Network Working Group L. Martini
Request for Comments: 4717 J. Jayakumar
Category: Standards Track Cisco Systems, Inc.
M. Bocci
Alcatel
N. El-Aawar
Level 3 Communications, LLC
J. Brayley
ECI Telecom Inc.
G. Koleyni
Nortel Networks
December 2006
Network Working Group L. Martini
Request for Comments: 4717 J. Jayakumar
Category: Standards Track Cisco Systems, Inc.
M. Bocci
Alcatel
N. El-Aawar
Level 3 Communications, LLC
J. Brayley
ECI Telecom Inc.
G. Koleyni
Nortel Networks
December 2006
Encapsulation Methods for Transport of Asynchronous Transfer Mode (ATM) over MPLS Networks
MPLS网络上异步传输模式（ATM）传输的封装方法
Status of This Memo
关于下段备忘
This document specifies an Internet standards track protocol for the Internet community, and requests discussion and suggestions for improvements. Please refer to the current edition of the "Internet Official Protocol Standards" (STD 1) for the standardization state and status of this protocol. Distribution of this memo is unlimited.
本文件规定了互联网社区的互联网标准跟踪协议，并要求进行讨论和提出改进建议。有关本协议的标准化状态和状态，请参考当前版本的“互联网官方协议标准”（STD 1）。本备忘录的分发不受限制。
Copyright Notice
版权公告
Copyright (C) The IETF Trust (2006).
版权所有（C）IETF信托基金（2006年）。
Abstract
摘要
An Asynchronous Transfer Mode (ATM) Pseudowire (PW) is used to carry ATM cells over an MPLS network. This enables service providers to offer "emulated" ATM services over existing MPLS networks. This document specifies methods for the encapsulation of ATM cells within a pseudowire. It also specifies the procedures for using a PW to provide an ATM service.
异步传输模式（ATM）伪线（PW）用于在MPLS网络上传输ATM信元。这使服务提供商能够在现有MPLS网络上提供“模拟”ATM服务。本文件规定了在伪线中封装ATM信元的方法。它还规定了使用PW提供ATM服务的程序。
Table of Contents
目录
1. Introduction ....................................................3
2. Specification of Requirements ...................................4
3. Applicability Statement .........................................4
4. Terminology .....................................................4
5. General Encapsulation Method ....................................6
5.1. The Control Word ...........................................6
5.1.1. The Generic Control Word ............................7
5.1.2. The Preferred Control Word ..........................8
5.1.3. Setting the Sequence Number Field in the
Control Word ........................................9
5.2. MTU Requirements ...........................................9
5.3. MPLS Shim S Bit Value .....................................10
5.4. MPLS Shim TTL Values ......................................10
6. Encapsulation Mode Applicability ...............................10
6.1. ATM N-to-One Cell Mode ....................................11
6.2. ATM One-to-One Cell Encapsulation .........................13
6.3. AAL5 SDU Frame Encapsulation ..............................13
6.4. AAL5 PDU Frame Encapsulation ..............................14
7. ATM OAM Cell Support ...........................................15
7.1. VCC Case ..................................................15
7.2. VPC Case ..................................................16
7.3. SDU/PDU OAM Cell Emulation Mode ...........................16
7.4. Defect Handling ...........................................17
8. ATM N-to-One Cell Mode .........................................18
8.1. ATM N-to-One Service Encapsulation ........................19
9. ATM One-to-One Cell Mode .......................................21
9.1. ATM One-to-One Service Encapsulation ......................21
9.2. Sequence Number ...........................................22
9.3. ATM VCC Cell Transport Service ............................22
9.4. ATM VPC Services ..........................................24
9.4.1. ATM VPC Cell Transport Services ....................25
10. ATM AAL5 CPCS-SDU Mode ........................................26
10.1. Transparent AAL5 SDU Frame Encapsulation .................27
11. AAL5 PDU Frame Mode ...........................................28
11.1. Transparent AAL5 PDU Frame Encapsulation .................28
11.2. Fragmentation ............................................30
11.2.1. Procedures in the ATM-to-PSN Direction ............30
11.2.2. Procedures in the PSN-to-ATM Direction ............31
12. Mapping of ATM and PSN Classes of Service .....................31
13. ILMI Support ..................................................32
14. ATM-Specific Interface Parameter Sub-TLVs .....................32
15. Congestion Control ............................................32
16. Security Considerations .......................................33
17. Normative References ..........................................34
18. Informative References ........................................34
19. Significant Contributors ......................................36
1. Introduction ....................................................3
2. Specification of Requirements ...................................4
3. Applicability Statement .........................................4
4. Terminology .....................................................4
5. General Encapsulation Method ....................................6
5.1. The Control Word ...........................................6
5.1.1. The Generic Control Word ............................7
5.1.2. The Preferred Control Word ..........................8
5.1.3. Setting the Sequence Number Field in the
Control Word ........................................9
5.2. MTU Requirements ...........................................9
5.3. MPLS Shim S Bit Value .....................................10
5.4. MPLS Shim TTL Values ......................................10
6. Encapsulation Mode Applicability ...............................10
6.1. ATM N-to-One Cell Mode ....................................11
6.2. ATM One-to-One Cell Encapsulation .........................13
6.3. AAL5 SDU Frame Encapsulation ..............................13
6.4. AAL5 PDU Frame Encapsulation ..............................14
7. ATM OAM Cell Support ...........................................15
7.1. VCC Case ..................................................15
7.2. VPC Case ..................................................16
7.3. SDU/PDU OAM Cell Emulation Mode ...........................16
7.4. Defect Handling ...........................................17
8. ATM N-to-One Cell Mode .........................................18
8.1. ATM N-to-One Service Encapsulation ........................19
9. ATM One-to-One Cell Mode .......................................21
9.1. ATM One-to-One Service Encapsulation ......................21
9.2. Sequence Number ...........................................22
9.3. ATM VCC Cell Transport Service ............................22
9.4. ATM VPC Services ..........................................24
9.4.1. ATM VPC Cell Transport Services ....................25
10. ATM AAL5 CPCS-SDU Mode ........................................26
10.1. Transparent AAL5 SDU Frame Encapsulation .................27
11. AAL5 PDU Frame Mode ...........................................28
11.1. Transparent AAL5 PDU Frame Encapsulation .................28
11.2. Fragmentation ............................................30
11.2.1. Procedures in the ATM-to-PSN Direction ............30
11.2.2. Procedures in the PSN-to-ATM Direction ............31
12. Mapping of ATM and PSN Classes of Service .....................31
13. ILMI Support ..................................................32
14. ATM-Specific Interface Parameter Sub-TLVs .....................32
15. Congestion Control ............................................32
16. Security Considerations .......................................33
17. Normative References ..........................................34
18. Informative References ........................................34
19. Significant Contributors ......................................36
Packet Switched Networks (PSNs) have the potential to reduce the complexity of a service provider's infrastructure by allowing virtually any existing digital service to be supported over a single networking infrastructure. The benefit of this model to a service provider is threefold:
分组交换网络（PSN）通过允许在单个网络基础设施上支持几乎任何现有的数字服务，有可能降低服务提供商基础设施的复杂性。这种模式对服务提供商的好处有三：
-i. Leveraging of the existing systems and services to provide increased capacity from a packet-switched core.
-一,。利用现有系统和服务从分组交换核心提供更大的容量。
-ii. Preserving existing network operational processes and procedures used to maintain the legacy services.
-二,。保留用于维护遗留服务的现有网络操作流程和过程。
-iii. Using the common packet-switched network infrastructure to support both the core capacity requirements of existing services and the requirements of new services supported natively over the packet-switched network.
-iii.使用通用分组交换网络基础设施来支持现有服务的核心容量需求和分组交换网络上本机支持的新服务的需求。
This document describes a method to carry ATM services over MPLS. It lists ATM-specific requirements and provides encapsulation formats and semantics for connecting ATM edge networks through a packet-switched network using MPLS.
本文档描述了通过MPLS承载ATM服务的方法。它列出了ATM的特定要求，并提供了通过使用MPLS的分组交换网络连接ATM边缘网络的封装格式和语义。
Figure 1, below, displays the ATM services reference model. This model is adapted from [RFC3985].
下图1显示了ATM服务参考模型。该模型改编自[RFC3985]。
|<----- Pseudowire ----->|
| |
| |<-- PSN Tunnel -->| |
ATM Service V V V V ATM Service
| +----+ +----+ |
+----+ | | PE1|==================| PE2| | +----+
| |----------|............PW1.............|----------| |
| CE1| | | | | | | |CE2 |
| |----------|............PW2.............|----------| |
+----+ | | |==================| | | +----+
^ +----+ +----+ | ^
| Provider Edge 1 Provider Edge 2 |
| |
|<-------------- Emulated Service ---------------->|
Customer Customer
Edge 1 Edge 2
|<----- Pseudowire ----->|
| |
| |<-- PSN Tunnel -->| |
ATM Service V V V V ATM Service
| +----+ +----+ |
+----+ | | PE1|==================| PE2| | +----+
| |----------|............PW1.............|----------| |
| CE1| | | | | | | |CE2 |
| |----------|............PW2.............|----------| |
+----+ | | |==================| | | +----+
^ +----+ +----+ | ^
| Provider Edge 1 Provider Edge 2 |
| |
|<-------------- Emulated Service ---------------->|
Customer Customer
Edge 1 Edge 2
Figure 1: ATM Service Reference Model
图1:ATM服务参考模型
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in [RFC2119].
本文件中的关键词“必须”、“不得”、“必需”、“应”、“不应”、“应”、“不应”、“建议”、“可”和“可选”应按照[RFC2119]中所述进行解释。
The ATM over PW service is not intended to perfectly emulate a traditional ATM service, but it can be used for applications that need an ATM transport service.
ATM over PW服务并不打算完美地模拟传统的ATM服务，但它可以用于需要ATM传输服务的应用。
The following are notable differences between traditional ATM service and the protocol described in this document:
以下是传统ATM服务与本文档中描述的协议之间的显著差异：
- ATM cell ordering can be preserved using the OPTIONAL sequence field in the control word; however, implementations are not required to support this feature. The use of this feature may impact other ATM quality of service (QoS) commitments.
- 使用控制字中的可选序列字段可以保留ATM信元顺序；但是，不需要实现来支持此功能。此功能的使用可能会影响其他ATM服务质量（QoS）承诺。
- The QoS model for traditional ATM can be emulated. However, the detailed specification of ATM QoS emulation is outside the scope of this document. The emulation must be able to provide the required ATM QoS commitments for the end-user application.
- 可以模拟传统ATM的QoS模型。然而，ATM QoS仿真的详细规范不在本文档的范围之内。仿真必须能够为最终用户应用程序提供所需的ATM QoS承诺。
- The ATM flow control mechanisms are transparent to the MPLS network and cannot reflect the status of the MPLS network.
- ATM流量控制机制对MPLS网络是透明的，不能反映MPLS网络的状态。
- Control plane support for ATM SVCs, SVPs, SPVCs, and SPVPs is outside the scope of this document.
- ATM SVC、SVP、SPVC和SPVP的控制平面支持不在本文件范围内。
Note that the encapsulations described in this specification are identical to those described in [Y.1411] and [Y.1412].
注意，本规范中描述的封装与[Y.1411]和[Y.1412]中描述的封装相同。
One-to-one mode: specifies an encapsulation method that maps one ATM Virtual Channel Connection (VCC) (or one ATM Virtual Path Connection (VPC)) to one pseudowire.
一对一模式：指定将一个ATM虚拟通道连接（VCC）（或一个ATM虚拟路径连接（VPC））映射到一条伪线的封装方法。
N-to-one mode (N >= 1): specifies an encapsulation method that maps one or more ATM VCCs (or one or more ATM VPCs) to one pseudowire.
N-to-one模式（N>=1）：指定将一个或多个ATM VCC（或一个或多个ATM VPC）映射到一条伪线的封装方法。
Packet-Switched Network (PSN): an IP or MPLS network.
分组交换网络（PSN）：IP或MPLS网络。
Pseudowire Emulation Edge to Edge (PWE3): a mechanism that emulates the essential attributes of a service (such as a T1 leased line or Frame Relay) over a PSN.
伪线模拟边到边（PWE3）：一种通过PSN模拟服务（如T1专线或帧中继）基本属性的机制。
Customer Edge (CE): a device where one end of a service originates and/or terminates. The CE is not aware that it is using an emulated service rather than a native service.
客户边缘（CE）：服务一端发起和/或终止的设备。CE不知道它正在使用模拟服务而不是本机服务。
Provider Edge (PE): a device that provides PWE3 to a CE.
提供者边缘（PE）：向CE提供PWE3的设备。
Pseudowire (PW): a connection between two PEs carried over a PSN. The PE provides the adaptation between the CE and the PW.
伪线（PW）：通过PSN传输的两个PEs之间的连接。PE提供CE和PW之间的自适应。
Pseudowire PDU: a PDU sent on the PW that contains all of the data and control information necessary to provide the desired service.
伪线PDU：在PW上发送的PDU，包含提供所需服务所需的所有数据和控制信息。
PSN Tunnel: a tunnel inside which multiple PWs can be nested so that they are transparent to core PSN devices.
PSN隧道：可以嵌套多个PW的隧道，以便它们对核心PSN设备透明。
PSN Bound: the traffic direction where information from a CE is adapted to a PW, and PW-PDUs are sent into the PSN.
PSN绑定：来自CE的信息适配到PW，并且PW PDU被发送到PSN的通信方向。
CE Bound: the traffic direction where PW-PDUs are received on a PW from the PSN, re-converted back in the emulated service, and sent out to a CE.
