length: This refers to the total length in octets of the element excluding the Type and Length fields.
长度：指元素的总长度（以八位字节为单位），不包括类型和长度字段。
Minimum IPv6 MTU: The field contains a 2-octet number indicating the minimum IPv6 MTU in the tunnel.
最小IPv6 MTU：该字段包含一个2个八位组的数字，指示隧道中的最小IPv6 MTU。
AR Information: This means Access Router Information Element. In this context, each address in AR information MUST be one of previously specified AR addresses.
AR信息：这意味着访问路由器信息元素。在此上下文中，AR信息中的每个地址必须是先前指定的AR地址之一。
Per this document, IANA has registered the following values in the existing "CAPWAP Message Element Type" registry, defined in [RFC5415].
根据本文件，IANA已在[RFC5415]中定义的现有“CAPWAP消息元素类型”注册表中注册了以下值。
o 54: Supported Alternate Tunnel Encapsulations Type as defined in Section 3.1.
o 54：第3.1节中定义的支撑备用隧道封装类型。
o 55: Alternate Tunnel Encapsulations Type as defined in Section 3.2.
o 55：第3.2节中定义的备用隧道封装类型。
o 1062: IEEE 802.11 WTP Alternate Tunnel Failure Indication as defined in Section 3.3.
o 1062:IEEE 802.11 WTP备用隧道故障指示，如第3.3节所定义。
Per this document, IANA has created a registry called "Alternate Tunnel-Types" under "CAPWAP Parameters". This specification defines the Alternate Tunnel Encapsulations Type message element. This element contains a field Tunnel-Type. The namespace for the field is 16 bits (0-65535). This specification defines values 0 through 6 and can be found in Section 3.2. Future allocations of values in this namespace are to be assigned by IANA using the "Specification Required" policy [RFC8126]. The registry format is given below.
根据本文件，IANA在“CAPWAP参数”下创建了一个名为“备用隧道类型”的注册表。本规范定义了备用隧道封装类型消息元素。此元素包含字段隧道类型。字段的命名空间为16位（0-65535）。本规范定义了0到6的值，可在第3.2节中找到。IANA将使用“所需规范”策略[RFC8126]分配此命名空间中未来的值分配。注册表格式如下所示。
Description Value Reference
CAPWAP 0 [RFC5415] [RFC5416]
L2TP 1 [RFC2661]
L2TPv3 2 [RFC3931]
IP-IP 3 [RFC2003]
PMIPv6-UDP 4 [RFC5844]
GRE 5 [RFC2784]
GTPv1-U 6 [TS.3GPP.29.281]
Description Value Reference
CAPWAP 0 [RFC5415] [RFC5416]
L2TP 1 [RFC2661]
L2TPv3 2 [RFC3931]
IP-IP 3 [RFC2003]
PMIPv6-UDP 4 [RFC5844]
GRE 5 [RFC2784]
GTPv1-U 6 [TS.3GPP.29.281]
Per this document, IANA has created a registry called "Alternate Tunnel Sub-elements" under "CAPWAP Parameters". This specification defines the Alternate Tunnel Sub-elements. Currently, these information elements can only be included in the Alternate Tunnel Encapsulations Type message element with the IEEE 802.11 WTP Alternate Tunnel Failure Indication message element as its sub-elements. These information elements contain a Type field. The namespace for the field is 16 bits (0-65535). This specification defines values 0 through 6 in Section 5. This namespace is managed by IANA, and assignments require an Expert Review [RFC8126].
根据本文件，IANA在“CAPWAP参数”下创建了一个名为“备用隧道子元素”的注册表。本规范规定了备用隧道子元件。目前，这些信息元素只能包含在备用隧道封装类型的消息元素中，IEEE 802.11 WTP备用隧道故障指示消息元素作为其子元素。这些信息元素包含一个类型字段。字段的命名空间为16位（0-65535）。本规范定义了第5节中的值0至6。此名称空间由IANA管理，分配需要专家审查[RFC8126]。
Description Value AR IPv4 List 0 AR IPv6 List 1 Tunnel DTLS Policy 2 IEEE 802.11 Tagging Mode Policy 3 CAPWAP Transport Protocol 4 GRE Key 5 IPv6 MTU 6
说明值AR IPv4列表0 AR IPv6列表1隧道DTLS策略2 IEEE 802.11标记模式策略3 CAPWAP传输协议4 GRE密钥5 IPv6 MTU 6
This document introduces three new CAPWAP WTP message elements. These elements are transported within CAPWAP Control messages as the existing message elements. Therefore, this document does not introduce any new security risks to the control plane compared to [RFC5415] and [RFC5416]. In the data plane, if the encapsulation type selected itself is not secured, it is suggested to protect the tunnel by using known secure methods, such as IPsec.
