[分享]分组传输网技术的发展

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<p class="MsoNormal"><span lang="ZH-CN" style="font-family: SimSun;"></span><span lang="EN-US"></span><span lang="ZH-CN" style="font-family: SimSun;">随着</span><st1chmetcnv wst="on" tcsc="0" numbertype="1" negative="False" hasspace="False" sourcevalue="3" unitname="g"><span lang="EN-US">3G</span></st1chmetcnv><span lang="ZH-CN" style="font-family: SimSun;">网络中</span><span lang="EN-US">TDM</span><span lang="ZH-CN" style="font-family: SimSun;">业务的逐步萎缩以及「</span><span lang="EN-US">ALLIP</span><span lang="ZH-CN" style="font-family: SimSun;">」的成熟，分组化多业务传送技术应运而生：</span><span lang="EN-US">TN</span><span lang="ZH-CN" style="font-family: SimSun;">（分组传送网络）和</span><span lang="EN-US">CE</span><span lang="ZH-CN" style="font-family: SimSun;">（电信级以太网）技术通过在统一的分组转发平面上承载不同的业务，简化了网络管理和维护，提高了业务汇聚的能力。</span><span lang="EN-US"><br/>
</span><span lang="EN-US"></span></p><p class="MsoNormal"><span lang="EN-US">——</span><span lang="EN-US"> PTN</span><span lang="ZH-CN" style="font-family: SimSun;">分组传送网络。</span><span lang="EN-US">TN</span><span lang="ZH-CN" style="font-family: SimSun;">定位于一种面向连接的网络技术，其思想是以</span><span lang="EN-US">T-MPLS</span><span lang="ZH-CN" style="font-family: SimSun;">（通用的多协议标记交换协议）和</span><span lang="EN-US">BT</span><span lang="ZH-CN" style="font-family: SimSun;">（电信级核心网传送协议）为核</span><span lang="ZH-CN">
                </span><span lang="ZH-CN" style="font-family: SimSun;">心、采用类似于</span><span lang="EN-US">SDH</span><span lang="ZH-CN" style="font-family: SimSun;">的端到端性能可管理的网络，来支持网络从当前向下一代网络的平滑演进。它主要用于多业务的环境，具备</span><span lang="ZH-CN">
                </span><span lang="EN-US">TDM/ATMoverPacket</span><span lang="ZH-CN" style="font-family: SimSun;">的业务接入、汇聚和传送能力及以太网的低成本和统计复用的特点，支持时钟</span><span lang="EN-US"></span><span lang="ZH-CN" style="font-family: SimSun;">同步、类似</span><span lang="EN-US">SDH</span><span lang="ZH-CN" style="font-family: SimSun;">的保护、以太网端到端的性能监控和管理维护。</span><span lang="EN-US"><br/>
</span><span lang="EN-US"></span></p><p class="MsoNormal"><span lang="EN-US">—— CE</span><span lang="ZH-CN" style="font-family: SimSun;">电信级以太网。</span><span lang="EN-US">CE</span><span lang="ZH-CN" style="font-family: SimSun;">电信级以太网是由以太网技术逐步发展而来的，同样以</span><span lang="EN-US">BT</span><span lang="ZH-CN" style="font-family: SimSun;">和</span><span lang="EN-US">T-MPLS</span><span lang="ZH-CN" style="font-family: SimSun;">协议为核心，可以支持电信级和可维护性的以太网业务的承</span><span lang="ZH-CN">
                </span><span lang="ZH-CN" style="font-family: SimSun;">载，同时可兼容</span><span lang="EN-US">TDM</span><span lang="ZH-CN" style="font-family: SimSun;">业务。目前</span><span lang="EN-US">CE</span><span lang="ZH-CN" style="font-family: SimSun;">虽然可以以较小的成本实现多业务的承载，但在全网端到端的安全可靠性、单波长系统带来的光纤资源问题上还没有好的解决</span><span lang="ZH-CN">
                </span><span lang="ZH-CN" style="font-family: SimSun;">办法。</span><span lang="EN-US"><br/>
</span><span lang="ZH-CN" style="font-family: SimSun;">事实上，</span><span lang="EN-US">CE</span><span lang="ZH-CN" style="font-family: SimSun;">与</span><span lang="EN-US">TN</span><span lang="ZH-CN" style="font-family: SimSun;">并没有本质的区别，两者都是分组业务传送技术，其不同之处在于，</span><span lang="EN-US">CE</span><span lang="ZH-CN" style="font-family: SimSun;">产品主要由数据设备厂家提供，是从数据层面来发展的，而</span><span lang="EN-US">PTN</span><span lang="ZH-CN" style="font-family: SimSun;">产品主要由传输设备厂家提供，是从光传输层面发展而来的。</span><span lang="EN-US"><br/>
</span><span lang="EN-US"></span></p><p class="MsoNormal"><span lang="EN-US">CE </span><span lang="ZH-CN" style="font-family: SimSun;">和</span><span lang="EN-US">PTN</span><span lang="ZH-CN" style="font-family: SimSun;">采用的主要协议有</span><span lang="EN-US">T-MPLS</span><span lang="ZH-CN" style="font-family: SimSun;">和</span><span lang="EN-US">PBT</span><span lang="ZH-CN" style="font-family: SimSun;">两个协议，其中</span><span lang="EN-US">T-MPLS</span><span lang="ZH-CN" style="font-family: SimSun;">是</span><span lang="EN-US">MPLS</span><span lang="ZH-CN" style="font-family: SimSun;">（多协议标记交换）的一个子集，是由</span><span lang="EN-US">ITU-T</span><span lang="ZH-CN" style="font-family: SimSun;">推荐的电信级分组传送</span><span lang="ZH-CN">