CE绑定：PW PDU在PW上从PSN接收、在模拟服务中重新转换并发送到CE的通信方向。
Ingress: the point where the ATM service is encapsulated into a pseudowire PDU (ATM to PSN direction).
入口：ATM服务封装到伪线PDU（ATM到PSN方向）的点。
Egress: the point where the ATM service is decapsulated from a pseudowire PDU (PSN to ATM direction).
出口：ATM服务从伪线PDU（PSN到ATM方向）解除封装的点。
CTD: Cell Transfer Delay.
细胞转移延迟。
MTU: Maximum Transmission Unit.
MTU：最大传输单位。
SDU: Service Data Unit.
SDU：服务数据单元。
OAM: Operations And Maintenance.
OAM：操作和维护。
PVC: Permanent Virtual Connection. An ATM connection that is provisioned via a network management interface. The connection is not signaled.
永久虚拟连接。通过网络管理接口提供的ATM连接。连接未发出信号。
VCC: Virtual Circuit Connection. An ATM connection that is switched based on the cell header's VCI.
虚拟电路连接。基于信元报头的VCI交换的ATM连接。
VPC: Virtual Path Connection. An ATM connection that is switched based on the cell header's VPI.
VPC：虚拟路径连接。基于信元报头的VPI交换的ATM连接。
Additional terminology relevant to pseudowires and Layer 2 Virtual Private Networking (L2VPN) in general may be found in [RFC4026].
[RFC4026]中提供了一般与伪线和第2层虚拟专用网络（L2VPN）相关的其他术语。
This section describes the general encapsulation format for ATM over PSN pseudowires.
本节描述了PSN伪线上ATM的通用封装格式。
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| PSN Transport Header (As Required) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Pseudowire Header |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ATM Control Word |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ATM Service Payload |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| PSN Transport Header (As Required) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Pseudowire Header |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ATM Control Word |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ATM Service Payload |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2: General format for ATM encapsulation over PSNs
图2:PSN上ATM封装的通用格式
The PSN Transport Header depends on the particular tunneling technology in use. This header is used to transport the encapsulated ATM information through the packet-switched core.
PSN传输头取决于使用的特定隧道技术。该报头用于通过分组交换核心传输封装的ATM信息。
The Pseudowire Header identifies a particular ATM service on a tunnel. In case of MPLS, the pseudowire header is one or more MPLS labels at the bottom of the MPLS label stack.
伪线报头标识隧道上的特定ATM服务。对于MPLS，伪线报头是MPLS标签堆栈底部的一个或多个MPLS标签。
The ATM Control Word is inserted before the ATM service payload. It may contain a length and sequence number in addition to certain control bits needed to carry the service.
ATM控制字插入ATM服务有效负载之前。除了承载服务所需的某些控制位之外，它还可能包含长度和序列号。
The Control Words defined in this section are based on the Generic PW MPLS Control Word as defined in [RFC4385]. They provide the ability to sequence individual frames on the PW, avoidance of equal-cost multiple-path load-balancing (ECMP) [RFC2992], and OAM mechanisms including VCCV [VCCV].
本节中定义的控制字基于[RFC4385]中定义的通用PW MPLS控制字。它们提供对PW上的各个帧进行排序的能力，避免等成本多路径负载平衡（ECMP）[RFC2992]，以及包括VCCV[VCCV]在内的OAM机制。
[RFC4385] states, "If a PW is sensitive to packet misordering and is being carried over an MPLS PSN that uses the contents of the MPLS payload to select the ECMP path, it MUST employ a mechanism which prevents packet misordering." This is necessary because ECMP implementations may examine the first nibble after the MPLS label stack to determine whether or not the labelled packet is IP. Thus, if the VPI of an ATM connection carried over the PW using N-to-one cell mode encapsulation, without a control word present, begins with 0x4 or 0x6, it could be mistaken for an IPv4 or IPv6 packet. This
[RFC4385]指出，“如果PW对数据包错序非常敏感，并且正在通过使用MPLS有效载荷的内容来选择ECMP路径的MPLS PSN进行传输，则必须采用防止数据包错序的机制。”这是必要的，因为ECMP实现可能会检查MPLS标签堆栈之后的第一个半字节，以确定标记的数据包是否为IP。因此，如果使用N对1信元模式封装通过PW承载的ATM连接的VPI（不存在控制字）以0x4或0x6开始，则可能会将其误认为IPv4或IPv6数据包。这
could, depending on the configuration and topology of the MPLS network, lead to a situation where all packets for a given PW do not follow the same path. This may increase out-of-order frames on a given PW, or cause OAM packets to follow a different path than actual traffic (see section 4.4.3 on Frame Ordering).
根据MPLS网络的配置和拓扑，可能导致给定PW的所有数据包不遵循相同路径的情况。这可能会增加给定PW上的无序帧，或导致OAM数据包遵循与实际流量不同的路径（参见第4.4.3节关于帧顺序）。
The features that the control word provides may not be needed for a given ATM PW. For example, ECMP may not be present or active on a given MPLS network, strict frame sequencing may not be required, etc. If this is the case, and the control word is not REQUIRED by the encapsulation mode for other functions (such as length or the transport of ATM protocol specific information), the control word provides little value and is therefore OPTIONAL. Early ATM PW implementations have been deployed that do not include a control word or the ability to process one if present. To aid in backwards compatibility, future implementations MUST be able to send and receive frames without a control word present.
给定ATM PW可能不需要控制字提供的功能。例如，ECMP在给定MPLS网络上可能不存在或不活动，可能不需要严格的帧排序等。如果是这种情况，则封装模式不要求控制字用于其他功能（例如ATM协议特定信息的长度或传输），控制字提供的值很少，因此是可选的。早期的ATM PW实现已经部署，不包括控制字或处理控制字（如果存在）的能力。为了帮助实现向后兼容性，未来的实现必须能够在不存在控制字的情况下发送和接收帧。
In all cases, the egress PE MUST be aware of whether the ingress PE will send a control word over a specific PW. This may be achieved by configuration of the PEs, or by signaling, as defined in [RFC4447].
在所有情况下，出口PE必须知道入口PE是否将通过特定PW发送控制字。如[RFC4447]中所定义，这可以通过配置PEs或通过信令来实现。
If the pseudowire traverses a network link that requires a minimum frame size (Ethernet is a practical example), with a minimum frame size of 64 octets, then such links will apply padding to the pseudowire PDU to reach its minimum frame size. In this case, the control word must include a length field set to the PDU length. A mechanism is required for the egress PE to detect and remove such padding.
如果伪线通过需要最小帧大小（以太网是一个实际示例）的网络链路，最小帧大小为64个八位字节，则此类链路将对伪线PDU应用填充以达到其最小帧大小。在这种情况下，控制字必须包括设置为PDU长度的长度字段。出口PE需要一种机制来检测并移除此类填充物。
This control word is used in the following encapsulation modes:
此控制字用于以下封装模式：
- ATM One-to-one Cell Mode - AAL5 PDU Frame Mode
- ATM一对一信元模式-AAL5 PDU帧模式
The PWE3 control word document [RFC4385] provides the following structure for the generic control word:
PWE3控制字文档[RFC4385]为通用控制字提供了以下结构：
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0 0 0 0| Specified by PW Encapsulation |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0 0 0 0| Specified by PW Encapsulation |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The detailed structure for the ATM One-to-one Cell Mode and for the AAL5 PDU Frame Mode is as follows:
ATM一对一信元模式和AAL5 PDU帧模式的详细结构如下：
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0 0 0 0| Resvd | Sequence Number | ATM Specific |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0 0 0 0| Resvd | Sequence Number | ATM Specific |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
In the above diagram, the first 4 bits MUST be set to 0 to indicate PW data. They MUST be ignored by the receiving PE.
在上图中，前4位必须设置为0以指示PW数据。接收PE必须忽略它们。
The next four bits are reserved and MUST be set to 0 upon transmission and ignored upon reception.
接下来的四位是保留的，在传输时必须设置为0，在接收时忽略。
The next 16 bits provide a sequence number that can be used to guarantee ordered packet delivery. The processing of the sequence number field is OPTIONAL.
接下来的16位提供了一个序列号，可以用来保证有序的数据包传递。序列号字段的处理是可选的。
The sequence number space is a 16-bit, unsigned circular space. The sequence number value 0 is used to indicate that the sequence number check algorithm is not used.
序列号空间是一个16位的无符号循环空间。序号值0用于指示未使用序号检查算法。
The last 8 bits provide space for carrying ATM-specific flags. These are defined in the protocol-specific details below.
最后8位为承载ATM特定标志提供空间。这些在以下特定于协议的详细信息中定义。
There is no requirement for a length field for the One-to-one Cell and PDU Frame modes because the PSN PDU is always greater than 64 bytes; therefore, no padding is applied in Ethernet links in the PSN.
一对一单元和PDU帧模式不需要长度字段，因为PSN PDU始终大于64字节；因此，PSN中的以太网链路中不应用填充。
This control word is used in the following encapsulation modes:
此控制字用于以下封装模式：
- ATM N-to-one Cell Mode - AAL5 SDU Frame Mode
- ATM N对一信元模式-AAL5 SDU帧模式
It is defined as follows:
其定义如下：
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0 0 0 0| Flags |Res| Length | Sequence Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0 0 0 0| Flags |Res| Length | Sequence Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
In the above diagram, the first 4 bits MUST be set to 0 to indicate PW data. They MUST be ignored by the receiving PE.
在上图中，前4位必须设置为0以指示PW数据。接收PE必须忽略它们。
The next 4 bits provide space for carrying protocol-specific flags. These are defined in the protocol-specific details below.
接下来的4位提供用于承载协议特定标志的空间。这些在以下特定于协议的详细信息中定义。
The next 6 bits provide a length field, which is used as follows: If the packet's length (defined as the length of the layer 2 payload plus the length of the control word) is less than 64 bytes, the length field MUST be set to the packet's length. Otherwise, the length field MUST be set to zero. The value of the length field, if non-zero, can be used to remove any padding. When the packet reaches the service provider's egress router, it may be desirable to remove the padding before forwarding the packet. Note that the length field is not used in the N-to-one mode and MUST be set to 0.
接下来的6位提供一个长度字段，其使用如下：如果数据包的长度（定义为第2层有效负载的长度加上控制字的长度）小于64字节，则长度字段必须设置为数据包的长度。否则，长度字段必须设置为零。长度字段的值（如果非零）可用于删除任何填充。当分组到达服务提供商的出口路由器时，可能希望在转发分组之前移除填充。请注意，长度字段不用于N对1模式，必须设置为0。
The last 16 bits provide a sequence number that can be used to guarantee ordered packet delivery. The processing of the sequence number field is OPTIONAL.
最后16位提供一个序列号，可用于保证有序的数据包传递。序列号字段的处理是可选的。
The sequence number space is a 16-bit, unsigned circular space. The sequence number value 0 is used to indicate that the sequence number check algorithm is not used.
序列号空间是一个16位的无符号循环空间。序号值0用于指示未使用序号检查算法。
This section applies to the sequence number field of both the Generic and Preferred Control Words.
本节适用于通用和首选控制字的序列号字段。
For a given emulated VC and a pair of routers PE1 and PE2, if PE1 supports packet sequencing, then the sequencing procedures defined in [RFC4385] MUST be used.
对于给定的仿真VC和一对路由器PE1和PE2，如果PE1支持分组排序，则必须使用[RFC4385]中定义的排序过程。
Packets that are received out of order MAY be dropped or reordered at the discretion of the receiver.
接收方可自行决定丢弃或重新排序无序接收的数据包。
A simple extension of the processing algorithm in [RFC4385] MAY be used to detect lost packets.
[RFC4385]中处理算法的简单扩展可用于检测丢失的分组。
If a PE router negotiated not to use receive sequence number processing, and it received a non-zero sequence number, then it SHOULD send a PW status message indicating a receive fault and disable the PW.
如果PE路由器协商不使用接收序列号处理，并且收到非零序号，则应发送指示接收故障的PW状态消息并禁用PW。
The network MUST be configured with an MTU that is sufficient to transport the largest encapsulation frames. If MPLS is used as the tunneling protocol, for example, this is likely to be 12 or more bytes greater than the largest frame size. Other tunneling protocols may have longer headers and require larger MTUs. If the ingress
网络必须配置足以传输最大封装帧的MTU。例如，如果将MPLS用作隧道协议，则这可能比最大帧大小大12个或更多字节。其他隧道协议可能具有更长的标头，并且需要更大的MTU。如果入口
router determines that an encapsulated layer 2 PDU exceeds the MTU of the tunnel through which it must be sent, the PDU MUST be dropped. If an egress router receives an encapsulated layer 2 PDU whose payload length (i.e., the length of the PDU itself without any of the encapsulation headers) exceeds the MTU of the destination layer 2 interface, the PDU MUST be dropped.
路由器确定封装的第2层PDU超过了它必须通过的隧道的MTU，必须丢弃PDU。如果出口路由器接收到一个封装的第2层PDU，其有效负载长度（即，没有任何封装头的PDU本身的长度）超过目的地第2层接口的MTU，则必须丢弃该PDU。
The ingress label switching router (LSR), PE1, MUST set the S bit of the PW label to a value of 1 to denote that the VC label is at the bottom of the stack. For more information on setting the S Bit, see [RFC3032].
入口标签交换路由器（LSR）PE1必须将PW标签的S位设置为1，以表示VC标签位于堆栈底部。有关设置S位的更多信息，请参阅[RFC3032]。
The setting of the TTL value in the PW label is application dependent. In any case, [RFC3032] TTL processing procedure, including handling of expired TTLs, MUST be followed.