本文档介绍三个新的CAPWAP WTP消息元素。这些元素作为现有的消息元素在CAPWAP控制消息中传输。因此，与[RFC5415]和[RFC5416]相比，本文件不会给控制平面带来任何新的安全风险。在数据平面中，如果选择的封装类型本身不安全，建议使用已知的安全方法（如IPsec）来保护隧道。
[RFC2003] Perkins, C., "IP Encapsulation within IP", RFC 2003, DOI 10.17487/RFC2003, October 1996, <https://www.rfc-editor.org/info/rfc2003>.
[RFC2003]Perkins，C.，“IP内的IP封装”，RFC 2003，DOI 10.17487/RFC2003，1996年10月<https://www.rfc-editor.org/info/rfc2003>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, <https://www.rfc-editor.org/info/rfc2119>.
[RFC2119]Bradner，S.，“RFC中用于表示需求水平的关键词”，BCP 14，RFC 2119，DOI 10.17487/RFC2119，1997年3月<https://www.rfc-editor.org/info/rfc2119>.
[RFC2661] Townsley, W., Valencia, A., Rubens, A., Pall, G., Zorn, G., and B. Palter, "Layer Two Tunneling Protocol "L2TP"", RFC 2661, DOI 10.17487/RFC2661, August 1999, <https://www.rfc-editor.org/info/rfc2661>.
[RFC2661]W.汤斯利，巴伦西亚，A.鲁本斯，A.帕尔，G.佐恩，G.和B.帕尔特，“第二层隧道协议“L2TP”，RFC 2661，DOI 10.17487/RFC26611999年8月<https://www.rfc-editor.org/info/rfc2661>.
[RFC2784] Farinacci, D., Li, T., Hanks, S., Meyer, D., and P. Traina, "Generic Routing Encapsulation (GRE)", RFC 2784, DOI 10.17487/RFC2784, March 2000, <https://www.rfc-editor.org/info/rfc2784>.
[RFC2784]Farinaci，D.，Li，T.，Hanks，S.，Meyer，D.，和P.Traina，“通用路由封装（GRE）”，RFC 2784，DOI 10.17487/RFC27842000年3月<https://www.rfc-editor.org/info/rfc2784>.
[RFC2890] Dommety, G., "Key and Sequence Number Extensions to GRE", RFC 2890, DOI 10.17487/RFC2890, September 2000, <https://www.rfc-editor.org/info/rfc2890>.
[RFC2890]Dommety，G.，“GRE的密钥和序列号扩展”，RFC 2890，DOI 10.17487/RFC2890，2000年9月<https://www.rfc-editor.org/info/rfc2890>.
[RFC3828] Larzon, L-A., Degermark, M., Pink, S., Jonsson, L-E., Ed., and G. Fairhurst, Ed., "The Lightweight User Datagram Protocol (UDP-Lite)", RFC 3828, DOI 10.17487/RFC3828, July 2004, <https://www.rfc-editor.org/info/rfc3828>.
[RFC3828]Larzon，L-A.，Degermark，M.，Pink，S.，Jonsson，L-E.，Ed.，和G.Fairhurst，Ed.，“轻量级用户数据报协议（UDP Lite）”，RFC 3828，DOI 10.17487/RFC3828，2004年7月<https://www.rfc-editor.org/info/rfc3828>.
[RFC3931] Lau, J., Ed., Townsley, M., Ed., and I. Goyret, Ed., "Layer Two Tunneling Protocol - Version 3 (L2TPv3)", RFC 3931, DOI 10.17487/RFC3931, March 2005, <https://www.rfc-editor.org/info/rfc3931>.
