Voip
- 2. Contents • Abstract • PSTN vs. INTERNET • What is VoIP? • How VoIP works? • VoIP Architecture. • Components of VOIP. • References.
- 3. Abstract • Voice over Internet Protocol (VoIP) is a technology that enables one to make and receive phone calls through the Internet instead of using the traditional analogy PSTN (Public Switched Telephone Network) lines.
- 4. PBX Circuit Switched Networks (Voice) PBX Packet Switched Networks (Data) Router Router Router Router Router • Separated networks • Separated applications/services • PBX: private branch exchange PSTN vs. INTERNETPSTN vs. INTERNET
- 5. PSTN • Voice network use circuit switching. • Dedicated path between calling and called party. • Bandwidth reserved in advance. • Cost is based on distance and time. INTERNET • Data network use packet switching. • No dedicated path between sender and receiver. • It acquires and releases bandwidth, as it needed. • Cost is not based on distance and time.
- 7. What is VoIP? • VoIP is packeting and transporting of classic public switched telephone system audio over an IP network. • It allows 2-way voice transmission over broadband connection. • It is also called IP telephony, internet telephony, voice over broadband, broadband telephony.
- 8. How does it work? • Converting the voice signal • ADC (analog to digital) • DAC (digital to analog) Voice (source) - - ADC - - - Internet - - - DAC - - Voice (destination) • Transmission of voice traffic in packets.
- 9. IP Network Multimedia PC Multimedia PC Initially, PC to PC voice calls over the Internet VoIP Architecture? PSTN (DC) Gateway PSTN (NY) Gateway Public Switched Telephone Network Gateways allow PCs to also reach phones …or phones to reach phones
- 11. VoIP Protocols - H.323 - Session Initiation Protocol (SIP) - Media Gateway Control Protocol (MGCP) - Gateway Control Protocol (Megaco, H.248) - Real-time Transport Protocol (RTP) - Real-time Transport Control Protocol (RTCP) - Secure Real-time Transport Protocol (SRTP) - Session Description Protocol (SDP) - Inter-Asterisk exchange (IAX) - Jingle XMPP VoIP extensions - Skype protocol
- 12. H.323 • H.323 is an architectural overview of internet telephony than a specific protocol • Supports G.711 (64Kbps) voice by default • H.245 let the terminals negotiate encoding algorithms, bit rate, etc. • ITU Q.931 is used for signaling • Gatekeeper controls end-points in a Zone • H.225 manages PC-to-gatekeeper channel called Registration/Admission/Status • Gateway connects Internet and PSTN
- 15. • H.245: It negotiates other aspects of the connection such as the bit rate. • RTCP is need for the control of the RTP channels. • H.225: Used when the terminals need a protocol for talking to the gatekeeper (if present). • RAS: The PC-to-gatekeeper channel it manages . • Q.931 :Used when need a protocol for establishing and releasing connections, providing dial tones, making ringing sounds, and the rest of the standard telephony.
- 16. Session Initiation Protocol (SIP) • Designed by Internet Engineering Task Force (IETF) • Describes how to set up VoIP calls, video conferences, etc. • Defined phone numbers as URLs • Main “methods” are Invite, Ack, Bye, Options, Cancel, and Register • Runs over UDP or TCP
- 18. SIP Example A proxy server is used as a redirection server
- 19. The REGISTER method relates to SIP's ability to track down and connect to a user who is away from home. This message is sent to a SIP location server that keeps track of who is where. That server can later be queried to find the user's current location. The operation of redirection is illustrated in Figure above. Here the caller sends the INVITE message to a proxy server to hide the possible redirection. The proxy then looks up where the user is and sends the INVITE message there. It then acts as a relay for the subsequent messages in the three-way handshake. The LOOKUP and REPLY messages are not part of SIP; any convenient protocol can be used, depending on what kind of location server is used.
- 20. VoIP SIP
- 21. Comparison of H.323 and SIP
- 22. VoIP Gateway • A VoIP gateway is a gateway device that uses Internet Protocols to transmit and receive voice communications (VoIP).
- 24. Advantages of VOIP • Low Cost • Portability • Features • Flexibility • video-conferencing
- 25. Disadvantages of VOIP • No service during a power outage • Emergency calls • Reliability • VoIP Voice Quality • Security: As VoIP uses the Internet, for example, it is vulnerable to the same type as security risks(Hacking , Denial of service , Eavesdropping)
- 26. Recommendation All these disadvantages will be overcome in time. There is a tremendous amount of work being done to increase the reliability and usefulness of VoIP. By 2008 most of the kinks will be worked out and VoIP will receive widespread consumer acceptance.
- 27. References 1- Andrew S. Tanenbaum (Computer Networks 4th Ed ) 2- A Seminar On “Voip” S. P. Vyas “Sri Balaji College Of Engineering &Technology” 3- Voice Over IP (VOIP) – An Overview “Montana State University” Ali Kujoory, Ph.D. 4- VoIP VOICE OVER IP Peter R. Egli INTERNET URLs •https://en.wikipedia.org/wiki/Voice_over_IP •https://en.wikipedia.org/wiki/Session_Initiation_Protocol •https://en.wikipedia.org/wiki/H.323 •https://en.wikipedia.org/wiki/Media_Gateway_Control_Protocol •https://en.wikipedia.org/wiki/H.248 •https://en.wikipedia.org/wiki/Real-time_Transport_Protocol •https://en.wikipedia.org/wiki/RTP_Control_Protocol •https://en.wikipedia.org/wiki/Secure_Real-time_Transport_Protocol •https://en.wikipedia.org/wiki/Session_Description_Protocol •https://en.wikipedia.org/wiki/Inter-Asterisk_eXchange •https://en.wikipedia.org/wiki/Skype_protocol
Editor's Notes
- #24: MOS- Mean Opinion Score, a measure of voice quality score, each codecs has its own bandwidth requirements, VoIP normal delay is 100ms, so 3.5 is a good quality achievement