Internet Engineering Task Force (IETF) S. Belotti, Ed.
Request for Comments: 7096 P. Grandi
Category: Informational Alcatel-Lucent
ISSN: 2070-1721 D. Ceccarelli, Ed.
D. Caviglia
Ericsson
F. Zhang
D. Li
Huawei Technologies
January 2014
Internet Engineering Task Force (IETF) S. Belotti, Ed.
Request for Comments: 7096 P. Grandi
Category: Informational Alcatel-Lucent
ISSN: 2070-1721 D. Ceccarelli, Ed.
D. Caviglia
Ericsson
F. Zhang
D. Li
Huawei Technologies
January 2014
Evaluation of Existing GMPLS Encoding against G.709v3 Optical Transport Networks (OTNs)
针对G.709v3光传输网络（OTN）评估现有GMPLS编码
Abstract
摘要
ITU-T recommendation G.709-2012 has introduced new fixed and flexible Optical channel Data Unit (ODU) containers in Optical Transport Networks (OTNs).
ITU-T建议G.709-2012在光传输网络（OTN）中引入了新的固定和灵活光信道数据单元（ODU）容器。
This document provides an evaluation of existing Generalized Multiprotocol Label Switching (GMPLS) routing and signaling protocols against the G.709 OTNs.
本文档针对G.709 OTN对现有的通用多协议标签交换（GMPLS）路由和信令协议进行了评估。
Status of This Memo
关于下段备忘
This document is not an Internet Standards Track specification; it is published for informational purposes.
本文件不是互联网标准跟踪规范；它是为了提供信息而发布的。
This document is a product of the Internet Engineering Task Force (IETF). It represents the consensus of the IETF community. It has received public review and has been approved for publication by the Internet Engineering Steering Group (IESG). Not all documents approved by the IESG are a candidate for any level of Internet Standard; see Section 2 of RFC 5741.
本文件是互联网工程任务组（IETF）的产品。它代表了IETF社区的共识。它已经接受了公众审查，并已被互联网工程指导小组（IESG）批准出版。并非IESG批准的所有文件都适用于任何级别的互联网标准；见RFC 5741第2节。
Information about the current status of this document, any errata, and how to provide feedback on it may be obtained at http://www.rfc-editor.org/info/rfc7096.
有关本文件当前状态、任何勘误表以及如何提供反馈的信息，请访问http://www.rfc-editor.org/info/rfc7096.
Copyright Notice
版权公告
Copyright (c) 2014 IETF Trust and the persons identified as the document authors. All rights reserved.
版权所有（c）2014 IETF信托基金和确定为文件作者的人员。版权所有。
This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License.
本文件受BCP 78和IETF信托有关IETF文件的法律规定的约束(http://trustee.ietf.org/license-info)自本文件出版之日起生效。请仔细阅读这些文件，因为它们描述了您对本文件的权利和限制。从本文件中提取的代码组件必须包括信托法律条款第4.e节中所述的简化BSD许可证文本，并提供简化BSD许可证中所述的无担保。
Table of Contents
目录
1. Introduction ....................................................3
2. G.709 Mapping and Multiplexing Capabilities .....................4
3. Tributary Slot Granularity ......................................6
3.1. Data-Plane Considerations ..................................7
3.1.1. Payload Type and TS Granularity Relationship ........7
3.1.2. Fallback Procedure ..................................8
3.2. Control-Plane Considerations ...............................9
4. Tributary Port Number ..........................................13
5. Signal Type ....................................................13
6. Bit Rate and Tolerance .........................................15
7. Unreserved Resources ...........................................15
8. Maximum LSP Bandwidth ..........................................15
9. Distinction between Terminating and Switching Capabilities .....16
10. Priority Support ..............................................18
11. Multi-stage Multiplexing ......................................18
12. Generalized Label .............................................19
13. Security Considerations .......................................19
14. Contributors ..................................................20
15. Acknowledgements ..............................................20
16. References ....................................................20
16.1. Normative References .....................................20
16.2. Informative References ...................................21
1. Introduction ....................................................3
2. G.709 Mapping and Multiplexing Capabilities .....................4
3. Tributary Slot Granularity ......................................6
3.1. Data-Plane Considerations ..................................7
3.1.1. Payload Type and TS Granularity Relationship ........7
3.1.2. Fallback Procedure ..................................8
3.2. Control-Plane Considerations ...............................9
4. Tributary Port Number ..........................................13
5. Signal Type ....................................................13
6. Bit Rate and Tolerance .........................................15
7. Unreserved Resources ...........................................15
8. Maximum LSP Bandwidth ..........................................15
9. Distinction between Terminating and Switching Capabilities .....16
10. Priority Support ..............................................18
11. Multi-stage Multiplexing ......................................18
12. Generalized Label .............................................19
13. Security Considerations .......................................19
14. Contributors ..................................................20
15. Acknowledgements ..............................................20
16. References ....................................................20
16.1. Normative References .....................................20
16.2. Informative References ...................................21
GMPLS routing [RFC4203] [RFC5307] and signaling [RFC3473] [RFC4328] provide the mechanisms for basic GMPLS control of Optical Transport Networks (OTNs) based on the 2001 revision of the G.709 specification [G.709-2001]. The 2012 revision of the G.709 specification [G.709-2012] includes new OTN features that are not supported by GMPLS.
GMPLS路由[RFC4203][RFC5307]和信令[RFC3473][RFC4328]提供了基于2001年修订的G.709规范[G.709-2001]的光传输网络（OTN）基本GMPLS控制机制。2012年修订的G.709规范[G.709-2012]包括GMPLS不支持的新OTN功能。
This document provides an evaluation of exiting GMPLS signaling and routing protocols against G.709 requirements. Background information and a framework for the GMPLS protocol extensions needed to support G.709 is provided in [RFC7062]. Specific routing and signaling extensions defined in [OTN-OSPF] and [OTN-RSVP] specifically address the gaps identified in this document.
本文件根据G.709要求对现有的GMPLS信令和路由协议进行了评估。[RFC7062]中提供了支持G.709所需的GMPLS协议扩展的背景信息和框架。[OTN-OSPF]和[OTN-RSVP]中定义的特定路由和信令扩展专门解决了本文件中确定的差距。
The digital OTN-layered structure is comprised of the digital path layer (ODU) and the digital section layer (OTU). An OTU (Optical channel Transport Unit) section layer supports one ODU path layer as a client and provides monitoring capability for the Optical Channel (OCh), which is the optical path carrying the digital OTN structure. An ODU path layer may transport a heterogeneous assembly of ODU clients. Some types of ODUs (i.e., ODU1, ODU2, ODU3, and ODU4) may assume either a client or server role within the context of a particular networking domain. The terms ODU1, ODU2, ODU3, ODU4, and flexible ODU (ODUflex) are explained in G.709. G.872 [G.872] provides two tables defining mapping and multiplexing capabilities of OTNs, which are reported below.
