The Research of Packet Transmission Network (PTN) based on T-MPLS

我这纯属自投罗网……大米在QQ签名上求好人帮译东西，我看到翻译俩字就兴奋……

然后就自投罗网了

不过还好，大米说有张电影票，崔崔说他也提供一张

那就是两张……谁陪我去看呢？

这个交易真是复杂啊：大米欠崔崔的人情答应帮译，结果转嫁到我头上……而崔崔好像是被某位老师栽到的……

于是我有了第一次翻译学术论文的尝试

Google翻译其实挺不错的，很多专业词汇表达都省了，我只用调整语法结构……纯技术活，没什么创作感，不好玩。下次不干了。还是译着玩玩好！

中英文都在下面

只翻了三分之一，大米说我只用翻一半就OK了

查看最新进度在这个google文档 蓝色的是最新进度点。

这篇日志会有人看吗？

基于 T-MPLS 的 分组传送网 (PTN) 的研究

摘要: DSL 技术的成功应用 、FTTH技术的逐步普及、 传统网络向 NGN 的演进 ， 业务承载的 IP 化趋势已 经 形成，未来 面向全业务运营 的光传输网络将主要负责 IP/ 以太网流量的传送，为分组的流量特征而优化，向着智能、融合、宽带、 高效、可靠的分组传送技术(PTN) 方向发展 。基于 T - MPLS技术的 PTN ，能够支持所有类型的业务（Ethernet, IP/MPLS, FR, ATM, TDM, …） ， 能够同时支持普通用户（有线/无线）和商业用户的各种业务发展 ， 将成为 新一代 融合网络的 PTN 平台。 本文从 T-MPLS 协议体系的框架、分层结构、网络模型、业务承载、保护倒换机制等方面分析 PTN的 关键技术。并提出面向全业务运营的 PTN 建设 方案 。

关键词： PTN T - MPLS 网络模型 业务承载 保护倒换机制

1 引言

在固网中，一方面 DSL 技术的成功应用 、FTTH技术的逐步普及， 已经把 2M 甚至更高的 带宽送到了最终用户家中，宽带用户数的持续增长导致了巨大的带宽需求，省际干线以上的传输网中数据流量已占到总流量的 90% 以上；另一方面，传统网络向 NGN 的演进也使得长途话音流量中 VoIP 流量超过了总通话时长的 60% 。 可以确定，不久的将来 ， 基于IP的视频 业务 迅猛增长和 xDSL/xPON/FTTH 技术的进一步发展将加速固网中 IP 业务量的增长 势头 。 同时 ，移动核心网 IP 化 已成为现实； 3G /B3G无线接入侧 也将从初期的 E1/IMA E1 转为以以太网接口为主。由政府和企业主导，运营商积极推动的行业信息化进程也带动了一系列新型宽带增值业务的蓬勃开展，安全、可管理并易操作的 VPN 业务需求迅速增长，而 IP 技术内在的优势能够使得这些应用的实现方式更丰富、更便捷、更灵活。业务承载的 IP 化趋势已在业内形成共识，未来 面向全业务运营 的光传输网络将主要负责 IP/ 以太网流量的传送，为分组的流量特征而优化，向着智能、融合、宽带、 高效、可靠的分组传送技术 方向发展。分组传送网 (PTN) 的概念就是在这样的背景下应运而生的。

PTN 的出现是光传送网技术发展在通信业务提供商现实的网络和业务环境下的必然结果。最初设想的理想光传送网 IP over WDM 方案是 IP 分组通过简单的封装适配直接架构在智能的光层之上，适配层功能尽量简化从而限制在接口信号格式的范围内，然后由统一的控制平面在所有层面上 ( 分组，电路，波长，波带，光纤等 ) 实现最高效率的光纤带宽资源调度。这一目标很早就已明确，但其技术的成熟还有待时日。

由于光层智能化技术、分组 TDM 仿真和生存性机制还远未成熟，现在就彻底抛弃电路层的绝大多数功能将会使得网络过分依赖 IP 层，导致 IP 设备过分庞大，总体成本居高不下。 所以 在经济有效地光层带宽复用和调度技术出现之前，仍然需要一个智能的传送层面将各类业务高效、灵活地填充到光纤巨大的带宽通道中去， IP 与光层的融合焦点依然是承载效率和业务的可靠性、可管理性和扩展性。

PTN作为传送网技术，最低的每比特传送成本依然是最核心的要求，高可靠性、多业务同时基于分组业务特征而优化、可确定的服务质量、强大的OAM机制和网管能力等依然是其核心技术特征。在现有的技术条件和业务环境下，新建PTN层需要解决以下一些关键的技术问题：

• 在网络中的定位。PTN应该为L3/L2乃至L1用户提供符合IP流量特征而优化的传送层服务，往下可以构建在各种光/L1/以太网物理层之上；
• 承载的业务。PTN应承载以IP为主的各类现有业务，包括以太帧、MPLS (IP) 、ATM VP和VC、PDH、FR等等；
• 网络架构。PTN应该具有分层的网络体系架构，例如划分为段、通道和电路各个层面，每一层的功能定义完善，各层之间的相互接口关系明确清晰，使得网络具有较强的扩展性，适合大规模组网；
• 设备形态。PTN需要定义功能具体的设备形态，同时明确各种设备的网络中的位置以及所扮演的角色，从而便于产品的开发及组建实际网络；
• 业务服务质量 (QoS) 。要求确保IP业务电信级QoS，将SDH和ATM/IP技术中的带宽保证、优先级划分、同步等技术和概念结合起来，实现承载在IP之上的QoS敏感业务的有效传送。

