H.248 protocol
Media Gataway Control Protocal, IETF, ITU-T Developed Media Gateway Control Protocol, for communication between media gateway controllers and media gateways; H.248 protocol is also known as Megaco / H.248.
The H.248 / MeGaco protocol is the product of the gateway separation concept. The core of the gateway separation is the service and control separation, control and bearer separation. This allows business, control and carrying independently, operators can provide colorful business while making full use of new technologies, and enhance network value through continuous innovative business.
H.248 / megaco is based on the MGCP protocol (RFC2705 definition), which combines the development of other media gateway control protocols, providing control of the establishment, modification, and release mechanism of the media, and can also carry some With the call signaling, support the call of the traditional network terminal. The protocol plays an important role in building an open and multi-network-integrated NGN.
【basic concepts】
* Termination
One of the two main abstraction concepts of the H.248 / MeGaco protocol is the MG logic entity, which can send and / or receive one or more media, such as analog users to access the telephone line in the gateway, relay gateway The relay circuit, one terminal belongs to any time and can only belong to a context.
* Context)
The context is also one of the two main abstraction concepts of the H.248 / MeGaco protocol. It is a connection between terminals, which describes the parameters of terminal topology relationships and media mixing / exchange, can be created via Subtract, The move command is deleted.
* Introduction to the protocol
A message of the H.248 / MeGaco protocol contains one or more transaction processing, each transaction process contains one or more contexts, each context contains one or more commands, each command contains one or more descriptors.
H.248 / Megaco contains eight commands: add, subs, modi, modify, audit value, audit capabilities, notify, service change, and various commands through their carrying parameters.
[Typical Call Process]
* The caller is taken, and the MG is detected to report the event (Off-hook) to MGC after passing the notify command;
* MGC lets MG add a CONTEXT to the calling port via the add command and call the call;
* User dial, MG will report the number to MGC by the notify command;
* MGC Analysis The called number, finds the called port, and the command MG adds the called port to a context;
* MGC command MG feeds back ring tones to the main call, and send a ringing tone to the called;
* The called picking, the MGC command MG connection master is called;
* Master / called hang up, the MGC command MG releases the main called connection, put the main / called port to the Context.
Points: http://rockychen.blogchina.com/blog/refer.446168.html