数字OTN分层结构由数字路径层（ODU）和数字部分层（OTU）组成。OTU（光信道传输单元）部分层支持一个ODU路径层作为客户端，并为光信道（OCh）提供监控能力，OCh是承载数字OTN结构的光路径。ODU路径层可以传输ODU客户端的异构组件。某些类型的ODU（即ODU1、ODU2、ODU3和ODU4）可以在特定网络域的上下文中承担客户机或服务器角色。术语ODU1、ODU2、ODU3、ODU4和灵活ODU（ODUflex）在G.709中进行了解释。G.872[G.872]提供了两个定义OTN映射和复用能力的表，如下所述。
+--------------------+--------------------+
| ODU client | OTU server |
+--------------------+--------------------+
| ODU0 | - |
+--------------------+--------------------+
| ODU1 | OTU 1 |
+--------------------+--------------------+
| ODU2 | OTU 2 |
+--------------------+--------------------+
| ODU2e | - |
+--------------------+--------------------+
| ODU3 | OTU 3 |
+--------------------+--------------------+
| ODU4 | OTU 4 |
+--------------------+--------------------+
| ODUflex | - |
+--------------------+--------------------+
+--------------------+--------------------+
| ODU client | OTU server |
+--------------------+--------------------+
| ODU0 | - |
+--------------------+--------------------+
| ODU1 | OTU 1 |
+--------------------+--------------------+
| ODU2 | OTU 2 |
+--------------------+--------------------+
| ODU2e | - |
+--------------------+--------------------+
| ODU3 | OTU 3 |
+--------------------+--------------------+
| ODU4 | OTU 4 |
+--------------------+--------------------+
| ODUflex | - |
+--------------------+--------------------+
Figure 1: OTN Mapping Capability
图1:OTN映射能力
+=================================+=========================+
| ODU client | ODU server |
+---------------------------------+-------------------------+
| 1.25 Gbit/s client | |
+---------------------------------+ ODU0 |
| - | |
+=================================+=========================+
| 2.5 Gbit/s client | |
+---------------------------------+ ODU1 |
| ODU0 | |
+=================================+=========================+
| 10 Gbit/s client | |
+---------------------------------+ ODU2 |
| ODU0,ODU1,ODUflex | |
+=================================+=========================+
| 10.3125 Gbit/s client | |
+---------------------------------+ ODU2e |
| - | |
+=================================+=========================+
| 40 Gbit/s client | |
+---------------------------------+ ODU3 |
| ODU0,ODU1,ODU2,ODU2e,ODUflex | |
+=================================+=========================+
| 100 Gbit/s client | |
+---------------------------------+ ODU4 |
|ODU0,ODU1,ODU2,ODU2e,ODU3,ODUflex| |
+=================================+=========================+
|CBR* clients from greater than | |
|2.5 Gbit/s to 100 Gbit/s: or | |
|GFP-F** mapped packet clients | ODUflex |
|from 1.25 Gbit/s to 100 Gbit/s. | |
+---------------------------------+ |
| - | |
+=================================+=========================+
(*) - Constant Bit Rate
(**) - Generic Framing Procedure - Framed (GFP-F)
+=================================+=========================+
| ODU client | ODU server |
+---------------------------------+-------------------------+
| 1.25 Gbit/s client | |
+---------------------------------+ ODU0 |
| - | |
+=================================+=========================+
| 2.5 Gbit/s client | |
+---------------------------------+ ODU1 |
| ODU0 | |
+=================================+=========================+
| 10 Gbit/s client | |
+---------------------------------+ ODU2 |
| ODU0,ODU1,ODUflex | |
+=================================+=========================+
| 10.3125 Gbit/s client | |
+---------------------------------+ ODU2e |
| - | |
+=================================+=========================+
| 40 Gbit/s client | |
+---------------------------------+ ODU3 |
| ODU0,ODU1,ODU2,ODU2e,ODUflex | |
+=================================+=========================+
| 100 Gbit/s client | |
+---------------------------------+ ODU4 |
|ODU0,ODU1,ODU2,ODU2e,ODU3,ODUflex| |
+=================================+=========================+
|CBR* clients from greater than | |
|2.5 Gbit/s to 100 Gbit/s: or | |
|GFP-F** mapped packet clients | ODUflex |
|from 1.25 Gbit/s to 100 Gbit/s. | |
+---------------------------------+ |
| - | |
+=================================+=========================+
(*) - Constant Bit Rate
(**) - Generic Framing Procedure - Framed (GFP-F)
Figure 2: OTN Multiplexing Capability
图2:OTN多路复用能力
In the following, the terms Optical channel Data Unit-j (ODUj) and Optical channel Data Unit-k (ODUk) are used in a multiplexing scenario to identify the lower order signal (ODUj) and the higher order signal (ODUk). How an ODUk connection service is transported within an operator network is governed by operator policy. For example, the ODUk connection service might be transported over an ODUk path over an Optical channel Transport Unit-k (OTUk) section, with the same path and section rates as that of the connection
在下文中，在复用场景中使用术语光信道数据单元-j（ODUj）和光信道数据单元-k（ODUk）来识别低阶信号（ODUj）和高阶信号（ODUk）。ODUk连接服务在运营商网络中的传输方式由运营商策略决定。例如，ODUk连接服务可以通过光信道传输单元k（OTUk）部分上的ODUk路径进行传输，具有与连接相同的路径和部分速率
service (see Figure 1). In this case, an entire lambda of capacity is consumed in transporting the ODUk connection service. On the other hand, the operator might exploit different multiplexing capabilities in the network to improve infrastructure efficiencies within any given networking domain. In this case, ODUk multiplexing may be performed prior to transport over various rate ODU servers (as per Figure 2) over associated OTU sections.
服务（参见图1）。在这种情况下，在传输ODUk连接服务时消耗了整个λ的容量。另一方面，运营商可以利用网络中的不同多路复用能力来提高任何给定网络域内的基础设施效率。在这种情况下，可以在通过相关OTU部分的不同速率ODU服务器（如图2所示）传输之前执行ODUk多路复用。
From the perspective of multiplexing relationships, a given ODUk may play different roles as it traverses various networking domains.
从复用关系的角度来看，一个给定的ODUk在穿越不同的网络域时可能扮演不同的角色。
As detailed in [RFC7062], client ODUk connection services can be transported over:
如[RFC7062]所述，客户端ODUk连接服务可以通过以下方式传输：
Case A: one or more wavelength subnetworks connected by optical links, or
案例A：通过光链路连接的一个或多个波长子网，或
Case B: one or more ODU links (having sub-lambda and/or lambda bandwidth granularity), or
情况B：一个或多个ODU链路（具有子λ和/或λ带宽粒度），或
Case C: a mix of ODU links and wavelength subnetworks.
案例C：ODU链路和波长子网的混合。
This document considers the Traffic Engineering (TE) information needed for ODU path computation and the parameters needed to be signaled for Label Switched Path (LSP) setup.
本文件考虑了ODU路径计算所需的流量工程（TE）信息以及标签交换路径（LSP）设置所需的信号参数。
The following sections list and analyze what GMPLS already has and what it is missing with regard to each type of data that needs to be advertised and signaled.
以下各节列出并分析了GMPLS已经拥有的内容，以及需要公布和发出信号的每种数据类型缺少的内容。
G.709 defines two types of Tributary Slot (TS) granularities. This TS granularity is defined per layer, meaning that both ends of a link can select proper TS granularity differently for each supported layer, based on the rules below:
G.709定义了两种类型的分支槽（TS）粒度。该TS粒度是按层定义的，这意味着链路的两端可以根据以下规则为每个受支持的层选择不同的TS粒度：
o If both ends of a link are new cards supporting both 1.25 Gbit/s TS and 2.5 Gbit/s TS, then the link will work with 1.25 Gbit/s TS.
o 如果链路两端都是支持1.25 Gbit/s TS和2.5 Gbit/s TS的新卡，则链路将使用1.25 Gbit/s TS。
o If one end of a link is a new card supporting both the 1.25 Gbit/s and 2.5 Gbit/s TS granularities, and the other end is an old card supporting just the 2.5 Gbit/s TS granularity, the link will work with 2.5 Gbit/s TS granularity.
o 如果链路的一端是同时支持1.25 Gbit/s和2.5 Gbit/s TS粒度的新卡，而另一端是仅支持2.5 Gbit/s TS粒度的旧卡，则链路将以2.5 Gbit/s TS粒度工作。
As defined in G.709, an ODUk container consists of an Optical channel Payload Unit-k (OPUk) plus a specific ODUk Overhead (OH). OPUk OH information is added to the OPUk information payload to create an OPUk. It includes information to support the adaptation of client signals. Within the OPUk overhead, there is the payload structure identifier (PSI) that includes the payload type (PT). The PT is used to indicate the composition of the OPUk signal. When an ODUj signal is multiplexed into an ODUk, the ODUj signal is first extended with the frame alignment overhead and then mapped into an Optical channel Data Tributary Unit (ODTU). Two different types of ODTUs are defined:
如G.709所定义，ODUk容器由光信道有效负载单元k（OPUk）加上特定的ODUk开销（OH）组成。OPUk OH信息被添加到OPUk信息负载中以创建OPUk。它包括支持客户机信号自适应的信息。在OPUk开销中，存在包括有效负载类型（PT）的有效负载结构标识符（PSI）。PT用于指示OPUk信号的组成。当ODUj信号被复用到ODUk中时，ODUj信号首先用帧对准开销扩展，然后映射到光信道数据支路单元（ODTU）。定义了两种不同类型的ODTU：
o ODTUjk ((j,k) = {(0,1), (1,2), (1,3), (2,3)}; ODTU01, ODTU12, ODTU13, and ODTU23) in which an ODUj signal is mapped via the Asynchronous Mapping Procedure (AMP), as defined in Section 19.5 of [G.709-2012].
o ODTUjk（（j，k）={（0,1）、（1,2）、（1,3）、（2,3）}；ODTU01、ODTU12、ODTU13和ODTU23），其中ODUj信号通过[G.709-2012]第19.5节中定义的异步映射程序（AMP）进行映射。
o ODTUk.ts ((k,ts) = (2,1..8), (3,1..32), (4,1..80)) in which a lower order ODU (ODU0, ODU1, ODU2, ODU2e, ODU3, and ODUflex) signal is mapped via the Generic Mapping Procedure (GMP), as defined in Section 19.6 of [G.709-2012].
o ODTUk.ts（（k，ts）=（2,1..8），（3,1..32），（4,1..80）），其中较低阶ODU（ODU0、ODU1、ODU2、ODU2e、ODU3和ODUflex）信号通过通用映射程序（GMP）进行映射，如[G.709-2012]第19.6节所定义。
G.709 also introduces a logical entity, called Optical channel Data Tributary Unit Group (ODTUGk), characterizing the multiplexing of the various ODTU. The ODTUGk is then mapped into OPUk. Optical channel Data Tributary Unit j into k (ODTUjk) and Optical channel Data Tributary Unit k with ts tributary slots (ODTUk.ts) are directly time-division multiplexed into the tributary slots of an OH OPUk.
