Network Working Group A. Malis
Request for Comments: 5143 Verizon Communications
Obsoleted by: 4842 J. Brayley
Category: Historic J. Shirron
ECI Telecom Inc.
L. Martini
Cisco Systems, Inc.
S. Vogelsang
Alcatel-Lucent
February 2008
Network Working Group A. Malis
Request for Comments: 5143 Verizon Communications
Obsoleted by: 4842 J. Brayley
Category: Historic J. Shirron
ECI Telecom Inc.
L. Martini
Cisco Systems, Inc.
S. Vogelsang
Alcatel-Lucent
February 2008
Synchronous Optical Network/Synchronous Digital Hierarchy (SONET/SDH) Circuit Emulation Service over MPLS (CEM) Encapsulation
基于MPLS（CEM）封装的同步光网络/同步数字体系（SONET/SDH）电路仿真服务
Status of This Memo
关于下段备忘
This memo defines a Historic Document for the Internet community. It does not specify an Internet standard of any kind. Distribution of this memo is unlimited.
此备忘录定义了互联网社区的历史文档。它没有规定任何类型的互联网标准。本备忘录的分发不受限制。
IESG Note
IESG注释
The IESG thinks that this work is related to IETF work done in WG PWE3, but this does not prevent publishing.
IESG认为这项工作与工作组PWE3中完成的IETF工作有关，但这并不妨碍发布。
Abstract
摘要
This document describes a historical method for encapsulating Synchronous Optical Network/Synchronous Digital Hierarchy (SONET/SDH) Path signals for transport across packet-switched networks (PSNs). The PSNs explicitly supported by this document include MPLS and IP. Note that RFC 4842 describes the standards-track protocol for this functionality, and new implementations must use RFC 4842 rather than this document except when interoperability with older implementations is desired.
本文档描述了一种封装同步光网络/同步数字体系（SONET/SDH）路径信号的历史方法，用于跨分组交换网络（PSN）传输。本文档明确支持的PSN包括MPLS和IP。请注意，RFC 4842描述了此功能的标准跟踪协议，新实现必须使用RFC 4842而不是本文档，除非需要与旧实现的互操作性。
Table of Contents
目录
1. Introduction ....................................................3
2. Conventions Used in This Document ...............................3
3. Scope ...........................................................3
4. CEM Encapsulation Format ........................................4
4.1. Transport Encapsulation ....................................6
4.1.1. MPLS Transport ......................................6
4.1.2. IP Transport ........................................7
5. CEM Operation ...................................................8
5.1. Introduction and Terminology ...............................8
5.1.1. CEM Packetizer and De-Packetizer ....................9
5.1.2. CEM DBA .............................................9
5.2. Description of Normal CEM Operation .......................10
5.3. Description of CEM Operation during DBA ...................10
5.4. Packet Synchronization ....................................11
5.4.1. Acquisition of Packet Synchronization ..............11
5.4.2. Loss of Packet Synchronization .....................11
6. SONET/SDH Maintenance Signals ..................................12
6.1. SONET/SDH to PSN ..........................................12
6.1.1. AIS-P Indication ...................................13
6.1.2. STS SPE Unequipped Indication ......................14
6.1.3. CEM-RDI ............................................14
6.2. PSN to SONET/SDH ..........................................15
6.2.1. AIS-P Indication ...................................15
6.2.2. STS SPE Unequipped Indication ......................15
7. Clocking Modes .................................................16
7.1. Synchronous ...............................................16
7.1.1. Synchronous Unstructured CEM .......................16
7.1.2. Synchronous Structured CEM .........................16
7.2. Asynchronous ..............................................17
8. CEM LSP Signaling ..............................................17
9. Security Considerations ........................................18
10. IANA Considerations ...........................................18
11. References ....................................................18
11.1. Normative References .....................................18
11.2. Informative References ...................................19
Appendix A. SONET/SDH Rates and Formats ...........................20
Appendix B. ECC-6 Definition ......................................21
1. Introduction ....................................................3
2. Conventions Used in This Document ...............................3
3. Scope ...........................................................3
4. CEM Encapsulation Format ........................................4
4.1. Transport Encapsulation ....................................6
4.1.1. MPLS Transport ......................................6
4.1.2. IP Transport ........................................7
5. CEM Operation ...................................................8
5.1. Introduction and Terminology ...............................8
5.1.1. CEM Packetizer and De-Packetizer ....................9
5.1.2. CEM DBA .............................................9
5.2. Description of Normal CEM Operation .......................10
5.3. Description of CEM Operation during DBA ...................10
5.4. Packet Synchronization ....................................11
5.4.1. Acquisition of Packet Synchronization ..............11
5.4.2. Loss of Packet Synchronization .....................11
6. SONET/SDH Maintenance Signals ..................................12
6.1. SONET/SDH to PSN ..........................................12
6.1.1. AIS-P Indication ...................................13
6.1.2. STS SPE Unequipped Indication ......................14
6.1.3. CEM-RDI ............................................14
6.2. PSN to SONET/SDH ..........................................15
6.2.1. AIS-P Indication ...................................15
6.2.2. STS SPE Unequipped Indication ......................15
7. Clocking Modes .................................................16
7.1. Synchronous ...............................................16
7.1.1. Synchronous Unstructured CEM .......................16
7.1.2. Synchronous Structured CEM .........................16
7.2. Asynchronous ..............................................17
8. CEM LSP Signaling ..............................................17
9. Security Considerations ........................................18
10. IANA Considerations ...........................................18
11. References ....................................................18
11.1. Normative References .....................................18
11.2. Informative References ...................................19
Appendix A. SONET/SDH Rates and Formats ...........................20
Appendix B. ECC-6 Definition ......................................21
This document describes a historical method for encapsulating SONET/SDH Path signals for transport across packet-switched networks (PSNs).
本文档描述了一种封装SONET/SDH路径信号的历史方法，用于跨分组交换网络（PSN）传输。
The native transmission system for circuit-oriented Time Division Multiplexing (TDM) signals is the Synchronous Optical Network (SONET) [T1.105], [GR-253]/Synchronous Digital Hierarchy (SDH) [G.707]. To support TDM traffic (which includes voice, data, and private leased line services), PSNs must emulate the circuit characteristics of SONET/SDH payloads. MPLS labels and a new circuit emulation header are used to encapsulate TDM signals and provide the Circuit Emulation Service over MPLS (CEM) function. The MPLS encapsulation may be further encapsulated in IP for carriage across IP PSNs [RFC4023].
面向电路的时分复用（TDM）信号的本机传输系统是同步光网络（SONET）[T1.105]，[GR-253]/同步数字体系（SDH）[G.707]。为了支持TDM业务（包括语音、数据和专用专线服务），PSN必须模拟SONET/SDH有效负载的电路特性。MPLS标签和一个新的电路仿真报头用于封装TDM信号，并通过MPLS（CEM）功能提供电路仿真服务。MPLS封装可以进一步封装在IP中，以便跨IP PSN传输[RFC4023]。
This document also describes an optional extension to CEM called Dynamic Bandwidth Allocation (DBA). This is a method for dynamically reducing the bandwidth utilized by emulated SONET/SDH circuits in the packet network. This bandwidth reduction is accomplished by not sending the SONET/SDH payload through the packet network under certain conditions, such as Alarm Indication Signal - Path (AIS-P) or Synchronous Transport Signal Synchronous Payload Envelope (STS SPE) Unequipped.
本文档还描述了CEM的一个可选扩展，称为动态带宽分配（DBA）。这是一种动态减少分组网络中模拟SONET/SDH电路所使用带宽的方法。这种带宽减少是通过在某些条件下不通过分组网络发送SONET/SDH有效载荷来实现的，例如未设置的报警指示信号路径（AIS-P）或同步传输信号同步有效载荷包络（STS SPE）。
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。
This document describes how to provide CEM for the following digital signals:
本文件描述了如何为以下数字信号提供CEM：
1. SONET STS-1 synchronous payload envelope (SPE)/SDH VC-3
1. SONET STS-1同步有效载荷包络（SPE）/SDH VC-3
2. STS-Nc SPE (N = 3, 12, or 48)/SDH VC-4, VC-4-4c, VC-4-16c
2. STS Nc SPE（N=3、12或48）/SDH VC-4、VC-4-4c、VC-4-16c
3. Unstructured SONET Emulation, where the entire SONET bit-stream (including the transport overhead) is packetized and transported across the PSN.
3. 非结构化SONET仿真，其中整个SONET比特流（包括传输开销）被打包并跨PSN传输。
For the remainder of this document, these constructs will be referred to as SONET/SDH channels.
在本文件的其余部分中，这些结构称为SONET/SDH信道。
Other SONET/SDH signals, such as virtual tributary (VT) structured sub-rate mapping, are not explicitly discussed in this document; however, it can be extended in the future to support VT and lower speed non-SONET/SDH services. OC-192c SPE/VC-4-64c are also not included at this point, since most PSNs use OC-192c or slower trunks, and thus would not have sufficient capacity. As trunk capacities increase in the future, the scope of this document can be accordingly extended.
