Interworking Between SIP/SDP and H.323

There are currently two standards for signaling and control of Internet telephone calls, namely ITU-T Recommendation H.323 and the IETF Session Initiation Protocol (SIP). We describe how an interworking function (IWF) can allow SIP user agents to call H.323 terminals and vice versa. Our solution addresses user registration, call sequence mapping and session description. We also describe and compare various approaches for multi-party conferencing and call transfer

Programming Internet Telephony Services

Internet telephony enables a wealth of new service possibilities. Traditional telephony services, such as call forwarding, transfer, and 800 number services, can be enhanced by interaction with email, web, and directory services. Additional media types, like video and interactive chat, can be added as well. One of the challenges in providing these services is how to effectively program them. Programming these services requires decisions regarding where the code executes, how it interfaces with the protocols that deliver the services, and what level of control the code has. In this paper, we consider this problem in detail. We develop requirements for programming Internet telephony services, and we show that at least two solutions are required --- one geared for service creation by trusted users (such as administrators), and one geared for service creation by untrusted users (such as consumers). We review existing techniques for service programmability in the Internet and in the telephone network,and extract the best components of both. The result is a Common Gateway Interface (CGI) that allows trusted users to develop services, and the Call Processing Language (CPL) that allows untrusted users to develop services

A SIP-based Programming Framework for Advanced Telephony Applications

International audienceThe scope of telephony is significantly broadening, providing users with a variety of communication modes, including presence status, instant messaging and videoconferencing. Furthermore, telephony is being increasingly combined with a number of non-telephony, heterogeneous resources, consisting of software entities, such as Web services, and hardware entities, such as location-tracking devices. This heterogeneity, compounded with the intricacies of underlying technologies, make the programming of new telephony applications a daunting task. This paper proposes an approach to supporting the development of advanced telephony applications. To do so, we introduce a declarative language over Java to define the entities of a target telephony application area. This definition is passed to a generator to produce a Java programming framework, dedicated to the application area. The generated frameworks provide service discovery and high-level communication mechanisms. These mechanisms are automatically mapped into SIP, making our approach compatible with existing SIP infrastructures and entities. Our work is implemented and has been validated on various advanced telephony applications

A criação de redes de próxima geração IMS usando produtos Open Source

Estágio realizado na PT InovaçãoTese de mestrado integrado. Engenharia Electrotécnica e de Computadores. Faculdade de Engenharia. Universidade do Porto. 200

An Economic Analysis of Domain Name Policy

One of the most important features of the architecture of the Internet is the Domain Name System (DNS), which is administered by the Internet Corporation for Assigned Names and Numbers (ICANN). Logically, the DNS is organized into Top Level Domains (such as .com), Second Level Domains (such as amazon.com), and third, fourth, and higher level domains (such as www.amazon.com). The physically infrastructure of the DNS consists of name servers, including the Root Server System which provides the information that directs name queries for each Top Level Domain to the appropriate server. ICANN is responsible for the allocation of the root and the creation or reallocation of Top Level Domains. The Root Server System and associated name space are scarce resources in the economic sense. The root servers have a finite capacity and expansion of the system is costly. The name space is scarce, because each string (or set of characters) can only be allocated to one Registry (or operator of a Top Level Domain). In addition, name service is not a public good in the economic sense, because it is possible to exclude strings from the DNS and because the allocation of a string to one firm results in the inability of other firms to use that name string. From the economic perspective, therefore, the question arises: what is the most efficient method for allocating the root resource? There are only five basic options available for allocation of the root. (1) a static root, equivalent to a decision to waste the currently unallocated capacity; (2) public interest hearings (or beauty contests); (3) lotteries; (4) a queuing mechanism; or (5) an auction. The fundamental economic question about the Domain Name System is which of these provides the most efficient mechanism for allocating the root resource? This resource allocation problem is analogous to problems raised in the telecommunications sector, where the Federal Communications Commission has a long history of attempting to allocate broadcast spectrum and the telephone number space. This experience reveals that a case-by-case allocation on the basis of ad hoc judgments about the public interest is doomed to failure, and that auctions (as opposed to lotteries or queues) provide the best mechanism for insuring that such public-trust resources find their highest and best use. Based on the telecommunications experience, the best method for ICANN to allocate new Top Level Domains would be to conduct an auction. Many auction designs are possible. One proposal is to auction a fixed number of new Top Level Domain slots each year. This proposal would both expand the root resource at a reasonable pace and insure that the slots went to their highest and best use. Public interest Top Level Domains could be allocated by another mechanism such as a lottery and their costs to ICANN could be subsidized by the proceeds of the auction