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有线电缆数据服务接口规范DOCSIS(Data-Over-Cable Sevice Interface Specifications),是一个由有线电缆标准组织CableLabs制定的国际标准。DOCSIS定义了在有线电缆上提供数据服务所需的通信和运营支撑的接口。它的制订使得在现有的有线电视系统上进行高速数据通信成为可能。它被许多有线电视运营商采用在现有光纤混合同轴电缆(HFC)的基础设施上提供互联网接入。最新推出的3.0版本(2006年发布)极大地增加了上、下行速率并且引入了对IPv6的支持。所有这些DOCSIS的版本均保持了终端(Cable Modem)和Cable Model头端设备(Cable Model Termination System)之间的交叉后向兼容。随着三网融合的推进,各地广电正在掀起一轮新的网络改造高潮,将原有单向HFC网络建设成可承载视频、语音、宽带等多业务的双向网络。在技术选择上以传统基于HFC的CMTS+CM方式,或xPON+LAN方式,或xPON+EOC方式。本文选择传统CMTS+CM方式,浅谈原有Docsis 2.0体系、当前Docsis 3.0体系及未来技术的优劣特性。
Cable Data Service Interface Specification DOCSIS (Data-Over-Cable-Sevice Interface Specifications) is an international standard developed by CableLabs, a cable standards body. DOCSIS defines the interface for communication and operational support required to provide data services over wired cable. Its formulation makes it possible to carry out high-speed data communications over existing cable television systems. It is used by many cable operators to provide Internet access over existing Fiber Coax Hybrid (HFC) infrastructure. The latest version 3.0 (released in 2006) greatly increased upstream and downstream rates and introduced IPv6 support. All of these DOCSIS versions maintain cross-backwards compatibility between the Cable Modem and Cable Model Termination System. With the advancement of triple play, radio and television around the world are setting off a new wave of network transformation to build the original one-way HFC network into a bidirectional network capable of carrying multiple services such as video, voice and broadband. In the technical choice of the traditional HFC-based CMTS + CM mode, or xPON + LAN mode, or xPON + EOC mode. This paper selects the traditional CMTS + CM way to talk about the advantages and disadvantages of the original Docsis 2.0 system, current Docsis 3.0 system and future technologies.