1. VoIP EE 548 Ashish Kapoor

2. Characteristics – Centralized and Distributed Control • H.323 pushes call control functionality to the endpoint, while still providing the service provider or enterprise with the option to control every aspect of a call. • Endpoints can communicate directly. • Endpoints can communicate through a server.

3. Characteristics - Focused • H.323 was designed with one clear objective: to provide users with voice, video, and data conferencing capabilities over a packet-switched network. • H.323 does not try to do more than it should and does not try to pretend to be something that it is not.

4. Characteristics - Extensibility • Fully backward compatible with previous versions. • Equipment manufactures can extend functionality by inserting their own additions to the protocol.

5. Characteristics - Integration with Internet Standards • The first standards-based protocol to adopt RTP/RTCP for multimedia transmission. • Makes use of existing Internet technologies like URLs and DNS. • Ability to click on URL to place call. • Capable of performing DNS queries to locate a user or service.

6. H.323 System and Components

7. Client endpoints on the LAN Must support voice; data and video are optional All terminals must support H.245 Protocol Q.931 RAS RTP/RTCP Components - Terminals

8. Terminal Side Protocol Stack

9. Components – Gateways I

10. Components Gateways II • Connects 2 dissimilar networks. • The Gateway is an optional element in an H.323 conference • Establishing links with analog PSTN terminals. • Establishing links with remote H.320-compliant terminals over ISDN-based switched-circuit networks. • Establishing links with remote H.324-compliant terminals over PSTN networks

11. Gateway Protocol Stack

12. Components – Gatekeepers I

13. Components – Gatekeepers II • Acts as the central point for all calls within its zone • Provides call control services to registered endpoints • Translation from LAN aliases for terminals and gateways to IP or IPX addresses • Bandwidth Control • Optional Functions: • Call Control Signaling • Call Authorization • Bandwidth Management • Call Management

14. Gatekeeper Components

15. Components - Multipoint Control Units I

16. Components - Multipoint Control Units II • Consists of • Multipoint Controller (MC) - required. • The MC handles H.245 negotiations between all terminals to determine common capabilities for audio and video processing. • The MC also controls conference resources by determining which, if any, of the audio and video streams will be multicast. • Zero or more Multipoint Processors (MPs) • Mixes, switches, and processes audio, video, and/or data bits

17. Components - Multipoint Control Units III

18. H.225 AAAAarrrrrrrgggghhhhhh • The H.225 RAS is used between H.323 endpoints (terminals and gateways) and gatekeepers for the following: • Gatekeeper Discovery (GRQ) - Static and Dynamic • Endpoint Registration - used by the endpoints to join a zone and inform the gatekeeper of the zone's transport and alias addresses • Endpoint Location - transport address of an endpoint is determined and given its alias name • Admission Control • Access Tokens

19. Establish Release H.225 Call Establishment and Release

20. References • A Primer on the H.323 Series Standard • http://www.packetizer.com/iptel/h323/papers/primer/ • Why H.323? • http://www.packetizer.com/iptel/h323/why_h323.html • IEC H.323 • http://www.iec.org/online/tutorials/h323/index.html