其他SONET/SDH信号，如虚拟支路（VT）结构化子速率映射，在本文件中未明确讨论；但是，它可以在将来扩展以支持VT和低速非SONET/SDH服务。OC-192c SPE/VC-4-64c在此也不包括在内，因为大多数PSN使用OC-192c或更慢的中继，因此没有足够的容量。随着未来中继容量的增加，本文件的范围可以相应扩展。
In order to transport SONET/SDH SPEs through a packet-oriented network, the SPE is broken into fragments. A 32-bit CEM header is pre-pended to each fragment. The Basic CEM packet appears in Figure 1.
为了通过面向分组的网络传输SONET/SDH SPE，SPE被分为多个片段。32位CEM报头被预先挂起到每个片段。基本CEM数据包如图1所示。
+-----------------------------------+
| CEM Header |
+-----------------------------------+
| |
| |
| SONET/SDH SPE Fragment |
| |
| |
+-----------------------------------+
+-----------------------------------+
| CEM Header |
+-----------------------------------+
| |
| |
| SONET/SDH SPE Fragment |
| |
| |
+-----------------------------------+
Figure 1. Basic CEM Packet
图1。基本CEM数据包
The 32-bit CEM header has the following format:
32位CEM标头具有以下格式：
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|D|R|Rvd| Sequence Num | Structure Pointer |N|P| ECC-6 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|D|R|Rvd| Sequence Num | Structure Pointer |N|P| ECC-6 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2. CEM Header Format
图2。CEM头格式
The above fields are defined as follows:
上述字段定义如下：
D-bit: This bit signals DBA Mode. It MUST be set to zero for normal operation, and it MUST be set to one if CEM is currently in DBA mode. DBA is an optional mode during which trivial SPEs are not transmitted into the packet network. See Table 1 and sections 7 and 8 for further details.
D位：该位表示DBA模式。正常运行时必须将其设置为零，如果CEM当前处于DBA模式，则必须将其设置为1。DBA是一种可选模式，在此模式下，普通SPE不会传输到分组网络中。详见表1以及第7节和第8节。
Note: for unstructured CEM, the D-bit MUST be set to zero.
注意：对于非结构化CEM，D位必须设置为零。
R bit: CEM-RDI (Remote Defect Indicator). This bit is set to one to signal to the remote CEM function that a loss of packet synchronization has occurred.
R位：CEM-RDI（远程缺陷指示器）。该位设置为1，以向远程CEM功能发送数据包同步丢失的信号。
Rvd: These bits are reserved for future use, and MUST be set to zero.
Rvd：这些位保留供将来使用，必须设置为零。
Sequence Number: This is a packet sequence number, which MUST continuously cycle from 0 to 1023. It SHOULD begin at zero when a CEM LSP (Label Switched Path) is created.
序列号：这是一个数据包序列号，必须从0到1023连续循环。当创建CEM LSP（标签交换路径）时，它应该从零开始。
Structure Pointer: The Structure Pointer MUST contain the offset of the J1 byte within the CEM payload. The value is from 0 to 1,022, where 0 means the first byte after the CEM header. The Structure Pointer MUST be set to 0x3FF (1,023) if a packet does not carry the J1 byte. See [T1.105], [G.707], and [GR-253] for more information On the J1 byte and the SONET/SDH payload pointer.
结构指针：结构指针必须包含CEM有效负载内J1字节的偏移量。该值从0到1022，其中0表示CEM头后的第一个字节。如果数据包不包含J1字节，则结构指针必须设置为0x3FF（1023）。有关J1字节和SONET/SDH有效负载指针的更多信息，请参阅[T1.105]、[G.707]和[GR-253]。
Note: for unstructured CEM, the Structure Pointer field MUST be set to 0x3FF.
注意：对于非结构化CEM，结构指针字段必须设置为0x3FF。
The N and P bits: These bits indicate negative and positive pointer adjustment events. They are also used to relay SONET/SDH maintenance signals, such as AIS-P. See Table 1 and sections 7 and 8 for more details.
N位和P位：这些位表示指针的正负调整事件。它们还用于中继SONET/SDH维护信号，如AIS-P。有关更多详细信息，请参见表1以及第7节和第8节。
Note: for unstructured CEM, the N and P bits MUST both be set to zero.
注意：对于非结构化CEM，N和P位都必须设置为零。
+---+---+---+----------------------------------------------+
| D | N | P | Interpretation |
+---+---+---+-------------+--------------------------------+
| 0 | 0 | 0 | Normal Mode | No Ptr Adjustment |
| 0 | 0 | 1 | Normal Mode | Positive Ptr Adjustment |
| 0 | 1 | 0 | Normal Mode | Negative Ptr Adjustment |
| 0 | 1 | 1 | Normal Mode | AIS-P |
| | | | | |
| 1 | 0 | 0 | DBA Mode | STS SPE Unequipped |
| 1 | 0 | 1 | DBA Mode | STS SPE Unequipped Pos Ptr Adj |
| 1 | 1 | 0 | DBA Mode | STS SPE Unequipped Neg Ptr Adj |
| 1 | 1 | 1 | DBA Mode | AIS-P |
+---+---+---+-------------+--------------------------------+
+---+---+---+----------------------------------------------+
| D | N | P | Interpretation |
+---+---+---+-------------+--------------------------------+
| 0 | 0 | 0 | Normal Mode | No Ptr Adjustment |
| 0 | 0 | 1 | Normal Mode | Positive Ptr Adjustment |
| 0 | 1 | 0 | Normal Mode | Negative Ptr Adjustment |
| 0 | 1 | 1 | Normal Mode | AIS-P |
| | | | | |
| 1 | 0 | 0 | DBA Mode | STS SPE Unequipped |
| 1 | 0 | 1 | DBA Mode | STS SPE Unequipped Pos Ptr Adj |
| 1 | 1 | 0 | DBA Mode | STS SPE Unequipped Neg Ptr Adj |
| 1 | 1 | 1 | DBA Mode | AIS-P |
+---+---+---+-------------+--------------------------------+
Table 1. Interpretation of D, N, and P bits
表1。D、N和P位的解释
ECC-6: An Error Correction Code to protect the CEM header. This offers the ability to correct single bit errors and detect up to two bit errors. The ECC algorithm is described in Appendix B. The ECC-6 can be optionally disabled at provisioning time. If the ECC-6 is not utilized, it MUST be set to zero.
ECC-6：用于保护CEM标头的错误更正代码。这提供了纠正单位错误和检测最多两位错误的能力。ECC算法如附录B所述。ECC-6可在供应时选择性禁用。如果未使用ECC-6，则必须将其设置为零。
Note: Normal CEM packets are fixed in length for all of the packets of a particular emulated TDM stream. This length is signaled using the CEM Payload Bytes parameter defined in [RFC4447], or is statically provisioned for each TDM stream. Therefore, the length of each CEM packet does not need to be carried in the CEM header.
注意：对于特定模拟TDM流的所有数据包，普通CEM数据包的长度是固定的。该长度使用[RFC4447]中定义的CEM Payload Bytes参数发出信号，或为每个TDM流静态设置。因此，每个CEM分组的长度不需要在CEM报头中携带。
Note: Setting the D-bit to 0 and the R bit to 1 violates the Best Current Practice defined in [RFC4928] when operating on MPLS networks. In this situation, MPLS networks could mistake a CEM payload as the first nibble of an IPv4 packet, potentially causing mis-ordering of packets on the pseudowire in the presence of IP Equal Cost Multi-Path (ECMP) in the MPLS network. The use of this CEM header preceded the use of MPLS ECMP. As stated earlier, [RFC4842] describes the standards-track protocol for this functionality, and it does not share this violation.
注：在MPLS网络上操作时，将D位设置为0，将R位设置为1违反了[RFC4928]中定义的最佳当前实践。在这种情况下，MPLS网络可能会将CEM有效负载误认为IPv4数据包的第一个半字节，在MPLS网络中存在IP等成本多路径（ECMP）的情况下，可能会导致伪线上数据包的错误排序。此CEM头的使用先于MPLS ECMP的使用。如前所述，[RFC4842]描述了此功能的标准跟踪协议，它不共享此冲突。
In principle, CEM packets can be transported over any packet-oriented network. The following sections describe specifically how CEM packets MUST be encapsulated for transport over MPLS or IP networks.
原则上，CEM数据包可以在任何面向数据包的网络上传输。以下各节具体描述了必须如何封装CEM数据包，以便通过MPLS或IP网络进行传输。
To transport a CEM packet over an MPLS network, an MPLS label stack MUST be pushed on top of the CEM packet.
要通过MPLS网络传输CEM数据包，必须将MPLS标签堆栈推到CEM数据包的顶部。
The last two labels prior to the CEM header are referred to as the Tunnel and Virtual Circuit (VC) labels.
CEM标头之前的最后两个标签称为隧道和虚拟电路（VC）标签。
The VC label is required, and is the last label prior to the CEM Header. The VC label MUST be used to identify the CEM connection within the MPLS tunnel.