PTN 的概念比较宽泛，在目前的网络和技术条件下有许多实现方案。许多厂家和标准化组织纷纷推出了不同程度 地 满足 PTN 功能需求的产品和技术，总体来说可分为以太网增强技术和 传输 技术 结合 MPLS 两大类，前者以 PBB-TE 为代表，后者以 T-MPLS 为代表。从目前发展来看，这两项技术更好地满足 了 PTN 目标网络的要求，可能成为未来 PTN 的主流技术方案。

(未完待续）

Abstract: With the successful application of DSL technology, the gradual popularization of FTTH technology ,and the evolution from traditional network to NGN, IP business bearing the trend has been formed. In the future, the optical transmission network of the entire business operations will be primarily responsible for IP / Ethernet traffic transmission, be optimized for the characteristics of data flow in groups, and will develop in a smart, integration, broadband, efficient, reliable packet transmission technology (PTN) direction. The PTN based on T-MPLS technology, supporting all types of business (Ethernet, IP / MPLS, FR, ATM, TDM,…), simultaneously supporting general users (wired / wireless) and commercial users in various types of business development, would become a new generation of converged networks of PTN platform. This article, analyzes the crucial technologies of PTN in respects of the T-MPLS system of the framework agreement, the hierarchical structure, the network model, operational capacity, protection switching mechanism, etc, and puts forward a PTN-building program facing the entire business operations.
Key words: PTN, T-MPLS, network business model, bearing ,protection switching mechanism
1 INTRODUCTION
In the fixed network, on the one hand the successful application of DSL technology and the gradual popularization of FTTH technology have sent bandwidth of 2M or even higher to the end-user’s home. The continuing grow of the number of broadband subscribers led to a huge demand for bandwidth. In the transmission network above inter-provincial route, the data flow has accounted for over 90 percent of the total flow. On the other hand, the evolution from traditional network to NGN also increases long-distance voice traffic flow in the VoIP calls over a total length of 60 percent. It is identified that, in the near future, IP-based video services and the rapid growth of xDSL / xPON / FTTH technology will accelerate the further development of IP in the fixed network business momentum of growth. At the same time, mobile core network IP has become a reality, and 3G/B3G wireless access side will also develop from the early E1/IMA E1 to Ethernet-based interface. Led by the government and enterprises, and actively promoted by operators, the process of the information industry has led a series of new broadband value-added business flourished. The demand for secure, easy to operate and manage VPN services grows rapidly. The inherent advantages of IP technology would be able to make the ways of these applications achieve a richer, more convenient, and more flexible level. The IP化趋势 of 业务负载 have come to a consensus in the industry. In the future, the entire business operations of the optical transmission network will be primarily responsible for IP / Ethernet transmission flow, be optimized for the characteristics of data flow in groups, and will develop in a smart, integration, broadband, efficient, reliable packet transmission technology (PTN) direction. The concept of Packet Transport Network (PTN) came into being against this background.
The emergence of PTN is an inevitable result of optical transport network technology development in the communications network service providers realistic business environment. Initially envisaged program of ideal optical transport network IP over WDM is that, IP packages are directly built above the framework of intelligent optical layer via a simple package adapter. The adaptation layer functions are condensed so as to limit the scope of the interface signal format, froming a unified control plane at all levels (sub-circuits, wavelength, the wave band, optical fiber, etc.) to achieve maximum efficiency of fiber bandwidth scheduling. This objective has been clear long ago, but its technical maturity is still in process.
Because the intelligent optical technology, simulation and TDM division survival mechanism are still far from mature. Completely abandoning the vast major functions of the circuit layer in a shot time will make excessive reliance on the IP network layer, resulting in massive over-IP equipment and the overall high cost. So before the emergence of an economic effective bandwidth multiplexing and scheduling technology , we still need an intelligent layer of transmission sending all kinds of business efficiently and flexibly to fill the enormous bandwidth fiber optic channels. The focus for the integrationof IP-layer and optic layer remains the reliability, manageability and scalability of carrying efficiency and operations.
PTN as a transmission network technology, the lowest cost per bit transmission is still the core requirements. Its core technology still involves high reliability, multi-service packet-based business also features optimized, determinable quality of services, strong OAM mechanisms and network management capabilities. Under the existing technology and business environment, the following key technical issues of the new PTN are still in a need to address :

• The orientation in the network. PTN should provide L3/L2 and L1 users with optimized service of transmission layer in accordance with IP traffic features, down able to be build on all kinds of light / L1 / Ethernet physical layers;
• Bearing the business. PTN should be capable to bear all types of existing IP-based business, including Ethernet frame, MPLS (IP), ATM VP and VC, PDH, FR, etc.;
• Network architecture. PTN should have a layered network architecture, such as the capability to be divided into paragraphs, accesses and circuit levels, each layer with well-defined functions, and all levels with clear interactions between interfaces in different levels, endowing the network with strong expansion, and suitable for large-scale network;
• Equipment shape. PTN need to define the specific functions of the form of equipment, the location and role of all the equipment in the network, thus facilitating product development and the formation of the actual network;
• Business quality of service (QoS). It requires to ensure the telecommunications business-class IP QoS, and combine the technilogies and concepts involving SDH and ATM / IP technology in the bandwidth that the level of priority, and synchronization, realizing the bearing in IP QoS on the effective transmission of sensitive business.

The concept of PTN is broad. There are many programs to realize it under the current network and technical conditions. Many manufacturers and standardization organizations have launched products and technologies in different levels of functionality to meet the needs of PTN. In general, they can be divided into two categories: the Ethernet technology and enhanced transmission technology with MPLS , the former to PBB-TE as the representative, the latter to T-MPLS as the representative. Judging from the current development of the two technologies, these two better meet the requirements of PTN goal of the network, and may become the mainstream of the future PTN technology programmes.

（to be continued)