Specifications created to achieve interoperability, quality of service for users of emerging communications capability.
A European organization is heading a global effort to develop standards for an emerging market in telecommunications—voice over Internet protocol. Aiming to write specifications that will achieve worldwide acceptance among industry, administrators, regulators and other standards bodies, this group is gathering support from related organizations and experts in the field of Internet protocol telephony.
The project, known as TIPHON, focuses on interoperability between Internet protocol-based networks and switched-circuit networks. TIPHON stands for telecommunications and Internet protocol (IP) harmonization over networks. The European Telecommunications Standards Institute, Valbonne, France, is spearheading this effort to enable communities worldwide to combine telecommunications and Internet technologies for real-time voice communications and related voiceband communication between users.
Responding to high demand for interoperable voice, data and multimedia services, the telecommunications industry is eager to achieve widespread use of voice over IP to maximize the capability of network infrastructure to exchange voice transmissions. Voice over IP can provide high-speed, efficient communications alternatives through an integrated networked architecture. Demand for the technology is driving the commercial market because customers are anxious to use voice over IP to realize the cost savings that this capability could afford.
In this rapidly evolving environment, standards organizations are seeking to finalize policies to equip users with quality voice alternatives, and industry is trying to meet user demand for interoperable services. Interoperability between IP-based network users and switched-circuit network-based users is the linchpin of efforts to fully develop IP telephony.
Voice over IP entails using the packet technology associated with IP to transmit a point-to-point communication. The objective is to send voice calls across a private network, such as a local area network, or eventually over the public Internet without compromising quality. In addition to interoperability and quality, high-priority issues for standardizing voice over IP include naming, numbering and addressing, security, and billing procedures.
The European Telecommunications Standards Institute, more commonly referred to as ETSI, has been working on the project since 1997. Throughout its deliberations, ETSI has sought to maintain an atmosphere of openness, according to its officials. Approximately 140 attendees representing 30 companies participated in a recent meeting, and ETSI leaders say they are committed to reaching decisions based on consensus. Nearly 500 delegates receive electronic mail messages updating them on ETSI voice over IP initiatives. ETSI documents related to development of voice over IP policy are posted on the World Wide Web for public review.
Leaders working on the voice over IP project through ETSI have taken steps to avoid duplicating the efforts of other standards organizations. The body has worked with the International Telecommunications Union (ITU), the Internet Engineering Task Force, the International Multimedia Teleconferencing Consortium Incorporated and the International Standards Organization, often using existing policies in related areas to help frame voice over IP standards. Also, an effort is underway to bring greater participation from companies in Asia to the voice over IP standards project. The committee hopes to strengthen its relationship with companies in that region to further global commitment to the resulting guidelines.
While most of the work done by standards organizations is carried out by volunteers, ETSI has committed funding to pay for three experts to work on the project. Several working groups within the committee are looking at specific issues related to voice over IP, and experts are working to solve the technical challenges inherent in the use of voice transfer over IP- and switched-circuit-based networks.
ETSI has broken down its examination of voice over IP into four scenarios and is addressing technical specifications of each scenario independently. The first scenario involves a communication made by an IP network-based user to a switched-circuit network-based user. Scenario two involves communication made by a switched-circuit network-based user to the IP network-based user. Communications between two switched-circuit network-based users with IP-based networks as the connection between them is outlined in the third scenario. And, the fourth scenario entails communications between IP network-based users with switched-circuit networks as the connection.
The institute’s TIPHON committee focused first on specifications that cover the basic call, approving between one and three specifications at each meeting, according to committee chairman Helmut Schink. The project is planned for completion in three phases with the first phase addressing the first scenario—the IP network-based call to the switched-circuit network-based user. The second phase would include amendments to the first-phase documents and work on the second scenario involving the call from the switched-circuit network-based user to the IP network-based user. The third phase is slated to include amendments to the first- and second-phase documents and should cover all issues for each of the four scenarios. Schink believes all three phases of the TIPHON project could be completed as early as this fall.
The project will provide technical descriptions of information flows needed to handle basic calls from an IP-based network H.323 terminal to the switched-circuit-based terminal using the E.164 standard. The E.164 standard is an ITU-recommended numbering structure for networks that use circuit-switched technology to transmit voice communications. H.323 is the ITU standard that defines the capabilities of the unit that allows point-to-point or multipoint conferences in packet-based networks. An H.323 terminal can provide audio, video and data communications.