VC标签是必需的，并且是CEM标题之前的最后一个标签。VC标签必须用于标识MPLS隧道内的CEM连接。
The optional tunnel label is immediately above the VC label on the label stack. If present, the tunnel label MUST be used to identify the MPLS LSP used to tunnel the TDM packets through the MPLS network (the tunnel LSP).
可选通道标签位于标签堆栈上VC标签的正上方。如果存在，则必须使用隧道标签来标识用于通过MPLS网络隧道TDM数据包的MPLS LSP（隧道LSP）。
This is similar to the label stack usage defined in [RFC4447].
这类似于[RFC4447]中定义的标签堆栈用法。
+-----------------------------------+
| Additional MPLS Labels (Optional) |
+-----------------------------------+
| Tunnel Label (Optional) |
+-----------------------------------+
| VC Label |
+-----------------------------------+
| CEM Header |
+-----------------------------------+
| |
| |
| SONET/SDH SPE Fragment |
| |
| |
+-----------------------------------+
+-----------------------------------+
| Additional MPLS Labels (Optional) |
+-----------------------------------+
| Tunnel Label (Optional) |
+-----------------------------------+
| VC Label |
+-----------------------------------+
| CEM Header |
+-----------------------------------+
| |
| |
| SONET/SDH SPE Fragment |
| |
| |
+-----------------------------------+
Figure 3. Typical MPLS Transport Encapsulation
图3。典型的MPLS传输封装
It is highly desirable to define a single encapsulation format that will work for both IP and MPLS. Furthermore, it is desirable that the encapsulation mechanism be as efficient as possible.
非常需要定义一种既适用于IP又适用于MPLS的封装格式。此外，希望封装机制尽可能有效。
One way to achieve these goals is to map CEM directly onto IP by mapping the previously described MPLS packets onto IP.
实现这些目标的一种方法是通过将前面描述的MPLS数据包映射到IP，将CEM直接映射到IP。
A mechanism for carrying MPLS over IP is described in [RFC4023].
[RFC4023]中描述了通过IP承载MPLS的机制。
Using this encapsulation scheme would result in the packet format illustrated in Figure 4.
使用此封装方案将产生图4所示的数据包格式。
+-----------------------------------+
| |
| IPv6/v4 Header [RFC4023] |
| |
+-----------------------------------+
| Tunnel Label (Optional) |
+-----------------------------------+
| VC Label |
+-----------------------------------+
| CEM Header |
+-----------------------------------+
| |
| |
| SONET/SDH SPE Fragment |
| |
| |
+-----------------------------------+
+-----------------------------------+
| |
| IPv6/v4 Header [RFC4023] |
| |
+-----------------------------------+
| Tunnel Label (Optional) |
+-----------------------------------+
| VC Label |
+-----------------------------------+
| CEM Header |
+-----------------------------------+
| |
| |
| SONET/SDH SPE Fragment |
| |
| |
+-----------------------------------+
Figure 4. MPLS Transport Encapsulation
图4。MPLS传输封装
The following sections describe CEM operation.
以下各节介绍CEM操作。
There are two types of CEM: structured and unstructured.
CEM有两种类型：结构化和非结构化。
Unstructured CEM packetizes the entire SONET/SDH bit-stream (including transport overhead).
非结构化CEM将整个SONET/SDH比特流（包括传输开销）打包。
Structured CEM terminates the transport overhead and packetizes individual channels (STS-1/Nc) within the SONET/SDH frame. Because structured CEM terminates the transport overhead, structured CEM implementations SHOULD meet the generic requirements for SONET/SDH Line Terminating Equipment as defined in [T1.105], [G.707], and [GR-253].
结构化CEM终止传输开销，并将SONET/SDH帧内的单个信道（STS-1/Nc）打包。由于结构化CEM终止了传输开销，因此结构化CEM实施应满足[T1.105]、[G.707]和[GR-253]中定义的SONET/SDH线路终端设备的一般要求。
Implementations MUST support structured CEM and MAY support unstructured CEM.
实施必须支持结构化CEM，也可以支持非结构化CEM。
Structured CEM MUST support a normal mode of operation and MAY support an optional extension called Dynamic Bandwidth Allocation (DBA). During normal operation, SONET/SDH payloads are fragmented, pre-pended with the CEM header, the VC label, and the PSN header, and
结构化CEM必须支持正常操作模式，并可能支持称为动态带宽分配（DBA）的可选扩展。在正常运行期间，SONET/SDH有效负载被分段，与CEM报头、VC标签和PSN报头一起挂起，以及
then transmitted into the packet network. During DBA mode, only the CEM header, the VC label, and PSN header are transmitted. This is done to conserve bandwidth when meaningful user data is not present in the SPE, such as during AIS-P or STS SPE Unequipped.
然后传输到分组网络。在DBA模式下，仅传输CEM报头、VC标签和PSN报头。这样做是为了在SPE中不存在有意义的用户数据时节省带宽，例如在AIS-P或STS SPE未装备期间。
As with all adaptation functions, CEM has two distinct components: adapting TDM SONET/SDH into a CEM packet stream, and converting the CEM packet stream back into a TDM SONET/SDH. The first function will be referred to as CEM packetizer and the second as CEM de-packetizer. This terminology is illustrated in Figure 5.
与所有适配功能一样，CEM有两个不同的组件：将TDM SONET/SDH适配为CEM分组流，以及将CEM分组流转换回TDM SONET/SDH。第一个函数称为CEM打包器，第二个函数称为CEM反打包器。该术语如图5所示。
+------------+ +---------------+
| | | |
SONET --> | CEM | --> PSN --> | CEM | --> SONET
SDH | Packetizer | | De-Packetizer | SDH
| | | |
+------------+ +---------------+
+------------+ +---------------+
| | | |
SONET --> | CEM | --> PSN --> | CEM | --> SONET
SDH | Packetizer | | De-Packetizer | SDH
| | | |
+------------+ +---------------+
Figure 5. CEM Terminology
图5。CEM术语
Note: the CEM de-packetizer requires a buffering mechanism to account for delay variation in the CEM packet stream. This buffering mechanism will be generically referred to as the CEM jitter buffer.
注意：CEM解包器需要一个缓冲机制来解释CEM数据包流中的延迟变化。这种缓冲机制一般称为CEM抖动缓冲。
DBA is an optional mode of operation for structured CEM that only transmits the CEM header, the VC label, and PSN header into the packet network under certain circumstances, such as AIS-P or STS SPE Unequipped.
DBA是结构化CEM的可选操作模式，在某些情况下（如AIS-P或STS SPE未配备）仅将CEM报头、VC标签和PSN报头传输到分组网络。
If DBA is supported by a CEM implementation, the user SHOULD be able to configure if DBA will be triggered by AIS-P, STS SPE Unequipped, both, or neither on a per channel basis.
如果CEM实现支持DBA，则用户应能够配置每个通道上是否由AIS-P、STS SPE（未配备）触发DBA，或者两者都触发DBA，或者两者都不触发DBA。
If DBA is supported, the determination of AIS-P and STS SPE Unequipped MUST be based on the state of SONET/SDH Section, Line, and Path Overhead bytes. DBA based on pattern detection within the SPE (i.e., all zeros, 7Es, or ATM idle cells) is for further study.
如果支持DBA，则必须根据SONET/SDH段、线路和路径开销字节的状态来确定未装备的AIS-P和STS SPE。基于SPE内模式检测（即全零、7Es或ATM空闲信元）的DBA有待进一步研究。
During AIS-P, there is no valid payload pointer, so pointer adjustments cannot occur. During STS SPE Unequipped, the SONET/SDH payload pointer is valid, and therefore pointer adjustments MUST be supported even during DBA. See Table 1 for details.
在AIS-P期间，没有有效的有效负载指针，因此无法进行指针调整。在未配备STS SPE期间，SONET/SDH有效负载指针有效，因此即使在DBA期间也必须支持指针调整。详见表1。
During normal operation, the CEM packetizer will receive a fixed rate byte stream from a SONET/SDH interface. When a packet's worth of data has been received from a SONET/SDH channel, the CEM header, the VC Label, and PSN header are pre-pended to the SPE fragment and the resulting CEM packet is transmitted into the packet network. Because all normal CEM packets associated with a specific SONET/SDH channel will have the same length, the transmission of CEM packets for that channel SHOULD occur at regular intervals.
在正常操作期间，CEM打包器将从SONET/SDH接口接收固定速率字节流。当从SONET/SDH信道接收到相当于数据包价值的数据时，CEM报头、VC标签和PSN报头被预先挂起到SPE片段，并且产生的CEM数据包被传输到数据包网络。由于与特定SONET/SDH信道相关的所有正常CEM数据包将具有相同的长度，因此该信道的CEM数据包传输应定期进行。
At the far-end of the packet network, the CEM de-packetizer will receive packets into a jitter buffer and then play out the received byte stream at a fixed rate onto the corresponding SONET/SDH channel. The jitter buffer SHOULD be adjustable in length to account for varying network delay behavior. The received packet rate from the packet network should be exactly balanced by the transmission rate onto the SONET/SDH channel, on average. The time over which this average is taken corresponds to the depth of the jitter buffer for a specific CEM channel.