PW标签中TTL值的设置取决于应用程序。在任何情况下，必须遵循[RFC3032]TTL处理程序，包括处理过期的TTL。
This document defines two methods for encapsulation of ATM cells, namely, One-to-one mode and N-to-one mode.
本文档定义了两种ATM信元封装方法，即一对一模式和N对一模式。
The N-to-one mode (N >= 1) specifies an encapsulation method that maps one or more ATM VCCs (or one or more ATM VPCs) to one pseudowire. This is the only REQUIRED mode. One format is used for both the VCC or VPC mapping to the tunnel. The 4-octet ATM header is unaltered in the encapsulation; thus, the VPI/VCI is always present. Cells from one or more VCCs (or one or more VPCs) may be concatenated.
N对1模式（N>=1）指定将一个或多个ATM VCC（或一个或多个ATM VPC）映射到一条伪线的封装方法。这是唯一需要的模式。一种格式用于VCC或VPC到隧道的映射。4-octet ATM报头在封装中保持不变；因此，VPI/VCI始终存在。可以连接来自一个或多个VCC（或一个或多个VPC）的小区。
The One-to-one mode specifies an encapsulation method that maps one ATM VCC or one ATM VPC to one pseudowire. For VCCs, the VPI/VCI is not included. For VPCs, the VPI is not included. Cells from one VCC or one VPC may be concatenated. This mode is OPTIONAL.
一对一模式指定将一个ATM VCC或一个ATM VPC映射到一条伪线的封装方法。对于VCC，不包括VPI/VCI。对于VPC，不包括VPI。可以连接来自一个VCC或一个VPC的小区。此模式是可选的。
Furthermore, different OPTIONAL encapsulations are supported for ATM AAL5 transport: one for ATM AAL5 SDUs, and another for ATM AAL5 PDUs.
此外，ATM AAL5传输支持不同的可选封装：一个用于ATM AAL5 SDU，另一个用于ATM AAL5 PDU。
Three deployment models are supported by the encapsulations described in this document:
本文档中描述的封装支持三种部署模型：
-i. Single ATM Connection: A PW carries the cells of only one ATM VCC or VPC. This supports both the transport of multiservice ATM and L2VPN service over a PSN for all AAL types.
-一,。单个ATM连接：一个PW只携带一个ATM VCC或VPC的信元。对于所有AAL类型，它支持通过PSN传输多服务ATM和L2VPN服务。
-ii. Multiple ATM Connections: A PW carries the cells of multiple ATM VCCs and/or VPCs. This also supports both the transport of multiservice ATM and L2VPN service over a PSN for all AAL types.
-二,。多个ATM连接：PW承载多个ATM VCC和/或VPC的信元。对于所有AAL类型，它还支持通过PSN传输多服务ATM和L2VPN服务。
-iii. AAL5: A PW carries the AAL5 frames of only one ATM VCC. A large proportion of the data carried on ATM networks is frame based and therefore uses AAL5. The AAL5 mapping takes advantage of the delineation of higher-layer frames in the ATM layer to provide increased bandwidth efficiency compared with the basic cell mapping. The nature of the service, as defined by the ATM service category [TM4.0] or the ATM transfer capability [I.371], should be preserved.
-iii.AAL5：PW仅承载一个ATM VCC的AAL5帧。ATM网络上承载的大部分数据是基于帧的，因此使用AAL5。与基本信元映射相比，AAL5映射利用ATM层中更高层帧的描绘来提供更高的带宽效率。应保留ATM服务类别[TM4.0]或ATM传输能力[I.371]定义的服务性质。
This encapsulation supports both the Single and Multiple ATM Connection deployment models. This encapsulation is REQUIRED.
这种封装支持单个和多个ATM连接部署模型。这种封装是必需的。
The encapsulation allows multiple VCCs/VPCs to be carried within a single pseudowire. However, a service provider may wish to provision a single VCC to a pseudowire in order to satisfy QoS or restoration requirements.
封装允许多个VCC/VPC在一条伪线内传输。然而，服务提供商可能希望向伪线提供单个VCC，以满足QoS或恢复要求。
The encapsulation also supports the binding of multiple VCCs/VPCs to a single pseudowire. This capability is useful in order to make more efficient use of the PW demultiplexing header space as well as to ease provisioning of the VCC/VPC services.
封装还支持将多个VCC/VPC绑定到单个伪线。为了更有效地利用PW解复用报头空间以及简化VCC/VPC服务的供应，此功能非常有用。
In the simplest case, this encapsulation can be used to transmit a single ATM cell per PSN PDU. However, in order to provide better PSN bandwidth efficiency, several ATM cells may optionally be encapsulated in a single PSN PDU. This process is called cell concatenation.
在最简单的情况下，这种封装可用于每个PSN PDU传输单个ATM信元。然而，为了更好地封装单个PSN信元，可以选择性地封装多个PSN信元。这个过程称为单元连接。
The encapsulation has the following attributes:
封装具有以下属性：
-i. Supports all ATM Adaptation Layer Types.
-一,。支持所有ATM适配层类型。
-ii. Non-terminating OAM/Admin cells are transported among the user cells in the same order as they are received. This requirement enables the use of various performance management and security applications.
-二,。非终止OAM/Admin小区在用户小区之间的传输顺序与接收的顺序相同。此要求允许使用各种性能管理和安全应用程序。
-iii. In order to gain transport efficiency on the PSN, multiple cells may be encapsulated in a single PW PDU. This process is called cell concatenation. How many cells to insert or how long to wait for cell arrival before sending a PW PDU is an implementation decision. Cell concatenation adds latency and delay variation to a cell relay service.
-iii.为了在PSN上获得传输效率，可以将多个单元封装在单个PW PDU中。这个过程称为单元连接。在发送PW PDU之前要插入多少个小区或等待小区到达的时间是一个实现决策。小区连接增加了小区中继服务的延迟和延迟变化。
-iv. The CLP bit from each cell may be mapped to a corresponding marking on the PW PDU. This allows the drop precedence to be preserved across the PSN.
-iv.每个单元的CLP位可映射到PW PDU上的相应标记。这允许在整个PSN中保留删除优先级。
-v. If the Single ATM connection deployment model is used, then it is simpler to provide an ATM layer service. The nature of the service, as defined by the ATM service category [TM4.0] or ATM transfer capability [I.371], should be preserved.
-五,。如果使用单ATM连接部署模型，则提供ATM层服务更简单。应保留ATM服务类别[TM4.0]或ATM传输能力[I.371]定义的服务性质。
The limitations of the ATM N-to-one cell encapsulation are:
ATM N-to-1信元封装的局限性是：
-vi. There is no currently defined method to translate the forward congestion indication (EFCI) to a corresponding function in the PSN. Nor is there a way to translate PSN congestion to the EFCI upon transmission by the egress PE.
-vi.目前没有定义的方法将前向拥塞指示（EFCI）转换为PSN中的相应功能。从EFN到PSCI的传输路径也没有从EFPE到PSCI的传输路径。
-vii. The ATM cell header checksum can detect a 2-bit error or detect and correct a single-bit error in the cell header. Analogous functionality does not exist in most PSNs. A single bit error in a PW PDU will most likely cause the packet to be dropped due to an L2 Frame Check Sequence (FCS) failure.
-七,。ATM信元报头校验和可以检测2位错误或检测并纠正信元报头中的单位错误。大多数PSN中不存在类似的功能。PW PDU中的一个位错误很可能会导致由于L2帧检查序列（FCS）故障而丢弃数据包。
-viii. Cells can be concatenated from multiple VCCs or VPCs belonging to different service categories and QoS requirements. In this case, the PSN packet must receive treatment by the PSN to support the highest QoS of the ATM VCCs/VPCs carried.
-八,。小区可以从属于不同服务类别和QoS要求的多个VCC或VPC连接起来。在这种情况下，PSN数据包必须接受PSN的处理，以支持所承载的ATM VCC/VPC的最高QoS。
-ix. Cell encapsulation only supports point-to-point Label Switched Paths (LSPs). Multipoint-to-point and point-to-multi-point are for further study (FFS).
-单元封装仅支持点对点标签交换路径（LSP）。多点对点和点对多点用于进一步研究（FFS）。
-x. The number of concatenated ATM cells is limited by the MTU size and the cell transfer delay (CTD) and cell delay variation (CDV) objectives of multiple ATM connections that are multiplexed into a single PW.
-十,。级联ATM信元的数量受MTU大小以及多路复用到单个PW中的多个ATM连接的信元传输延迟（CTD）和信元延迟变化（CDV）目标的限制。
This OPTIONAL encapsulation supports the Single ATM Connection deployment model.
此可选封装支持单个ATM连接部署模型。
Like the N-to-one cell encapsulation mode, the One-to-one mode supports cell concatenation. The advantage of this encapsulation is that it utilizes less bandwidth that the N-to-one encapsulation, for a given number of concatenated cells. Since only one ATM VCC or VPC is carried on a PW, the VCI and/or VPI of the ATM VCC or VPC can be derived from the context of the PW using the PW label. These fields therefore do not need to be encapsulated for a VCC, and only the VCI needs to be encapsulated for a VPC. This encapsulation thus allows service providers to achieve a higher bandwidth efficiency on PSN links than the N-to-one encapsulation for a given number of concatenated cells.
与N-to-one单元封装模式一样，一对一模式支持单元串联。这种封装的优点是，对于给定数量的级联单元，它使用的带宽比N-to-one封装更少。由于一个PW上只携带一个ATM VCC或VPC，因此可以使用PW标签从PW的上下文中导出ATM VCC或VPC的VCI和/或VPI。因此，VCC不需要封装这些字段，而VPC只需要封装VCI。因此，这种封装允许服务提供商在PSN链路上实现比给定数量的级联小区的N对1封装更高的带宽效率。
The limitations vi, vii, ix, and x of N-to-one mode apply.
N对1模式的限制vi、vii、ix和x适用。
This OPTIONAL encapsulation supports the AAL5 model. This mode allows the transport of ATM AAL5 CSPS-SDUs traveling on a particular ATM PVC across the network to another ATM PVC. This encapsulation is used by a PW of type 0x0002 "ATM AAL5 SDU VCC transport" as allocated in [RFC4446].
此可选封装支持AAL5型号。此模式允许通过网络将在特定ATM PVC上运行的ATM AAL5 CSP SDU传输到另一个ATM PVC。该封装由[RFC4446]中分配的0x0002“ATM AAL5 SDU VCC传输”类型的PW使用。
The AAL5 SDU encapsulation is more efficient for small AAL5 SDUs than the VCC cell encapsulations. In turn, it presents a more efficient alternative to the cell relay service when carrying [RFC2684]- encapsulated IP PDUs across a PSN.
对于小型AAL5 SDU，AAL5 SDU封装比VCC单元封装更有效。反过来，当通过PSN承载[RFC2684]封装的IP PDU时，它提供了一种更有效的小区中继服务替代方案。
The AAL5-SDU encapsulation requires Segmentation and Reassembly (SAR) on the PE-CE ATM interface. This SAR function is provided by common off-the-shelf hardware components. Once reassembled, the AAL5-SDU is carried via a pseudowire to the egress PE. Herein lies another advantage of the AAL5-SDU encapsulation.
AAL5-SDU封装要求在PE-CE ATM接口上进行分段和重新组装（SAR）。此SAR功能由通用现货硬件组件提供。重新组装后，AAL5-SDU通过一根假导线连接至出口PE。这里是AAL5-SDU封装的另一个优点。
The limitations of the AAL5 SDU encapsulation are:
AAL5 SDU封装的局限性包括：
-i. If an ATM OAM cell is received at the ingress PE, it is sent before the cells of the surrounding AAL5 frame. Therefore, OAM cell reordering may occur, which may cause certain ATM OAM performance monitoring and ATM security applications to operate incorrectly.
-一,。如果在入口PE处接收到ATM OAM信元，则在周围AAL5帧的信元之前发送该信元。因此，可能会发生OAM信元重新排序，这可能会导致某些ATM OAM性能监视和ATM安全应用程序无法正常运行。
-ii. If the ALL5 PDU is scrambled using ATM security standards, a PE will not be able to extract the ALL5 SDU, and therefore the whole PDU will be dropped.
-二,。如果使用ATM安全标准对ALL5 PDU进行加扰，则PE将无法提取ALL5 SDU，因此整个PDU将被丢弃。
-iii. The AAL5 PDU CRC is not transported across the PSN. The CRC must therefore be regenerated at the egress PE since the CRC has end-to-end significance in ATM security. This means that the AAL5 CRC may not be used to accurately check for errors on the end-to-end ATM VCC.
-iii.AAL5 PDU CRC不通过PSN传输。因此，必须在出口PE处重新生成CRC，因为CRC在ATM安全中具有端到端的重要性。这意味着AAL5 CRC可能无法用于准确检查端到端ATM VCC上的错误。
-iv. The Length of AAL5 frame may exceed the MTU of the PSN. This requires fragmentation, which may not be available to all nodes at the PW endpoint.
-iv.AAL5框架的长度可能超过PSN的MTU。这需要分段，PW端点上的所有节点可能都无法使用分段。
-v. This mode does not preserve the value of the CLP bit for every ATM cell within an AAL5 PDU. Therefore, transparency of the CLP setting may be violated. Additionally, tagging of some cells may occur when tagging is not allowed by the conformance definition [TM4.0].
-五,。此模式不会为AAL5 PDU内的每个ATM信元保留CLP位的值。因此，可能会违反CLP设置的透明度。此外，当一致性定义[TM4.0]不允许标记时，可能会对某些单元格进行标记。
-vi. This mode does not preserve the EFCI state for every ATM cell within an AAL5 PDU. Therefore, transparency of the EFCI state may be violated.
