媒体网关上基于SIP的实时IP传真功能的研究与实现
摘要
传真业务是一种重要的商业通信手段,企业用户对于传真业务的需求巨大,而且需求仍然在不断增长。目前传真业务主要在公共电话网上承载,这种传真业务的使用给企业带来了巨额的支出。随着Internet的迅速发展,IP技术与传统电信技术的融合不断加快,基于IP的新应用层出不穷。IP电话,即Voice over IP (VoIP) ,便是其中最为成功的例子。IP网络可以动态地分配和使用带宽资源,具有更高的带宽利用率。另外,IP电话业务的计费方式属于网间结算,无需缴付高昂的国际结算费,这使得IP电话业务的运营成本和使用价格远远低于传统电话业务。正是因为看到了传真需求的不断增长和IP技术的价格优势,要求实现IP传真功能的呼声日益高涨。
所谓IP传真,就是利用IP网络全部或者部分代替PSTN (Public Switched Telephone Network)进行的传真通信方式。借鉴传统电话网的结构,传真终端与电话终端共享同样的用户接口,在NGN的媒体网关上实现IP传真的功能是提供IP传真切实可行的方案。
本文给出了在基于SIP的媒体网关上实现T.38实时IP传真功能的原理和方法,分析了基于T.30的三类传真机和媒体网关之间的通信规程、基于T.38的媒体网关之间的通信规程以及基于SIP/SDP的传真呼叫通信规程。结合具体的实际应用,本文描述了实时IP传真的设计方案和实现过程。另外,本文也给出了对T.38传真业务的测试方案。
同时,作为T.38实时IP传真的补充,VBD (Voice-band data)传真模式保证了在T.38传真尝试失败时传真通信仍有可能完成。这大大提高了媒体网关上IP传真业务的完成率。本文也分析了V.152 VBD传真模式的相关原理,描述了如何在媒体网关上实现VBD传真模式用以补充T.38实时IP传真的方法。
测试结果表明,实现实时IP传真之后,提高了网络资源的利用率,大大降低了传真费用,扩展了媒体网关语音接口卡的功能。利用VBD传真模式对T.38实时IP传真进行补充进一步提高了媒体网关上传真业务的成功率,提高了产品的竞争力。
IP传真系统所涉及的知识面比较广,接口复杂,参数众多。本文只对在POTS (Plain Old Telephone Service)接口上如何设计与实现进行了讨论,并且没有考虑任何附加业务。对于在ISDN (Integrated Services Digital Network)接口上的实时IP传真、如何实现各种附加业务(呼叫转移、三方通信等)、如何实现传真广播以及传真业务安全性的讨论,这些都有待于做进一步研究。
Facsimile is an important way of business communication. The demand for facsimile communication from commercial organizations is really huge and is still on steady increase. So far, facsimile is mostly carried on PSTN (Public Switched Telephone Network), which brings numerous expenses together with the service. With the development of Internet, IP technology and traditional telecommunication technologies merge a lot and give birth to many new applications. VoIP (Voice over IP) is one of the most successful examples. First, VoIP provides higher bandwidth utility; second, VoIP avoids expensive international charge, which greatly benefits the users. On account of the increasing demand of facsimile communication and the great economy of IP technology, FoIP (Fax over IP) is widely required.
FoIP is the facsimile mode that substitutes IP networks for PSTN, either completely or partially. When we look back to the structure of PSTN, we find that facsimile terminals and voice terminals share the same subscriber interfaces. This sharing hints the possibility of implementing FoIP on media gateways in NGN.
This thesis provides a solution of implementing real-time IP facsimile on SIP-based media gateway, analyzes Procedures for Document Facsimile Transmission in the General Switched Telephone Network (ITU-T Recommendation T.30), Procedure for Real-Time Group 3 Facsimile Communication over IP Networks (ITU-T Recommendation T.38) and FoIP call control procedure based on SIP/SDP protocol. Afterwards, the thesis describes the system architecture and programming implementation of T.38 real-time IP facsimile functionality on SIP-based media gateway. Test principle and scenarios are also introduced.
As a supplement of T.38 facsimile, VBD (Voice-band data) mode will take effect when T.38 attempts fail. With V.152 VBD mode as a backup, fax calls on media gateway get more stability. In this thesis, the implement of VBD mode fax and how to use it as a backup for T.38 fax is also described.
