The New Trend Of Telecom And Network Converging Technique--SIP/Enum Technique

TWNIC executive director Chen Wen Shen(wschen@twnic.net.tw)
TWNIC Yiang Zhen Bao(abelyang@twnic.net.tw)

Preface
Before the prosperity of the Internet, end users and Service Providers are both used to think in three different formats of network: Networks for Data, Networks for Voice, and Networks for Television/video. However, these three formats of network would not reconcile, and they have their own Telephony Numbering Plans, Signaling, Audio Encoding, numerous TV standards, numerous so-called Networks of Data in telecom industry etc. All these facts make it impossible for these three to integrate into a single global network. The earliest Data Networks in the telecom industry have many various formats, including Leased line, X.25, ISDN, Frame relay, SMDS, and ATM network, but these still derived mainly from the idea of Circuit-switched telephony of Networks for Voice. The fundamental design of Networks for Voice, which indeed was used to communicate data and fax in the past, is based on voice; Networks for Television/video is designed to deliver Video Streams, and all the other network formats have their own End-user Devices, which would not reconcile. On top of this, the speedy development of wireless Ethernet and Mobile Internet have made all kinds of networks more complicated and various.
Compared with the traditional networks mentioned above, the Internet, with the magnificent development of Computing Technology and globalization, has developed enormous potentiality to integrate Data, Voice, and Video into the same network, and this converging stream is like a quiet revolution, which is taking place in all the related areas.
The Voice Service of the Internet
Including analog phones, wireless telephones, mobile phones, and ISDN phones, Telephone network, sometimes called PSTN (Public Switched Telephone Network) is proved to be a successful technology with the prevalence in every family. Due to the quality of Highly-reliable and real time, Telephone network acquires the confidence of users. However, contrasting the relative cost and Value-Added Service, can telephone network provide as low cost and high Value-Added Service as the Internet? By moving Voice Service from PSTN network to the Internet and making the Internet to simulate all the PSTN functions? In the past, the development of the Voice Service on the Internet was very slow, not because of the insufficient bandwidth to run high quality Voice Service but the lack of Signaling protocol needed in the Voice Service, that is according different signaling and control design there will be various ways to run the Voice on the Internet. H.323 was made according the idea of signaling in telephone industry, Soft Switches the idea of Control, and SIP (Session Initiation Protocol) the idea of Internet-centric related Protocol. Among them, SIP is considered to be the most likely one to become the third important Internet Protocol, the second and third of which are TCP/IP and HTTP. Besides replacing all the Value-Added Service of SS7 Signaling and Internet, the visual multimedia real-time messages combined with the Internet, such as Mobile Video Phone, is predicted to be fulfilled in this whole new protocol technique OS.

All-IP Network
The future Internet, whether wireless core Internet or wired ADSL, will integrate into a Telecom-Internet of All IP Network framework; the application of IP Network, such as Voice over IP, Video over IP, Multimedia Messaging etc., and related equipments like IP Phone, SIP Proxy, IP-PBX, Media Server, and Softswitch will be new industry in the future. For the prosperous development of these, SIP and ENUM are considered to be two important issues.

SIP/Enum technique
SIP (IETF RFC 3261) has replaced H.232 and become the Communication Protocol of call control and service control of the future multimedia communication. Not only can it be DCS of the Internet phone's end-user device, it can also the Communication Protocol between different equipments. Especially in the next generation, SIP Proxy will be the main technique of communication control in the core network of wireless communication (3G/B3G).

On the other hand, ENUM (IETF RFC 2916) has become the switching standard between traditional telephone number (ITU-T E.164) and Internet phone (Voice over IP: VoIp). VoIP related techniques have been developing for many years; however, in the application it can never be prevalent in common families. The most important reason is the using habits of VoIP and the addressing of phone numbers are totally different from traditional telephones, which is absolutely not friendly use for people. Nowadays the biggest problem of combining VoIP (Voice over IP) technique and traditional telephone is on the interflowing of Internet/PSTN (Public Switched Telephone Network). Besides the issue of cost, whether users can accept the change of habits is another problem because people who seldom surf the Internet would have trouble with this kind of new technology. However, ENUM (E.164 Number, Telephone Number Mapping) can avoid all of these and provide even more value-added service.

ENUM can completely get rid of the problems resulted from using VoIP. In ENUM, users can, by traditional telephone number dialing, simply connect to VoIP, even to Voice mailbox, Email, or personal websites without memorizing or dial those annoying IP address or URI (Universal Resource Identity). ITU-T, the organization managing the worldwide telecom standard and examination has also come up with a common consensus—ENUM will be the switch standard between traditional telecom and the Internet. Therefore, ENUM will not be a temporary fad, but an important switching standard which integrates two worldwide numbers. In the present, not only every standard organization, such as ITU-T and ETSI, are earnestly discussing about the framework and interflow standard of ENUM, but also every country is activating related organization to examine the implementation of ENUM and how national policy should cooperate with it. Because it is a worldwide interflow standard, which is the important loadstar to the possibility of the prosperous development of future Internet-Telecom Service, advanced countries put much emphasis on this standard and have started ENUM Trail to prepare for its commercialization. Currently international community considers that the key factor of the success in converging IP Internet and PSTN Internet will be SIP and ENUM (see picture 1).

SIP/Enum trail OS
After SIP has made the standard, many manufacturers has started to do the research, for example, Verisign—the register organization of “.com,” Neustar—the manage cooperation of north American Number Portability, and Netnymber and Verusugn which mainly work on Enum and Netnumber, which are backed up by big telephone companies. It shows that reliable experiments have proved the theory and techniques are absolutely workable although service is not on the market yet.

Through DNS, Enum technique provides the switch system between phone number and Internet address. DNS and PSTN both have a standard to follow; through RFC (Request for Comment), these two can be combined. In our country, there has been some partial SIP/Enum tests, participated by TWNIC, the computer and communication research lab in ITRI and some Telecom Operators. The test framework of PSTN to SIP (IP) and SIP (IP) to PSTN are as picture 2 and 3.

Those two frameworks above are workable; the interflowing framework of PSTN and SIP is able to work now.
Our country has been working hard on the research of the equipment of VoIP, but the application has not started. At the same time, our country is also planning to make us a tele-tech service island; SIP/ENUM are considered to be the catalyst to the success of the application of VoIP and Internet related sevice. Therefore, to arrange SIP/ENUM trail to understand its issues in the aspects of technique, policy, application, and comer is very important. Computer and communication research lab in ITRI, TWNIC, NTPO (National Telecommunication Program Office), TCA Enum forum Taiwna etc. are trying to invite the policy making departments, Telecom dealers, ISP, equipment provider, and service providers to arrange SIP/SNUM Trail, hoping to discuss the telecom technique and service application in the next generation. The environment framework of SIP/SNUM Trail is as picture4.

Conclusion
With the potential of low cost and high Value-Added Service, the big trend in the development of telecom and Internet converging Technique. In the angle of telecom Fix-line Operators、Mobile Operators、ISPs、Network Systems、Access Devices、and Network Value-Added Services, what does converging technique represent and how will the market move are both the concerns of telecom related industry dealers. It is important for the business in our country, including the 3G mobile phones, IP exchanger/Gateway, IP phones, and End-user Device based on SIP, to handle possess the technique and raise the attached values of products. Besides, dealers of Value-Added Service with emphasis on SIP/ENUM need to construct a perfect service environment and measurements to cooperate with the policy in order to fully promote the quality. In all, the competitive ability relies on how all the related business race to get the best chance in the coming trend.