Published on February 25, 2014
IP TELEPHONY 1
What Is IP Telephony? VoIP and Internet Telephony both refers to communications services carried over IP (Internet Protocol) rather than over the Public Switched Telephone Network (PSTN) 2
Definition : Internet Telephony, or Voice over Internet Protocol, is a method for taking analog audio signals, like the kind you hear when you talk on the phone, and turning them into digital data that can be transmitted over the Internet. 3
ABSTRACT Internet telephony is a novel and cheaper method of communication and conducting business over the Internet. The practical upshot of this is that by using some of the free Internet Telephony software that is available to make Internet phone calls, you are bypassing the phone company (and its charges) entirely. IP Telephony 4
INTRODUCTION Internet telephony uses the Internet protocol to send audio, video an data between two or more users in the real time. IP telephony is the integration and convergence of voice and data networks, services, and applications. The main motivation of development of IP Telephony is the cost saving & integrating new services. 5
Introduction (cont…) Vocaltec introduced the first Internet telephony software product in early 1995. Running a multimedia PC, the Vocaltec Internet Phone. In 1996, Vocaltec with an Intel Company announced to produce the first IP telephony gateway. 6
Classification of IP Telephony : The classification of IP Telephony is based on three characteristics. They are., * Terminal devices * Gateways * Means of transmission 7
Terminal devices & Gateways: The most common way of classifying IP Telephony combines the first two of these three characteristics the nature of the terminal devices used and the physical location of the gateways which must be employed to interconnect IP networks and the PSTN to provide end-to-end service. IP Telephony 8
Means of transmission: The third characteristic introduced above, the nature of the principal underlying means of transmission. The following definitions are offered as a means of interpreting the many different terms which are thrown about in this field: • Internet Protocol (IP) Telephony • Public Telephony 9
Types of IP Telephony: PC-to-PC PC-to-PHONE PHONE-to-PHONE PHONE-to-PC 10
PC-to-PC It was the first generation IP Telephony.Users on both ends of a PC-to-PC ‘call’ require a personal computer (PC) equipped with audio capabilities, the same software, and an Internet connection. Calls generally have to be pre-arranged because there is no way of ‘ringing’ the other user, if he or she is not online at the desired time. PC-to-PC calling is well-suited to Internet applications such as “chat rooms”service . 11
PC to PC
Phone-to-phone over IP using Gateways
Phone-to-phone over IP Using Adapter Boxes 14
PC-to-PHONE: • From the service provider’s point of view, PC-toPhone calling is more complex than simple PC-to-PC calling because calls need to be billed and routing arrangements negotiated. • For that reason, many service providers restrict this service to a limited range where qualityof-service requirements are not so demanding (because duplex communication is not a requirement).15
PC-to-Phone or Phone-to-PC
Different types of IP telephony Standards H.323 standard Session initiation protocol (SIP) Media gateway to media controller protocol (MGCP) 17
What is H.323 The H.323 standard for the transmission of real-time audio, video, and data communications over packetbased networks based on IP telephony. H.323 is a standard produced by the ITU-T Study Group 16. Currently the most widely-supported IP telephony signaling protocol. 18
H.323 Components Terminals Gateways Multipoint Control Units (MCUs) 19
Terminals : H.323 terminal can either be a personal computer or a stand-alone device, running an H.323 and the multimedia applications. Gateways : An H.323 gateway provides connectivity between an H.323 network and a non-H.323 network. 20
Multipoint Control Units: MCUs provide support for conferences of three or more H.323 terminals. All terminals participating in the conference establish a connection with the MCU. 21
Protocols Specified by H.323 : real-time transfer protocol (RTP) real-time control protocol (RTCP) 22
Real-Time Transport Protocol Real-time transport protocol (RTP) provides end- to-end delivery services of real time audio and video. RTP is used to transport data via the user datagram protocol Real-Time Control Protocol (RTCP) RTCP provides control services for RTP. 23
H.323 Call Establishment 24
H.323 Control signaling Flows 25
Advantages: 1.Reduced administration as well as network costs 2.Guaranteed service delivery 3.Enhanced operational efficiencies 4.Effectively bring together mobile and remote employees 5.Add innovative features including hardware 6.Reduced telecom cost via toll by pass 7.Effective as well as efficient management of your fax, voicemail, and email messages 8.free of cost 26
Dis-advantages: Exposure to Denial of Service attacks Challenging emergency calls Easy congestion Limited or no use in the absence of a dedicated internet access
CONCLUSION Internet telephony is cost savings and integrating new services. Many public telecommunication operators are establishing their own IP telephony services, and using IP-based networks as alternative transmission platforms. 28
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