本文介绍了软交换系统分布式呼叫服务器 (Call Server,简称CS)中SIP协议DNS的实现,讨论了支持DNS域名对系统的影响及需求,分析了分布式CS如何支持对端SIP实体以 域名呈现,以及其如何支持以域名呈现给对端SIP实体。软交换系统通过对DNS域名的支持,CS不仅能和以域名方式呈现的其他SIP实体互通,更重要的通过以DNS域名方式呈现给其SIP实体,一个CS或者多个CS组成一个DNS域,简化了网络,提高了系统的可靠性。 关键词:SIP,DNS,分布式呼叫服务器 Abstract: This paper gives an introduction of the design and realization of SIP DNS in the call server based on soft switch system. It not only discusses the influence to the existed system for supporting DNS,but also analyses how to support DNS of SIP entity. Due to supporting DNS in the system, CS not only can communicate with other SIP entity through domain name. But also can present itself through domain name. More than one CS forms a DNS domain, so the network is simplified and the system is more reliable. Key words: SIP,DNS,CS