-vi.此模式不会为AAL5 PDU内的每个ATM信元保留EFCI状态。因此，EFCI国家的透明度可能受到侵犯。
This OPTIONAL encapsulation supports the AAL5 model.
此可选封装支持AAL5型号。
The primary application supported by AAL5 PDU frame encapsulation over PSN is the transparent carriage of ATM layer services that use AAL5 to carry higher-layer frames. The main advantage of this AAL5 mode is that it is transparent to ATM OAM and ATM security applications.
PSN上AAL5 PDU帧封装支持的主要应用程序是ATM层服务的透明传输，这些服务使用AAL5承载更高层的帧。这种AAL5模式的主要优点是对ATM OAM和ATM安全应用程序透明。
One important consideration is to allow OAM information to be treated as in the original network. This encapsulation mode allows this transparency while performing AAL5 frame encapsulation. This mode supports fragmentation, which may be performed in order to maintain the position of the OAM cells with respect to the user cells.
一个重要的考虑因素是允许将OAM信息视为原始网络中的信息。在执行AAL5帧封装时，此封装模式允许此透明度。该模式支持分段，可以执行分段以保持OAM小区相对于用户小区的位置。
Fragmentation may also be performed to maintain the size of the packet carrying the AAL5 PDU within the MTU of the link. Fragmentation provides a means for the PE to set the size of the PW packet to a different value than that of the original AAL5 PDU. This means that the PE has control on the delay and jitter provided to the ATM cells.
还可以执行分段以保持链路的MTU内承载AAL5 PDU的分组的大小。分段为PE提供了将PW数据包的大小设置为与原始AAL5 PDU不同的值的方法。这意味着PE可以控制提供给ATM信元的延迟和抖动。
The whole AAL5-PDU is encapsulated. In this case, all necessary parameters, such as CPCS-UU (CPCS User-to-User indicator), CPI (Common Part Indicator), Length (Length of the CPCS-SDU) and CRC (Cyclic Redundancy Check), are transported as part of the payload. Note that carrying of the full PDU also allows the simplification of the fragmentation operation since it is performed at cell boundaries and the CRC in the trailer of the AAL5 PDU can be used to check the integrity of the PDU.
整个AAL5-PDU是封装的。在这种情况下，所有必要的参数，如CPCS-UU（CPCS用户对用户指示符）、CPI（公共部分指示符）、长度（CPCS-SDU的长度）和CRC（循环冗余校验）都作为有效负载的一部分传输。注意，携带完整的PDU还允许简化分段操作，因为它是在小区边界处执行的，并且AAL5 PDU的拖车中的CRC可用于检查PDU的完整性。
Reassembly is not required at the egress PE for the PSN-to-ATM direction.
PSN至ATM方向的出口PE无需重新组装。
The limitations v and vi of the AAL5 SDU mode apply to this mode as well.
AAL5 SDU模式的限制v和vi也适用于此模式。
In general, when configured for ATM VCC service, both PEs SHOULD act as a VC switch, in accordance with the OAM procedures defined in [I.610].
一般来说，当为ATM VCC服务配置时，两个PE应根据[I.610]中定义的OAM程序充当VC交换机。
The PEs SHOULD be able to pass the following OAM cells transparently:
PEs应能够透明地通过以下OAM单元：
- F5 Alarm Indication Signal (AIS) (segment and end-to-end) - F5 Remote Defect Indicator (RDI) (segment and end-to-end) - F5 loopback (segment and end-to-end) - Resource Management - Performance Management - Continuity Check - Security
- F5报警指示信号（AIS）（段和端到端）-F5远程缺陷指示器（RDI）（段和端到端）-F5环回（段和端到端）-资源管理-性能管理-连续性检查-安全
However, if configured to be an administrative segment boundary, the PE SHOULD terminate and process F5 segment OAM cells.
但是，如果配置为管理段边界，则PE应终止并处理F5段OAM单元。
F4 OAM cells are inserted or extracted at the VP link termination. These OAM cells are not seen at the VC link termination and are therefore not sent across the PSN.
F4 OAM单元在VP链路终端插入或提取。这些OAM单元在VC链路端看不到，因此不会通过PSN发送。
When the PE is operating in AAL5 CPCS-SDU transport mode if it does not support transport of ATM cells, the PE MUST discard incoming MPLS frames on an ATM PW that contain a PW label with the T bit set.
当PE在AAL5 CPCS-SDU传输模式下运行时，如果它不支持ATM信元的传输，则PE必须丢弃ATM PW上包含设置了T位的PW标签的传入MPLS帧。
When configured for a VPC cell relay service, both PEs SHOULD act as a VP cross-connect in accordance with the OAM procedures defined in [I.610].
当为VPC小区中继服务配置时，两个PE应根据[I.610]中定义的OAM程序充当VP交叉连接。
The PEs SHOULD be able to process and pass the following OAM cells transparently according to [I.610]:
PEs应能够根据[I.610]透明地处理和传递以下OAM单元：
- F4 AIS (segment and end-to-end) - F4 RDI (segment and end-to-end) - F4 loopback (segment and end-to-end)
- F4 AIS（段和端到端）-F4 RDI（段和端到端）-F4环回（段和端到端）
However, if configured to be an administrative segment boundary, the PE SHOULD terminate and process F4 segment OAM cells.
但是，如果配置为管理段边界，则PE应终止并处理F4段OAM单元。
F5 OAM are not inserted or extracted here. The PEs MUST be able to pass the following OAM cells transparently:
F5 OAM不在此插入或提取。PEs必须能够透明地通过以下OAM单元：
- F5 AIS (segment and end-to-end) - F5 RDI (segment and end-to-end) - F5 loopback (segment and end-to-end) - Resource Management - Performance Management - Continuity Check - Security
- F5 AIS（段和端到端）-F5 RDI（段和端到端）-F5环回（段和端到端）-资源管理-性能管理-连续性检查-安全
The OAM cell MAY be encapsulated together with other user data cells if multiple cell encapsulation is used.
如果使用多个小区封装，则OAM小区可以与其他用户数据小区一起封装。
A PE operating in ATM SDU or PDU transport mode that does not support transport of OAM cells across a PW MAY provide OAM support on ATM PVCs using the following procedures:
在ATM SDU或PDU传输模式下运行且不支持跨PW传输OAM信元的PE可使用以下程序在ATM PVC上提供OAM支持：
- Loopback cells response
- 环回单元响应
If an F5 end-to-end OAM cell is received from an ATM VC, by either PE that is transporting this ATM VC, with a loopback indication value of 1, and the PE has a label mapping for the ATM VC, then the PE MUST decrement the loopback indication value and loop back the cell on the ATM VC. Otherwise, the loopback cell MUST be discarded by the PE.
如果传输此ATM VC的任一PE接收到来自ATM VC的F5端到端OAM信元，且回送指示值为1，且该PE具有ATM VC的标签映射，则该PE必须减小回送指示值，并在ATM VC上回送信元。否则，PE必须丢弃环回单元。
- AIS alarm
- AIS警报
If an ingress PE, PE1, receives an AIS F4/F5 OAM cell, it MUST notify the remote PE of the failure. The remote PE, PE2, MUST in turn send F5 OAM AIS cells on the respective PVCs. Note that if the PE supports forwarding of OAM cells, then the received OAM AIS alarm cells MUST be forwarded along the PW as well.
如果入口PE PE1接收到AIS F4/F5 OAM单元，则必须将故障通知远程PE。在PVF5上，各OAPE单元必须在PVF5上发送。注意，如果PE支持OAM小区的转发，那么接收到的OAM AIS报警小区也必须沿着PW转发。
- Interface failure
- 接口故障
If the PE detects a physical interface failure, or the interface is administratively disabled, the PE MUST notify the remote PE for all VCs associated with the failure.
如果PE检测到物理接口故障，或该接口被管理性禁用，则PE必须通知远程PE与该故障相关的所有VCs。
- PSN/PW failure detection
- PSN/PW故障检测
If the PE detects a failure in the PW, by receiving a label withdraw for a specific PW ID, or the targeted Label Distribution Protocol (LDP) session fails, or a PW status TLV notification is received, then a proper AIS F5 OAM cell MUST be generated for all the affected ATM PVCs. The AIS OAM alarm will be generated on the ATM output port of the PE that detected the failure.
如果PE通过接收特定PW ID的标签撤销，或目标标签分发协议（LDP）会话失败，或接收到PW状态TLV通知，检测到PW中的故障，则必须为所有受影响的ATM PVC生成适当的AIS F5 OAM信元。AIS OAM警报将在检测到故障的PE的ATM输出端口上生成。
Figure 3 illustrates four possible locations for defects on the PWE3 service:
图3说明了PWE3服务上缺陷的四个可能位置：
- (a) On the ATM connection from CE to PE - (b) On the ATM side of the PW - (c) On the PSN side of the PE - (d) In the PSN
- （a） 在从CE到PE-（b）的ATM连接上，在PW的ATM侧，在PSN的PE-（d）的PSN侧，在PSN中
+----+ +----+
+----+ | PE1|==================| PE2| +----+
| |---a------|b..c........PW1...d.........|----------| |
| CE1| | | | | |CE2 |
| |----------|............PW2.............|----------| |
+----+ | |==================| | +----+
^ +----+ +----+ ^
| Provider Edge 1 Provider Edge 2 |
| |
|<-------------- Emulated Service ---------------->|
Customer Customer
Edge 1 Edge 2
+----+ +----+
+----+ | PE1|==================| PE2| +----+
| |---a------|b..c........PW1...d.........|----------| |
| CE1| | | | | |CE2 |
| |----------|............PW2.............|----------| |
+----+ | |==================| | +----+
^ +----+ +----+ ^
| Provider Edge 1 Provider Edge 2 |
| |
|<-------------- Emulated Service ---------------->|
Customer Customer
Edge 1 Edge 2
Figure 3: Defect Locations
图3：缺陷位置
For failures at (a) or (b), in the VPC case, the ingress PE MUST be able to generate an F4 AIS upon reception of a lower-layer defect (such as LOS). In the VCC case, the ingress PE SHOULD be able to generate an F5 AIS upon reception of a corresponding F4 AIS or lower-layer defect (such as LOS). These messages are sent across the PSN.
对于（a）或（b）处的故障，在VPC情况下，入口PE必须能够在接收到较低层缺陷（如LOS）时生成F4 AIS。在VCC情况下，入口PE应能够在接收到相应的F4 AIS或较低层缺陷（例如LOS）时生成F5 AIS。这些消息通过PSN发送。
For failures at (c) or (d), in the VCC case, the egress PE SHOULD be able to generate an F5 AIS based on a PSN failure (such as a PSN tunnel failure or LOS on the PSN port). In the VPC case, the egress PE SHOULD be able to generate an F4 AIS based on a PSN failure (such as a PSN tunnel failure or LOS on the PSN port).
对于（c）或（d）处的故障，在VCC情况下，出口PE应能够基于PSN故障（例如PSN隧道故障或PSN端口上的服务水平）生成F5 AIS。在VPC情况下，出口PE应能够基于PSN故障（例如PSN隧道故障或PSN端口上的服务水平）生成F4 AIS。
If the ingress PE cannot support the generation of OAM cells, it MAY notify the egress PE using a pseudowire-specific maintenance mechanism such as the PW status message defined in [RFC4447]. Alternatively, for example, the ingress PE MAY withdraw the pseudowire (PW label) label associated with the service. Upon receiving such a notification, the egress PE SHOULD generate the appropriate F4 AIS (for VPC) or F5 AIS (for VCC).
如果入口PE不能支持OAM小区的生成，它可以使用伪线特定的维护机制（如[RFC4447]中定义的PW状态消息）通知出口PE。或者，例如，入口PE可以撤回与服务相关联的伪线（PW标签）标签。收到此类通知后，出口PE应生成适当的F4 AI（用于VPC）或F5 AI（用于VCC）。
If the PW in one direction fails, then the complete bidirectional service is considered to have failed.
如果一个方向的PW失败，则认为完整的双向服务失败。
The N-to-one mode (N >= 1) described in this document allows a service provider to offer an ATM PVC- or SVC-based service across a network. The encapsulation allows multiple ATM VCCs or VPCs to be carried within a single PSN tunnel. A service provider may also use N-to-one mode to provision either one VCC or one VPC on a tunnel. This section defines the VCC and VPC cell relay services over a PSN and their applicability.
本文档中描述的N对1模式（N>=1）允许服务提供商通过网络提供基于ATM PVC或SVC的服务。封装允许在单个PSN隧道中承载多个ATM VCC或VPC。服务提供商还可以使用N对1模式在隧道上提供一个VCC或一个VPC。本节定义了PSN上的VCC和VPC小区中继服务及其适用性。
This section describes the general encapsulation format for ATM over PSN pseudowires.
本节描述了PSN伪线上ATM的通用封装格式。
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| PSN Transport Header (As Required) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| pseudowire Header |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0 0 0 0| Flags |Res| Length | Sequence Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ATM Service Payload |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| PSN Transport Header (As Required) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| pseudowire Header |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0 0 0 0| Flags |Res| Length | Sequence Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ATM Service Payload |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 4: General format for ATM encapsulation over PSNs
图4:PSN上ATM封装的通用格式
The PSN Transport Header depends on the particular tunneling technology in use. This header is used to transport the encapsulated ATM information through the packet-switched core.
PSN传输头取决于使用的特定隧道技术。该报头用于通过分组交换核心传输封装的ATM信息。
The Pseudowire Header identifies a particular ATM service on a tunnel. Non-ATM services may also be carried on the PSN tunnel.