在数据包网络的远端，CEM解包器将数据包接收到抖动缓冲器中，然后以固定速率将接收到的字节流播放到相应的SONET/SDH信道上。抖动缓冲区的长度应可调，以考虑不同的网络延迟行为。平均而言，从分组网络接收的分组速率应与SONET/SDH信道上的传输速率完全平衡。采取该平均值的时间对应于特定CEM信道的抖动缓冲器的深度。
The CEM sequence numbers provide a mechanism to detect lost and/or mis-ordered packets. The CEM de-packetizer MUST detect lost or mis-ordered packets. The CEM de-packetizer MUST play out a programmable byte pattern in place of any dropped packets. The CEM de-packetizer MAY re-order packets received out of order. If the CEM de-packetizer does not support re-ordering, it MUST drop mis-ordered packets.
CEM序列号提供了一种检测丢失和/或误序数据包的机制。CEM反打包器必须检测丢失或错误订购的数据包。CEM反打包器必须播放一个可编程字节模式，以代替任何丢弃的数据包。CEM反打包器可以对无序接收的数据包重新排序。如果CEM反打包器不支持重新排序，则必须丢弃错误排序的数据包。
(Note: DBA is only applicable to structured CEM.)
（注：DBA仅适用于结构化CEM。）
There are several issues that should be addressed by a workable CEM DBA mechanism. First, when DBA is invoked, there should be a substantial savings in bandwidth utilization in the packet network. The second issue is that the transition in and out of DBA should be tightly coordinated between the local CEM packetizer and CEM de-packetizer at the far side of the packet network. A third is that the transition in and out of DBA should be accomplished with minimal disruption to the adapted data stream.
有几个问题应该由一个可行的CEM DBA机制来解决。首先，当调用DBA时，分组网络中的带宽利用率应该有很大的节省。第二个问题是DBA的进出转换应该在分组网络远端的本地CEM打包器和CEM去打包器之间紧密协调。第三个是，DBA的进出转换应该在对适应的数据流中断最小的情况下完成。
Another goal is that the reduction of CEM traffic due to DBA should not be mistaken for a fault in the packet network or vice-versa. Finally, the implementation of DBA should require minimal modifications beyond what is necessary for the nominal CEM case. The mechanism described below is a reasonable balance of these goals.
另一个目标是，由于DBA导致的CEM流量减少不应被误认为是分组网络中的故障，反之亦然。最后，DBA的实现应该只需要对标称CEM情况所需的最小修改。下面描述的机制是这些目标的合理平衡。
During DBA, packets MUST be emitted at exactly the same rate as they would be during normal operation. This SHOULD be accomplished by transmitting each DBA packet after a complete packet of data has been received from the SONET/SDH channel. The only change from normal operation is that the CEM packets during DBA MUST only carry the CEM header, the VC label, and the PSN header.
在DBA期间，数据包必须以与正常操作期间完全相同的速率发出。这应该通过在从SONET/SDH信道接收到完整的数据包后发送每个DBA数据包来实现。与正常操作相比的唯一变化是，DBA期间的CEM数据包必须仅携带CEM头、VC标签和PSN头。
Because some links have a minimum supported packet size, the CEM packetizer MAY append a configurable number of bytes immediately after the CEM header to pad out the CEM packet to reach the minimum supported packet size. The value of the padding bytes is implementation specific. The D-bit MUST be set to one, to indicate that DBA is active.
由于某些链路具有最小支持的数据包大小，CEM打包器可在CEM报头之后立即附加可配置数量的字节，以填充CEM数据包以达到最小支持的数据包大小。填充字节的值是特定于实现的。D位必须设置为1，以指示DBA处于活动状态。
The CEM de-packetizer MUST assume that each packet received with the D-bit set represents a normal-sized packet containing an AIS-P or STS SPE Unequipped payload as noted by N and P, (see Table 1). The CEM de-packetizer MUST accept DBA packets with or without padding.
CEM解包器必须假设使用D位集接收的每个数据包代表一个正常大小的数据包，其中包含AIS-P或STS SPE未装备的有效载荷，如N和P所述（见表1）。CEM反打包器必须接受带或不带填充的DBA数据包。
This allows the CEM packetization and de-packetization logic during DBA to be similar to the nominal case. It insures that the correct SONET/SDH indication is reliably transmitted between CEM adaptation points. It minimizes the risk of under or over running the jitter buffer during the transition in and out of DBA. And, it guarantees that faults in the packet network are recognized as distinctly different from line conditioning on the SONET/SDH interfaces.
这使得DBA期间的CEM打包和反打包逻辑与标称情况类似。它确保在CEM适配点之间可靠地传输正确的SONET/SDH指示。它最大限度地降低了在进出DBA的转换过程中抖动缓冲区运行不足或过度的风险。并且，它保证分组网络中的故障被识别为与SONET/SDH接口上的线路调节明显不同。
A key component in declaring the state of a CEM service is whether or not the CEM de-packetizer is in or out of packet synchronization. The following paragraphs describe how that determination is made.
声明CEM服务状态的一个关键组件是CEM反打包器是否处于数据包同步状态。以下段落描述了如何作出该决定。
At startup, a CEM de-packetizer will be out of packet synchronization by default. To declare packet synchronization at startup or after a loss of packet synchronization, the CEM de-packetizer must receive a configurable number of CEM packets with sequential sequence numbers.
在启动时，默认情况下，CEM反打包器将失去数据包同步。要在启动时或数据包同步丢失后声明数据包同步，CEM反打包器必须接收具有序列号的可配置数量的CEM数据包。
Once a CEM de-packetizer is in packet sync, it may encounter a set of events that will cause it to lose packet synchronization.
一旦CEM反打包器处于数据包同步状态，它可能会遇到一组事件，导致其丢失数据包同步。
As discussed in section 5.2, a CEM de-packetizer MAY support the re-ordering of mis-ordered packets.
如第5.2节所述，CEM解包器可支持对错误排序的数据包进行重新排序。
If a CEM de-packetizer supports re-ordering, then the determination that packet synchronization has been lost cannot be made at the time the packets are received from the PSN. Instead, the determination MUST be made as the packets are being played out onto the SONET/SDH interface. This is because it is only at play-out time that the determination can be made as to whether the entire emulated SONET/SDH stream was received from the PSN.
如果CEM解包器支持重新排序，则在从PSN接收数据包时无法确定数据包同步已丢失。相反，必须在数据包在SONET/SDH接口上播放时进行确定。这是因为只有在播放时间才能确定是否从PSN接收到整个模拟SONET/SDH流。
If a CEM de-packetizer does not support re-ordering, a number of approaches may be used to minimize the impact of mis-ordered or lost packets on the final re-assembled SONET/SDH stream. For example, ATM Adaptation Layer 1 (AAL1) [I.363.1] uses a simple state-machine to re-order packets in a subset of possible cases. The algorithm for these state-machines is outside of the scope of CEM. However, the final determination as to whether or not to declare loss of packet synchronization MUST be based on the same criteria as for implementations that do support re-ordering.
如果CEM解包器不支持重新排序，可以使用多种方法来最小化错误排序或丢失的数据包对最终重新组装的SONET/SDH流的影响。例如，ATM适配层1（AAL1）[I.363.1]使用简单的状态机在可能情况的子集中对数据包重新排序。这些状态机的算法不在CEM的范围内。然而，关于是否声明数据包同步丢失的最终决定必须基于与支持重新排序的实现相同的标准。
Whether or not a CEM implementation supports re-ordering, the declaration of loss of packet synchronization MUST be based on the following criteria.
无论CEM实现是否支持重新排序，数据包同步丢失的声明必须基于以下标准。
As packets are played out towards the SONET/SDH interface, the CEM de-packetizer will encounter empty packets in the place of packets that were dropped by the PSN, or effectively dropped due to limitations of the CEM implementation. If the CEM de-packetizer encounters more than a configurable number of sequential dropped packets, the CEM de-packetizer MUST declare loss of packet synchronization.
当数据包向SONET/SDH接口播放时，CEM解包器将在PSN丢弃的数据包处遇到空数据包，或由于CEM实现的限制而有效丢弃的数据包。如果CEM反打包器遇到超过可配置数量的顺序丢弃数据包，则CEM反打包器必须声明数据包同步丢失。
There are several issues that must be considered in the mapping of maintenance signals between SONET/SDH and a PSN. A description of how these signals and conditions are mapped between the two domains is given below.
在SONET/SDH和PSN之间的维护信号映射中，必须考虑几个问题。下面给出了如何在两个域之间映射这些信号和条件的描述。
For clarity, the mappings are split into two groups: SONET/SDH to PSN and PSN to SONET/SDH.
为清楚起见，映射分为两组：SONET/SDH到PSN和PSN到SONET/SDH。
The following sections describe how SONET/SDH Maintenance Signals and Alarm conditions are mapped into a Packet-Switched Network.
以下各节描述SONET/SDH维护信号和报警条件如何映射到分组交换网络。
In a SONET/SDH network, SONET/SDH Path outages are signaled using maintenance alarms, such as Path AIS (AIS-P). In particular, AIS-P indicates that the SONET/SDH Path is not currently transmitting valid end-user data, and the SPE contains all ones.
