本文介紹了軟交換系統分布式呼叫服務器 (Call Server，簡稱CS)中SIP協議DNS的實現，討論了支持DNS域名對系統的影響及需求，分析了分布式CS如何支持對端SIP實體以
域名呈現，以及其如何支持以域名呈現給對端SIP實體。軟交換系統通過對DNS域名的支持，CS不僅能和以域名方式呈現的其他SIP實體互通，更重要的通過以DNS域名方式呈現給其SIP實體，一個CS或者多個CS組成一個DNS域，簡化了網絡，提高了系統的可靠性。
關鍵詞：SIP，DNS，分布式呼叫服務器
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