伪线报头标识隧道上的特定ATM服务。非ATM服务也可以在PSN隧道上进行。
As shown above, in Figure 4, the ATM Control Word is inserted before the ATM service payload. It may contain a length field and a sequence number field in addition to certain control bits needed to carry the service.
如上所示，在图4中，ATM控制字插入到ATM服务有效负载之前。除了承载服务所需的某些控制位之外，它还可能包含长度字段和序列号字段。
The ATM Service Payload is specific to the service being offered via the pseudowire. It is defined in the following sections.
ATM服务有效载荷特定于通过伪线提供的服务。以下各节对其进行了定义。
In this encapsulation mode, ATM cells are transported individually. The encapsulation of a single ATM cell is the only REQUIRED encapsulation for ATM. The encapsulation of more than one ATM cell in a PSN frame is OPTIONAL.
在这种封装模式下，ATM信元单独传输。单个ATM信元的封装是ATM唯一需要的封装。在PSN帧中封装多个ATM信元是可选的。
The ATM cell encapsulation consists of an OPTIONAL control word and one or more ATM cells, each consisting of a 4-byte ATM cell header and the 48-byte ATM cell payload. This ATM cell header is defined as in the FAST encapsulation [FBATM] section 3.1.1, but without the trailer byte. The length of each frame, without the encapsulation headers, is a multiple of 52 bytes. The maximum number of ATM cells that can be fitted in a frame, in this fashion, is limited only by the network MTU and by the ability of the egress router to process them. The ingress router MUST NOT send more cells than the egress
ATM信元封装由一个可选控制字和一个或多个ATM信元组成，每个信元由一个4字节的ATM信元头和48字节的ATM信元有效载荷组成。该ATM信元报头的定义如快速封装[FBATM]第3.1.1节所述，但没有尾部字节。没有封装头的每个帧的长度是52字节的倍数。以这种方式，可以安装在一个帧中的最大ATM信元数仅受网络MTU和出口路由器处理它们的能力的限制。入口路由器发送的信元不得超过出口路由器发送的信元
router is willing to receive. The number of cells that the egress router is willing to receive may either be configured in the ingress router or be signaled, for example using the methods described later in this document and in [RFC4447]. The number of cells encapsulated in a particular frame can be inferred by the frame length. The control word is OPTIONAL. If the control word is used, then the flag and length bits in the control word are not used. These bits MUST be set to 0 when transmitting, and MUST be ignored upon receipt.
路由器愿意接收。出口路由器愿意接收的小区数量可以在入口路由器中配置，或者例如使用本文档后面和[RFC4447]中描述的方法发送信号。封装在特定帧中的单元数可以通过帧长度推断。控制字是可选的。如果使用控制字，则不使用控制字中的标志位和长度位。这些位在传输时必须设置为0，并且在接收时必须忽略。
The EFCI and CLP bits are carried across the network in the ATM cell header. The edge routers that implement this document MAY, when either adding or removing the encapsulation described herein, change the EFCI bit from zero to one in order to reflect congestion in the network that is known to the edge router, and change the CLP bit from zero to one in order to reflect marking from edge policing of the ATM Sustained Cell Rate. The EFCI and CLP bits SHOULD NOT be changed from one to zero.
EFCI和CLP位在ATM信元报头中通过网络传输。实现本文档的边缘路由器可在添加或移除本文所述的封装时，将EFCI位从0更改为1，以反映边缘路由器已知的网络中的拥塞，以及将CLP位从0更改为1，以反映ATM持续信元速率的边缘监控标记。EFCI和CLP位不应从1更改为0。
This diagram illustrates an encapsulation of two ATM cells:
此图显示了两个ATM信元的封装：
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Control word ( Optional ) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| VPI | VCI | PTI |C|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ATM Payload ( 48 bytes ) |
| " |
| " |
| " |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| VPI | VCI | PTI |C|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ATM Payload ( 48 bytes ) |
| " |
| " |
| " |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Control word ( Optional ) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| VPI | VCI | PTI |C|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ATM Payload ( 48 bytes ) |
| " |
| " |
| " |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| VPI | VCI | PTI |C|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ATM Payload ( 48 bytes ) |
| " |
| " |
| " |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 5: Multiple Cell ATM Encapsulation
图5：多信元ATM封装
* When multiple VCCs or VPCs are transported in one pseudowire, VPI/VCI values MUST be unique. When the multiple VCCs or VPCs are from different a physical transmission path, it may be necessary to assign unique VPI/VCI values to the ATM connections. If they are from the same physical transmission path, the VPI/VCI values are unique.
* 当在一条伪线中传输多个VCC或VPC时，VPI/VCI值必须是唯一的。当多个VCC或VPC来自不同的物理传输路径时，可能需要为ATM连接分配唯一的VPI/VCI值。如果它们来自相同的物理传输路径，则VPI/VCI值是唯一的。
* VPI
* VPI
The ingress router MUST copy the VPI field from the incoming cell into this field. For particular emulated VCs, the egress router MAY generate a new VPI and ignore the VPI contained in this field.
入口路由器必须将VPI字段从传入单元复制到此字段中。对于特定的仿真VCs，出口路由器可以生成新的VPI并忽略该字段中包含的VPI。
* VCI
* VCI
The ingress router MUST copy the VCI field from the incoming ATM cell header into this field. For particular emulated VCs, the egress router MAY generate a new VCI.
入口路由器必须将VCI字段从传入ATM信元报头复制到此字段中。对于特定的仿真vc，出口路由器可以生成新的VCI。
* PTI & CLP (C bit)
* PTI和CLP（C位）
The PTI and CLP fields are the PTI and CLP fields of the incoming ATM cells. The cell headers of the cells within the packet are the ATM headers (without Header Error Check (HEC) field) of the incoming cell.
PTI和CLP字段是传入ATM信元的PTI和CLP字段。数据包内信元的信元报头是传入信元的ATM报头（无报头错误检查（HEC）字段）。
The One-to-one mode described in this document allows a service provider to offer an ATM PVC- or SVC-based service across a network. The encapsulation allows one ATM VCC or VPC to be carried within a single pseudowire.
本文档中描述的一对一模式允许服务提供商通过网络提供基于ATM PVC或SVC的服务。这种封装允许一条ATM VCC或VPC在一条伪线内传输。
This section describes the general encapsulation format for ATM over pseudowires on an MPLS PSN. Figure 6 provides a general format for encapsulation of ATM cells into packets.
本节描述了MPLS PSN上伪线ATM的通用封装格式。图6提供了将ATM信元封装到数据包中的通用格式。
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| PSN Transport Header (As Required) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Pseudowire Header |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0 0 0 0| Resvd | Optional Sequence Number | ATM Specific |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ATM Service Payload |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| PSN Transport Header (As Required) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Pseudowire Header |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0 0 0 0| Resvd | Optional Sequence Number | ATM Specific |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ATM Service Payload |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 6: General format for One-to-one mode encapsulation over PSNs
图6:PSN上一对一模式封装的通用格式
The MPLS PSN Transport Header depends on how the MPLS network is configured. The Pseudowire Header identifies a particular ATM service within the PSN tunnel created by the PSN Transport Header.
MPLS PSN传输头取决于MPLS网络的配置方式。伪线报头标识PSN传输报头创建的PSN隧道内的特定ATM服务。
This header is used to transport the encapsulated ATM information through the packet-switched core.
该报头用于通过分组交换核心传输封装的ATM信息。
The generic control word is inserted after the Pseudowire Header. The presence of the control word is REQUIRED.
将在伪导线标头后插入通用控制字。需要控制字的存在。
The ATM Specific Header is inserted before the ATM service payload. The ATM Specific Header contains control bits needed to carry the service. These are defined in the ATM service descriptions below. The length of ATM Specific Header may not always be one octet. It depends on the service type.
在ATM服务有效负载之前插入特定于ATM的报头。ATM特定报头包含承载服务所需的控制位。这些在下面的ATM服务描述中定义。ATM特定报头的长度不一定总是一个八位字节。这取决于服务类型。
The ATM payload octet group is the payload of the service that is being encapsulated.
ATM有效负载八位组是被封装的服务的有效负载。
The sequence number is not required for all services.
并非所有服务都需要序列号。
Treatment of the sequence number is according to section 5.1.3.
按照第5.1.3节处理序列号。
The VCC cell transport service is characterized by the mapping of a single ATM VCC (VPI/VCI) to a pseudowire. This service is fully transparent to the ATM Adaptation Layer. The VCC single cell transport service is OPTIONAL. This service MUST use the following encapsulation format:
VCC信元传输服务的特点是将单个ATM VCC（VPI/VCI）映射到伪线。该服务对ATM适配层是完全透明的。VCC单小区传输服务是可选的。此服务必须使用以下封装格式：
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| PSN Transport Header (As Required) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Pseudowire Header |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0 0 0 0| Resvd | Optional Sequence Number |M|V|Res| PTI |C|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| ATM Cell Payload ( 48 bytes ) |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| PSN Transport Header (As Required) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Pseudowire Header |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0 0 0 0| Resvd | Optional Sequence Number |M|V|Res| PTI |C|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| ATM Cell Payload ( 48 bytes ) |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 7: Single ATM VCC Cell Encapsulation
图7：单个ATM VCC信元封装
* M (transport mode) bit
* M（传输模式）位
Bit (M) of the control byte indicates whether the packet contains an ATM cell or a frame payload. If set to 0, the packet contains an ATM cell. If set to 1, the PDU contains an AAL5 payload.
控制字节的位（M）指示数据包是包含ATM信元还是帧有效载荷。如果设置为0，则数据包包含一个ATM信元。如果设置为1，则PDU包含AAL5有效负载。
* V (VCI present) bit
* V（VCI当前）位
Bit (V) of the control byte indicates whether the VCI field is present in the packet. If set to 1, the VCI field is present for the cell. If set to 0, no VCI field is present. In the case of a VCC, the VCI field is not required. For VPC, the VCI field is required and is transmitted with each cell.
控制字节的位（V）指示数据包中是否存在VCI字段。如果设置为1，则单元格中存在VCI字段。如果设置为0，则不存在VCI字段。对于VCC，不需要VCI字段。对于VPC，VCI字段是必需的，并随每个小区一起传输。
* Reserved bits
* 保留位
The reserved bits should be set to 0 at the transmitter and ignored upon reception.
发射机上的保留位应设置为0，并在接收时忽略。
* PTI Bits
* PTI位
The 3-bit Payload Type Identifier (PTI) incorporates ATM Layer PTI coding of the cell. These bits are set to the value of the PTI of the encapsulated ATM cell.
3位有效负载类型标识符（PTI）包含信元的ATM层PTI编码。这些位被设置为封装的ATM信元的PTI值。
* C (CLP) Bit
* C（CLP）位
The Cell Loss Priority (CLP) field indicates CLP value of the encapsulated cell.
单元丢失优先级（CLP）字段指示封装单元的CLP值。
For increased transport efficiency, the ingress PE SHOULD be able to encapsulate multiple ATM cells into a pseudowire PDU. The ingress and egress PE MUST agree to a maximum number of cells in a single pseudowire PDU. This agreement may be accomplished via a pseudowire-specific signaling mechanism or via static configuration.
为了提高传输效率，入口PE应该能够将多个ATM信元封装到伪线PDU中。入口和出口PE必须与单个伪线PDU中的最大单元数一致。该协议可通过特定于伪线的信令机制或通过静态配置来实现。
When multiple cells are encapsulated in the same PSN packet, the ATM-specific byte MUST be repeated for each cell. This means that 49 bytes are used to encapsulate each 53 byte ATM cell.
当多个信元封装在同一个PSN数据包中时，必须为每个信元重复ATM特定字节。这意味着49字节用于封装每个53字节的ATM信元。
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| PSN Transport Header (As Required) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Pseudowire Header |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0 0 0 0| Resvd | Optional Sequence Number |M|V|Res| PTI |C|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| ATM Cell Payload ( 48 bytes ) |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|M|V|Res| PTI |C| |
+-+-+-+-+-+-+-+-+ |
| ATM Cell Payload ( 48 bytes ) |
| |
| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+-+-+-+-+-+-+-+-+
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| PSN Transport Header (As Required) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Pseudowire Header |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0 0 0 0| Resvd | Optional Sequence Number |M|V|Res| PTI |C|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| ATM Cell Payload ( 48 bytes ) |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|M|V|Res| PTI |C| |
+-+-+-+-+-+-+-+-+ |
| ATM Cell Payload ( 48 bytes ) |
| |
| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+-+-+-+-+-+-+-+-+
Figure 8: Multiple ATM VCC Cell Encapsulation
图8：多个ATM VCC信元封装
The VPC service is defined by mapping a single VPC (VPI) to a pseudowire. As such, it emulates a Virtual Path cross-connect across the PSN. All VCCs belonging to the VPC are carried transparently by the VPC service.
VPC服务是通过将单个VPC（VPI）映射到伪线来定义的。因此，它模拟跨PSN的虚拟路径交叉连接。属于专有网络的所有VCC都由专有网络服务透明承载。
The egress PE may choose to apply a different VPI other than the one that arrived at the ingress PE. The egress PE MUST choose the outgoing VPI based solely upon the pseudowire header. As a VPC service, the egress PE MUST NOT change the VCI field.
出口PE可以选择应用不同于到达入口PE的VPI。出口PE必须仅基于伪线报头选择输出VPI。作为VPC服务，出口PE不得更改VCI字段。
The ATM VPC cell transport service is OPTIONAL.
