Point-to-Point communication is the most basic and common configuration for video conferencing limited to only two endpoints just like a normal telephone call. AVer's point-to-point systems includes HVC130 and EVC100/130/130P. Check our product introduction for more info: http://communication.aver.com/lines/video-conferencing.
For three or more endpoints to communicate with each other simultaneously, a multipoint control unit (MCU) is served as a bridge that initiates and receives calls from participants. A MCU is a host endpoint located at the end of a LAN and is composed of a multipoint controller (MC) and multipoint processors (MPs). From the beginning, MCUs have been developed as dedicated, stand-alone devices. Their functions, however, can also be integrated into the video conferencing system (i.e. codec) which is then called as a built-in or embedded MCU.
AVer EVC300/EVC900 is our solution for multipoint video conferencing. Its embedded MCU allows up to 4/10 sites to connect with the flexibility to upgrade from EVC300 to EVC900 simply by license. It also supports our EZMeetup software for PC and mobile devices making it ideal for users outside the conference room.
H.320, titled “Narrow-band visual telephone systems and terminal equipment”, is the ITU-U umbrella recommendation for video conferencing and multimedia communication over ISDN-based telephone networks at bit rates from 64 Kbps to 2 Mbps. It mainly consists of H.261 for video, G.711 for audio and other three for signal and call control.
It is the audio-visual communication recommendation which specifies call signaling, call control and media/data streaming protocols for VoIP over packet-based networks (e.g. the internet). It includes H.261/H.263/H.264 for video, G.711/G.722/G.728 for audio and H.225.0/H.245 for control.
There are four major components in a packet-based communication system:
- Terminal/Endpoint: video, audio & data client
- MCU: conference control & content sharing
- Gatekeeper: address resolution & admission control
Two main functions of a gatekeeper are Call Admission Control (CAC) and address resolution among endpoints. It can communicate with known peer gatekeepers or discover remote gatekeepers through DNS query, as well as route calls when NAT/firewall traversal. Terminals need to register to a gatekeeper before connecting to a MCU.
- Gateway (Optional): protocol translation between networks
When a packet is transmitted between two networks, it has to pass through a node called gateway for converting different protocols. A gateway can be combined with a gatekeeper to proxy calls, which refers to as a Border Controller.
SIP (Session Initiation Protocol)
SIP is a text-based signaling protocol over IP networks used for controlling communication sessions such as multimedia distribution, interactive gaming, VoIP and video conferencing. It also supports the call processing functions and features in PSTN-based communications. SIP usually works with Session Description Protocol (SDP) and Real-Time Transport Protocol (RTP) which help identify the session media and deliver audio/video respectively.
SIP clients use TCP and UDP on port 5060 for non-encrypted signaling traffic whereas port 5061 for traffic encrypted with Transport Layer Security (TLS).
Typically, a SIP network contains three main elements:
- User Agent: SIP message sending & receiving endpoint
- Proxy Server: routing & request making on behalf of other user agents
- Register Server (Registrar): user agents registration control by the uniform resource identifier (URI)
- Gateway: interface between SIP and other networks
For AVer EVC300/900 to act as a SIP server, decide your User Name, Authentication Name and Server ID for clients to dial in. On the other hand, AVer EVC300/900 can act as a SIP client by entering information about the SIP server such as IP address and Server ID.