[RFC3931]Lau，J.，Ed.，Townsley，M.，Ed.，和I.Goyret，Ed.，“第二层隧道协议-版本3（L2TPv3）”，RFC 3931，DOI 10.17487/RFC3931，2005年3月<https://www.rfc-editor.org/info/rfc3931>.
[RFC5415] Calhoun, P., Ed., Montemurro, M., Ed., and D. Stanley, Ed., "Control And Provisioning of Wireless Access Points (CAPWAP) Protocol Specification", RFC 5415, DOI 10.17487/RFC5415, March 2009, <https://www.rfc-editor.org/info/rfc5415>.
[RFC5415]Calhoun，P.，Ed.，Montemurro，M.，Ed.，和D.Stanley，Ed.，“无线接入点的控制和供应（CAPWAP）协议规范”，RFC 5415，DOI 10.17487/RFC5415，2009年3月<https://www.rfc-editor.org/info/rfc5415>.
[RFC5416] Calhoun, P., Ed., Montemurro, M., Ed., and D. Stanley, Ed., "Control and Provisioning of Wireless Access Points (CAPWAP) Protocol Binding for IEEE 802.11", RFC 5416, DOI 10.17487/RFC5416, March 2009, <https://www.rfc-editor.org/info/rfc5416>.
[RFC5416]Calhoun，P.，Ed.，Montemurro，M.，Ed.，和D.Stanley，Ed.，“IEEE 802.11无线接入点（CAPWAP）协议绑定的控制和供应”，RFC 5416，DOI 10.17487/RFC5416，2009年3月<https://www.rfc-editor.org/info/rfc5416>.
[RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for Writing an IANA Considerations Section in RFCs", BCP 26, RFC 8126, DOI 10.17487/RFC8126, June 2017, <https://www.rfc-editor.org/info/rfc8126>.
[RFC8126]Cotton，M.，Leiba，B.，和T.Narten，“在RFC中编写IANA考虑事项部分的指南”，BCP 26，RFC 8126，DOI 10.17487/RFC8126，2017年6月<https://www.rfc-editor.org/info/rfc8126>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017, <https://www.rfc-editor.org/info/rfc8174>.
[RFC8174]Leiba，B.，“RFC 2119关键词中大写与小写的歧义”，BCP 14，RFC 8174，DOI 10.17487/RFC8174，2017年5月<https://www.rfc-editor.org/info/rfc8174>.
[RFC8200] Deering, S. and R. Hinden, "Internet Protocol, Version 6 (IPv6) Specification", STD 86, RFC 8200, DOI 10.17487/RFC8200, July 2017, <https://www.rfc-editor.org/info/rfc8200>.
[RFC8200]Deering，S.和R.Hinden，“互联网协议，第6版（IPv6）规范”，STD 86，RFC 8200，DOI 10.17487/RFC8200，2017年7月<https://www.rfc-editor.org/info/rfc8200>.
[ARCH-TUNNELS] Touch, J. and M. Townsley, "IP Tunnels in the Internet Architecture", Work in Progress, draft-ietf-intarea-tunnels-08, January 2018.
[ARCH-TUNNELS]Touch，J.和M.Townsley，“互联网体系结构中的IP隧道”，正在进行的工作，草案-ietf-intarea-TUNNELS-082018年1月。
[RFC5213] Gundavelli, S., Ed., Leung, K., Devarapalli, V., Chowdhury, K., and B. Patil, "Proxy Mobile IPv6", RFC 5213, DOI 10.17487/RFC5213, August 2008, <https://www.rfc-editor.org/info/rfc5213>.
[RFC5213]Gundavelli，S.，Ed.，Leung，K.，Devarapalli，V.，Chowdhury，K.，和B.Patil，“代理移动IPv6”，RFC 5213，DOI 10.17487/RFC5213，2008年8月<https://www.rfc-editor.org/info/rfc5213>.
[RFC5844] Wakikawa, R. and S. Gundavelli, "IPv4 Support for Proxy Mobile IPv6", RFC 5844, DOI 10.17487/RFC5844, May 2010, <https://www.rfc-editor.org/info/rfc5844>.