The committee must also explore transferring information between terminals where multiple gatekeepers, gateways and domains are involved. The gateway is a network end point that allows real-time, two-way communications between IP network-based H.323 terminals and switched-circuit network-based terminals. The gatekeeper provides address translation and controls access to the network for H.323 terminals and gateways. The units can also provide bandwidth management and gateway location.
To link communications between terminals on IP and switched-circuit networks, specifications for naming, numbering and addressing are needed. The TIPHON committee has worked to resolve these issues but is still working to gain worldwide acceptance of a standard numbering convention to promote interoperability among users.
Schink delineates the problems inherent with IP numbering, noting that the IP number is long and each user does not have a fixed number. He explains that there are different ways the number can be used to make the connection, so there could be many national standards or a global standard. The committee began researching the possibility of a global numbering system to facilitate voice over IP about one year ago.
The option of allocating telephone numbers to IP end points with the adoption of a global numbering system is outlined by TIPHON committee vice chairwoman Louise Spergel. Spergel is leading the working group that specifically looks at the naming, numbering and addressing issues of voice over IP. A global numbering system, she says, would entail action by the ITU, which is studying the possibility. In addition, a global database would be needed that can operate in real time. According to Spergel, a decision could come as early as this year.
Those working on the TIPHON standards have also sought to identify and define service mechanisms that interoperability will require. In particular, the committee has explored the technical aspects of accounting, but according to Schink, the committee has not yet suggested specific billing models. “That [billing procedure] should be very flexible and market driven,” he emphasizes.
For the purposes of billing and accounting, the committee has concluded that TIPHON systems should include detailed service records on each call. The records must track basic calls, toll-free calls, operator-assisted or collect calls, premium-rate calls and credit-card calls. The records must also contain information about the type of service, time of day, source and destination of the call, the quality level of the service, length of the call and resource utilization.
The TIPHON committee is also working on security issues to prevent eavesdropping on IP links. TIPHON-compliant systems must support authentication to prove user identity and must provide proof of the origin of information to prevent wrongdoers from denying involvement in illegal transactions. The committee is seeking to ensure end-to-end security support in TIPHON systems.
A major concern when using IP-based networks is quality of service. Call setup and call quality must be explored, giving particular attention to end-to-end delay in voice conversations and end-to-end speech quality, Schink says. The first step the committee faced in defining service quality levels entailed defining what constitutes an acceptable quality of service. He notes that users will often accept lower quality as a trade-off for other benefits such as mobility. Once the levels are defined, users can select different classes of service that might be connected to different pricing modules, thus making quality of service negotiable.
The TIPHON committee has described four service classes. The highest level, called “best,” is expected to be used in quality-of-service-engineered IP networks and local area network environments. It is envisioned to be similar to or better than a public switched telephone network (PSTN). The next level of service, designated “high,” provides service that is equal to the PSTN and is to be used to optimize bandwidth usage over IP quality-of-service-engineered networks. Third, yielding levels of quality similar to that of mobile telephony services, is the “medium” level, which is for IP networks that are not congested. Finally, the “best effort” service level will provide basic service but with the possibility of impaired speech and frequent end-to-end delays. The best effort service is expected over the public Internet. Three classes of terminals that achieve these performance objectives have also been designated.
Currently, the TIPHON commit tee is working on issues related to wireless communications and mobility. The idea is to have an end-to-end wireless mobile network for IP, Schink says. He estimates that specifications for this can come as early as 2000.
As the committee agrees on various TIPHON guidelines, validation processes will be used to test the procedures and work out problems. Temporary networks have been established throughout stages of the process for this purpose. Feedback about proposed TIPHON guidelines will be used to fix problems before the standards are presented to the communications community as a completed product.
Originally thought to be a short-term effort to define standards for voice over IP, the task has grown to include defining areas for back-end services that are not needed in real time such as directory services and call-back services. The TIPHON committee must also examine caller identification and emergency services. In the future, the committee will be paying greater attention to these issues as standards for voice over IP are further developed.