G.709还引入了一个逻辑实体，称为光信道数据分支单元组（ODTUGk），描述了各种ODTU的多路复用特性。然后将ODTUGk映射到OPUk。光信道数据支路单元j到k（ODTUjk）和具有ts支路时隙（ODTUk.ts）的光信道数据支路单元k被直接时分复用到OH OPUk的支路时隙中。
When PT is assuming values 0x20 or 0x21, together with OPUk type (k=1, 2, 3, 4), it is used to discriminate two different ODU multiplex structures for ODTUGx:
当PT假设值0x20或0x21以及OPUk类型（k=1、2、3、4）时，它用于区分ODTUGx的两种不同ODU多路复用结构：
o Value 0x20: supporting ODTUjk only
o 值0x20：仅支持ODTUjk
o Value 0x21: supporting ODTUk.ts or ODTUk.ts and ODTUjk
o 值0x21：支持ODTUk.ts或ODTUk.ts和ODTUjk
The distinction is needed for OPUk with k=2 or 3 since OPU2 and OPU3 are able to support both the different ODU multiplex structures. For OPU4 and OPU1, only one type of ODTUG is supported: ODTUG4 with PT=0x21 and ODTUG1 with PT=0x20 (see Figure 6). The relationship between PT and TS granularity is due to the fact that the two
由于OPU2和OPU3能够支持两种不同的ODU多路复用结构，因此需要对k=2或3的OPUk进行区分。对于OPU4和OPU1，只支持一种类型的ODTUG：PT=0x21的ODTUG4和PT=0x20的ODTUG1（见图6）。PT和TS粒度之间的关系是由于
different ODTUGk types discriminated by PT and OPUk are characterized by two different TS granularities of the related OPUk, the former at 2.5 Gbit/s and the latter at 1.25 Gbit/s.
由PT和OPUk区分的不同ODTUGk类型的特征是相关OPUk的两种不同TS粒度，前者为2.5 Gbit/s，后者为1.25 Gbit/s。
In order to complete the picture, in the PSI OH, there is also the Multiplex Structure Identifier (MSI) that provides the information on which tributary slots of the different ODTUjk or ODTUk.ts are mapped into the related OPUk. The following figure shows how the client traffic is multiplexed till the OPUk layer.
为了完成该图，在PSI OH中还存在复用结构标识符（MSI），其提供关于不同ODTUjk或ODTUk.t的哪个分支时隙被映射到相关OPUk的信息。下图显示了客户端流量如何多路传输到OPUk层。
+--------+ +------------+
+----+ | !------| ODTUjk |-----Client
| | | ODTUGk | +-----.------+
| |-----| PT=0x21| .
| | | | +-----.------+
| | | |------| ODTUk.ts |-----Client
|OPUk| +--------+ +------------+
| |
| | +--------+ +------------+
| | | |------| ODTUjk |-----Client
| |-----| | +-----.------+
+----+ | ODTUGk | .
| PT=0x20| +-----.------+
| |------| ODTUjk |-----Client
+--------+ +------------+
+--------+ +------------+
+----+ | !------| ODTUjk |-----Client
| | | ODTUGk | +-----.------+
| |-----| PT=0x21| .
| | | | +-----.------+
| | | |------| ODTUk.ts |-----Client
|OPUk| +--------+ +------------+
| |
| | +--------+ +------------+
| | | |------| ODTUjk |-----Client
| |-----| | +-----.------+
+----+ | ODTUGk | .
| PT=0x20| +-----.------+
| |------| ODTUjk |-----Client
+--------+ +------------+
Figure 3: OTN Client Multiplexing
图3:OTN客户端多路复用
G.798 [G.798] describes the so-called PT=0x21-to-PT=0x20 interworking process that explains how two nodes with interfaces that have different payload types and, hence, different TS granularity (1.25 Gbit/s vs. 2.5 Gbit/s), can be coordinated to permit the equipment with 1.25 Gbit/s TS granularity to adapt the TS allocation according to the different TS granularity (2.5 Gbit/s) of a neighbor.
G.798[G.798]描述了所谓的PT=0x21到PT=0x20的互通过程，该过程解释了两个节点如何使用具有不同负载类型的接口，从而使用不同的TS粒度（1.25 Gbit/s与2.5 Gbit/s），可以进行协调，以允许TS粒度为1.25 Gbit/s的设备根据邻居的不同TS粒度（2.5 Gbit/s）调整TS分配。
Therefore, in order to let the Network Element (NE) change TS granularity accordingly to the neighbor requirements, the AUTOpayloadtype [G.798] needs to be set. When both the neighbors (link or trail) have been configured as structured, the payload type received in the overhead is compared to the transmitted PT. If they are different and the transmitted one is PT=0x21, the node must fall back to PT=0x20. In this case, the fallback process makes the system self-consistent, and the only reason for signaling the TS granularity is to provide the correct label (i.e., the label for PT=0x21 has twice the TS number of PT=0x20). On the other side, if the
因此，为了让网元（NE）根据邻居的要求改变TS粒度，需要设置AUTOpayloadtype[G.798]。当两个邻居（链路或踪迹）都被配置为结构化时，将开销中接收的有效负载类型与发送的PT进行比较。如果它们不同，且传输的节点为PT=0x21，则节点必须返回到PT=0x20。在这种情况下，回退过程使系统自一致，发送TS粒度信号的唯一原因是提供正确的标签（即，PT=0x21的标签具有两倍于PT=0x20的TS编号）。另一方面，如果
AUTOpayloadtype is not configured, the Resource Reservation Protocol-Traffic Engineering (RSVP-TE) consequent actions need to be defined in case of a TS mismatch.
未配置AUTOpayloadtype，在TS不匹配的情况下，需要定义资源预留协议流量工程（RSVP-TE）后续操作。
When setting up an ODUj over an ODUk, it is possible to identify two types of TS granularity (TSG): the server and the client. The server TS granularity is used to map an end-to-end ODUj onto a server ODUk LSP or links. This parameter cannot be influenced in any way from the ODUj LSP: the ODUj LSP will be mapped on tributary slots available on the different links / ODUk LSPs. When setting up an ODUj at a given rate, the fact that it is carried over a path composed by links / Forwarding Adjacencies (FAs) structured with 1.25 Gbit/s or 2.5 Gbit/s TS granularity is completely transparent to the end-to-end ODUj.
在ODUk上设置ODUj时，可以识别两种类型的TS粒度（TSG）：服务器和客户端。服务器TS粒度用于将端到端ODUj映射到服务器ODUk LSP或链路。ODUj LSP不会以任何方式影响此参数：ODUj LSP将映射到不同链路/ODUk LSP上可用的分支插槽上。当以给定速率设置ODUj时，它通过由1.25 Gbit/s或2.5 Gbit/s TS粒度结构的链路/转发邻接（FA）组成的路径传输的事实对端到端ODUj是完全透明的。
The client TS granularity information is one of the parameters needed to correctly select the adaptation towards the client layers at the end nodes, and this is the only thing that the ODUj has to guarantee.
客户端TS粒度信息是在终端节点正确选择对客户端层的适配所需的参数之一，这是ODUj必须保证的唯一事项。
In Figure 4, an example of client and server TS granularity utilization in a scenario with mixed OTN [RFC4328] and OTN interfaces [G.709-2012] is shown.
图4显示了混合OTN[RFC4328]和OTN接口[G.709-2012]的场景中客户端和服务器TS粒度利用的示例。
ODU1-LSP
.........................................
TSG-C| |TSG-C
1.25| ODU2-H-LSP |1.25 Gbit/s
Gbit/s+------------X--------------------------+
| TSG-S| |TSG-S
| 2.5| |2.5 Gbit/s
| Gbit/s| ODU3-H-LSP |
| |------------X-------------|
| | |
+--+--+ +--+--+ +---+-+
| | | | +-+ +-+ | |
| A +------+ B +-----+ +***+ +-----+ Z |
| V.3 | OTU2 | V.1 |OTU3 +-+ +-+ OTU3| V.3 |
+-----+ +-----+ +-----+
ODU1-LSP
.........................................