According to the test results we get, FoIP can enhance the utility of network resources and hence significantly lowers the expenses of facsimile communication. With VBD mode as a backup, fax call completion rate can easily reach the level of 99.95%. It makes the product more competitive in market.
This thesis only focuses on the basic FoIP functionality on POTS (Plain Old Telephone Service) interfaces without any discussion of supplementary services. Further researches are expected on the topics such as FoIP functionality on ISDN (Integrated Services Digital Network) interfaces, supplementary services (fax call transfer, fax call waiting, conference fax call etc.), fax broadcasting, security issues of FoIP etc.
所谓IP传真,就是利用IP网络全部或者部分代替PSTN (Public Switched Telephone Network)进行的传真通信方式。借鉴传统电话网的结构,传真终端与电话终端共享同样的用户接口,在NGN的媒体网关上实现IP传真的功能是提供IP传真切实可行的方案。
本文给出了在基于SIP的媒体网关上实现T.38实时IP传真功能的原理和方法,分析了基于T.30的三类传真机和媒体网关之间的通信规程、基于T.38的媒体网关之间的通信规程以及基于SIP/SDP的传真呼叫通信规程。结合具体的实际应用,本文描述了实时IP传真的设计方案和实现过程。另外,本文也给出了对T.38传真业务的测试方案。
同时,作为T.38实时IP传真的补充,VBD (Voice-band data)传真模式保证了在T.38传真尝试失败时传真通信仍有可能完成。这大大提高了媒体网关上IP传真业务的完成率。本文也分析了V.152 VBD传真模式的相关原理,描述了如何在媒体网关上实现VBD传真模式用以补充T.38实时IP传真的方法。
测试结果表明,实现实时IP传真之后,提高了网络资源的利用率,大大降低了传真费用,扩展了媒体网关语音接口卡的功能。利用VBD传真模式对T.38实时IP传真进行补充进一步提高了媒体网关上传真业务的成功率,提高了产品的竞争力。
IP传真系统所涉及的知识面比较广,接口复杂,参数众多。本文只对在POTS (Plain Old Telephone Service)接口上如何设计与实现进行了讨论,并且没有考虑任何附加业务。对于在ISDN (Integrated Services Digital Network)接口上的实时IP传真、如何实现各种附加业务(呼叫转移、三方通信等)、如何实现传真广播以及传真业务安全性的讨论,这些都有待于做进一步研究。
Facsimile is an important way of business communication. The demand for facsimile communication from commercial organizations is really huge and is still on steady increase. So far, facsimile is mostly carried on PSTN (Public Switched Telephone Network), which brings numerous expenses together with the service. With the development of Internet, IP technology and traditional telecommunication technologies merge a lot and give birth to many new applications. VoIP (Voice over IP) is one of the most successful examples. First, VoIP provides higher bandwidth utility; second, VoIP avoids expensive international charge, which greatly benefits the users. On account of the increasing demand of facsimile communication and the great economy of IP technology, FoIP (Fax over IP) is widely required.
FoIP is the facsimile mode that substitutes IP networks for PSTN, either completely or partially. When we look back to the structure of PSTN, we find that facsimile terminals and voice terminals share the same subscriber interfaces. This sharing hints the possibility of implementing FoIP on media gateways in NGN.
This thesis provides a solution of implementing real-time IP facsimile on SIP-based media gateway, analyzes Procedures for Document Facsimile Transmission in the General Switched Telephone Network (ITU-T Recommendation T.30), Procedure for Real-Time Group 3 Facsimile Communication over IP Networks (ITU-T Recommendation T.38) and FoIP call control procedure based on SIP/SDP protocol. Afterwards, the thesis describes the system architecture and programming implementation of T.38 real-time IP facsimile functionality on SIP-based media gateway. Test principle and scenarios are also introduced.
As a supplement of T.38 facsimile, VBD (Voice-band data) mode will take effect when T.38 attempts fail. With V.152 VBD mode as a backup, fax calls on media gateway get more stability. In this thesis, the implement of VBD mode fax and how to use it as a backup for T.38 fax is also described.
