一种基于应用层路由的SIP穿越NAT方案设计与实现
摘要
本论文的研究目标是为SIP技术能够无缝地应用在NAT网络服务。SIP协议是一种新兴的网络协议,它能够将VoIP、多媒体会议、push-to-talk(按键通话)、定位服务、在线信息和即时通信等功能组合起来,形成更大规模的无缝通信服务。然而网络中已大量部署的NAT设备对SIP正常通信造成困难,阻碍了SIP技术的推广。为了解决SIP消息无法通过NAT传输的问题,本论文首先详细介绍了SIP协议,并对其特有的应用层路由机制进行了深入分析,指出现有技术无法实现SIP穿越NAT的关键在于SIP的应用层路由信息没有得到合理的转换与解释。
我们对NAT技术的研究现状进行了调查,发现现有技术方案并没有正确解决这方面存在的问题,与之相反,却对网络的拓扑做出了特定假设,使SIP技术的应用必须增加部署服务器的成本,同样阻碍了企业对于采用SIP技术的信心。在此基础上我们设计并实现了一种有效的SIP穿越NAT方案,它主要关注SIP应用层路由信息的正确网络地址转换,并设计了其核心算法。该方案的优点在于:不限于任何NAT体系结构,可以作为任意现有应用层协议NAT穿越方案的SIP处理构件;可以满足任意SIP网络拓扑的通信,不要求部署额外的服务器;只对必要的信息进行处理,而不必识别整个SIP消息,提高了NAT设备的处理速度,也降低了必要的NAT设备存储占用。除此之外,本文还提出了“栈模式”的SIP应用层路由机制分析方法,以及“约减法”归纳SIP NAT网络拓扑情况。前者提高了对SIP技术的认识,后者则对加入NAT设备的SIP网络可能的拓扑情况进行了简化,利用有限的简化拓扑模式表达无限的拓扑空间,使本论文设计的SIP穿越NAT方案的有效性得以验证。
总而言之,本论文不仅仅解决了SIP穿越NAT的难题,还提高研究者对SIP以及NAT等相关领域的认识,为这两个领域相关应用的设计与开发提供了丰富的参考。
The purpose of this paper is to seamlessly connect SIP services in the network containing NAT devices. Although SIP is a newly proposed network protocol, it is able to combine all the communication capabilities into a larger scale seamlessly, like VoIP, multi-media conference, push-to-talk, locating service, online messaging and instant messaging. Nevertheless, the NAT services having been deployed in the network make transferring SIP messages difficult, thus prohibit the popularity of SIP applications. In order to solve this problem, this paper will introduce SIP in detail firstly, and find the key of the issue is the inability of NAT devices to translate the special information containing SIP application-layer routing.
We investigate present researches on NAT, and discover that present researches do not solve the problem correctly. On the contrary, they make assumptions on the network topologies. As a result, the cost for applying SIP technology in an organization is increased greatly, which will discourage enterprise from deploying SIP applications. Basing on our analysis, we implement an effective scheme for SIP message traversing NAT, which focuses on network address translation for application-layer routing information in SIP messages and designs a core algorithm for it. The advantage of our scheme includes following aspects: Our implementation is not restricted to any NAT architecture, it could be used a SIP processing component in any present application-layer NAT scheme; It is applicable to any SIP topologies, that is to say no additional servers are required; There is no need to recognize the entire SIP message, but only those that must be translating, therefore it could not only make NAT process SIP packets more quickly, but also lower the occupancy of NAT storage. Moreover, this paper makes use of "stack" to analyze the application-layer routing of SIP, and reduces the topology space of SIP NAT network, which will be used for validation of our scheme.
Generally, this paper not only solve the problem of SIP traversing in NAT network, but also increase our knowledge of SIP and NAT, thus makes rich references for designing and developing for both fields.