TSG-C| |TSG-C
1.25| ODU2-H-LSP |1.25 Gbit/s
Gbit/s+------------X--------------------------+
| TSG-S| |TSG-S
| 2.5| |2.5 Gbit/s
| Gbit/s| ODU3-H-LSP |
| |------------X-------------|
| | |
+--+--+ +--+--+ +---+-+
| | | | +-+ +-+ | |
| A +------+ B +-----+ +***+ +-----+ Z |
| V.3 | OTU2 | V.1 |OTU3 +-+ +-+ OTU3| V.3 |
+-----+ +-----+ +-----+
... Service LSP
--- Hierarchical-LSP (H-LSP)
... Service LSP
--- Hierarchical-LSP (H-LSP)
Figure 4: Client-Server TS Granularity Example
图4：客户机-服务器TS粒度示例
In this scenario, an ODU3 LSP is set up from nodes B to Z. Node B has an old interface that is able to support 2.5 Gbit/s TS granularity; hence, only client TS granularity equal to 2.5 Gbit/s can be exported to ODU3 H-LSP-possible clients. An ODU2 LSP is set up from nodes A to Z with client TS granularity 1.25 Gbit/s signaled and exported towards clients. The ODU2 LSP is carried by ODU3 H-LSP from nodes B to Z. Due to the limitations of the old node B interface, the ODU2 LSP is mapped with 2.5 Gbit/s TS granularity over the ODU3 H-LSP. Then, an ODU1 LSP is set up from nodes A to Z, which is carried by the ODU2 H-LSP and mapped over it using 1.25 Gbit/s TS granularity.
在此场景中，从节点B到Z设置ODU3 LSP。节点B有一个旧接口，能够支持2.5 Gbit/s TS粒度；因此，只有等于2.5 Gbit/s的客户机TS粒度才能导出到ODU3 H-LSP可能的客户机。ODU2 LSP从节点A到Z设置，客户端TS粒度为1.25 Gbit/s，并向客户端发送信号和导出。ODU2 LSP由ODU3 H-LSP从节点B传送到Z。由于旧节点B接口的限制，ODU2 LSP在ODU3 H-LSP上映射为2.5 Gbit/s TS粒度。然后，从节点A到节点Z建立ODU1 LSP，由ODU2 H-LSP承载并使用1.25 Gbit/s TS粒度在其上映射。
What is shown in the example is that the TS granularity processing is a per-layer issue: even if the ODU3 H-LSP is created with the TS granularity client at 2.5 Gbit/s, the ODU2 H-LSP must guarantee a 1.25 Gbit/s TS granularity client. The ODU3 H-LSP is eligible from an ODU2 LSP perspective since it is known from the routing that this ODU3 interface at node Z supports an ODU2 termination exporting a TS granularity at 1.25 Gbit/s / 2.5 Gbit/s.
示例中显示的是TS粒度处理是一个每层问题：即使ODU3 H-LSP是在TS粒度客户端以2.5 Gbit/s的速度创建的，ODU2 H-LSP也必须保证1.25 Gbit/s的TS粒度客户端。从ODU2 LSP的角度来看，ODU3 H-LSP是合格的，因为从路由中可以知道，节点Z处的ODU3接口支持ODU2终端导出1.25 Gbit/s/2.5 Gbit/s的TS粒度。
The TS granularity information is needed in the routing protocol as the ingress node (A in the previous example) needs to know if the interfaces at the last hop can support the required TS granularity. In case they cannot, A will compute an alternate path from itself to Z (see Figure 4).
在路由协议中需要TS粒度信息，因为入口节点（前一示例中的A）需要知道最后一跳的接口是否能够支持所需的TS粒度。如果不能，A将计算从自身到Z的备用路径（见图4）。
Moreover, TS granularity information also needs to be signaled. As an example, consider the setup of an ODU3 forwarding adjacency that is going to carry an ODU0; hence, the support of 1.25 Gbit/s TS is needed. The information related to the TS granularity has to be carried in the signaling to permit node C (see Figure 5) to choose the right one among the different interfaces (with different TS granularities) towards D. In case the full Explicit Route Object (ERO) is provided in the signaling with explicit interface declaration, there is no need for C to choose the right interface towards D as it has been already decided by the ingress node or by the Path Computation Element (PCE).
此外，TS粒度信息也需要发送信号。作为一个例子，考虑建立一个ODU3转发邻接，它将携带一个ODU0；因此，需要支持1.25 Gbit/s TS。必须在信令中携带与TS粒度相关的信息，以允许节点C（见图5）在朝向D的不同接口（具有不同TS粒度）中选择正确的一个。如果信令中提供了带有显式接口声明的完整显式路由对象（ERO），C不需要选择对D正确的接口，因为它已经由入口节点或路径计算元素（PCE）决定。
ODU3
<---------------------->
ODU3
<---------------------->
ODU0
<-------------------------------------->
| |
+--------+ +--------+ +--------+ +--------+
| | | | | | 1.25 | |
| Node | | Node | | Node +------+ Node |
| A +------+ B +------+ C | ODU3 | D |
| | ODU3 | | ODU3 | +------+ |
+--------+ 1.25 +--------+ 2.5 +--------+ 2.5 +--------+
ODU0
<-------------------------------------->
| |
+--------+ +--------+ +--------+ +--------+
| | | | | | 1.25 | |
| Node | | Node | | Node +------+ Node |
| A +------+ B +------+ C | ODU3 | D |
| | ODU3 | | ODU3 | +------+ |
+--------+ 1.25 +--------+ 2.5 +--------+ 2.5 +--------+
Figure 5: TS Granularity in Signaling
图5：信令中的TS粒度
In case an ODUk FA_LSP needs to be set up as nesting another ODUj (as depicted in Figure 5), there might be the need to know the hierarchy of nested LSPs in addition to TS granularity to permit the penultimate hop (i.e., C) to choose the correct interface towards the egress node or any intermediate node (i.e., B) to choose the right path when performing the ERO expansion. This is not needed in case we allow bundling only component links with homogeneous hierarchies. In the case in which a specific implementation does not specify the last hop interface in the ERO, crankback can be a solution.
如果需要将一个ODUk FA_LSP设置为嵌套另一个ODUj（如图5所示），那么除了TS粒度之外，可能还需要知道嵌套LSP的层次结构，以允许倒数第二个跃点（即C）选择朝向出口节点或任何中间节点（即B）的正确接口在执行ERO扩展时选择正确的路径。如果我们只允许绑定具有同构层次结构的组件链接，则不需要这样做。在特定实现未在ERO中指定最后一跳接口的情况下，回退可以是一种解决方案。
In a multi-stage multiplexing environment, any layer can have a different TS granularity structure; for example, in a multiplexing hierarchy such as ODU0->ODU2->ODU3, the ODU3 can be structured at TS granularity = 2.5 Gbit/s in order to support an ODU2 connection, but this ODU2 connection can be a tunnel for ODU0 and, hence, structured with 1.25 Gbit/s TS granularity. Therefore, any multiplexing level has to advertise its TS granularity capabilities in order to allow a correct path computation by the end nodes (both the ODUk trail and the H-LSP/FA).
在多级复用环境中，任何层都可以具有不同的TS粒度结构；例如，在诸如ODU0->ODU2->ODU3的多路复用层次结构中，ODU3可以以TS粒度=2.5 Gbit/s的方式构造以支持ODU2连接，但是该ODU2连接可以是ODU0的隧道，因此，以1.25 Gbit/s的TS粒度构造。因此，任何复用级别都必须宣传其TS粒度能力，以便允许终端节点（ODUk trail和H-LSP/FA）进行正确的路径计算。
The following table shows the different mapping possibilities depending on the TS granularity types. The client types are shown in the left column, while the different OPUk server and related TS granularities are listed in the top row. The table also shows the relationship between the TS granularity and the payload type.
