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RTMP SIP Gateway

What is RTMP

RTMP is the abbreviation for Real Time Messaging Protocol. It was developed for streaming video, audio and data over the Internet, between a Flash player and a server. The RTMP has four variations: plain, RTMPS, RTMPE, RTMPT. RTMP is a TCP-based protocol which maintains persistent connections and allows low-latency communication. To deliver streams smoothly and transmit as much information as possible, it splits streams into fragments and their size is negotiated dynamically between the client and server while sometimes it is kept unchanged. Fragments from different streams may then be interleaved, and multiplexed over a single connection.

What is SIP

SIP is the abbreviation for Session Initiation Protocol. SIP is an application-layer control protocol that can establish, modify, and terminate multimedia sessions such as Internet telephony calls. SIP can also invite participants to already existing sessions, such as multicast conferences. Media can be added to and removed from an existing session.

SIP supports five facets of establishing and terminating multimedia communications:

User location: determination of the end system to be used for communication;
User availability: determination of the willingness of the called party to engage in communications;
User capabilities: determination of the media and media parameters to be used;
Session setup: "ringing", establishment of session parameters at both called and calling party;
Session management: including transfer and termination of sessions, modifying session parameters, and invoking services.

What is a Gateway

A gateway interconnects networks with different network protocol technologies by preforming the required protocol conversion. It allows communication between the webphone using the RTMP and the SIP phone. A gateway is a network point that acts as an entrance to another network. In enterprises, the gateway is the computer that routes the traffic from a workstation to the outside network that is serving the Web pages. In homes, the gateway is the Internet Service Providers that connects the user to the internet. In enterprises, the gateway node often acts as a proxy server and a firewall. The gateway is also associated with both a router, which use headers and forwarding tables to determine where packets are sent, and a switch, which provides the actual path for the packet in and out of the gateway.

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RTMP SIP Gateway

There is a server, in this case the Ozeki Webphone Gateway, which is responsible for building, maintaining and breaking down sessions and the media data also flows through it between the clients. The call can go between the flash webphone and any kind of SIP client back and forth, meaning anyone can start the call. It only works with browsers, which support flash, you can download the flash plugin from

The webphone communicates with the Ozeki Webphone Gateway through the JavaScript API of the Ozeki Webphone Gateway.

Make peer-to-peer calls based on RTMP with OZEKI Webphone Gateway learn more >>