我们对NAT技术的研究现状进行了调查,发现现有技术方案并没有正确解决这方面存在的问题,与之相反,却对网络的拓扑做出了特定假设,使SIP技术的应用必须增加部署服务器的成本,同样阻碍了企业对于采用SIP技术的信心。在此基础上我们设计并实现了一种有效的SIP穿越NAT方案,它主要关注SIP应用层路由信息的正确网络地址转换,并设计了其核心算法。该方案的优点在于:不限于任何NAT体系结构,可以作为任意现有应用层协议NAT穿越方案的SIP处理构件;可以满足任意SIP网络拓扑的通信,不要求部署额外的服务器;只对必要的信息进行处理,而不必识别整个SIP消息,提高了NAT设备的处理速度,也降低了必要的NAT设备存储占用。除此之外,本文还提出了“栈模式”的SIP应用层路由机制分析方法,以及“约减法”归纳SIP NAT网络拓扑情况。前者提高了对SIP技术的认识,后者则对加入NAT设备的SIP网络可能的拓扑情况进行了简化,利用有限的简化拓扑模式表达无限的拓扑空间,使本论文设计的SIP穿越NAT方案的有效性得以验证。
总而言之,本论文不仅仅解决了SIP穿越NAT的难题,还提高研究者对SIP以及NAT等相关领域的认识,为这两个领域相关应用的设计与开发提供了丰富的参考。
The purpose of this paper is to seamlessly connect SIP services in the network containing NAT devices. Although SIP is a newly proposed network protocol, it is able to combine all the communication capabilities into a larger scale seamlessly, like VoIP, multi-media conference, push-to-talk, locating service, online messaging and instant messaging. Nevertheless, the NAT services having been deployed in the network make transferring SIP messages difficult, thus prohibit the popularity of SIP applications. In order to solve this problem, this paper will introduce SIP in detail firstly, and find the key of the issue is the inability of NAT devices to translate the special information containing SIP application-layer routing.
We investigate present researches on NAT, and discover that present researches do not solve the problem correctly. On the contrary, they make assumptions on the network topologies. As a result, the cost for applying SIP technology in an organization is increased greatly, which will discourage enterprise from deploying SIP applications. Basing on our analysis, we implement an effective scheme for SIP message traversing NAT, which focuses on network address translation for application-layer routing information in SIP messages and designs a core algorithm for it. The advantage of our scheme includes following aspects: Our implementation is not restricted to any NAT architecture, it could be used a SIP processing component in any present application-layer NAT scheme; It is applicable to any SIP topologies, that is to say no additional servers are required; There is no need to recognize the entire SIP message, but only those that must be translating, therefore it could not only make NAT process SIP packets more quickly, but also lower the occupancy of NAT storage. Moreover, this paper makes use of "stack" to analyze the application-layer routing of SIP, and reduces the topology space of SIP NAT network, which will be used for validation of our scheme.
Generally, this paper not only solve the problem of SIP traversing in NAT network, but also increase our knowledge of SIP and NAT, thus makes rich references for designing and developing for both fields.
引文
[1]P.Srisuresh,M.Holdrege.IP Network Address Translator(NAT)Terminology and Considerations.Internet RFC 2663,August 1999.
[2]Rosenberg J,Schulzrinne H,Schulzrinne G.SIP:Session Initiation Protocol.Internet RFC 3261,June 2002.
[3]Biggs B.A SIP Application Level Gateway for Network Address Translation.Internet Draft,March 2000.
[4]程延伟.利用SIP协议扩展实现SIP-NAT网关.小型微型计算机系统,2003,24(1):151-153.
[5]Fredrik Themelius,Bertil Engelholm.SIP Firewall Solution.lnternet Draft,2000.
[6]何永林,林浒等.一种SIP NAT应用网关的设计与实现.小型微型计算机系统,2002,23(8):913-916
[7]罗强,常致全等.针对SIP的ALG解决方案及实现.计算机应用,2003,23(2):120-122.
[8]Martin M,Brunner M,Stiemeding M.SIP NSIS Interactions for NAT/Firewall Traversal.Internet Draft,2004.
[9]Rosenberg J,Weinberger J,Schulzrinne H.SIP Extensions for NAT Traversal.Internet Draft,2001.
[10]Rosenberg J,Camarillo G.Examples of Network Address Translation(NAT)and Firewall Traversal for the Session Initiation Protocol(SIP).Internet Draft,2003.
[11]张波,胡瑞敏,边学工.一种实现SIP穿越NAT的新方案.计算机工程,2005,31(2):119-121.
[12]M.Handley,H.Schulzrinne,E.Schooler,et al.SIP:Session Initiation Protocol.Internet RFC 2543,March 1999.
[13]Rosenberg J,Schulzrinne H,Schulzrinne G.SIP:Session Initiation Protocol.Internet RFC 3261,June 2002.
[14] M. Handley, V. Jacobson. SDP: Session Description Protocol. Internet 2327, April 1998.
[15]R. Fielding, J. Gettys, J. Mogul, et al. Hypertext Transfer Protocol - HTTP/1.1. Internet RFC 2616, June 1999.
[16] J. Klensin. Simple Mail Transfer Protocol. Internet RFC 2821. April 2001.
[17] H. Schulzrinne, S. Casner, R. Frederick, et al. RTP: A Transport Protocol for Real-Time Applications. Internet RFC 3550, July 03
[18] H. Schulzrinne, A. Rao, R. Lanphier. Real Time Streaming Protocol (RTSP). Internet RFC 2326, April 1998
[19] F. Cuervo, N. Greene, A. Rayhan. Megaco Protocol Version 1.0. Internet RFC 3015, November 2000.