下表显示了根据TS粒度类型的不同映射可能性。客户机类型显示在左列中，而不同的OPUk服务器和相关的TS粒度则列在最上面一行中。该表还显示了TS粒度和有效负载类型之间的关系。
+------------------------------------------------+
| 2.5 Gbit/s TS || 1.25 Gbit/s TS |
| OPU2 | OPU3 || OPU1 | OPU2 | OPU3 | OPU4 |
+-------+------------------------------------------------+
| | - | - || AMP | GMP | GMP | GMP |
| ODU0 | | ||PT=0x20|PT=0x21|PT=0x21|PT=0x21|
+-------+------------------------------------------------+
| | AMP | AMP || - | AMP | AMP | GMP |
| ODU1 |PT=0x20|PT=0x20|| |PT=0x21|PT=0x21|PT=0x21|
+-------+------------------------------------------------+
| | - | AMP || - | - | AMP | GMP |
| ODU2 | |PT=0x20|| | |PT=0x21|PT=0x21|
+-------+------------------------------------------------+
| | - | - || - | - | GMP | GMP |
| ODU2e | | || | |PT=0x21|PT=0x21|
+-------+------------------------------------------------+
| | - | - || - | - | - | GMP |
| ODU3 | | || | | |PT=0x21|
+-------+------------------------------------------------+
| | - | - || - | GMP | GMP | GMP |
| ODUfl | | || |PT=0x21|PT=0x21|PT=0x21|
+-------+------------------------------------------------+
+------------------------------------------------+
| 2.5 Gbit/s TS || 1.25 Gbit/s TS |
| OPU2 | OPU3 || OPU1 | OPU2 | OPU3 | OPU4 |
+-------+------------------------------------------------+
| | - | - || AMP | GMP | GMP | GMP |
| ODU0 | | ||PT=0x20|PT=0x21|PT=0x21|PT=0x21|
+-------+------------------------------------------------+
| | AMP | AMP || - | AMP | AMP | GMP |
| ODU1 |PT=0x20|PT=0x20|| |PT=0x21|PT=0x21|PT=0x21|
+-------+------------------------------------------------+
| | - | AMP || - | - | AMP | GMP |
| ODU2 | |PT=0x20|| | |PT=0x21|PT=0x21|
+-------+------------------------------------------------+
| | - | - || - | - | GMP | GMP |
| ODU2e | | || | |PT=0x21|PT=0x21|
+-------+------------------------------------------------+
| | - | - || - | - | - | GMP |
| ODU3 | | || | | |PT=0x21|
+-------+------------------------------------------------+
| | - | - || - | GMP | GMP | GMP |
| ODUfl | | || |PT=0x21|PT=0x21|PT=0x21|
+-------+------------------------------------------------+
Figure 6: ODUj into OPUk Mapping Types (Source: [G.709-2012], Tables7-10)
图6:ODUj到OPUk映射类型（来源：[G.709-2012]，表7-10）
Specific information could be defined in order to carry the multiplexing hierarchy and adaptation information (i.e., TS granularity / PT and AMP / GMP) to enable precise path selection. That way, when the penultimate node (or the intermediate node performing the ERO expansion) receives such an object, together with the Traffic Parameters Object, it is possible to choose the correct interface towards the egress node.
可以定义特定信息以携带复用层次结构和适配信息（即TS粒度/PT和AMP/GMP），从而实现精确的路径选择。这样，当倒数第二个节点（或执行ERO扩展的中间节点）接收到这样的对象以及业务参数对象时，可以选择朝向出口节点的正确接口。
In conclusion, both routing and signaling need to be extended to appropriately represent the TS granularity/PT information. Routing needs to represent a link's TS granularity and PT capabilities as well as the supported multiplexing hierarchy. Signaling needs to represent the TS granularity/PT and multiplexing hierarchy encoding.
总之，路由和信令都需要扩展以适当地表示TS粒度/PT信息。路由需要表示链路的TS粒度和PT能力以及支持的多路复用层次结构。信令需要表示TS粒度/PT和复用层次编码。
[RFC4328] supports only the deprecated auto-MSI mode, which assumes that the Tributary Port Number (TPN) is automatically assigned in the transmit direction and is not checked in the receive direction.
[RFC4328]仅支持不推荐使用的自动MSI模式，该模式假定支路端口号（TPN）在传输方向上自动分配，而在接收方向上不检查。
As described in [G.709-2012] and [G.798], the OPUk overhead in an OTUk frame contains n (n = the total number of TSs of the ODUk) MSI bytes (in the form of multiframe), each of which is used to indicate the association between the TPN and TS of the ODUk.
如[G.709-2012]和[G.798]所述，OTUk帧中的OPUk开销包含n个（n=ODUk的TSs总数）MSI字节（以多帧的形式），每个字节用于指示ODUk的TPN和TS之间的关联。
The association between the TPN and TS has to be configured by the control plane and checked by the data plane on each side of the link. (Please refer to [RFC7062] for further details.) As a consequence, the RSVP-TE signaling needs to be extended to support the TPN assignment function.
TPN和TS之间的关联必须由控制平面配置，并由链路每侧的数据平面检查。（详情请参考[RFC7062]）因此，RSVP-TE信令需要扩展以支持TPN分配功能。
From a routing perspective, GMPLS OSPF [RFC4203] and GMPLS IS-IS [RFC5307] only allow advertising interfaces [RFC4328] (the single TS type) without the capability of providing precise information about bandwidth-specific allocation. For example, in case of link bundling, when dividing the unreserved bandwidth by the MAX LSP bandwidth, it is not possible to know the exact number of LSPs at MAX LSP bandwidth size that can be set up (see the example in Figure 3).
从路由的角度来看，GMPLS OSPF[RFC4203]和GMPLS IS-IS[RFC5307]只允许广告接口[RFC4328]（单一TS类型），而不能提供有关特定带宽分配的精确信息。例如，在链路捆绑的情况下，当将无保留带宽除以最大LSP带宽时，不可能知道可以设置的最大LSP带宽大小下LSP的确切数量（参见图3中的示例）。
The lack of spatial allocation heavily impacts the restoration process because the lack of information on free resources highly increases the number of crankbacks affecting network convergence time.
空间分配的缺乏严重影响了恢复过程，因为缺少有关可用资源的信息会大大增加影响网络收敛时间的回退次数。
Moreover, actual tools provided by [RFC4203] and [RFC5307] only allow advertising signal types with fixed bandwidth and implicit hierarchy (e.g., Synchronous Digital Hierarchy (SDH) networks / Synchronous Optical Networks (SONETs)) or variable bandwidth with no hierarchy (e.g., packet switching networks); but, they do not provide the means for advertising networks with a mixed approach (e.g., ODUflex Constant Bit Rate (CBR) and ODUflex packet).
此外，[RFC4203]和[RFC5307]提供的实际工具仅允许具有固定带宽和隐式层次结构的广告信号类型（例如，同步数字层次结构（SDH）网络/同步光网络（SONET））或不具有层次结构的可变带宽（例如，分组交换网络）；但是，它们不提供混合方法（例如，ODUflex恒定比特率（CBR）和ODUflex分组）的广告网络方法。
For example, when advertising ODU0 as MIN LSP bandwidth and ODU4 as MAX LSP bandwidth, it is not possible to state whether the advertised link supports ODU4 and ODUflex or ODU4, ODU3, ODU2, ODU1, ODU0, and ODUflex. Such ambiguity is not present in SDH networks where the hierarchy is implicit and flexible containers like ODUflex do not exist. The issue could be resolved by declaring 1 Interface Switching Capability Descriptor (ISCD) for each signal type actually supported by the link.
例如，当将ODU0公布为最小LSP带宽而将ODU4公布为最大LSP带宽时，不可能说明公布的链路是否支持ODU4和ODUflex或ODU4、ODU3、ODU2、ODU1、ODU0和ODUflex。这种模糊性在SDH网络中不存在，因为SDH网络的层次结构是隐式的，并且不存在像ODUflex这样的灵活容器。该问题可以通过为链路实际支持的每种信号类型声明1个接口交换能力描述符（ISCD）来解决。
Suppose, for example, there is an equivalent ODU2 unreserved bandwidth in a TE link (with bundling capability) distributed on 4 ODU1; it would be advertised via the ISCD in this way:
例如，假设分布在4个ODU1上的TE链路（具有捆绑功能）中存在等效的ODU2无保留带宽；它将通过ISCD以以下方式进行宣传：
MAX LSP Bandwidth: ODU1
最大LSP带宽：ODU1
MIN LSP Bandwidth: ODU1
最小LSP带宽：ODU1
- Maximum Reservable Bandwidth (of the bundle) set to ODU2
- （捆绑包的）最大可保留带宽设置为ODU2
- Unreserved Bandwidth (of the bundle) set to ODU2
- （捆绑包的）未保留带宽设置为ODU2
In conclusion, the routing extensions defined in [RFC4203] and [RFC5307] require a different ISCD per signal type in order to advertise each supported container. This motivates an attempt to look for a more optimized solution without proliferation of the number of ISCDs advertised.
总之，[RFC4203]和[RFC5307]中定义的路由扩展需要每个信号类型具有不同的ISCD，以便公布每个受支持的容器。这促使人们试图寻找一种更优化的解决方案，而不增加所宣传的ISCD数量。
Per [RFC2328], OSPF messages are directly encapsulated in IP datagrams and depend on IP fragmentation when transmitting packets larger than the network's MTU. [RFC2328] recommends that "IP fragmentation should be avoided whenever possible". This recommendation further constrains solutions since OSPF does not support any generic mechanism to fragment OSPF Link State Advertisements (LSAs). Even when used in IP environments, IS-IS [RFC1195] does not support message sizes larger than a link's maximum frame size.
根据[RFC2328]，OSPF消息直接封装在IP数据报中，并在传输大于网络MTU的数据包时依赖IP碎片。[RFC2328]建议“尽可能避免IP碎片化”。该建议进一步限制了解决方案，因为OSPF不支持任何将OSPF链路状态播发（LSA）分段的通用机制。即使在IP环境中使用，IS-IS[RFC1195]也不支持大于链路最大帧大小的消息大小。
With respect to link bundling [RFC4201], the utilization of the ISCD as it is would not allow precise advertising of spatial bandwidth allocation information unless using only one component link per TE link.