在SONET/SDH网络中，SONET/SDH路径中断通过维护警报（如路径AIS（AIS-P））发出信号。特别是，AIS-P表示SONET/SDH路径当前未传输有效的最终用户数据，SPE包含所有数据。
It should be noted that for structured CEM, nearly every type of service-effecting section or line defect will result in an AIS-P condition.
应注意的是，对于结构化CEM，几乎每种影响区段或线路缺陷的服务类型都会导致AIS-P状况。
The SONET/SDH hierarchy is illustrated below.
SONET/SDH层次结构如下所示。
+----------+
| PATH |
+----------+
^
|
AIS-P
|
|
+----------+
| LINE |
+ ---------+
^ ^
| |
AIS-L +------ LOP
|
|
+----------+
| SECTION |
+----------+
^ ^
| |
| |
LOS LOF
+----------+
| PATH |
+----------+
^
|
AIS-P
|
|
+----------+
| LINE |
+ ---------+
^ ^
| |
AIS-L +------ LOP
|
|
+----------+
| SECTION |
+----------+
^ ^
| |
| |
LOS LOF
Figure 6. SONET/SDH Fault Hierarchy
图6。SONET/SDH故障层次
Should the Section Layer detect a Loss of Signal (LOS) or Loss of Frame (LOF) condition, it sends AIS-L up to the Line Layer. If the Line Layer detects AIS-L or Loss of Path (LOP), it sends AIS-P to the Path Layer.
如果剖面层检测到信号丢失（LOS）或帧丢失（LOF）情况，它会向线路层发送AIS-L。如果线路层检测到AIS-L或路径丢失（LOP），则将AIS-P发送到路径层。
In normal mode during AIS-P, structured CEM packets are generated as usual. The N and P bits MUST be set to 11 binary to signal AIS-P explicitly through the packet network. The D-bit MUST be set to zero
在AIS-P期间的正常模式下，结构化CEM数据包按常规生成。N位和P位必须设置为11二进制，以便通过分组网络显式发送AIS-P信号。D位必须设置为零
to indicate that the SPE is being carried through the packet network. Normal CEM packets with the SPE fragment, CEM header, the VC label, and PSN header MUST be transmitted into the packet network.
指示SPE正在通过数据包网络传输。带有SPE片段、CEM头、VC标签和PSN头的正常CEM数据包必须传输到数据包网络中。
However, to conserve network bandwidth during AIS-P, DBA MAY be employed. If DBA has been enabled for AIS-P and AIS-P is currently occurring, the N and P bits MUST be set to 11 binary to signal AIS, and the D-bit MUST be set to one to indicate that the SPE is not being carried through the packet network. Only the CEM header, the VC label, and the PSN header MUST be transmitted into the packet network.
然而，为了在AIS-P期间节省网络带宽，可以使用DBA。如果已为AIS-P启用DBA，且AIS-P当前正在发生，则必须将N位和P位设置为11二进制以表示AIS，并且必须将D位设置为1，以指示SPE未通过分组网络传输。只有CEM报头、VC标签和PSN报头必须传输到分组网络中。
Also note that this differs from the outage mechanism in [RFC4447], which withdraws the VC label as a result of an endpoint outage. TDM circuit emulation requires the ability to distinguish between the de-provisioning of a circuit (which causes the VC label to be withdrawn), and temporary outages (which are signaled using AIS-P).
还请注意，这与[RFC4447]中的中断机制不同，后者由于端点中断而撤销VC标签。TDM电路仿真需要能够区分电路的断电（导致撤销VC标签）和临时断电（使用AIS-P发出信号）。
The STS SPE Unequipped Indication is a slightly different case than AIS-P. When byte C2 of the Path Overhead (STS path signal label) is 00h and Byte B3 (STS Path BIP-8) is valid, it indicates that the STS SPE is unequipped. Note: this is typically signaled by setting the entire SPE to zeros.
STS SPE未装备指示与AIS-P的情况稍有不同。当路径开销（STS路径信号标签）的字节C2为00h且字节B3（STS路径BIP-8）有效时，表示STS SPE未装备。注意：这通常通过将整个SPE设置为零来表示。
For normal structured CEM operation during STS SPE Unequipped, the N and P bits MUST be interpreted as usual. The SPE MUST be transmitted into the packet network along with the CEM header, the VC label, and PSN header, and the D-Bit MUST be set to zero.
对于STS SPE未配备期间的正常结构化CEM操作，N和P位必须按常规进行解释。SPE必须与CEM报头、VC标签和PSN报头一起传输到数据包网络，并且D位必须设置为零。
If DBA has been enabled for STS SPE Unequipped and the Unequipped condition is occurring on the SONET/SDH channel, the D-bit MUST be set to one to indicate DBA is active. Only the CEM header, the VC Label, and PSN header MUST be transmitted into the packet network. The N and P bits MUST be used to signal pointer adjustments as normal. See Table 1 and section 8 for details.
如果已为STS SPE未装备启用DBA，并且SONET/SDH信道上出现未装备情况，则必须将D位设置为1，以指示DBA处于活动状态。只有CEM报头、VC标签和PSN报头必须传输到分组网络中。正常情况下，必须使用N和P位发出指针调整信号。详见表1和第8节。
The CEM function MUST send CEM-RDI towards the packet network during loss of packet synchronization. This MUST be accomplished by setting the R bit to one in the CEM header. This applies for both structured and unstructured CEM.
在数据包同步丢失期间，CEM功能必须向数据包网络发送CEM-RDI。这必须通过在CEM头中将R位设置为1来实现。这适用于结构化和非结构化CEM。
The following sections discuss how the various conditions on the packet network are converted into SONET/SDH indications.
以下各节讨论如何将分组网络上的各种条件转换为SONET/SDH指示。
There are several conditions in the packet network that will cause the structured CEM de-packetization function to send an AIS-P indication onto a SONET/SDH channel.
分组网络中有几种情况会导致结构化CEM去分组功能向SONET/SDH信道发送AIS-P指示。
The first of these is the receipt of structured CEM packets with the N and P bits set to one, and the D-bit set to zero. This is an explicit indication of AIS-P being received at the far-end of the packet network, with DBA disabled for AIS-P. The CEM de-packetizer MUST play out the received SPE fragment (which will incidentally be carrying all ones), and MUST configure the SONET/SDH Overhead to signal AIS-P as defined in [T1.105], [G.707], and [GR-253].
第一个是接收结构化CEM数据包，其中N位和P位设置为1，D位设置为0。这是在数据包网络远端接收到AIS-P的明确指示，对于AIS-P，DBA被禁用。CEM解包器必须播放接收到的SPE片段（附带携带所有SPE片段），并且必须按照[T1.105]、[G.707]和[GR-253]中的定义，配置SONET/SDH开销以向AIS-P发送信号。
The second case is the receipt of structured CEM packets with the N and P bits set to one, and the D-bit set to one. This is an explicit indication of AIS-P being received at the far-end of the packet network, with DBA enabled for AIS-P. The CEM de-packetizer MUST play out one packet's worth of all ones for each packet received, and MUST configure the SONET/SDH Overhead to signal AIS-P as defined in [T1.105], [G.707], and [GR-253].
第二种情况是接收N位和P位设置为1、D位设置为1的结构化CEM数据包。这是在数据包网络远端接收AIS-P的明确指示，且为AIS-P启用了DBA。CEM解包器必须为每个接收的数据包播放所有数据包中的一个数据包，并且必须按照[T1.105]、[G.707]和[GR-253]中的定义配置SONET/SDH开销以发送AIS-P信号。
A third case that will cause a structured CEM de-packetization function to send an AIS-P indication onto a SONET/SDH channel is loss of packet synchronization.
导致结构化CEM去分组功能将AIS-P指示发送到SONET/SDH信道的第三种情况是数据包同步丢失。
There are three conditions in the packet network that will cause the CEM function to transmit STS SPE Unequipped Indications onto the SONET/SDH channel.
分组网络中有三种情况会导致CEM功能将STS SPE未配备的指示传输到SONET/SDH信道。
The first, which is transparent to CEM, is the receipt of regular CEM packets that happen to be carrying an SPE that contains the appropriate Path Overhead to signal STS SPE Unequipped. This case does not require any special processing on the part of the CEM de-packetizer.
第一个对CEM是透明的，它接收到的常规CEM数据包恰好携带一个SPE，该SPE包含适当的路径开销，以向未装备的STS SPE发送信号。这种情况不需要CEM去包装商进行任何特殊处理。
The second case is the receipt of structured CEM packets that have the D-bit set to one to indicate that DBA is active and the N and P bits set to 00 binary, 01 binary, or 10 binary to indicate STS SPE
第二种情况是接收结构化CEM数据包，其中D位设置为1表示DBA处于活动状态，N位和P位设置为00二进制、01二进制或10二进制表示STS SPE
Unequipped with or without pointer adjustments. The CEM de-packetizer MUST use this information to transmit a packet of all zeros onto the SONET/SDH interface, and adjust the payload pointer as necessary.