According to the test results we get, FoIP can enhance the utility of network resources and hence significantly lowers the expenses of facsimile communication. With VBD mode as a backup, fax call completion rate can easily reach the level of 99.95%. It makes the product more competitive in market.
This thesis only focuses on the basic FoIP functionality on POTS (Plain Old Telephone Service) interfaces without any discussion of supplementary services. Further researches are expected on the topics such as FoIP functionality on ISDN (Integrated Services Digital Network) interfaces, supplementary services (fax call transfer, fax call waiting, conference fax call etc.), fax broadcasting, security issues of FoIP etc.
引文
[1] 李翔. 基于下一代网络的实时传真的研究[硕士论文]. 武汉:华中科技大学. 2005.
[2] 盖应金. 在未来的通信领域里,IP 必将成为技术发展的主流之一——IP 传真技术. 中国传媒科技. 2002 (8).
[3] 钟涛,薛质. H.248 协议下 T.38 传真业务的实现. 电信快报. 2004 (12).
[4] 信息产业部. 综合接入媒体网关设备技术规范. 2000.
[5] 刘长瑞. 综合业务接入网关中呈现业务的设计与实现[硕士论文]. 北京:北京邮电大学. 2006.
[6] 郭晋铎. 语音网关 IP 传真模块的设计与实现[硕士论文]. 西安:西南交通大学. 2005.
[7] 丁永军,马小姝,刘慧鹏. IP 传真技术的设计与实现. 天水师范学院学报. 2006 (2).
[8] ITU-T Recommendation T.30: Procedures for document facsimile transmission in the general switched telephone network. 2005.9
[9] 华慧雅. 基于 IP 的实时传真通信. 江苏通信技术. 2001 (3).
[10] 顾恺,孙精科. 基于 IP 的传真技术. 电信快报. 1999 (12).
[11] 刘辉,刘玉贵. IP 传真技术及实现. 电信科学. 2001 (9).
[12] 张长城,聂秀英. 影响 IP 电话和传真业务服务质量的因素. 通信世界. 1999 (5).
[13] 林晓勇,邵园园,金伟,蔡丽,成际镇. 基于 SIP 协议的 IP-PBX 的研究与实现. 西安邮电学院学报. 2007 (3).
[14] 王会进,黄家永. 一个基于 IP 技术的传真网关的设计与实现. 计算机工程. 2000 (4).
[15] ITU-T Recommendation T.38: Procedures for Real-time Group 3 Facsimile communication over IP network. 2007.4
[16] 游明星,刘立柱. 基于 Internet 现状的 IP 传真设计探讨. 电讯技术. 2001 (2).
[17] 刘辉,刘玉贵,张权利. 实时 IP 传真纠错协议 UDPTL 的应用. 现代电信科技. 2002,(8).
[18] ITU-T Recommendation T.38 Annex D: SIP/SDP call establishment procedures 2007.4
[19] J. Rosenberg, H. Schulzrinne, G. Camarillo, A. Johnston, J. Peterson, R. Sparks, M. Handley, E. Schooler. IETF: RFC3261: SIP: Session Initiation Protocol. 2002.6
[20] D. Crocker. IETF: RFC822: Standard For The Format of ARPA Internet Text Messages. 1982.8
[21] M. Handley, V. Jacobson. IETF: RFC2327: SDP: Session Description Protocol. 1998.4
[22] F. Yergeau. IETF: RFC2044: UTF-8, a transformation format of Unicode and ISO 10646. 1996.10
[23] ITU-T Recommendation V.152: Procedures for supporting voice-band data over IP networks. 2005.1
[24] 中国电信. 中国电信软交换网络传真和Modem业务技术规范. 2007.1
[25] 夏晨,苏应飚,杨学军,黄本雄. IP 实时传真协议需求与解决方案. 电信快报. 2001 (6).
[26] 赵眉,徐全生. 基于 T.38 的实时 IP 传真技术难点分析. 沈阳工业大学学报. 2005 (5).
[27] ITU-T Recommendation T.22: Standardized Test Charts For Document Facsimile Transmissions. 1993.3
[28] ITU-T Recommendation E.453: Facsimile Image Quality As Corrupted By Transmission-Included Scan Line Errors. 1994.8
[29] ITU-T Recommendation E.458: Figure Of Merit For Facsimile Transmission Performance. 1996.2
[30] 陈楚华,史林. IP 传真的分析与改进. 计算机与信息技术. 2006 (5).