关于链路捆绑[RFC4201]，除非每个TE链路仅使用一个组件链路，否则ISCD的使用将不允许空间带宽分配信息的精确广告。
On the other hand, from a signaling point of view, [RFC4328] describes GMPLS signaling extensions to support the control of G.709 OTNs defined before 2011 [G.709-2001]. However, [RFC4328] needs to be updated because it does not provide the means to signal all the new signal types and related mapping and multiplexing functionalities.
另一方面，从信令的角度来看，[RFC4328]描述了GMPLS信令扩展，以支持2011年之前定义的G.709 OTN的控制[G.709-2001]。但是，[RFC4328]需要更新，因为它不提供所有新信号类型和相关映射和多路复用功能的信号方式。
In the current traffic parameters signaling, bit rate and tolerance are implicitly defined by the signal type. ODUflex CBR and ODUflex packet can have variable bit rates (please refer to [RFC7062], Table 2); hence, signaling traffic parameters need to be upgraded. With respect to tolerance, there is no need to upgrade GMPLS protocols as a fixed value (+/-100 parts per million (ppm) or +/-20 ppm depending on the signal type) is defined for each signal type.
在当前的业务参数信令中，比特率和容差由信号类型隐式定义。ODUflex CBR和ODUflex数据包可以具有可变比特率（请参阅[RFC7062]，表2）；因此，需要升级信令业务参数。关于公差，无需升级GMPLS协议，因为为每种信号类型定义了固定值（+/-100 ppm）或+/-20 ppm，具体取决于信号类型。
Unreserved resources need to be advertised per priority and per signal type in order to allow the correct functioning of the restoration process. [RFC4203] only allows advertising unreserved resources per priority; this leads to uncertainty about how many LSPs of a specific signal type can be restored. As an example, consider the scenario depicted in the following figure.
需要按优先级和信号类型公布未保留的资源，以便恢复过程正常运行。[RFC4203]仅允许按优先级发布无保留资源；这导致了特定信号类型的LSP可恢复数量的不确定性。作为一个例子，考虑下面图中描述的场景。
+------+ component link 1 +------+
| +------------------+ |
| | component link 2 | |
| N1 +------------------+ N2 |
| | component link 3 | |
| +------------------+ |
+------+ +---+--+
+------+ component link 1 +------+
| +------------------+ |
| | component link 2 | |
| N1 +------------------+ N2 |
| | component link 3 | |
| +------------------+ |
+------+ +---+--+
Figure 7: Concurrent Path Computation
图7：并发路径计算
Consider the case where a TE link is composed of three ODU3 component links with 32 TSs available on the first one, 24 TSs on the second, and 24 TSs on the third and is supporting ODU2 and ODU3 signal types. The node would advertise a TE link with unreserved bandwidth equal to 80 TSs and a MAX LSP bandwidth equal to 32 TSs. In case of restoration, the network could try to restore two ODU3s (64 TSs) in such a TE link while only a single ODU3 can be set up, and a crankback would be originated. In more complex network scenarios, the number of crankbacks can be much higher.
考虑TE链路由三个ODU3组件链路组成的情况，其中第一个可用32个TSS，第二个24个TSS，第三个上有24个TSS，并且支持ODU2和ODU3信号类型。该节点将公布一个TE链路，其无保留带宽等于80 TSs，最大LSP带宽等于32 TSs。在恢复的情况下，网络可以尝试在这样一个TE链路中恢复两个ODU3（64个TSs），而只能设置一个ODU3，并且会启动回退。在更复杂的网络场景中，回退的数量可能要高得多。
Maximum LSP bandwidth is currently advertised per priority in the common part of the ISCD. Section 5 reviews some of the implications of advertising OTN information using ISCDs and identifies the need for a more optimized solution. While strictly not required, such an optimization effort should also consider the optimization of the per-priority maximum LSP bandwidth advertisement of both fixed and variable ODU types.
最大LSP带宽当前在ISCD的公共部分按优先级公布。第5节回顾了使用ISCD广告OTN信息的一些含义，并确定了对更优化解决方案的需求。虽然严格地不需要，这样的优化工作还应该考虑优化固定和可变ODU类型的每个优先级最大LSP带宽广告。
The capability advertised by an interface needs further distinction in order to separate terminating and switching capabilities. Due to internal constraints and/or limitations, the type of signal being advertised by an interface could just be switched (i.e., forwarded to the switching matrix without multiplexing/demultiplexing actions), terminated (demultiplexed), or both. The following figures help explain the switching and terminating capabilities.
接口公布的功能需要进一步区分，以便分离终端和交换功能。由于内部约束和/或限制，接口正在播发的信号类型可以只是切换（即，在没有多路复用/解多路复用动作的情况下转发到交换矩阵）、终止（解多路复用）或两者兼而有之。下图有助于解释切换和端接功能。
MATRIX LINE INTERFACE
+-----------------+ +-----------------+
| +-------+ | ODU2 | |
----->| ODU2 |----|----------|--------\ |
| +-------+ | | +----+ |
| | | \__/ |
| | | \/ |
| +-------+ | ODU3 | | ODU3 |
----->| ODU3 |----|----------|------\ | |
| +-------+ | | \ | |
| | | \| |
| | | +----+ |
| | | \__/ |
| | | \/ |
| | | ---------> OTU3
+-----------------+ +-----------------+
MATRIX LINE INTERFACE
+-----------------+ +-----------------+
| +-------+ | ODU2 | |
----->| ODU2 |----|----------|--------\ |
| +-------+ | | +----+ |
| | | \__/ |
| | | \/ |
| +-------+ | ODU3 | | ODU3 |
----->| ODU3 |----|----------|------\ | |
| +-------+ | | \ | |
| | | \| |
| | | +----+ |
| | | \__/ |
| | | \/ |
| | | ---------> OTU3
+-----------------+ +-----------------+
Figure 8: Switching and Terminating Capabilities
图8：交换和端接功能
The figure in the example shows a line interface that is able to:
示例中的图显示了一个行接口，它能够：
o Multiplex an ODU2 coming from the switching matrix into an ODU3 and map it into an OTU3
o 将来自交换矩阵的ODU2多路复用到ODU3，并将其映射到OTU3
o Map an ODU3 coming from the switching matrix into an OTU3
o 将来自交换矩阵的ODU3映射到OTU3
In this case, the interface bandwidth advertised is ODU2 with switching capability and ODU3 with both switching and terminating capabilities.
在这种情况下，公布的接口带宽是具有交换能力的ODU2和具有交换和终止能力的ODU3。
This piece of information needs to be advertised together with the related unreserved bandwidth and signal type. As a consequence, signaling must have the capability to set up an LSP, allowing the local selection of resources to be consistent with the limitations considered during the path computation.
此信息需要与相关的无保留带宽和信号类型一起发布。因此，信令必须具有建立LSP的能力，允许资源的本地选择与路径计算期间考虑的限制一致。
In Figure 9 and Figure 10, there are two examples of the terminating/ switching capability differentiation. In both examples, all nodes only support single-stage capability. Figure 9 represents a scenario in which a failure on link B-C forces node A to calculate another ODU2 LSP carrying ODU0 service along the nodes B-E-D. As node D is a single stage capable node, it is able to extract ODU0 service only from the ODU2 interface. Node A has to know that from E to D exists an available OTU2 link from which node D can extract the ODU0 service. This information is required in order to avoid the OTU3 link being considered in the path computation.
在图9和图10中，有两个端接/交换能力差异的示例。在这两个示例中，所有节点都只支持单级功能。图9显示了一个场景，其中链路B-C上的故障迫使节点a计算另一个ODU2 LSP，该ODU2 LSP沿着节点B-E-D承载ODU0服务。由于节点D是具有单级功能的节点，因此它只能从ODU2接口提取ODU0服务。节点A必须知道从E到D存在一个可用的OTU2链路，节点D可以从中提取ODU0服务。为了避免在路径计算中考虑OTU3链路，需要此信息。
ODU0 Transparently Transported
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
| ODU2 LSP Carrying ODU0 Service |
| |'''''''''''''''''''''''''''''''''''''''''''| |
| | | |
| +----++ OTU2 +-----+ OTU2 +-----+ OTU2 ++----+ |
ODU0 | | Link | | Link | | Link | | ODU0
---->| A |_________| B |_________| C |_________| D |---->
| | | | | | | |
+-----+ +--+--+ +-----+ ++--+-+
| | |
OTU3| | |
Link| +-----+__________________| |
| | | OTU3 Link |
|____| E | |
| |_____________________|
+-----+ OTU2 Link
ODU0 Transparently Transported
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
| ODU2 LSP Carrying ODU0 Service |
| |'''''''''''''''''''''''''''''''''''''''''''| |
| | | |
| +----++ OTU2 +-----+ OTU2 +-----+ OTU2 ++----+ |
ODU0 | | Link | | Link | | Link | | ODU0
---->| A |_________| B |_________| C |_________| D |---->
| | | | | | | |
+-----+ +--+--+ +-----+ ++--+-+
| | |
OTU3| | |
Link| +-----+__________________| |
| | | OTU3 Link |
|____| E | |
| |_____________________|
+-----+ OTU2 Link
Figure 9: Switching and Terminating Capabilities - Example 1
图9：交换和端接功能-示例1
Figure 10 addresses the scenario in which the restoration of the ODU2 LSP (A-B-C-D) is required. The two bundled component links between B and E could be used, but the ODU2 over the OTU2 component link can only be terminated and not switched. This implies that it cannot be used to restore the ODU2 LSP (A-B-C-D). However, such ODU2 unreserved bandwidth must be advertised since it can be used for a different ODU2 LSP terminating on E, e.g., F-B-E. Node A has to know that the ODU2 capability on the OTU2 link can only be terminated, and that the restoration of A-B-C-D can only be performed using the ODU2 bandwidth available on the OTU3 link.
