A seminar on Internet Telephony

Transcription

1 A seminar on Internet Telephony Presented by: Nitin Prakash Sharma M. Tech. I.T IIT Kharagpur Internet Telephony 1

2 Contents Introduction H.323 standard Classes of connections and billing Requirements for IPT Management Conclusion References Internet Telephony 2

3 Introduction History VocalTec* introduced the first IP telephony software product in early 1995 March of 1996, VocalTec announced to produce the first IP telephony gateway Gateways are the key to bringing IP telephony into the mainstream What is Internet telephony? IP telephony (Internet Protocol telephony) is a general term for the technologies that use the Internet Protocol's packetswitched connections to exchange voice, fax, and other forms of information that have traditionally been carried over the dedicated circuit-switched connections of the public switched telephone network (PSTN). Internet Telephony 3

4 Introduction Factors making Internet telephony possible: Voice quality is increasing, thanks to new codec technology There are ongoing improvements in compression techniques Full-duplex PC sound cards enable two-way simultaneous calls The typical PC is getting more and more powerful, making it possible to perform processor-intensive functions without specialized hardware. Internet Telephony 4

5 What is H.323? Basic Protocols H.323 Standard RAS RTP and RTCP Resource Reservation Protocol (RSVP) Components Terminals Gateways Gatekeeper Internet Telephony 5

6 What is H.323? H.323 Recommendation describes terminals and other entities that provide multimedia communications services over Packet Based Networks (PBN) which may not provide a guaranteed Quality of Service. Internet Telephony 6

7 Registration/Admission/ Status (RAS) The RAS channel is a User Datagram Protocol (UDP)- based protocol Used for: Endpoint Registration/ Deregistration Admission Control Bandwidth Change Request Endpoint Status Control. Internet Telephony 7

8 RTP and RTCP (Real-time Transport Protocol and Real-time Control Protocol) The functions provided by RTP include: Sequencing Payload Identification Frame Indication Source Identification Intramedia Synchronization The function provided by RTCP include: QoS feedback Session Control Identification Intermedia Synchronization Internet Telephony 8

9 RSVP RSVP is a transport layer protocol It is receiver oriented It supports both unicast and multicast It maintains soft state in routers and hosts, providing graceful support for dynamic membership changes It provides transparent operation through routers that do not support it Enables a network to provide differentiated levels of service to specific flows of data Internet Telephony 9

10 H.323 basic protocols Gatekeeper Annex G Q.931/H.245 Gatekeeper RAS Q.931/ H.245 Q.931/ H.245 RAS Endpoint Signalling (Q.931) H.245 RTP/RTCP Endpoint Gatekeeper Routed Signaling Direct Routed Signaling Internet Telephony 10

11 Component - Terminal H.323 terminal can be either a personal computer or a standalone device, running an H.323 and the multimedia applications Supports audio communications and optionally supports video and data communications Internet Telephony 11 *H.323 Primer

12 Component - GateKeeper Acts as the central point for all calls within its zone Does address translation Bandwidth management Admissions Control Zone Management Call Control Signaling Call Authorization *H.323 Primer Internet Telephony 12

13 Component - Gateway Function performed by Gateway: Translation function between H.323 conferencing endpoints and other terminals Translates between audio and video Terminals communicate with Gateways using the H.245 and Q.931 protocols. Not required in LAN. Internet Telephony 13 *H.323 Primer

14 H.323 Network Elements H.323 Terminal H.323 MCU H.323 Gatekeeper H.323 Gateway H.323 Terminal H.323 Terminal GSTN GQOS LAN N-ISDN B-ISDN V.70 Terminal H.324 Terminal Speech Terminal H.322 Terminal Speech Terminal H.320 Terminal H.321 Terminal Internet Telephony 14

15 Phone-to-Phone via the Internet Server of IP Telephony Internet Calling SCN Network of calling Gateway of calling Gateway of called SCN Network of called Called IP Telephony Class1 connection (Phone-to-Phone via the Internet) Internet Telephony 15

16 Phone-to-PC in the Internet Network of calling SCN Gateway of calling and called s Calling Network of called Server of IP Telephony Internet Called IP Telephony Class2-1 connection (Phone-to-PC in the Internet) Internet Telephony 16

17 PC in the Internet-to-Phone Network of calling Internet Calling Server of IP Telephony Network of called Gateway of calling and called SCN Called IP Telephony Class2-2 connection (PC in the Internet-to-Phone) Internet Telephony 17

18 PC-to-PC in the Internet Network of calling and called Server of IP Telephony Calling Internet Called IP Telephony Class3 connection (PC-to-PC in the Internet) Internet Telephony 18

19 PC in the Internet-to-PC in the separate IP-based network via SCN Network of calling Server of IP Telephony Internet Calling Gateway of calling Gateway of called IP-based network Network of called Called SCN Identical to PC-to-Phone (Class 2-2) connection (Routing is based on E.164 number.) (Routing is based on the proprietary address.) A part of path in Class 4-1 connection is identical to the path in PC-to-Phone (Class 2-2) connection Internet Telephony 19

20 PC in the separate IP-based network-to-pc in the Internet via SCN Network of calling IP-based network Internet Server of IP Telephony Calling Gateway of calling Gateway of called SCN Network of called Called (Routing is based on the proprietary address.) Identical to Phone-to-PC (Class 2-1) connection IP Telephony Class 4-2 connection (PC in the separate IP-based network-to-pc in the Internet via SCN) Internet Telephony 20

21 PC-to-PC via SCN Network of calling Calling IP-based network Gateway of calling Gateway of called SCN IP-based network Network of called Called (Routing is based on the proprietary address.) (Routing is based on E.164 address.) (Routing is based on the proprietary address.) IP Telephony Class 4-3 connection (PC-to-PC via SCN) Internet Telephony 21

22 IPT Management Requirements Pre-Deployment Assessment Post-Deployment QoS Monitoring Performance from the End-User Perspective Managing Security Troubleshooting Automated Management Call Management Internet Telephony 22

23 Conclusion Internet Telephony is a powerful and economical communication options which is gaining its popularity The most significant obstacles in reaching the height of success is the unsatisfactory voice quality and the lack of means of commercial deployments. Both of them are under investigation. The voice quality will increase with special QoS means and generic increasing bandwidth. Commercial deployment should be designed by both, commercial and academic world. The standard for addressing a millions of PSTN should be made so that they can be able to use it. Simultaneously Internet telephony systems that are currently deployed should be maintains and managed so that they will encourage others for deploying internet telephony. Internet Telephony 23