查看“媒体接口配置”的源代码

;;;Media Interface 介绍
媒体接口负责SBC语音的媒体流的处理，具有以下功能：
*媒体接口负责处理语音编码的转换
**例如，G.729 到 G.722转换。
*媒体接口同时负责处理和媒体相关的功能，例如(RTP/SRTP)。

Media interfaces 实际上执行RTP语音流数据之间的转换。媒体接口实际上也是网络设备，也需要有IP地址等等相关信息(IP addr, Netmask, Gateway)。

如果有的环境使用了sangoma D100 (无外网端口) ，此IP地址可以是任何IP地址，这个地址保持“隐藏” ，设备RTP语音流将使用这个地址来通信。

;;;Media Interface 配置
第一步需要选择一个media mode模式。目前系统支持3种IP modes: 
*Hidden
**DSP Media interface IP addresses隐藏在网络中
**默认，推荐的模式
**使用单个IP address 来处理所有的Media/RTP
*Exposed
**DSP Media interface IP addresses将暴露在网络环境中
**使用多个IP addresses 来处理Media/RTP，但是CPU使用效率更高
*Disabled
**Software mode. 无 DSP interfaces
**使用在VM 环境中
 默认环境下，我们将使用hidden mode，用户访问“Configuration -> IP Settings -> Media Interfaces”. 
 用户必须点击 Modify 来修改添加媒体接口，以便系统可以发现默认的媒体接口。

http://manula.s3.amazonaws.com/user/1885/img/nsc-cfg-media-if.png

;;;Hidden Mode
The “Hidden” mode is simpler to operate. In this mode all the media interfaces are hidden within the system and all the IP traffic generated by the media interfaces is routed/forwarded through the NSC host operating system and NATed. This mode is simpler because you don’t have to worry about multiple IP addresses for your media interfaces. The media interfaces will still need an IP, but there is no possible conflict with your network as those interfaces will be hidden within NSC. You just have to choose a network that does not conflict with your real networks (ie, 192.168.168.0/24). The disadvantage of this mode is that all RTP is relayed thru the NSC host and therefore has an impact in the CPU load. Hidden mode works fine for call loads of up to 1,500 calls (3,000 call legs/sessions). If you require higher density you need to use “Exposed”.

 Note that appliances using D100 cards have no other option but to use “Hidden” mode because the D100 card has no external Ethernet port. In practice this is not a    problem because D100 users do not reach the high call loads at which “Hidden” mode is limited.

;;;Exposed Mode
The “Exposed” mode requires more careful configuration as the media interfaces will be exposed to your network (whatever network you plug the Ethernet cable to), so you must choose the IP network information carefully to avoid conflicts with other network equipment. The clear advantage of this mode is that RTP does not go through the host operating system, instead the media interfaces send the RTP directly to the external Ethernet port to its destination. No interrupt or system load at all in the host operating system for any RTP stream.

SBC Media Config Exposed

The first time you modify the media interfaces configuration you must go through a discovery procedure to find all media interfaces. Unless you are using a D150 device (stand-alone media interface) you should only select the network devices named “sngdsp[N]” for discovery (see “Detect Media Interfaces” field). If you are using a D150 (or several) you must select the ethernet interface the D150 device is attached to (they should share the same broadcast domain).

If you select the “Exposed” IP mode, the web ui will allow you to configure the IP settings for the media interfaces it finds.

In “Hidden” mode you are only asked to provide a starting UDP port range for the RTP streams. You can leave the default if you don’t require a particular port range.

Once you click “Save”, the web ui will perform the device discovery procedure which will take a few seconds. The discovery procedure will send Ethernet broadcast messages to auto-discover Sangoma media interfaces attached to the same network(s) of the selected Ethernet interfaces. Once done, you will receive a report of the hardware found.

SBC Media Config IP Addresses

In the example above, there is 2 network interfaces (sngdsp0 and sngdsp1) which correspond to one D500 card each. The first network interface (sngdsp0) has 4 media interfaces (also referred to as “media modules”). The network interface “sngdsp1” has attached 5 media interfaces.

Each media interface was assigned a network configuration based on the discovery page input. You can manually edit each media module network configuration by clicking “Edit”.

;;;Disabled Mode
Software SBC installations will not have any hardware DSP resources.
In this scenario one must set the Media Interface mode to Disable.

In this mode RTP Media will be handled in software.

Limitations of Software SBCs are
*Limited Transcoding capability
**Sangoma SBC currently only support free software voice codecs, such as iLBC, GSM, G726
**G729, AMR and other royalty codecs are not supported in software.
*Limited Transcoding capacity
**The transcoding capacity depends on VM or Host resources.
**It is possible to transcode hundreds of calls using a VM with significant resources
*Limited Session capacity
**Session capacity depends on VM or Host resources