图10描述了需要恢复ODU2 LSP（A-B-C-D）的场景。可以使用B和E之间的两个捆绑组件链路，但OTU2组件链路上的ODU2只能终止，不能切换。这意味着它不能用于恢复ODU2 LSP（A-B-C-D）。然而，这种ODU2非保留带宽必须被公布，因为它可以用于在E上终止的不同ODU2 LSP，例如F-B-E。节点a必须知道OTU2链路上的ODU2能力只能被终止，并且a-B-C-D的恢复只能使用OTU3链路上可用的ODU2带宽来执行。
ODU0 Transparently Transported
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
| ODU2 LSP Carrying ODU0 Service |
| |'''''''''''''''''''''''''''''''''''''''''''| |
| | | |
| +----++ OTU2 +-----+ OTU2 +-----+ OTU2 ++----+ |
ODU0 | | Link | | Link | | Link | | ODU0
---->| A |_________| B |_________| C |_________| D |---->
| | | | | | | |
+-----+ ++-+-++ +-----+ +--+--+
| | | |
OTU2| | | |
+-----+ Link| | | OTU3 +-----+ |
| | | | | Link | | |
| F |_______| | |___________| E |___________|
| | |_____________| | OTU2 Link
+-----+ OTU2 Link +-----+
ODU0 Transparently Transported
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
| ODU2 LSP Carrying ODU0 Service |
| |'''''''''''''''''''''''''''''''''''''''''''| |
| | | |
| +----++ OTU2 +-----+ OTU2 +-----+ OTU2 ++----+ |
ODU0 | | Link | | Link | | Link | | ODU0
---->| A |_________| B |_________| C |_________| D |---->
| | | | | | | |
+-----+ ++-+-++ +-----+ +--+--+
| | | |
OTU2| | | |
+-----+ Link| | | OTU3 +-----+ |
| | | | | Link | | |
| F |_______| | |___________| E |___________|
| | |_____________| | OTU2 Link
+-----+ OTU2 Link +-----+
Figure 10: Switching and Terminating Capabilities - Example 2
图10：交换和端接能力-示例2
The issue shown above is analyzed in an OTN context, but it is a general technology-independent GMPLS limitation.
上面所示的问题是在OTN上下文中分析的，但它是一个与一般技术无关的GMPLS限制。
[RFC4202] defines eight priorities for resource availability and usage. As defined, each is advertised independent of the number of priorities supported by a network, and even unsupported priorities are included. As is the case in Section 8, addressing any inefficiency with such advertisements is not required to support OTNs. But, any such inefficiency should also be considered as part of the optimization effort identified in Section 5.
[RFC4202]定义了资源可用性和使用的八个优先级。根据定义，每一个都独立于网络支持的优先级数量进行广告，甚至包括不支持的优先级。与第8节中的情况一样，解决此类广告的任何低效问题不需要支持OTN。但是，任何此类低效也应被视为第5节中确定的优化工作的一部分。
With reference to [RFC7062], the introduction of multi-stage multiplexing implies the advertisement of cascaded adaptation capabilities together with the matrix access constraints. The structure defined by the IETF for the advertisement of adaptation capabilities is the Interface Adaptation Capability Descriptor (IACD), as defined in [RFC6001].
参考[RFC7062]，多级多路复用的引入意味着级联自适应能力以及矩阵访问约束的公布。IETF为发布适配能力而定义的结构是[RFC6001]中定义的接口适配能力描述符（IACD）。
With respect to routing, please note that in case of multi-stage multiplexing hierarchy (e.g., ODU1->ODU2->ODU3), not only the ODUk/ OTUk bandwidth (ODU3) and service-layer bandwidth (ODU1) are needed but also the intermediate one (ODU2). This is a typical case of a spatial allocation problem.
关于路由，请注意，在多级复用层次结构（例如ODU1->ODU2->ODU3）的情况下，不仅需要ODUk/OTUk带宽（ODU3）和服务层带宽（ODU1），还需要中间带宽（ODU2）。这是一个典型的空间分配问题。
In this scenario, suppose the following advertisement:
在此场景中，假设以下广告：
Hierarchy: ODU1->ODU2->ODU3
Hierarchy: ODU1->ODU2->ODU3
Number of ODU1==5
ODU1的数量==5
The number of ODU1 suggests that it is possible to have an ODU2 FA, but it depends on the spatial allocation of such ODU1s.
ODU1的数量表明可能有ODU2 FA，但这取决于ODU1的空间分配。
It is possible that two links are bundled together and three ODU1->ODU2->ODU3 are available on a component link and two on the other one; in such a case, the ODU2 FA could not be set up. The advertisement of the ODU2 is needed because in case of ODU1 spatial allocation (3+2), the ODU2 available bandwidth would be 0 (ODU2 FA cannot be created), while in case of ODU1 spatial allocation (4+1), the ODU2 available bandwidth would be 1 (1 ODU2 FA can be created).
可能两个链接捆绑在一起，一个组件链接上有三个ODU1->ODU2->ODU3，另一个组件链接上有两个；在这种情况下，无法设置ODU2 FA。需要公布ODU2，因为在ODU1空间分配（3+2）的情况下，ODU2可用带宽将为0（无法创建ODU2 FA），而在ODU1空间分配（4+1）的情况下，ODU2可用带宽将为1（可以创建1个ODU2 FA）。
The information stated above implies augmenting both the ISCD and the IACD.
上述信息意味着增加ISCD和IACD。
The ODUk label format defined in [RFC4328] could be updated to support new signal types as defined in [G.709-2012], but it would be difficult to further enhance it to support possible new signal types.
[RFC4328]中定义的ODUk标签格式可以更新，以支持[G.709-2012]中定义的新信号类型，但很难进一步增强它以支持可能的新信号类型。
Furthermore, such a label format may have scalability issues due to the high number of labels needed when signaling large LSPs. For example, when an ODU3 is mapped into an ODU4 with 1.25 Gbit/s tributary slots, it would require the utilization of 31 labels (31*4*8=992 bits) to be allocated, while an ODUflex into an ODU4 may need up to 80 labels (80*4*8=2560 bits).
此外，由于在发信号通知大型lsp时需要大量标签，因此这种标签格式可能存在可伸缩性问题。例如，当ODU3映射到具有1.25 Gbit/s分支插槽的ODU4时，需要使用31个标签（31*4*8=992位）进行分配，而ODU4中的ODUflex可能需要多达80个标签（80*4*8=2560位）。
A new flexible and scalable ODUk label format needs to be defined.
需要定义一种新的灵活且可扩展的ODUk标签格式。
This document provides an evaluation of OTN requirements against actual routing ([RFC4202], [RFC4203], and [RFC5307]) and signaling mechanisms ([RFC3471], [RFC3473], and [RFC4328]) in GMPLS.
本文件针对GMPLS中的实际路由（[RFC4202]、[RFC4203]和[RFC5307]）和信令机制（[RFC3471]、[RFC3473]和[RFC4328]）对OTN需求进行了评估。
This document defines new types of information to be carried that describes OTN containers and hierarchies. It does not define any new protocol elements, and from a security standpoint, this memo does not introduce further risks with respect to the information that can be currently conveyed via GMPLS protocols. For a general discussion on MPLS and GMPLS-related security issues, see the MPLS/GMPLS security framework [RFC5920].
本文档定义了描述OTN容器和层次结构的新信息类型。它没有定义任何新的协议元素，并且从安全角度来看，本备忘录不会对当前可通过GMPLS协议传输的信息带来进一步的风险。有关MPLS和GMPLS相关安全问题的一般性讨论，请参阅MPLS/GMPLS安全框架[RFC5920]。
Jonathan Sadler Tellabs EMail: jonathan.sadler@tellabs.com
乔纳森·萨德勒告诉我们电子邮件：乔纳森。sadler@tellabs.com
John Drake Juniper EMail: jdrake@juniper.net
John Drake Juniper电子邮件：jdrake@juniper.net
Francesco Fondelli Ericsson Via Moruzzi 1 Pisa - 56100 EMail: francesco.fondelli@ericsson.com
Francesco Fondelli Ericsson通过Moruzzi 1 Pisa-56100电子邮件：Francesco。fondelli@ericsson.com
The authors would like to thank Lou Berger, Eve Varma, and Sergio Lanzone for their precious collaboration and review.