[20] F. Yergeau. UTF-8, a transformation format of ISO 10646. Internet RFC 2279, January 1998.
[21] N. Freed, N. Borenstein. Multipurpose Internet Mail Extensions (MIME) Part Two: Media Types. Internet RFC 2046, November 1996.
[22] M. Stiemerling, J. Quittek, T. Taylor. Middlebox Communications (MIDCOM) Protocol Semantics. Internet RFC 3989, February 2005.
[23] J. Rosenberg, J. Weinberger, C. Huitema, et al. STUN - Simple Traversal of User Datagram Protocol (UDP) Through Network Address Translators (NATs). Internet RFC 3489, March 2003.
[24] Biggs B. A SIP Application Level Gateway for Network Address Translation. Internet Draft, March 2000.
[25] Fredrik Thernelius, Bertil Engelholm. SIP Firewall Solution. Internet Draft, 2000.
[26]司端锋,韩心慧,龙勤等．SIP标准中的核心技术与研究进展．软件学报,2005,16(2)：239—250．
[2]Rosenberg J,Schulzrinne H,Schulzrinne G.SIP:Session Initiation Protocol.Internet RFC 3261,June 2002.
[3]Biggs B.A SIP Application Level Gateway for Network Address Translation.Internet Draft,March 2000.
[4]程延伟.利用SIP协议扩展实现SIP-NAT网关.小型微型计算机系统,2003,24(1):151-153.
[5]Fredrik Themelius,Bertil Engelholm.SIP Firewall Solution.lnternet Draft,2000.
[6]何永林,林浒等.一种SIP NAT应用网关的设计与实现.小型微型计算机系统,2002,23(8):913-916
[7]罗强,常致全等.针对SIP的ALG解决方案及实现.计算机应用,2003,23(2):120-122.
[8]Martin M,Brunner M,Stiemeding M.SIP NSIS Interactions for NAT/Firewall Traversal.Internet Draft,2004.
[9]Rosenberg J,Weinberger J,Schulzrinne H.SIP Extensions for NAT Traversal.Internet Draft,2001.
[10]Rosenberg J,Camarillo G.Examples of Network Address Translation(NAT)and Firewall Traversal for the Session Initiation Protocol(SIP).Internet Draft,2003.
[11]张波,胡瑞敏,边学工.一种实现SIP穿越NAT的新方案.计算机工程,2005,31(2):119-121.
[12]M.Handley,H.Schulzrinne,E.Schooler,et al.SIP:Session Initiation Protocol.Internet RFC 2543,March 1999.
[13]Rosenberg J,Schulzrinne H,Schulzrinne G.SIP:Session Initiation Protocol.Internet RFC 3261,June 2002.
[14] M. Handley, V. Jacobson. SDP: Session Description Protocol. Internet 2327, April 1998.
[15]R. Fielding, J. Gettys, J. Mogul, et al. Hypertext Transfer Protocol - HTTP/1.1. Internet RFC 2616, June 1999.
[16] J. Klensin. Simple Mail Transfer Protocol. Internet RFC 2821. April 2001.
[17] H. Schulzrinne, S. Casner, R. Frederick, et al. RTP: A Transport Protocol for Real-Time Applications. Internet RFC 3550, July 03
[18] H. Schulzrinne, A. Rao, R. Lanphier. Real Time Streaming Protocol (RTSP). Internet RFC 2326, April 1998
[19] F. Cuervo, N. Greene, A. Rayhan. Megaco Protocol Version 1.0. Internet RFC 3015, November 2000.
[20] F. Yergeau. UTF-8, a transformation format of ISO 10646. Internet RFC 2279, January 1998.
[21] N. Freed, N. Borenstein. Multipurpose Internet Mail Extensions (MIME) Part Two: Media Types. Internet RFC 2046, November 1996.
[22] M. Stiemerling, J. Quittek, T. Taylor. Middlebox Communications (MIDCOM) Protocol Semantics. Internet RFC 3989, February 2005.
[23] J. Rosenberg, J. Weinberger, C. Huitema, et al. STUN - Simple Traversal of User Datagram Protocol (UDP) Through Network Address Translators (NATs). Internet RFC 3489, March 2003.
[24] Biggs B. A SIP Application Level Gateway for Network Address Translation. Internet Draft, March 2000.
[25] Fredrik Thernelius, Bertil Engelholm. SIP Firewall Solution. Internet Draft, 2000.
[26]司端锋,韩心慧,龙勤等．SIP标准中的核心技术与研究进展．软件学报,2005,16(2)：239—250．