Seminar Report on IP Telephony

Introduction to IP Telephony Seminar Topic:

Internet protocol telephony represents technologies that use the internet protocol’s packet switched connection to exchange voice, fax, and information which was traditionally been carried over dedicated circuit-switched connection. Calls travel as packets of data on shared lines using internet.

Telephone calls are transported over internet using IP, whether traditional telephony devices, dedicated terminals or multimedia PCs may take part in calls and calls can be either entirely or partially transmitted over internet.

IP telephony uses protocols for transport and for signaling. Transport is done using UDP over IP for voice packets and either UDP or TCP over IP for signals. Signaling protocols provide special features like: establishing a call, terminating a call, forwarding a call, call waiting and making conference calls.

The benefit of IP is money saving and easy implementation of services. IP telephony system consists of these elements:

  • End Devices: may be traditional telephones (analog/ISDN/GSM/..), audio equipped PC or single use appliances.
  • Gateways: the task of gateways is translating transmission format, signaling procedures, audio codec to/from the format for transport over internet.
  • Gatekeepers / proxies: provide centralized call management functions; call admission control, bandwidth management, address translation, authentication, user location, etc.
  • To manage multiparty conferences, multipoint conference units are used.

The two-way transmission of voice over packet-switched IP network is part of the TCP/IP protocol. IP is the universal transport for almost all data and video communications worldwide.

The calls between PC to PC or between phones and PCs using public internet became popular, but call quality over internet is erratic because internet provides no guarantee of QOS. But when organization has control over its network, quality can be excellent. Organizations with their own IP networks and IP telephony carriers have developed IP backbones, and provide voice quality that competes with the traditional PSTN.

Even though global telephone network has been converted to digital for some time, the circuit switched public telephone network is wasteful. One person talks and other listens, both “caller” and “callee” channels are always dedicated. IP voice codec cut the digital requirement from 64Kbps down to 8Kbps with good quality. Thus bandwidth requirement for voice on an IP network is 1/16th of PSTNs dedicated digital circuit.

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