ATM VPC信元传输服务是可选的。
This service MUST use the following cell mode encapsulation:
此服务必须使用以下单元模式封装：
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| PSN Transport Header (As Required) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Pseudowire Header |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0 0 0 0| Resvd | Optional Sequence Number |M|V|Res| PTI |C|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| VCI | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
| |
| ATM Cell Payload ( 48 bytes ) |
| |
| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| PSN Transport Header (As Required) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Pseudowire Header |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0 0 0 0| Resvd | Optional Sequence Number |M|V|Res| PTI |C|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| VCI | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
| |
| ATM Cell Payload ( 48 bytes ) |
| |
| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 9: Single Cell VPC Encapsulation
图9：单小区VPC封装
The ATM control byte contains the same information as in the VCC encapsulation except for the VCI field.
除VCI字段外，ATM控制字节包含与VCC封装中相同的信息。
* VCI Bits
* VCI位
The 16-bit Virtual Circuit Identifier (VCI) incorporates ATM Layer VCI value of the cell.
16位虚拟电路标识符（VCI）包含信元的ATM层VCI值。
For increased transport efficiency, the ingress PE SHOULD be able to encapsulate multiple ATM cells into a pseudowire PDU. The ingress and egress PE MUST agree to a maximum number of cells in a single pseudowire PDU. This agreement may be accomplished via a pseudowire-specific signaling mechanism or via static configuration.
为了提高传输效率，入口PE应该能够将多个ATM信元封装到伪线PDU中。入口和出口PE必须与单个伪线PDU中的最大单元数一致。该协议可通过特定于伪线的信令机制或通过静态配置来实现。
If the Egress PE supports cell concatenation, the ingress PE MUST only concatenate cells up to the "Maximum Number of concatenated ATM cells in a frame" interface parameter sub-TLV as received as part of the control protocol [RFC4447].
如果出口PE支持信元连接，则入口PE必须仅连接作为控制协议一部分接收的“帧中连接的ATM信元的最大数量”接口参数sub-TLV的信元[RFC4447]。
When multiple ATM cells are encapsulated in the same PSN packet, the ATM-specific byte MUST be repeated for each cell. This means that 51 bytes are used to encapsulate each 53-byte ATM cell.
当多个ATM信元封装在同一个PSN数据包中时，必须为每个信元重复ATM特定字节。这意味着51字节用于封装每个53字节的ATM信元。
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| PSN Transport Header (As Required) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Pseudowire Header |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0 0 0 0| Resvd | Optional Sequence Number |M|V|Res| PTI |C|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| VCI | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
| |
| ATM Cell Payload (48 bytes) |
| |
| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |M|V|Res| PTI |C| VCI |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| VCI | |
+-+-+-+-+-+-+-+-+ |
| ATM Cell Payload (48 bytes) |
| |
| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+-+-+-+-+-+-+-+-+
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| PSN Transport Header (As Required) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Pseudowire Header |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0 0 0 0| Resvd | Optional Sequence Number |M|V|Res| PTI |C|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| VCI | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
| |
| ATM Cell Payload (48 bytes) |
| |
| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |M|V|Res| PTI |C| VCI |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| VCI | |
+-+-+-+-+-+-+-+-+ |
| ATM Cell Payload (48 bytes) |
| |
| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+-+-+-+-+-+-+-+-+
Figure 10: Multiple Cell VPC Encapsulation
图10：多小区VPC封装
The AAL5 payload VCC service defines a mapping between the payload of an AAL5 VCC and a single pseudowire. The AAL5 payload VCC service requires ATM segmentation and reassembly support on the PE.
AAL5有效负载VCC服务定义AAL5 VCC有效负载与单个伪线之间的映射。AAL5有效负载VCC服务需要在PE上支持ATM分段和重新组装。
The AAL5 payload CPCS-SDU service is OPTIONAL.
AAL5有效负载CPCS-SDU服务是可选的。
Even the smallest TCP packet requires two ATM cells when sent over AAL5 on a native ATM device. It is desirable to avoid this padding on the pseudowire. Therefore, once the ingress PE reassembles the AAL5 CPCS-PDU, the PE discards the PAD and CPCS-PDU trailer, and then the ingress PE inserts the resulting payload into a pseudowire PDU.
在本机ATM设备上通过AAL5发送时，即使最小的TCP数据包也需要两个ATM信元。最好避免伪导线上的这种填充。因此，一旦入口PE重新组装AAL5 CPCS-PDU，PE丢弃PAD和CPCS-PDU拖车，然后入口PE将产生的有效负载插入伪线PDU。
The egress PE MUST regenerate the PAD and trailer before transmitting the AAL5 frame on the egress ATM port.
在出口ATM端口上传输AAL5帧之前，出口PE必须重新生成PAD和拖车。
This service does allow the transport of OAM and RM cells, but it does not attempt to maintain the relative order of these cells with respect to the cells that comprise the AAL5 CPCS-PDU. All OAM cells, regardless of their type, that arrive during the reassembly of a
该服务确实允许OAM和RM小区的传输，但它不试图维持这些小区相对于组成AAL5 CPCS-PDU的小区的相对顺序。所有的OAM单元，无论其类型如何，都是在重新组装组件时到达的
single AAL5 CPCS-PDU are sent immediately on the pseudowire using N-to-one cell encapsulation, followed by the AAL5 payload. Therefore, the AAL5 payload VCC service will not be suitable for ATM applications that require strict ordering of OAM cells (such as performance monitoring and security applications).
单个AAL5 CPC-PDU使用N-to-one单元封装在伪线上立即发送，随后是AAL5有效负载。因此，AAL5有效负载VCC服务不适用于需要严格订购OAM信元的ATM应用程序（如性能监控和安全应用程序）。
The AAL5 CPCS-SDU is prepended by the following header:
AAL5 CPCS-SDU由以下标题组成：
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Res |T|E|C|U|Res| Length | Sequence Number (Optional) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| " |
| ATM cell or AAL5 CPCS-SDU |
| " |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Res |T|E|C|U|Res| Length | Sequence Number (Optional) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| " |
| ATM cell or AAL5 CPCS-SDU |
| " |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 11: AAL5 CPCS-SDU Encapsulation
图11:AAL5 CPCS-SDU封装
The AAL5 payload service encapsulation requires the ATM control word. The Flag bits are described below.
AAL5有效负载服务封装需要ATM控制字。下面描述标志位。
* Res (Reserved)
* Res（保留）
These bits are reserved and MUST be set to 0 upon transmission and ignored upon reception.
这些位是保留的，在传输时必须设置为0，在接收时忽略。
* T (transport type) bit
* T（传输型）位
Bit (T) of the control word indicates whether the packet contains an ATM admin cell or an AAL5 payload. If T = 1, the packet contains an ATM admin cell, encapsulated according to the N-to-one cell relay encapsulation, Figure 4. If not set, the PDU contains an AAL5 payload. The ability to transport an ATM cell in the AAL5 SDU mode is intended to provide a means of enabling administrative functionality over the AAL5 VCC (though it does not endeavor to preserve user-cell and admin-cell arrival/transport ordering).
控制字的位（T）指示数据包是包含ATM管理信元还是AAL5有效负载。如果T=1，则数据包包含一个ATM管理信元，根据N对1信元中继封装进行封装，如图4所示。如果未设置，则PDU包含AAL5有效负载。在AAL5 SDU模式下传输ATM信元的能力旨在提供一种通过AAL5 VCC实现管理功能的方法（尽管它不努力保持用户信元和管理信元到达/传输顺序）。
* E (EFCI) Bit
* E（EFCI）位
The ingress router, PE1, SHOULD set this bit to 1 if the EFCI bit of the final cell of those that transported the AAL5 CPCS-SDU is set to 1, or if the EFCI bit of the single ATM cell to be transported in the packet is set to 1. Otherwise, this bit
如果传输AAL5 CPCS-SDU的最后一个信元的EFCI位设置为1，或者如果要在数据包中传输的单个ATM信元的EFCI位设置为1，则入口路由器PE1应将该位设置为1。否则，这一点
SHOULD be set to 0. The egress router, PE2, SHOULD set the EFCI bit of all cells that transport the AAL5 CPCS-SDU to the value contained in this field.
应设置为0。出口路由器PE2应将传输AAL5 CPCS-SDU的所有单元的EFCI位设置为该字段中包含的值。
* C (CLP) Bit
* C（CLP）位
The ingress router, PE1, SHOULD set this bit to 1 if the CLP bit of any of the ATM cells that transported the AAL5 CPCS-SDU is set to 1, or if the CLP bit of the single ATM cell to be transported in the packet is set to 1. Otherwise this bit SHOULD be set to 0. The egress router, PE2, SHOULD set the CLP bit of all cells that transport the AAL5 CPCS-SDU to the value contained in this field.
如果传输AAL5 CPCS-SDU的任何ATM信元的CLP位设置为1，或者如果要在数据包中传输的单个ATM信元的CLP位设置为1，则入口路由器PE1应将该位设置为1。否则，该位应设置为0。出口路由器PE2应将传输AAL5 CPCS-SDU的所有单元的CLP位设置为该字段中包含的值。
* U (Command/Response Field) Bit
* U（命令/响应字段）位
When FRF.8.1 Frame Relay/ATM PVC Service Interworking [RFC3916] traffic is being transported, the CPCS-UU Least Significant Bit (LSB) of the AAL5 CPCS-PDU may contain the Frame Relay C/R bit. The ingress router, PE1, SHOULD copy this bit to the U bit of the control word. The egress router, PE2, SHOULD copy the U bit to the CPCS-UU Least Significant Bit (LSB) of the AAL5 CPCS PDU.
当传输FRF.8.1帧中继/ATM PVC服务互通[RFC3916]业务时，AAL5 CPCS-PDU的CPCS-UU最低有效位（LSB）可能包含帧中继C/R位。入口路由器PE1应将该位复制到控制字的U位。出口路由器PE2应将U位复制到AAL5 CPCS PDU的CPCS-UU最低有效位（LSB）。
The AAL5 payload PDU service is OPTIONAL.
AAL5有效负载PDU服务是可选的。
In this mode, the ingress PE encapsulates the entire CPCS-PDU including the PAD and trailer.
在此模式下，入口PE封装整个CPCS-PDU，包括PAD和拖车。
This mode MAY support fragmentation procedures described in the "Fragmentation" section below, in order to maintain OAM cell sequencing.
此模式可支持下文“分段”部分中所述的分段程序，以维持OAM单元测序。
Like the ATM AAL5 payload VCC service, the AAL5 transparent VCC service is intended to be more efficient than the VCC cell transport service. However, the AAL5 transparent VCC service carries the entire AAL5 CPCS-PDU, including the PAD and trailer. Note that the AAL5 CPCS-PDU is not processed, i.e., an AAL5 frame with an invalid CRC or length field will be transported. One reason for this is that there may be a security agent that has scrambled the ATM cell payloads that form the AAL5 CPCS-PDU.
与ATM AAL5有效负载VCC服务一样，AAL5透明VCC服务旨在比VCC信元传输服务更高效。但是，AAL5透明VCC服务承载整个AAL5 CPCS-PDU，包括PAD和拖车。请注意，AAL5 CPCS-PDU未被处理，即带有无效CRC或长度字段的AAL5帧将被传输。这样做的一个原因是，可能有一个安全代理对形成AAL5 CPCS-PDU的ATM信元有效负载进行了加扰。
This service supports all OAM cell flows by using a fragmentation procedure that ensures that OAM cells are not repositioned in respect to AAL5 composite cells.
此服务通过使用分段过程支持所有OAM单元流，以确保OAM单元不会相对于AAL5复合单元重新定位。
The AAL5 transparent VCC service is OPTIONAL.
AAL5透明VCC服务是可选的。
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| PSN Transport Header (As Required) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Pseudowire Header |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0 0 0 0| Resvd | Optional Sequence Number |M|V| Res |U|E|C|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| " |
| AAL5 CPCS-PDU |
| (n * 48 bytes) |
| " |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| PSN Transport Header (As Required) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Pseudowire Header |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0 0 0 0| Resvd | Optional Sequence Number |M|V| Res |U|E|C|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| " |
| AAL5 CPCS-PDU |
| (n * 48 bytes) |
| " |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 12: AAL5 transparent service encapsulation
图12:AAL5透明服务封装
The generic control word is inserted after the Pseudowire Header. The presence of the control word is MANDATORY.
将在伪导线标头后插入通用控制字。必须存在控制字。
The M, V, Res, and C bits are as defined earlier for VCC One-to-one cell mode.
M、V、Res和C位如前面为VCC一对一单元模式定义的。
* U Bit
* U形钻头
This field indicates whether this frame contains the last cell of an AAL5 PDU and represents the value of the ATM User-to-User bit for the last ATM cell of the PSN frame. Note: The ATM User-to-User bit is the least significant bit of the PTI field in the ATM header. This field is used to support the fragmentation functionality described later in this section.
此字段指示此帧是否包含AAL5 PDU的最后一个信元，并表示PSN帧的最后一个ATM信元的ATM用户对用户位的值。注：ATM用户对用户位是ATM报头中PTI字段的最低有效位。此字段用于支持本节后面介绍的分段功能。
* E (EFCI) bit
* E（EFCI）位
This field is used to convey the EFCI state of the ATM cells. The EFCI state is indicated in the middle bit of each ATM cell's PTI field.
此字段用于传送ATM信元的EFCI状态。在每个ATM信元的PTI字段的中间位中指示EFCI状态。
ATM-to-PSN direction (ingress): The EFCI field of the control byte is set to the EFCI state of the last cell of the AAL5 PDU or AAL5 fragment.