未配备或未配备指针调整。CEM解包器必须使用此信息将全零数据包传输到SONET/SDH接口，并根据需要调整有效负载指针。
The third case when a structured CEM de-packetizer MUST send an STS SPE Unequipped Indication towards the SONET/SDH interface is when the VC-label has been withdrawn due to de-provisioning of the circuit.
第三种情况是，当结构化CEM反打包器必须向SONET/SDH接口发送STS SPE未配置指示时，由于电路反配置，VC标签已被撤回。
It is necessary to be able to regenerate the input service clock at the output interface. Two clocking modes are supported: synchronous and asynchronous. Selection of the clocking mode is made as part of service provisioning. Both ends of the emulated circuit must be configured with the same clocking mode.
必须能够在输出接口处重新生成输入服务时钟。支持两种时钟模式：同步和异步。选择时钟模式是服务供应的一部分。仿真电路的两端必须配置相同的时钟模式。
When synchronous SONET/SDH timing is available at both ends of the circuit, the issue of clock recovery becomes much simpler.
当同步SONET/SDH定时在电路两端都可用时，时钟恢复问题就变得简单得多。
For unstructured CEM, the external clock is used to clock each bit onto the optical carrier.
对于非结构化CEM，外部时钟用于对光载波上的每个位进行时钟。
For structured CEM, the external clock is used to clock the SONET/SDH carrier. The N and P bits are used to signal negative or positive pointer adjustment events between structured CEM endpoints.
对于结构化CEM，外部时钟用于对SONET/SDH载波进行时钟设置。N位和P位用于在结构化CEM端点之间发送负指针调整事件或正指针调整事件的信号。
If there is a frequency offset between the frame rate of the transport overhead and that of the SONET/SDH SPE, then the alignment of the SPE shall periodically slip back or advance in time through positive or negative stuffing. The N and P bits are used to replay the pointer adjustment events and eliminate transport jitter.
如果传输开销的帧速率与SONET/SDH SPE的帧速率之间存在频率偏移，则SPE的对齐应通过正或负填充周期性地向后滑动或提前。N和P位用于重播指针调整事件并消除传输抖动。
During a negative pointer adjustment event, the H3 byte from the SONET/SDH stream is incorporated into the CEM packet payload in order with the rest of the SPE. During a positive pointer adjustment event, the stuff byte is not included in the CEM packet payload.
在负指针调整事件期间，SONET/SDH流中的H3字节按顺序与SPE的其余部分合并到CEM数据包有效负载中。在正指针调整事件期间，填充字节不包括在CEM数据包有效负载中。
The pointer adjustment event MUST be transmitted in three consecutive packets by the packetizer. The de-packetizer MUST play out the pointer adjustment event when the first packet of the three with the N/P bits set is received.
指针调整事件必须由打包器以三个连续数据包的形式传输。当收到设置了N/P位的三个数据包中的第一个数据包时，解包器必须播放指针调整事件。
The CEM de-packetizer MUST utilize the CEM sequence numbers to insure that SONET/SDH pointer adjustment events are not played any more frequently than once per every three CEM packets transmitted by the remote CEM packetizer.
CEM解包器必须利用CEM序列号确保SONET/SDH指针调整事件的播放频率不会超过远程CEM包器传输的每三个CEM包播放一次。
References [T1.105], [G.707], and [GR-253] specify that pointer adjustment events MUST be separated by three SONET/SDH frames without a pointer adjustment event. In order to relay all legal pointer adjustment events, the packet size for a specific circuit MUST be no larger than (783 * 4 * N)/3, where N is the STS-Nc multiplier.
参考文献[T1.105]、[G.707]和[GR-253]规定，指针调整事件必须由三个SONET/SDH帧分隔，且无指针调整事件。为了中继所有合法指针调整事件，特定电路的数据包大小不得大于（783*4*N）/3，其中N是STS Nc乘法器。
However, some SONET/SDH equipment allows pointer adjustments to occur in back-to-back SONET/SDH frames. In order to support this possibility, the packet size for a particular circuit SHOULD be no larger than (783*N)/3, where N is the STS-Nc multiplier.
然而，一些SONET/SDH设备允许在背对背SONET/SDH帧中进行指针调整。为了支持这种可能性，特定电路的分组大小不应大于（783*N）/3，其中N是STS Nc乘法器。
Since the minimum value of N is one, CEM implementations SHOULD support a minimum payload length of 783/3 or 261 bytes. Smaller payload lengths MAY be supported as an option.
由于N的最小值为1，CEM实现应支持783/3或261字节的最小有效负载长度。作为一种选择，可支持较小的有效负载长度。
If synchronous timing is not available, other methods MAY be employed to regenerate the circuit timing.
如果同步定时不可用，则可采用其他方法来重新生成电路定时。
For structured CEM, the CEM packetizer SHOULD generate the N and P bits as usual. However, without external synchronization, this information is not sufficient to reliably justify the SPE within the SONET/SDH transport framing at the CEM de-packetizer. The de-packetizer MAY employ an adaptive algorithm to introduce pointer adjustment events to map the CEM SPE to the SONET/SDH transport framing. Regardless of whether the N and P bits are used by the de-packetizer as part of the adaptive clock recovery algorithm, they MUST still be used in conjunction with the D-bit to signal AIS-P, STS SPE Unequipped, and DBA.
对于结构化CEM，CEM打包器应像往常一样生成N位和P位。但是，如果没有外部同步，该信息不足以可靠地证明CEM数据打包器处SONET/SDH传输帧内的SPE。解包器可采用自适应算法引入指针调整事件，以将CEM SPE映射到SONET/SDH传输帧。无论解包器是否将N位和P位用作自适应时钟恢复算法的一部分，它们都必须与D位一起使用，以向AIS-P、STS SPE UNEquiped和DBA发送信号。
For unstructured CEM, the CEM de-packetizer MAY use an adaptive clock recovery technique to regenerate the SONET/SDH transport clock.
对于非结构化CEM，CEM解分组器可以使用自适应时钟恢复技术来重新生成SONET/SDH传输时钟。
An example adaptive clock recovery method can be found in section 3.4.2 of [VTOA].
可在[VTOA]第3.4.2节中找到示例自适应时钟恢复方法。
For maximum network scaling in MPLS applications, CEM LSP signaling may be performed using the Label Distribution Protocol (LDP) Extended Discovery mechanism as augmented by the Pseudo-Wire id Forward Error Correction (PWid FEC) Element defined in [RFC4447]. MPLS traffic
为了实现MPLS应用中的最大网络扩展，CEM LSP信令可以使用标签分发协议（LDP）扩展发现机制执行，该机制由[RFC4447]中定义的伪线路id前向纠错（PWid FEC）元素补充。MPLS流量
tunnels may be dedicated to CEM, or shared with other MPLS-based services. The value 0x8008 is used for the PWE3 PW Type in the PWid FEC Element in order to signify that the LSP being signaled is to carry CEM. Note that the generic control word defined in [GR-253] is not used, as its functionality is included in the CEM encapsulation header.
隧道可以专用于CEM，也可以与其他基于MPLS的服务共享。值0x8008用于PWid FEC元素中的PWE3 PW类型，以表示发送信号的LSP将携带CEM。请注意，未使用[GR-253]中定义的通用控制字，因为其功能包含在CEM封装头中。
Alternatively, static label assignment may be used, or a dedicated traffic engineered LSP may be used for each CEM service.
或者，可以使用静态标签分配，或者可以为每个CEM服务使用专用的流量工程LSP。
Normal CEM packets are fixed in length for all of the packets of a particular emulated TDM stream. This length is signaled using the CEM Payload Bytes parameter defined in [RFC4447], or it is statically provisioned for each CEM service.
对于特定仿真TDM流的所有数据包，普通CEM数据包的长度是固定的。使用[RFC4447]中定义的CEM Payload Bytes参数表示该长度，或者为每个CEM服务静态设置该长度。
At this time, other aspects of the CEM service MUST be statically provisioned.
此时，必须静态地提供CEM服务的其他方面。
The CEM encapsulation is subject to all of the general security considerations discussed in [RFC3985] and [RFC4447]. In addition, this document specifies only encapsulations, and not the protocols used to carry the encapsulated packets across the PSN. Each such protocol may have its own set of security issues, but those issues are not affected by the encapsulations specified herein. Note that the security of the transported CEM service will only be as good as the security of the PSN. This level of security may be less rigorous then that available from a native TDM service due to the inherent differences between circuit-switched and packet-switched public networks.
CEM封装受[RFC3985]和[RFC4447]中讨论的所有一般安全注意事项的约束。此外，本文档仅指定封装，而不指定用于跨PSN传输封装数据包的协议。每个这样的协议可能有其自己的一组安全问题，但是这些问题不受本文指定的封装的影响。请注意，传输的CEM服务的安全性仅与PSN的安全性相同。由于电路交换和分组交换公共网络之间的固有差异，这种安全级别可能不如本地TDM服务提供的安全级别严格。
IANA has already allocated the PWE3 PW Type value 0x0008 for this specification. No further actions are required.
IANA已经为此规范分配了PWE3 PW类型值0x0008。无需采取进一步行动。
[G.707] ITU Recommendation G.707, "Network Node Interface For The Synchronous Digital Hierarchy", 1996.