                </span><span lang="ZH-CN" style="font-family: SimSun;">技术。采用</span><span lang="EN-US">T-MPLS</span><span lang="ZH-CN" style="font-family: SimSun;">的</span><span lang="EN-US">PTN</span><span lang="ZH-CN" style="font-family: SimSun;">技术，非常好地结合了</span><span lang="EN-US">SDH</span><span lang="ZH-CN" style="font-family: SimSun;">和分组业务的处理能力，支持灵活的多业务承载和完善的链形、环形和</span><span lang="EN-US">MESH</span><span lang="ZH-CN" style="font-family: SimSun;">网络的保护，同时具</span><span lang="ZH-CN">
                </span><span lang="ZH-CN" style="font-family: SimSun;">备面向智能的</span><span lang="EN-US">ASON/GMPLS</span><span lang="ZH-CN" style="font-family: SimSun;">升级的能力。而</span><span lang="EN-US">PBT</span><span lang="ZH-CN" style="font-family: SimSun;">（</span><span lang="EN-US">Provider
backbone Transport</span><span lang="ZH-CN" style="font-family: SimSun;">）技术是</span><span lang="EN-US">IEEE<st1chmetcnv wst="on" tcsc="0" numbertype="1" negative="False" hasspace="False" sourcevalue="802.1" unitname="a">802.1a</st1chmetcnv>h</span><span lang="ZH-CN" style="font-family: SimSun;">标准规范的最新演进特性之一，其目的是要将以太网由无连接的技术变革为一种面向连接的隧道技术。采用</span><span lang="EN-US"> PBT</span><span lang="ZH-CN" style="font-family: SimSun;">为核心协议的</span><span lang="EN-US">CE</span><span lang="ZH-CN" style="font-family: SimSun;">技术对于分组业务承载非常高效，同时兼具了类似于</span><span lang="EN-US">SDH</span><span lang="ZH-CN" style="font-family: SimSun;">的安全可靠性和管理维护性，是一个具有极低成本的分组传送技术。但作为一种</span><span lang="ZH-CN">
                </span><span lang="ZH-CN" style="font-family: SimSun;">城域以太网技术，在</span><span lang="EN-US">PBT</span><span lang="ZH-CN" style="font-family: SimSun;">的实施过程中还面临一系列尚未解决的问题：</span><span lang="EN-US">T-MPLS</span><span lang="ZH-CN" style="font-family: SimSun;">与</span><span lang="EN-US">PBT</span><span lang="ZH-CN" style="font-family: SimSun;">相比较，两者各有优缺点，</span><span lang="EN-US">T-MPLS</span><span lang="ZH-CN" style="font-family: SimSun;">在电信级承载方面具备较大</span><span lang="ZH-CN">
                </span><span lang="ZH-CN" style="font-family: SimSun;">的优势，而</span><span lang="EN-US">PBT</span><span lang="ZH-CN" style="font-family: SimSun;">在设备数据业务承载上成本相对较低。</span><span lang="EN-US"><br/>
</span><span lang="ZH-CN" style="font-family: SimSun;"></span></p><p class="MsoNormal"><span lang="ZH-CN" style="font-family: SimSun;">目前</span><span lang="EN-US">PTN</span><span lang="ZH-CN" style="font-family: SimSun;">和</span><span lang="EN-US">CE</span><span lang="ZH-CN" style="font-family: SimSun;">技术标准正在不断发展之中，</span><span lang="EN-US">ITU-T</span><span lang="ZH-CN" style="font-family: SimSun;">、</span><span lang="EN-US">IEEE</span><span lang="ZH-CN" style="font-family: SimSun;">、</span><span lang="EN-US">MEF</span><span lang="ZH-CN" style="font-family: SimSun;">分别在近几年研究</span><span lang="ZH-CN">
                </span><span lang="ZH-CN" style="font-family: SimSun;">并发布了大量的分组传送标准，并且新的技术还在不断的立项和研究中。业界也有一些相应的产品出现，但是否可以真正应用于光传输网络，在保证电信级要求的前</span><span lang="ZH-CN">
                </span><span lang="ZH-CN" style="font-family: SimSun;">提下，有效地来承载城域网中的各类业务，还需要进一步验证。</span><span lang="EN-US"><br/>
</span><span lang="ZH-CN" style="font-family: SimSun;">光通信的发展一直在顺应通信网的发展需求，同时促进了通信网的发展。从目前通信网的发</span><span lang="ZH-CN">
                </span><span lang="ZH-CN" style="font-family: SimSun;">展来看，光通信技术和设备的发展有几个主流的发展趋势是不变的。如光传输网如何更好地适应</span><span lang="EN-US">IP</span><span lang="ZH-CN" style="font-family: SimSun;">业务承载的需求，如何建设一个更快、更安全的基础网络。光接</span><span lang="ZH-CN">
                </span><span lang="ZH-CN" style="font-family: SimSun;">入网的综合化发展趋势也早已为业界所认同。</span><span lang="EN-US"><br/>
</span><span lang="ZH-CN" style="font-family: SimSun;">（人民邮电报）</span></p>