ATM到PSN方向（入口）：控制字节的EFCI字段设置为AAL5 PDU或AAL5片段的最后一个单元的EFCI状态。
PSN-to-ATM direction (egress): The EFCI state of all constituent cells of the AAL5 PDU or AAL5 fragment is set to the value of the EFCI field in the control byte.
PSN到ATM方向（出口）：AAL5 PDU或AAL5片段的所有组成单元的EFCI状态设置为控制字节中EFCI字段的值。
* C (CLP) bit
* C（CLP）位
This field is used to convey the cell loss priority of the ATM cells.
此字段用于传送ATM信元的信元丢失优先级。
ATM-to-PSN direction (ingress): The CLP field of the control byte is set to 1 if any of the constituent cells of the AAL5 PDU or AAL5 fragment has its CLP bit set to 1; otherwise, this field is set to 0.
ATM到PSN方向（入口）：如果AAL5 PDU或AAL5片段的任何组成单元的CLP位设置为1，则控制字节的CLP字段设置为1；否则，此字段设置为0。
PSN-to-ATM direction (egress): The CLP bit of all constituent cells for an AAL5 PDU or AAL5 fragment is set to the value of the CLP field in the control byte. The payload consists of the re-assembled AAL5 CPCS-PDU, including the AAL5 padding and trailer or the AAL5 fragment.
PSN到ATM方向（出口）：AAL5 PDU或AAL5片段的所有组成单元的CLP位设置为控制字节中CLP字段的值。有效载荷包括重新组装的AAL5 CPCS-PDU，包括AAL5衬垫和拖车或AAL5碎片。
The ingress PE may not always be able to reassemble a full AAL5 frame. This may be because the AAL5 PDU exceeds the pseudowire MTU or because OAM cells arrive during reassembly of the AAL5 PDU. In these cases, the AAL5 PDU shall be fragmented. In addition, fragmentation may be desirable to bound ATM cell delay.
入口PE可能并不总是能够重新组装完整的AAL5机架。这可能是因为AAL5 PDU超过了伪线MTU，或者是因为OAM单元在AAL5 PDU重新组装期间到达。在这些情况下，AAL5 PDU应分段。此外，可能需要分段来限制ATM信元延迟。
When fragmentation occurs, the procedures described in the following subsections shall be followed.
发生碎片时，应遵循以下小节中描述的程序。
The following procedures shall apply while fragmenting AAL5 PDUs:
分割AAL5 PDU时，应采用以下程序：
- Fragmentation shall always occur at cell boundaries within the AAL5 PDU.
- 应始终在AAL5 PDU内的单元边界处发生碎片。
- Set the UU bit to the value of the ATM User-to-User bit in the cell header of the most recently received ATM cell.
- 将UU位设置为最近接收到的ATM信元的信元报头中的ATM用户对用户位的值。
- The E and C bits of the fragment shall be set as defined in section 9.
- 碎片的E和C位应按照第9节的规定进行设置。
- If the arriving cell is an OAM or an RM cell, send the current PSN frame and then send the OAM or RM cell using One-to-one single cell encapsulation (VCC).
- 如果到达的小区是OAM或RM小区，则发送当前PSN帧，然后使用一对一单小区封装（VCC）发送OAM或RM小区。
The following procedures shall apply:
以下程序应适用：
- The 3-bit PTI field of each ATM cell header is constructed as follows:
- 每个ATM信元报头的3位PTI字段构造如下：
-i. The most significant bit is set to 0, indicating a user data cell.
-一,。最高有效位设置为0，表示用户数据单元。
-ii. The middle bit is set to the E bit value of the fragment.
-二,。中间位设置为片段的E位值。
-iii. The least significant bit for the last ATM cell in the PSN frame is set to the value of the UU bit of Figure 12.
-iii.PSN帧中最后一个ATM信元的最低有效位设置为图12的UU位的值。
-iv. The least significant PTI bit is set to 0 for all other cells in the PSN frame.
-iv.对于PSN帧中的所有其他单元，最低有效PTI位设置为0。
- The CLP bit of each ATM cell header is set to the value of the C bit of the control byte in Figure 12.
- 每个ATM信元头的CLP位设置为图12中控制字节的C位的值。
- When a fragment is received, each constituent ATM cell is sent in correct order.
- 当接收到一个片段时，每个组成的ATM信元按正确的顺序发送。
This section is provided for informational purposes, and for guidance only. This section should not be considered part of the standard proposed in this document.
本节仅供参考，仅供参考。本节不应视为本文件中提议的标准的一部分。
When ATM PW service is configured over a PSN, the ATM service category of a connection SHOULD be mapped to a compatible class of service in the PSN network. A compatible class of service maintains the integrity of the service end to end. For example, the CBR service category SHOULD be mapped to a class of service with stringent loss and delay objectives. If the PSN implements the IP Diffserv framework, a class of service based on the EF PHB is a good candidate.
当通过PSN配置ATM PW服务时，连接的ATM服务类别应映射到PSN网络中的兼容服务类别。一个兼容的服务类可以维护端到端服务的完整性。例如，CBR服务类别应映射到具有严格损失和延迟目标的服务类别。如果PSN实现IP区分服务框架，那么基于EF PHB的服务类是一个很好的候选。
Furthermore, ATM service categories have support for multiple conformance definitions [TM4.0]. Some are CLP blind (e.g., CBR), meaning that the QoS objectives apply to the aggregate CLP0+1 conforming cell flow. Some are CLP significant (e.g., VBR.3), meaning that the QoS objectives apply to the CLP0 conforming cell flow only.
此外，ATM服务类别支持多个一致性定义[TM4.0]。有些是CLP盲的（例如CBR），这意味着QoS目标适用于符合CLP0+1的聚合小区流。一些是CLP重要的（例如VBR.3），这意味着QoS目标仅适用于符合CLP0的小区流。
When the PSN is MPLS based, a mapping between the CLP bit and the EXP field can be performed to provide visibility of the cell loss
当PSN基于MPLS时，可以执行CLP位和EXP字段之间的映射，以提供小区丢失的可见性
priority in the MPLS network. The actual value to be marked in the EXP field depends on the ATM service category, the ATM conformance definition, and the type of tunnel LSP used (E-LSP or L-LSP). The details of this mapping are outside the scope of this document. Operators have the flexibility to design a specific mapping that satisfies their own requirements.
MPLS网络中的优先级。EXP字段中要标记的实际值取决于ATM服务类别、ATM一致性定义和使用的隧道LSP类型（E-LSP或L-LSP）。此映射的详细信息不在本文档的范围内。操作员可以灵活地设计满足其自身需求的特定映射。
In both the ATM-to-PSN and PSN-to-ATM directions, the method used to transfer the CLP and EFCI information of the individual cells into the ATM-specific field, or flags, of the PW packet is described in detail in sections 6 through 9 for each encapsulation mode.
在ATM-to-PSN和PSN-to-ATM两个方向中，用于将单个信元的CLP和EFCI信息传输到PW分组的ATM特定字段或标志的方法在第6至9节中针对每个封装模式进行了详细描述。
An MPLS edge PE MAY provide an ATM Integrated Local Management Interface (ILMI) to the ATM edge switch. If an ingress PE receives an ILMI message indicating that the ATM edge switch has deleted a VC, or if the physical interface goes down, it MUST send a PW status notification message for all PWs associated with the failure. When a PW label mapping is withdrawn, or PW status notification message is received, the egress PE MUST notify its client of this failure by deleting the VC using ILMI.
MPLS边缘PE可以向ATM边缘交换机提供ATM集成本地管理接口（ILMI）。如果入口PE接收到一条ILMI消息，指示ATM边缘交换机已删除一个VC，或者如果物理接口关闭，则它必须为与故障相关的所有PW发送一条PW状态通知消息。当PW标签映射被撤销或收到PW状态通知消息时，出口PE必须通过使用ILMI删除VC来通知其客户机此故障。
The Interface parameter TLV is defined in [RFC4447], and the IANA registry with initial values for interface parameter sub-TLV types is defined in [RFC4446], but the ATM PW-specific interface parameter is specified as follows:
接口参数TLV在[RFC4447]中定义，带有接口参数子TLV类型初始值的IANA注册表在[RFC4446]中定义，但特定于ATM PW的接口参数指定如下：
- 0x02 Maximum Number of concatenated ATM cells.
- 0x02连接的ATM信元的最大数量。
A 2-octet value specifying the maximum number of concatenated ATM cells that can be processed as a single PDU by the egress PE. An ingress PE transmitting concatenated cells on this PW can concatenate a number of cells up to the value of this parameter, but MUST NOT exceed it. This parameter is applicable only to PW types 3, 9, 0x0a, 0xc, [RFC4446], and 0xd and is REQUIRED for these PWC types. This parameter does not need to match in both directions of a specific PW.
2个八位组的值，指定出口PE可以作为单个PDU处理的级联ATM信元的最大数量。在该PW上传输级联单元的入口PE可以级联多个单元，最多可达该参数的值，但不得超过该值。此参数仅适用于PW类型3、9、0x0a、0xc、[RFC4446]和0xd，这些PWC类型需要此参数。该参数不需要在特定PW的两个方向上匹配。
As explained in [RFC3985], the PSN carrying the PW may be subject to congestion, with congestion characteristics depending on PSN type, network architecture, configuration, and loading. During congestion the PSN may exhibit packet loss that will impact the service carried by the ATM PW. In addition, since ATM PWs carry a variety of
如[RFC3985]中所述，承载PW的PSN可能会发生拥塞，其拥塞特性取决于PSN类型、网络架构、配置和负载。在拥塞期间，PSN可能会出现分组丢失，这将影响ATM PW承载的服务。此外，由于ATM PW携带各种
services across the PSN, including but not restricted to TCP/IP, they may or may not behave in a TCP-friendly manner prescribed by [RFC2914]. In the presence of services that reduce transmission rate, ATM PWs may thus consume more than their fair share and in that case SHOULD be halted.
PSN上的服务，包括但不限于TCP/IP，它们可能以[RFC2914]规定的TCP友好方式运行，也可能不以[RFC2914]规定的方式运行。在存在降低传输速率的服务的情况下，ATM PW可能因此消耗超过其公平份额，在这种情况下，应停止。
Whenever possible, ATM PWs should be run over traffic-engineered PSNs providing bandwidth allocation and admission control mechanisms. IntServ-enabled domains providing the Guaranteed Service (GS) or Diffserv-enabled domains using EF (expedited forwarding) are examples of traffic-engineered PSNs. Such PSNs will minimize loss and delay while providing some degree of isolation of the ATM PW's effects from neighboring streams.
只要有可能，ATM PWs应在提供带宽分配和准入控制机制的流量工程PSN上运行。提供保证服务（GS）的支持IntServ的域或使用EF（加速转发）的支持Diffserv的域是流量工程PSN的示例。这种PSN将最大限度地减少损失和延迟，同时在一定程度上隔离ATM PW与相邻流的影响。
It should be noted that when transporting ATM, Diffserv-enabled domains may use AF (Assured Forwarding) and/or DF (Default Forwarding) instead of EF, in order to place less burden on the network and gain additional statistical multiplexing advantage. In particular, Table 1 of Appendix "V" in [ATM-MPLS] contains a detailed mapping between ATM classes and Diffserv classes.
应当注意，当传输ATM时，支持区分服务的域可以使用AF（保证转发）和/或DF（默认转发）而不是EF，以便减轻网络负担并获得额外的统计复用优势。具体而言，[ATM-MPLS]中附录“V”的表1包含ATM类和区分服务类之间的详细映射。
The PEs SHOULD monitor for congestion (by using explicit congestion notification, [VCCV], or by measuring packet loss) in order to ensure that the service using the ATM PW may be maintained. When a PE detects significant congestion while receiving the PW PDUs, the PE MAY use RM cells for ABR connections to notify the remote PE.
PEs应监控拥塞（通过使用显式拥塞通知[VCCV]或通过测量数据包丢失），以确保使用ATM PW的服务可以维持。当PE在接收PW PDU时检测到严重拥塞时，PE可将RM小区用于ABR连接以通知远程PE。
If the PW has been set up using the protocol defined in [RFC4447], then procedures specified in [RFC4447] for status notification can be used to disable packet transmission on the ingress PE from the egress PE. The PW may be restarted by manual intervention, or by automatic means after an appropriate waiting time.
如果已使用[RFC4447]中定义的协议设置PW，则[RFC4447]中指定的状态通知程序可用于禁用入口PE上来自出口PE的数据包传输。PW可通过手动干预或在适当的等待时间后通过自动方式重新启动。
This document specifies only encapsulations, not the protocols used to carry the encapsulated packets across the PSN. Each such protocol may have its own set of security issues [RFC4447][RFC3985], but those issues are not affected by the encapsulations specified herein. Note that the security of the transported ATM service will only be as good as the security of the PSN. This level of security might be less rigorous than a native ATM service.
本文档仅指定封装，而不是用于在PSN上传输封装数据包的协议。每个这样的协议可能有自己的一组安全问题[RFC4447][RFC3985]，但这些问题不受本文规定的封装的影响。请注意，传输的ATM服务的安全性仅与PSN的安全性相同。这种级别的安全性可能不如本机ATM服务严格。
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2119]Bradner，S.，“RFC中用于表示需求水平的关键词”，BCP 14，RFC 2119，1997年3月。
[RFC4447] Martini, L., Rosen, E., El-Aawar, N., Smith, T., and G. Heron, "Pseudowire Setup and Maintenance Using the Label Distribution Protocol (LDP)", RFC 4447, April 2006.
