SBC 1000/2000 4.1.x : Configuring the Media System

The Media System Configuration contains system-wide settings for the Media System, configuring the media system means setting the number of RTP/RTCP port pairs and the starting port. Other aspects of media handling, such as Media Profiles, Lists, and Media Crypto Profiles are handled in different sections of the UI and are explained on their own topic pages.

UDP ports are used for transmission of VoIP calls employing RTP protocols (RTP over UDP). The start port is the first port that can be used for a call. Calls require a pair of ports, one for the voice the other for the control information (RTP/RTCP). The number of port pairs determines the number of simultaneous IP Call Legs on the Sonus SBC 1000/2000. For example; if you have 100 pairs, you can have a maximum of 100 simultaneous IP Call Legs. This does not affect the number of TDM/TDM calls.

SBC Reserved Ports





















16384 through 16984


If you have 100 pairs, and every call has one IP call leg, and one TDM call leg, then you can have 100 calls. However, if a call is IP on the inbound, and also IP on the outbound leg, then it requires two port pairs and this reduces the total number of simultaneous call accordingly (i.e., maximum of 50 IP/IP calls vs. Max 100 IP/TDM calls).

Configuring the Media System

  1. In the WebUI, click the Settings tab.
  2. In the left navigation pane, go to Media > Media System Configuration.

Media System ConfigurationĀ 

Port Range - Field Definitions

Start Port

Specifies the starting number for the RTP and RTCP port range.

To determine the last port number:

First Port Number + (2*Number of Port pairs) - 1.

Given: default value for starting port number (16384) and the (default) number for port pairs is 600.
There are 600 pairs, meaning there are 1200 individual ports. 16384 + (1200-1) = 17583

Number of Port Pairs

The number of media port pairs used by the Sonus SBC 1000/2000 system. For example, if the default values are used for starting port number and number of ports, the last port number would be 10959. Valid entry: 1 to 4800.


Specifies the DSCP value for all RTP/RTCP packets from the Sonus SBC 1000/2000.

This is used whenever the Sonus SBC 1000/2000 is connected to an external gateway that handles both data and voice traffic. When large volumes of data traffic as well as all VoIP traffic flow through the same router, a policy may be created that used the DSCP value of the media packets. The policy should be structured such that VoIP media packets receive higher priority and are expedited while other packets receive a lower priority and are queued. Network administrators should ensure that the non-VOIP packets are tagged with a different DSCP value on their network. Typically, the choice of DSCP for various kinds of packet flows in the network is determined by the network administrator and is configured on all routers within that IP network.

Music on Hold - Field Definitions

Music on Hold Source

Specifies the audio source. Sources can be an uploaded music file (File) or live audio sourced from an FXS port (Live). Default option is File. If you select Live, the FXS Port option is displayed.

When uploading a Music file, the maximum file sizes are as follows:

  • For Sonus SBC 1000: 1MB
  • For Sonus SBC 2000: 4MB

Music files must be one of the following formats:

  • WAV
  • PCMA
  • PCMU
  • PCM
  • G726

For detailed information about how to upload a Music on Hold file, see Uploading Music on Hold Files.

FXS Port

A list of available FSX ports from which live audio may be sourced. The FXS Port field is only visible when Live is selected from the Music on Hold Service drop down list.

Other Options - Field Definitions

Echo Canceller Type Option

Specifies the type of Line Echo Cancellation (standard or dual filter).

The standard LEC covers 128ms tail length (echo delay) and employs a 24ms sparse (non-zero coefficients) filter. The Dual Filter (background and foreground) Line Echo Canceller (LEC) covers 128ms tail length and uses 48ms sparse foreground filter. The Dual Filter is expected to provide better performance during double talk or slow echo-path change. Selection of the Dual Filter option may result in reduced channel densities.


Sonus recommends that you not Apply any change to the Echo Canceller Type Option unless the system is idle (no calls). Applying a change while the system is not idle may result in unknown behavior.

Echo Cancel NLP Option

Specifies the level of echo cancellation employed by the Sonus SBC 1000/2000 Nonlinear Signal Processor.

The default value is Mild. However there are two additional levels of echo cancellation, Strong and Aggressive. As each telephony system implementation varies, their echo characteristics similarly vary. Adjust the level of echo cancellation to suit your particular deployment. Too little cancellation may result in a persistent echo, too aggressive and you may experience voice "clipping".

Send Stun Packets

Specifies whether STUN packets are generated from the Sonus SBC 1000/2000. The Sonus SBC 1000/2000 sends STUN packets on the RTP and RTCP ports on all outbound IP call legs to open ports in the firewall (between the Sonus SBC 1000/2000 and the Internet). The ability to enable/disable this option is for customers who do not have a firewall and would like a way to disable STUN packet generation. Two options are available: Enable (STUN packets are generated and sent by the Sonus SBC 1000/2000) or Disable (STUN packets are not generated). Default option: Enable.

Uploading Music on Hold Files