[31] 陈楚华. 媒体网关中 T38 传真的设计与实现[硕士论文]. 西安:西安电子科技大学. 2006.
[2] 盖应金. 在未来的通信领域里,IP 必将成为技术发展的主流之一——IP 传真技术. 中国传媒科技. 2002 (8).
[3] 钟涛,薛质. H.248 协议下 T.38 传真业务的实现. 电信快报. 2004 (12).
[4] 信息产业部. 综合接入媒体网关设备技术规范. 2000.
[5] 刘长瑞. 综合业务接入网关中呈现业务的设计与实现[硕士论文]. 北京:北京邮电大学. 2006.
[6] 郭晋铎. 语音网关 IP 传真模块的设计与实现[硕士论文]. 西安:西南交通大学. 2005.
[7] 丁永军,马小姝,刘慧鹏. IP 传真技术的设计与实现. 天水师范学院学报. 2006 (2).
[8] ITU-T Recommendation T.30: Procedures for document facsimile transmission in the general switched telephone network. 2005.9
[9] 华慧雅. 基于 IP 的实时传真通信. 江苏通信技术. 2001 (3).
[10] 顾恺,孙精科. 基于 IP 的传真技术. 电信快报. 1999 (12).
[11] 刘辉,刘玉贵. IP 传真技术及实现. 电信科学. 2001 (9).
[12] 张长城,聂秀英. 影响 IP 电话和传真业务服务质量的因素. 通信世界. 1999 (5).
[13] 林晓勇,邵园园,金伟,蔡丽,成际镇. 基于 SIP 协议的 IP-PBX 的研究与实现. 西安邮电学院学报. 2007 (3).
[14] 王会进,黄家永. 一个基于 IP 技术的传真网关的设计与实现. 计算机工程. 2000 (4).
[15] ITU-T Recommendation T.38: Procedures for Real-time Group 3 Facsimile communication over IP network. 2007.4
[16] 游明星,刘立柱. 基于 Internet 现状的 IP 传真设计探讨. 电讯技术. 2001 (2).
[17] 刘辉,刘玉贵,张权利. 实时 IP 传真纠错协议 UDPTL 的应用. 现代电信科技. 2002,(8).
[18] ITU-T Recommendation T.38 Annex D: SIP/SDP call establishment procedures 2007.4
[19] J. Rosenberg, H. Schulzrinne, G. Camarillo, A. Johnston, J. Peterson, R. Sparks, M. Handley, E. Schooler. IETF: RFC3261: SIP: Session Initiation Protocol. 2002.6
[20] D. Crocker. IETF: RFC822: Standard For The Format of ARPA Internet Text Messages. 1982.8
[21] M. Handley, V. Jacobson. IETF: RFC2327: SDP: Session Description Protocol. 1998.4
[22] F. Yergeau. IETF: RFC2044: UTF-8, a transformation format of Unicode and ISO 10646. 1996.10
[23] ITU-T Recommendation V.152: Procedures for supporting voice-band data over IP networks. 2005.1
[24] 中国电信. 中国电信软交换网络传真和Modem业务技术规范. 2007.1
[25] 夏晨,苏应飚,杨学军,黄本雄. IP 实时传真协议需求与解决方案. 电信快报. 2001 (6).
[26] 赵眉,徐全生. 基于 T.38 的实时 IP 传真技术难点分析. 沈阳工业大学学报. 2005 (5).
[27] ITU-T Recommendation T.22: Standardized Test Charts For Document Facsimile Transmissions. 1993.3
[28] ITU-T Recommendation E.453: Facsimile Image Quality As Corrupted By Transmission-Included Scan Line Errors. 1994.8
[29] ITU-T Recommendation E.458: Figure Of Merit For Facsimile Transmission Performance. 1996.2
[30] 陈楚华,史林. IP 传真的分析与改进. 计算机与信息技术. 2006 (5).
[31] 陈楚华. 媒体网关中 T38 传真的设计与实现[硕士论文]. 西安:西安电子科技大学. 2006.