[RFC4447]Martini，L.，Rosen，E.，El Aawar，N.，Smith，T.，和G.Heron，“使用标签分发协议（LDP）的伪线设置和维护”，RFC 4447，2006年4月。
[RFC3032] Rosen, E., Tappan, D., Fedorkow, G., Rekhter, Y., Farinacci, D., Li, T., and A. Conta, "MPLS Label Stack Encoding", RFC 3032, January 2001.
[RFC3032]Rosen，E.，Tappan，D.，Fedorkow，G.，Rekhter，Y.，Farinaci，D.，Li，T.，和A.Conta，“MPLS标签堆栈编码”，RFC 3032，2001年1月。
[RFC4446] Martini, L., "IANA Allocations for Pseudowire Edge to Edge Emulation (PWE3)", BCP 116, RFC 4446, April 2006.
[RFC4446]Martini，L.，“伪线边到边仿真（PWE3）的IANA分配”，BCP 116，RFC 4446，2006年4月。
[RFC4385] Bryant, S., Swallow, G., Martini, L., and D. McPherson, "Pseudowire Emulation Edge-to-Edge (PWE3) Control Word for Use over an MPLS PSN", RFC 4385, February 2006.
[RFC4385]Bryant，S.，Swallow，G.，Martini，L.，和D.McPherson，“用于MPLS PSN的伪线仿真边到边（PWE3）控制字”，RFC 43852006年2月。
[FBATM] ATM Forum Specification af-fbatm-0151.000 (2000), "Frame Based ATM over SONET/SDH Transport (FAST)"
[FBATM]ATM论坛规范af-FBATM-0151.000（2000），“基于帧的SONET/SDH传输ATM（FAST）”
[TM4.0] ATM Forum Specification af-tm-0121.000 (1999), "Traffic Management Specification Version 4.1"
[TM4.0]ATM论坛规范af-tm-0121.000（1999），“流量管理规范版本4.1”
[I.371] ITU-T Recommendation I.371 (2000), "Traffic control and congestion control in B-ISDN".
[I.371]ITU-T建议I.371（2000），“B-ISDN中的流量控制和拥塞控制”。
[I.610] ITU-T Recommendation I.610, (1999), "B-ISDN operation and maintenance principles and functions".
[I.610]ITU-T建议I.610，（1999），“B-ISDN操作和维护原则及功能”。
[Y.1411] ITU-T Recommendation Y.1411 (2003), ATM-MPLS Network Interworking - Cell Mode user Plane Interworking
[Y.1411]ITU-T建议Y.1411（2003），ATM-MPLS网络互通-信元模式用户平面互通
[Y.1412] ITU-T Recommendation Y.1412 (2003), ATM-MPLS network interworking - Frame mode user plane interworking
[Y.1412]ITU-T建议Y.1412（2003），ATM-MPLS网络互通-帧模式用户平面互通
[RFC3985] Bryant, S. and P. Pate, "Pseudo Wire Emulation Edge-to-Edge (PWE3) Architecture", RFC 3985, March 2005.
[RFC3985]Bryant，S.和P.Pate，“伪线仿真边到边（PWE3）架构”，RFC 39852005年3月。
[RFC3916] Xiao, X., McPherson, D., and P. Pate, "Requirements for Pseudo-Wire Emulation Edge-to-Edge (PWE3)", RFC 3916, September 2004.
[RFC3916]Xiao，X.，McPherson，D.，和P.Pate，“伪线仿真边到边（PWE3）的要求”，RFC 39162004年9月。
[RFC4026] Andersson, L. and T. Madsen, "Provider Provisioned Virtual Private Network (VPN) Terminology", RFC 4026, March 2005.
[RFC4026]Andersson，L.和T.Madsen，“提供商提供的虚拟专用网络（VPN）术语”，RFC 4026，2005年3月。
[VCCV] Nadeau, T., Pignataro, C., and R. Aggarwal, "Pseudowire Virtual Circuit Connectivity Verification (VCCV)", Work in Progress, June 2006.
[VCCV]Nadeau，T.，Pignataro，C.，和R.Aggarwal，“伪线虚拟电路连接验证（VCCV）”，正在进行的工作，2006年6月。
[RFC2992] Hopps, C., "Analysis of an Equal-Cost Multi-Path Algorithm", RFC 2992, November 2000.
[RFC2992]Hopps，C.，“等成本多径算法分析”，RFC 2992，2000年11月。
[ATM-MPLS] ATM Forum Specification af-aic-0178.001, "ATM-MPLS Network Interworking Version 2.0", August 2003.
[ATM-MPLS]ATM论坛规范af-aic-0178.001，“ATM-MPLS网络互通版本2.0”，2003年8月。
[RFC2914] Floyd, S., "Congestion Control Principles", BCP 41, RFC 2914, September 2000.
[RFC2914]Floyd，S.，“拥塞控制原则”，BCP 41，RFC 2914，2000年9月。
[RFC2684] Grossman, D. and J. Heinanen, "Multiprotocol Encapsulation over ATM Adaptation Layer 5", RFC 2684, September 1999.
[RFC2684]Grossman，D.和J.Heinanen，“ATM适配层5上的多协议封装”，RFC 2684，1999年9月。
Giles Heron Tellabs Abbey Place 24-28 Easton Street High Wycombe Bucks HP11 1NT UK EMail: giles.heron@tellabs.com
Giles Heron Tellabs Abbey Place 24-28 Easton Street High Wycombe Bucks HP11 1NT英国电子邮件：Giles。heron@tellabs.com
Dimitri Stratton Vlachos Mazu Networks, Inc. 125 Cambridgepark Drive Cambridge, MA 02140 EMail: d@mazunetworks.com
Dimitri Stratton Vlachos Mazu Networks，Inc.马萨诸塞州剑桥市剑桥公园大道125号邮编：02140电子邮件：d@mazunetworks.com
Dan Tappan Cisco Systems, Inc. 1414 Massachusetts Avenue Boxborough, MA 01719 EMail: tappan@cisco.com
Dan Tappan Cisco Systems，Inc.马萨诸塞州伯斯堡马萨诸塞大道1414号邮编01719电子邮件：tappan@cisco.com
Eric C. Rosen Cisco Systems, Inc. 1414 Massachusetts Avenue Boxborough, MA 01719 EMail: erosen@cisco.com
Eric C.Rosen Cisco Systems，Inc.马萨诸塞州伯斯堡马萨诸塞大道1414号邮编01719电子邮件：erosen@cisco.com
Steve Vogelsang ECI Telecom Omega Corporate Center 1300 Omega Drive Pittsburgh, PA 15205 EMail: stephen.vogelsang@ecitele.com
Steve Vogelsang ECI电信欧米茄公司中心宾夕法尼亚州匹兹堡欧米茄大道1300号15205电子邮件：stephen。vogelsang@ecitele.com
Gerald de Grace ECI Telecom Omega Corporate Center 1300 Omega Drive Pittsburgh, PA 15205 EMail: gerald.degrace@ecitele.com
Gerald de Grace ECI电信欧米茄公司中心宾夕法尼亚州匹兹堡欧米茄大道1300号15205电子邮件：Gerald。degrace@ecitele.com
John Shirron ECI Telecom Omega Corporate Center 1300 Omega Drive Pittsburgh, PA 15205 EMail: john.shirron@ecitele.com
John Shirron ECI电信欧米茄公司中心宾夕法尼亚州匹兹堡欧米茄大道1300号15205电子邮件：John。shirron@ecitele.com
Andrew G. Malis Verizon Communications 40 Sylvan Road Waltham, MA EMail: andrew.g.malis@verizon.com Phone: 781-466-2362
Andrew G.Malis Verizon Communications马萨诸塞州沃尔瑟姆Sylvan路40号电子邮件：Andrew.G。malis@verizon.com电话：781-466-2362
Vinai Sirkay Redback Networks 300 Holger Way San Jose, CA 95134 EMail: vsirkay@redback.com
Vinai Sirkay Redback Networks加利福尼亚州圣何塞霍尔格路300号95134电子邮件：vsirkay@redback.com
Chris Liljenstolpe Alcatel 11600 Sallie Mae Dr. 9th Floor Reston, VA 20193 EMail: chris.liljenstolpe@alcatel.com
Chris Liljenstolpe Alcatel 11600 Sallie Mae博士，弗吉尼亚州雷斯顿市9楼，邮编20193电子邮件：Chris。liljenstolpe@alcatel.com
Kireeti Kompella Juniper Networks 1194 N. Mathilda Ave Sunnyvale, CA 94089 EMail: kireeti@juniper.net
Kireeti Kompella Juniper Networks 1194 N.Mathilda Ave Sunnyvale，CA 94089电子邮件：kireeti@juniper.net
John Fischer Alcatel 600 March Rd Kanata, ON, Canada. K2K 2E6 EMail: john.fischer@alcatel.com
约翰·菲舍尔·阿尔卡特，加拿大安大略省卡纳塔市3月路600号。K2K 2E6电子邮件：john。fischer@alcatel.com
Mustapha Aissaoui Alcatel 600 March Rd Kanata, ON, Canada. K2K 2E6 EMail: mustapha.aissaoui@alcatel.com
Mustapha Aissaoui Alcatel，加拿大安大略省卡纳塔市3月路600号。K2K 2E6电子邮件：mustapha。aissaoui@alcatel.com
Tom Walsh Lucent Technologies 1 Robbins Road Westford, MA 01886 USA EMail: tdwalsh@lucent.com
美国马萨诸塞州罗宾斯路韦斯特福德1号汤姆·沃尔什·朗讯科技公司01886电子邮件：tdwalsh@lucent.com
John Rutemiller Marconi Networks 1000 Marconi Drive Warrendale, PA 15086 EMail: John.Rutemiller@marconi.com
John Rutemiller Marconi Networks宾夕法尼亚州沃伦代尔市马可尼大道1000号15086电子邮件：John。Rutemiller@marconi.com
Rick Wilder Alcatel 45195 Business Court Loudoun Gateway II Suite 300 M/S STERV-SMAE Sterling, VA 20166 EMail: Rick.Wilder@alcatel.com
Rick Wilder Alcatel 45195商务区Loudoun Gateway II套房300米/秒STERV-SMAE Sterling，弗吉尼亚州20166电子邮件：Rick。Wilder@alcatel.com
Laura Dominik Qwest Communications, Inc. 600 Stinson Blvd. Minneapolis, MN 55413 Email: ldomini@qwest.com
Laura Dominik Qwest通信公司，斯廷森大道600号。明尼苏达州明尼阿波利斯55413电子邮件：ldomini@qwest.com
Authors' Addresses
作者地址
Luca Martini Cisco Systems, Inc. 9155 East Nichols Avenue, Suite 400 Englewood, CO 80112 EMail: lmartini@cisco.com
Luca Martini Cisco Systems，Inc.地址：科罗拉多州恩格尔伍德东尼科尔斯大道9155号400室，邮编：80112电子邮件：lmartini@cisco.com
Jayakumar Jayakumar Cisco Systems, Inc. 225 E.Tasman, MS-SJ3/3 San Jose, CA 95134 EMail: jjayakum@cisco.com
Jayakumar Jayakumar Cisco Systems，Inc.225 E.Tasman，MS-SJ3/3加利福尼亚州圣何塞市95134电子邮件：jjayakum@cisco.com
Matthew Bocci Alcatel Grove House, Waltham Road Rd White Waltham, Berks, UK. SL6 3TN EMail: matthew.bocci@alcatel.co.uk
Matthew Bocci Alcatel Grove House，沃尔瑟姆路怀特沃尔瑟姆，伯克斯，英国。SL6 3TN电子邮件：matthew。bocci@alcatel.co.uk
Nasser El-Aawar Level 3 Communications, LLC. 1025 Eldorado Blvd. Broomfield, CO 80021 EMail: nna@level3.net
Nasser El Aawar三级通信有限责任公司，埃尔多拉多大道1025号。美国科罗拉多州布鲁姆菲尔德80021电子邮件：nna@level3.net
Jeremy Brayley ECI Telecom Inc. Omega Corporate Center 1300 Omega Drive Pittsburgh, PA 15205 EMail: jeremy.brayley@ecitele.com
Jeremy Brayley ECI Telecom Inc.美国宾夕法尼亚州匹兹堡欧米茄大道1300号欧米茄企业中心15205电子邮件：Jeremy。brayley@ecitele.com
Ghassem Koleyni Nortel Networks P O Box 3511, Station C Ottawa, Ontario, K1Y 4H7 Canada EMail: ghassem@nortelnetworks.com
Ghassem Koleyni Nortel Networks邮政信箱3511，加拿大安大略省渥太华C站K1Y 4H7电子邮件：ghassem@nortelnetworks.com
Full Copyright Statement
完整版权声明
Copyright (C) The IETF Trust (2006).
版权所有（C）IETF信托基金（2006年）。
This document is subject to the rights, licenses and restrictions contained in BCP 78, and except as set forth therein, the authors retain all their rights.
本文件受BCP 78中包含的权利、许可和限制的约束，除其中规定外，作者保留其所有权利。
This document and the information contained herein are provided on an "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST, AND THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
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Intellectual Property
知识产权
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The IETF invites any interested party to bring to its attention any copyrights, patents or patent applications, or other proprietary rights that may cover technology that may be required to implement this standard. Please address the information to the IETF at ietf-ipr@ietf.org.
IETF邀请任何相关方提请其注意任何版权、专利或专利申请，或其他可能涵盖实施本标准所需技术的专有权利。请将信息发送至IETF的IETF-ipr@ietf.org.
Acknowledgement
确认
Funding for the RFC Editor function is currently provided by the Internet Society.
RFC编辑功能的资金目前由互联网协会提供。