VOIP(SIP) Overview

                                Telecom Testing

                                                     |

                      --------------------                ----------------------   

                      Wireline                                     Wireless  

           (Broadband,SS7.....)          (GSM,CDMA,Wi-Fi,3G,4G.......technologies)    

          * VOIP(SIP) Technology  supports both Wireline and Wireless.

VOIP(Voice Over Internet Protocol):

                  It is the internet technology to carry  voice communication and multimedia sessions over Internet protocol networks such as internet.

          The steps involved in originating voip telephone call are signalling and media channel setup,digitization of the analog voice signal, encoding ,packetization and Transmission as Internet protocol packets over a packet switched network. 

              Voip systems employ session control  protocols to control the set-up and tear-down of calls.There are three types of  Voip tools that are commonly used, IP phones, Softphone and Mobile Softphone.

•     IP Phones: IP Phones are the most institutionally established but still the least obvious of the VOIP tools.
•     Softphones: It’s use has increased during the global recession as many persons, looking for ways to cut costs have turned to these tools for free or inexpensive calling or video conferencing applications.

              Three classes of software IP: Web calling,voice and video instant messaging and web conferencing.

•    Mobile Softphone: It is just another example of the adaptability of voip. Voip is available on may smart phones and internet  devices. 

                Voip  has been implemented in various ways using both proprietary and open protocols and standards.

PROTOCOLS:

Ø  H.323

Ø  Ip multimedia subsysem (IMS)

Ø  Media Gateway Control Protocol (MGCP)

Ø  Session Initiation protocol (SIP)

Ø  Real-Time transport protocal  (RTP)

Ø  Session Description Protocol (SDP)

The H.323 protocol was one of the, first viop protocol that found wide spread implementation for long-distance traffic as well as local area  networks. Since development of newer, less complex protocols , such as MGCP and SIP. The sip has gained wide spread voip market penetration. 

•        IETF Standard: Sip, Mgcp .

•        ITU Standard : H.323 ,Megaco .

•       Proprietory : IAX(Internation Asterix) , Sccp(Cisco) .

    SIP and H.323 are signalling protocols.

    Mgcp and Megaco are Media Gateway protocol

Voip Advantages:

1) Cheap calls or Free calls.

2) Low Equipment Cost .

3) Voice,Data,Video and cable,Iptv.

4) Qos (Quality of service).

Voip Dis-Advantages:

1)  Bandwidth.

2)  Electric Power

Voip Protocol Layers: