VoIP EE 548 Ashish Kapoor

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.

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.

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

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.

H.323 System and Components

Components - Terminals 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

Terminal Side Protocol Stack

Components – Gateways I

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

Gateway Protocol Stack

Components – Gatekeepers I

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

Gatekeeper Components

Components - Multipoint Control Units I

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

Components - Multipoint Control Units III

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

H.225 Call Establishment and Release Establish Release

References A Primer on the H.323 Series Standard Why H.323? IEC H.323