作者要感谢Lou Berger、Eve Varma和Sergio Lanzone的宝贵合作和评论。
[G.709-2001] ITU-T, "Interfaces for the Optical Transport Network (OTN)", G.709/Y.1331 Recommendation, February 2001.
[G.709-2001]ITU-T，“光传输网络（OTN）接口”，G.709/Y.1331建议，2001年2月。
[G.709-2012] ITU-T, "Interfaces for the Optical Transport Network (OTN)", G.709/Y.1331 Recommendation, February 2012.
[G.709-2012]ITU-T，“光传输网络（OTN）接口”，G.709/Y.1331建议，2012年2月。
[G.798] ITU-T, "Characteristics of Optical Transport Network Hierarchy Equipment Functional Blocks", G.798 Recommendation, December 2012.
[G.798]ITU-T，“光传输网络层次结构设备功能块的特征”，G.798建议，2012年12月。
[G.872] ITU-T, "Architecture of Optical Transport Networks", G.872 Recommendation, October 2012.
[G.872]ITU-T，“光传输网络体系结构”，G.872建议，2012年10月。
[RFC1195] Callon, R., "Use of OSI IS-IS for routing in TCP/IP and dual environments", RFC 1195, December 1990.
[RFC1195]Callon，R.，“OSI IS-IS在TCP/IP和双环境中的路由使用”，RFC 11951990年12月。
[RFC3471] Berger, L., "Generalized Multi-Protocol Label Switching (GMPLS) Signaling Functional Description", RFC 3471, January 2003.
[RFC3471]Berger，L.“通用多协议标签交换（GMPLS）信令功能描述”，RFC 3471，2003年1月。
[RFC3473] Berger, L., "Generalized Multi-Protocol Label Switching (GMPLS) Signaling Resource ReserVation Protocol-Traffic Engineering (RSVP-TE) Extensions", RFC 3473, January 2003.
[RFC3473]Berger，L.“通用多协议标签交换（GMPLS）信令资源预留协议流量工程（RSVP-TE）扩展”，RFC 3473，2003年1月。
[RFC4202] Kompella, K. and Y. Rekhter, "Routing Extensions in Support of Generalized Multi-Protocol Label Switching (GMPLS)", RFC 4202, October 2005.
[RFC4202]Kompella，K.和Y.Rekhter，“支持通用多协议标签交换（GMPLS）的路由扩展”，RFC 4202，2005年10月。
[RFC4203] Kompella, K. and Y. Rekhter, "OSPF Extensions in Support of Generalized Multi-Protocol Label Switching (GMPLS)", RFC 4203, October 2005.
[RFC4203]Kompella，K.和Y.Rekhter，“支持通用多协议标签交换（GMPLS）的OSPF扩展”，RFC 4203，2005年10月。
[RFC4328] Papadimitriou, D., "Generalized Multi-Protocol Label Switching (GMPLS) Signaling Extensions for G.709 Optical Transport Networks Control", RFC 4328, January 2006.
[RFC4328]Papadimitriou，D.，“G.709光传输网络控制的通用多协议标签交换（GMPLS）信令扩展”，RFC 4328，2006年1月。
[RFC5307] Kompella, K. and Y. Rekhter, "IS-IS Extensions in Support of Generalized Multi-Protocol Label Switching (GMPLS)", RFC 5307, October 2008.
[RFC5307]Kompella，K.和Y.Rekhter，“支持通用多协议标签交换（GMPLS）的IS-IS扩展”，RFC 5307，2008年10月。
[RFC6001] Papadimitriou, D., Vigoureux, M., Shiomoto, K., Brungard, D., and JL. Le Roux, "Generalized MPLS (GMPLS) Protocol Extensions for Multi-Layer and Multi-Region Networks (MLN/ MRN)", RFC 6001, October 2010.
[RFC6001]Papadimitriou，D.，Vigoureux，M.，Shiomoto，K.，Brungard，D.，和JL。Le Roux，“多层和多区域网络（MLN/MRN）的通用MPLS（GMPLS）协议扩展”，RFC 60012010年。
[OTN-OSPF] Ceccarelli, D., Ed., Zhang, F., Belotti, S., Rao, R., and J. Drake, "Traffic Engineering Extensions to OSPF for Generalized MPLS (GMPLS) Control of Evolving G.709 OTN Networks", Work in Progress, December 2013.
[OTN-OSPF]Ceccarelli，D.，Ed.，Zhang，F.，Belotti，S.，Rao，R.，和J.Drake，“用于通用MPLS（GMPLS）控制演进中的G.709 OTN网络的OSPF流量工程扩展”，正在进行中的工作，2013年12月。
[OTN-RSVP] Zhang, F., Ed., Zhang, G., Belotti, S., Ceccarelli, D., and K. Pithewan, "Generalized Multi-Protocol Label Switching (GMPLS) Signaling Extensions for the evolving G.709 Optical Transport Networks Control", Work in Progress, September 2013.
[OTN-RSVP]Zhang，F.，Ed.，Zhang，G.，Belotti，S.，Ceccarelli，D.，和K.Pithewan，“发展中的G.709光传输网络控制的通用多协议标签交换（GMPLS）信令扩展”，正在进行的工作，2013年9月。
[RFC2328] Moy, J., "OSPF Version 2", STD 54, RFC 2328, April 1998.
[RFC2328]Moy，J.，“OSPF版本2”，STD 54，RFC 2328，1998年4月。
[RFC4201] Kompella, K., Rekhter, Y., and L. Berger, "Link Bundling in MPLS Traffic Engineering (TE)", RFC 4201, October 2005.
[RFC4201]Kompella，K.，Rekhter，Y.，和L.Berger，“MPLS流量工程（TE）中的链路捆绑”，RFC 42012005年10月。
[RFC5920] Fang, L., "Security Framework for MPLS and GMPLS Networks", RFC 5920, July 2010.
[RFC5920]方，L，“MPLS和GMPLS网络的安全框架”，RFC 5920，2010年7月。
[RFC7062] Zhang, F., Li, D., Li, H., Belotti, S., and D. Ceccarelli, "Framework for GMPLS and PCE Control of G.709 Optical Transport Networks", RFC 7062, November 2013.
[RFC7062]Zhang，F.，Li，D.，Li，H.，Belotti，S.，和D.Ceccarelli，“G.709光传输网络的GMPLS和PCE控制框架”，RFC 7062，2013年11月。
Authors' Addresses
作者地址
Sergio Belotti (editor) Alcatel-Lucent Via Trento, 30 Vimercate Italy EMail: sergio.belotti@alcatel-lucent.com
塞尔吉奥·贝洛蒂（编辑）阿尔卡特·朗讯通过意大利维梅卡特30号特伦托发送电子邮件：塞尔吉奥。belotti@alcatel-朗讯网
Pietro Vittorio Grandi Alcatel-Lucent Via Trento, 30 Vimercate Italy EMail: pietro_vittorio.grandi@alcatel-lucent.com
皮埃特罗·维托里奥·格兰迪·阿尔卡特·朗讯通过意大利维梅卡特30号特伦托发送电子邮件：皮埃特罗·维托里奥。grandi@alcatel-朗讯网
Daniele Ceccarelli (editor) Ericsson Via A. Negrone 1/A Genova - Sestri Ponente Italy EMail: daniele.ceccarelli@ericsson.com
Daniele Ceccarelli（编辑）爱立信通过A.Negrone 1/A Genova-Sestri Ponente意大利电子邮件：Daniele。ceccarelli@ericsson.com
Diego Caviglia Ericsson Via A. Negrone 1/A Genova - Sestri Ponente Italy EMail: diego.caviglia@ericsson.com
Diego Caviglia Ericsson通过A.Negrone 1/A Genova-Sestri Ponente Italy电子邮件：Diego。caviglia@ericsson.com
Fatai Zhang Huawei Technologies F3-5-B R&D Center, Huawei Base Bantian, Longgang District Shenzhen 518129 P.R. China Phone: +86-755-28972912 EMail: zhangfatai@huawei.com
中国深圳市龙岗区华为基地坂田华为技术F3-5-B研发中心，邮编：518129电话：+86-755-28972912电子邮件：zhangfatai@huawei.com
Dan Li Huawei Technologies F3-5-B R&D Center, Huawei Base Bantian, Longgang District Shenzhen 518129 P.R. China Phone: +86-755-28973237 EMail: danli@huawei.com
中国深圳市龙岗区华为基地坂田华为技术F3-5-B研发中心李丹电话：+86-755-28973237电子邮件：danli@huawei.com