[RFC5844]Wakikawa，R.和S.Gundavelli，“代理移动IPv6的IPv4支持”，RFC 5844，DOI 10.17487/RFC5844，2010年5月<https://www.rfc-editor.org/info/rfc5844>.
[RFC5845] Muhanna, A., Khalil, M., Gundavelli, S., and K. Leung, "Generic Routing Encapsulation (GRE) Key Option for Proxy Mobile IPv6", RFC 5845, DOI 10.17487/RFC5845, June 2010, <https://www.rfc-editor.org/info/rfc5845>.
[RFC5845]Muhanna，A.，Khalil，M.，Gundavelli，S.，和K.Leung，“代理移动IPv6的通用路由封装（GRE）密钥选项”，RFC 5845，DOI 10.17487/RFC5845，2010年6月<https://www.rfc-editor.org/info/rfc5845>.
[RFC7494] Shao, C., Deng, H., Pazhyannur, R., Bari, F., Zhang, R., and S. Matsushima, "IEEE 802.11 Medium Access Control (MAC) Profile for Control and Provisioning of Wireless Access Points (CAPWAP)", RFC 7494, DOI 10.17487/RFC7494, April 2015, <https://www.rfc-editor.org/info/rfc7494>.
[RFC7494]邵，C.，邓，H.，帕兹扬努尔，R.，巴里，F.，张，R.，和S.松岛，“用于控制和提供无线接入点（CAPWAP）的IEEE 802.11媒体访问控制（MAC）配置文件”，RFC 7494，DOI 10.17487/RFC7494，2015年4月<https://www.rfc-editor.org/info/rfc7494>.
[TS.3GPP.29.281] 3GPP, "General Packet Radio System (GPRS) Tunnelling Protocol User Plane (GTPv1-U)", 3GPP TS 29.281, V13.1.0, March 2016.
[TS.3GPP.29.281]3GPP，“通用分组无线系统（GPRS）隧道协议用户平面（GTPv1-U）”，3GPP TS 29.281，V13.1.012016年3月。
Contributors
贡献者
The authors would like to thank Andreas Schultz, Hong Liu, Yifan Chen, Chunju Shao, Li Xue, Jianjie You, Jin Li, Joe Touch, Alexey Melnikov, Kathleen Moriarty, Mirja Kuehlewind, Catherine Meadows, and Paul Kyzivat for their valuable comments.
作者要感谢安德烈亚斯·舒尔茨、刘红、陈一凡、邵春菊、李雪、尤建杰、金丽、乔·图奇、阿列克谢·梅尔尼科夫、凯瑟琳·莫里亚蒂、米佳·库勒温德、凯瑟琳·梅多斯和保罗·基齐瓦特的宝贵评论。
Authors' Addresses
作者地址
Rong Zhang China Telecom No.109 Zhongshandadao avenue Guangzhou 510630 China
中国电信广州市中山大道109号荣章510630
Email: zhangr@gsta.com
Email: zhangr@gsta.com
Rajesh S. Pazhyannur Cisco 170 West Tasman Drive San Jose, CA 95134 United States of America
美国加利福尼亚州圣何塞市西塔斯曼大道170号，邮编95134
Email: rpazhyan@cisco.com
Email: rpazhyan@cisco.com
Sri Gundavelli Cisco 170 West Tasman Drive San Jose, CA 95134 United States of America
美国加利福尼亚州圣何塞市西塔斯曼大道170号，邮编95134
Email: sgundave@cisco.com
Email: sgundave@cisco.com
Zhen Cao Huawei Xinxi Rd. 3 Beijing 100085 China
中国北京市新西路3号真曹华为100085
Email: zhencao.ietf@gmail.com
Email: zhencao.ietf@gmail.com
Hui Deng Huawei Xinxi Rd. 3 Beijing 100085 China
惠登华为新西路3号北京100085
Email: denghui02@gmail.com
Email: denghui02@gmail.com
Zongpeng Du Huawei No.156 Beiqing Rd. Z-park, HaiDian District Beijing 100095 China
中国北京市海淀区北青路Z公园156号华为宗鹏大厦100095
Email: duzongpeng@huawei.com
Email: duzongpeng@huawei.com