[G.707]国际电联建议G.707，“同步数字体系的网络节点接口”，1996年。
[GR-253] Telcordia Technologies, "Synchronous Optical Network (SONET) Transport Systems: Common Generic Criteria", GR-253-CORE, Issue 3, September 2000.
[GR-253]Telcordia Technologies，“同步光网络（SONET）传输系统：通用标准”，GR-253-CORE，第3期，2000年9月。
[I.363.1] ITU-T, "Recommendation I.363.1, B-ISDN Adaptation Layer Specification: Type AAL1", Appendix III, August 1996.
[I.363.1]ITU-T，“建议I.363.1，B-ISDN适配层规范：AAL1型”，附录III，1996年8月。
[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。
[RFC4023] Worster, T., Rekhter, Y., and E. Rosen, Ed., "Encapsulating MPLS in IP or Generic Routing Encapsulation (GRE)", RFC 4023, March 2005.
[RFC4023]Worster，T.，Rekhter，Y.，和E.Rosen，编辑，“在IP或通用路由封装（GRE）中封装MPLS”，RFC4023，2005年3月。
[RFC4447] Martini, L., Ed., 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.，Ed.，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。
[RFC4842] Malis, A., Pate, P., Cohen, R., Ed., and D. Zelig, "Synchronous Optical Network/Synchronous Digital Hierarchy (SONET/SDH) Circuit Emulation over Packet (CEP)", RFC 4842, April 2007.
[RFC4842]Malis，A.，Pate，P.，Cohen，R.，Ed.，和D.Zelig，“同步光网络/同步数字体系（SONET/SDH）分组电路仿真（CEP）”，RFC 4842，2007年4月。
[RFC4928] Swallow, G., Bryant, S., and L. Andersson, "Avoiding Equal Cost Multipath Treatment in MPLS Networks", BCP 128, RFC 4928, June 2007.
[RFC4928]Swallow，G.，Bryant，S.和L.Andersson，“避免MPLS网络中的等成本多路径处理”，BCP 128，RFC 4928，2007年6月。
[T1.105] American National Standards Institute, "Synchronous Optical Network (SONET) - Basic Description including Multiplex Structure, Rates and Formats," ANSI T1.105- 1995.
[T1.105]美国国家标准协会，“同步光网络（SONET）-基本描述，包括多路复用结构、速率和格式”，ANSI T1.105-1995。
[VTOA] ATM Forum, "Circuit Emulation Service Interoperability Specification Version 2.0", af-vtoa-0078.000, January 1997.
[VTOA]ATM论坛，“电路仿真服务互操作性规范2.0版”，af-VTOA-0078.000，1997年1月。
[RFC3985] Bryant, S., Ed., and P. Pate, Ed., "Pseudo Wire Emulation Edge-to-Edge (PWE3) Architecture", RFC 3985, March 2005.
[RFC3985]Bryant，S.，Ed.，和P.Pate，Ed.，“伪线仿真边到边（PWE3）架构”，RFC 39852005年3月。
Appendix A. SONET/SDH Rates and Formats
附录A.SONET/SDH速率和格式
For simplicity, the discussion in this section uses SONET terminology, but it applies equally to SDH as well. SDH-equivalent terminology is shown in the tables.
为简单起见，本节中的讨论使用SONET术语，但它同样适用于SDH。SDH等效术语如表所示。
The basic SONET modular signal is the synchronous transport signal-level 1 (STS-1). A number of STS-1s may be multiplexed into higher-level signals denoted as STS-N, with N synchronous payload envelopes (SPEs). The optical counterpart of the STS-N is the Optical Carrier-level N, or OC-N. Table 2 lists standard SONET line rates discussed in this document.
基本SONET模块信号为1级同步传输信号（STS-1）。可以将多个STS-1复用成表示为STS-N的具有N个同步有效载荷包络（spe）的更高级别信号。STS-N的光学对应物是光载波电平N或OC-N。表2列出了本文件中讨论的标准SONET线速率。
OC Level OC-1 OC-3 OC-12 OC-48 OC-192 SDH Term - STM-1 STM-4 STM-16 STM-64 Line Rate(Mb/s) 51.840 155.520 622.080 2,488.320 9,953.280
OC级OC-1 OC-3 OC-12 OC-48 OC-192 SDH术语-STM-1 STM-4 STM-16 STM-64线路速率（Mb/s）51.840 155.520 622.080 2488.320 9953.280
Table 2. Standard SONET Line Rates
表2。标准SONET线路费率
Each SONET frame is 125 us and consists of nine rows. An STS-N frame has nine rows and N*90 columns. Of the N*90 columns, the first N*3 columns are transport overhead and the other N*87 columns are SPEs. A number of STS-1s may also be linked together to form a super-rate signal with only one SPE. The optical super-rate signal is denoted as OC-Nc, which has a higher payload capacity than OC-N.
每个SONET帧为125 us，由九行组成。STS-N帧有九行和N*90列。在N*90列中，前N*3列为传输开销，其他N*87列为SPE。多个STS-1也可连接在一起，以形成仅具有一个SPE的超速率信号。光学超速率信号表示为OC-Nc，其有效负载容量高于OC-N。
The first 9-byte column of each SPE is the Path Overhead (POH) and the remaining columns form the payload capacity with fixed stuff (STS-Nc only). The fixed stuff, which is purely overhead, is N/3-1 columns for STS-Nc. Thus, STS-1 and STS-3c do not have any fixed stuff, STS-12c has three columns of fixed stuff, and so on.
每个SPE的第一个9字节列是路径开销（POH），其余列构成固定内容的有效负载容量（仅限STS Nc）。对于STS Nc，固定内容（纯粹是开销）是N/3-1列。因此，STS-1和STS-3c没有任何固定内容，STS-12c有三列固定内容，依此类推。
The POH of an STS-1 or STS-Nc is always nine bytes in nine rows. The payload capacity of an STS-1 is 86 columns (774 bytes) per frame. The payload capacity of an STS-Nc is (N*87)-(N/3) columns per frame. Thus, the payload capacity of an STS-3c is (3*87 - 1)*9 = 2,340 bytes per frame. As another example, the payload capacity of an STS-192c is 149,760 bytes, which is exactly 64 times larger than the STS-3c.
STS-1或STS Nc的POH始终是九行中的九个字节。STS-1的有效负载容量为每帧86列（774字节）。STS Nc的有效负载容量为每帧（N*87）-（N/3）列。因此，STS-3c的有效负载容量是（3×87-1）×9＝2340字节/帧。另一个例子是，STS-192c的有效负载容量为149760字节，正好是STS-3c的64倍。
There are 8,000 SONET frames per second. Therefore, the SPE size, (POH plus payload capacity) of an STS-1 is 783*8*8,000 = 50.112 Mb/s. The SPE size of a concatenated STS-3c is 2,349 bytes per frame or 150.336 Mb/s. The payload capacity of an STS-192c is 149,760 bytes per frame, which is equivalent to 9,584.640 Mb/s. Table 3 lists the SPE and payload rates supported.
每秒有8000个SONET帧。因此，STS-1的SPE大小（POH加有效负载容量）为783*8*8000=50.112 Mb/s。级联STS-3c的SPE大小为每帧2349字节或150.336 Mb/s。STS-192c的有效负载容量为每帧149760字节，相当于9584.640 Mb/s。表3列出了支持的SPE和有效负载速率。
SONET STS Level STS-1 STS-3c STS-12c STS-48c STS-192c SDH VC Level - VC-4 VC-4-4c VC-4-16c VC-4-64c Payload Size(Bytes) 774 2,340 9,360 37,440 149,760 Payload Rate(Mb/s) 49.536 149.760 599.040 2,396.160 9,584.640 SPE Size(Bytes) 783 2,349 9,396 37,584 150,336 SPE Rate(Mb/s) 50.112 150.336 601.344 2,405.376 9,621.504
SONET STS级别STS-1 STS-3c STS-12c STS-48c STS-192c SDH VC级别-VC-4 VC-4-4c VC-4-64c有效负载大小（字节）774 2340 9360 37440 149760有效负载率（Mb/s）49.536 149.760 599.040 2396.160 9584.640 SPE大小（字节）783 2349 9396 37584 150336 SPE速率（Mb/s）50.112 150.336 601.344 2405.376 9621.504
Table 3. Payload Size and Rate
表3。有效载荷大小和速率
To support circuit emulation, the entire SPE of a SONET STS or SDH VC level is encapsulated into packets, using the encapsulation defined in section 5, for carriage across packet-switched networks.
为了支持电路仿真，SONET STS或SDH VC级别的整个SPE使用第5节中定义的封装封装到数据包中，用于跨数据包交换网络传输。
ECC-6 is an Error Correction Code to protect the CEM header. This provides single bit correction and the ability to detect up to two bit errors.
ECC-6是一种用于保护CEM报头的纠错代码。这提供了单位校正和检测最多两位错误的能力。
Error Correction Code:
纠错码：
|---------------Header bits 0-25 -------------------| ECC-6 code|
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|1 1 1 1 1 0 0 0 1 0 0 0 1 1 1 1 1 0 1 0 0 0 1 0 1 1|1 0 0 0 0 0|
|1 1 1 1 0 1 0 0 0 1 0 0 1 0 0 0 0 1 0 1 1 1 1 1 1 1|0 1 0 0 0 0|
|1 0 0 0 1 1 1 1 0 0 1 0 1 1 1 0 0 0 1 1 1 1 0 0 1 1|0 0 1 0 0 0|
|0 1 0 0 1 1 1 1 0 0 0 1 1 0 0 1 1 1 1 1 0 0 1 1 0 1|0 0 0 1 0 0|
|0 0 1 0 0 0 1 0 1 1 1 1 1 1 0 0 1 1 1 1 1 0 1 0 1 0|0 0 0 0 1 0|
|0 0 0 1 0 0 0 1 1 1 1 1 0 0 1 1 0 0 1 1 0 1 1 1 1 1|0 0 0 0 0 1|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|---------------Header bits 0-25 -------------------| ECC-6 code|
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|1 1 1 1 1 0 0 0 1 0 0 0 1 1 1 1 1 0 1 0 0 0 1 0 1 1|1 0 0 0 0 0|
|1 1 1 1 0 1 0 0 0 1 0 0 1 0 0 0 0 1 0 1 1 1 1 1 1 1|0 1 0 0 0 0|
|1 0 0 0 1 1 1 1 0 0 1 0 1 1 1 0 0 0 1 1 1 1 0 0 1 1|0 0 1 0 0 0|
|0 1 0 0 1 1 1 1 0 0 0 1 1 0 0 1 1 1 1 1 0 0 1 1 0 1|0 0 0 1 0 0|
|0 0 1 0 0 0 1 0 1 1 1 1 1 1 0 0 1 1 1 1 1 0 1 0 1 0|0 0 0 0 1 0|
|0 0 0 1 0 0 0 1 1 1 1 1 0 0 1 1 0 0 1 1 0 1 1 1 1 1|0 0 0 0 0 1|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 7. ECC-6 Check Matrix X
图7。ECC-6校验矩阵X
The ECC-6 code protects the 32-bit CEM header as follows:
ECC-6代码保护32位CEM标头，如下所示：
The encoder generates the 6-bit ECC using the matrix shown in Figure 7. In brief, the encoder builds another 26 column by 6 row matrix and calculates even parity over the rows. The matrix columns represent CEM header bits 0 through 25.
编码器使用图7所示的矩阵生成6位ECC。简而言之，编码器构建另一个26列6行矩阵，并计算行上的偶数奇偶校验。矩阵列表示CEM头位0到25。
Denote each column of the ECC-6 check matrix by X[], and each column of the intermediate encoder matrix as Y[]. CEM[] denotes the CEM header and ECC[] is the error correction code that is inserted into CEM header bits 26 through 31.
用X[]表示ECC-6校验矩阵的每一列，用Y[]表示中间编码器矩阵的每一列。CEM[]表示CEM报头，ECC[]是插入CEM报头位26到31的纠错码。
for i = 0 to 25 {
if CEM[i] = 0 {
Y[i] = 0;
} else {
Y[i] = X[i];
}
}
for i = 0 to 25 {
if CEM[i] = 0 {
Y[i] = 0;
} else {
Y[i] = X[i];
}
}
In other words, for each CEM header bit (i) set to one, set the resulting matrix column Y[i] according to Figure 7.
换句话说，对于设置为1的每个CEM头比特（i），根据图7设置结果矩阵列Y[i]。
The final ECC-6 code is calculated as even parity of each row in Y (i.e., ECC[k]=CEM[25+k]=even parity of row k).
最终的ECC-6代码计算为Y中每行的偶数奇偶校验（即ECC[k]=CEM[25+k]=行k的偶数奇偶校验）。
The receiver also uses matrix X to calculate an intermediate matrix Y' based on all 32 bits of the CEM header. Therefore, Y' is 32 columns wide and includes the ECC-6 code.
接收机还使用矩阵X根据CEM报头的所有32位计算中间矩阵Y’。因此，Y'为32列宽，包括ECC-6代码。
for i = 0 to 31 {
if CEM[i] = 0 {
Y'[i] = 0;
} else {
Y'[i] = X[i];
}
}
for i = 0 to 31 {
if CEM[i] = 0 {
Y'[i] = 0;
} else {
Y'[i] = X[i];
}
}
The receiver then appends the incoming ECC-6 code to Y as column 32 (ECC[0] should align with row 0) and calculates even parity for each row. The result is a single 6-bit column Z. If all 6 bits are 0, there are no bit errors (or at least no detectable errors). Otherwise, it uses Z to perform a reverse lookup on X[] from Figure 7. If Z matches column X[i], then there is a single bit error. The receiver should invert bit CEM[i] to correct the header. If Z fails to match any column of X, then the CEM header contains more than one bit error and the CEM packet MUST be discarded.
然后，接收器将传入的ECC-6代码作为第32列附加到Y（ECC[0]应与第0行对齐），并计算每行的偶数奇偶校验。结果是单个6位列Z。如果所有6位均为0，则不存在位错误（或至少不存在可检测错误）。否则，它将使用Z对图7中的X[]执行反向查找。如果Z与列X[i]匹配，则存在一个位错误。接收机应反转位CEM[i]以校正报头。如果Z未能匹配X的任何列，则CEM报头包含多个位错误，必须丢弃CEM数据包。
Note that the ECC-6 code provides single-bit correction and 2-bit detection of errors within the received ECC-6 code itself.
请注意，ECC-6代码在接收到的ECC-6代码本身内提供单位纠错和2位错误检测。
Acknowledgments
致谢
The authors would like to thank Mitri Halabi, Bob Colvin, and Ken Hsu, all formerly of Vivace Networks and Tellabs; Tom Johnson, Marlene Drost, Ed Hallman, and Dave Danenberg, all formerly of Litchfield Communications, for their contributions to the document.
作者要感谢Mitri Halabi、Bob Colvin和Ken Hsu，他们都是Vivace Networks和Tellabs的前任；汤姆·约翰逊、玛琳·卓斯特、埃德·哈尔曼和戴夫·达内伯格，他们都是利奇菲尔德通讯公司的前任，感谢他们对该文件的贡献。
Authors' Addresses
作者地址
Andrew G. Malis Verizon Communications 40 Sylvan Road Waltham, MA 02451 EMail: andrew.g.malis@verizon.com
Andrew G.Malis Verizon Communications马萨诸塞州沃尔瑟姆Sylvan路40号02451电子邮件：Andrew.G。malis@verizon.com
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
John Shirron ECI Telecom Inc. Omega Corporate Center 1300 Omega Drive Pittsburgh, PA 15205 EMail: john.shirron@ecitele.com
John Shirron 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：John。shirron@ecitele.com
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
Steve Vogelsang Alcatel-Lucent 600 March Road Kanata, ON K2K 2T6 Canada EMail: steve.vogelsang@alcatel-lucent.com
Steve Vogelsang Alcatel-Lucent 600 March Road Kanata，关于K2K 2T6加拿大电子邮件：Steve。vogelsang@alcatel-朗讯网
Full Copyright Statement
完整版权声明
Copyright (C) The IETF Trust (2008).
版权所有（C）IETF信托基金（2008年）。
This document is subject to the rights, licenses and restrictions contained in BCP 78 and at www.rfc-editor.org/copyright.html, and except as set forth therein, the authors retain all their rights.
本文件受BCP 78和www.rfc-editor.org/copyright.html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.
本文件及其包含的信息以“原样”为基础提供，贡献者、他/她所代表或赞助的组织（如有）、互联网协会、IETF信托基金和互联网工程任务组不承担任何明示或暗示的担保，包括但不限于任何保证，即使用本文中的信息不会侵犯任何权利，或对适销性或特定用途适用性的任何默示保证。
Intellectual Property
知识产权
The IETF takes no position regarding the validity or scope of any Intellectual Property Rights or other rights that might be claimed to pertain to the implementation or use of the technology described in this document or the extent to which any license under such rights might or might not be available; nor does it represent that it has made any independent effort to identify any such rights. Information on the procedures with respect to rights in RFC documents can be found in BCP 78 and BCP 79.
IETF对可能声称与本文件所述技术的实施或使用有关的任何知识产权或其他权利的有效性或范围，或此类权利下的任何许可可能或可能不可用的程度，不采取任何立场；它也不表示它已作出任何独立努力来确定任何此类权利。有关RFC文件中权利的程序信息，请参见BCP 78和BCP 79。
Copies of IPR disclosures made to the IETF Secretariat and any assurances of licenses to be made available, or the result of an attempt made to obtain a general license or permission for the use of such proprietary rights by implementers or users of this specification can be obtained from the IETF on-line IPR repository at http://www.ietf.org/ipr.
向IETF秘书处披露的知识产权副本和任何许可证保证，或本规范实施者或用户试图获得使用此类专有权利的一般许可证或许可的结果，可从IETF在线知识产权存储库获取，网址为http://www.ietf.org/ipr.
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.