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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 SBC Edge (SBC). 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 to17583



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).

How Ping affects Media

The SBC periodically (approximately every 30 seconds) pings all the media endpoints that are engaged in calls with the SBC. For local endpoints (that are on the same subnet as the SBC), this ping mechanism is used to keep the ARP cache refreshed in the SBC. If a local endpoint does not respond to the pings, and if media IP address is different than signaling IP address, the call may have audio issues.

Configuring the Media System

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

    Figure : Media System Configuration

Media System Configuration 

Port Range - Field Definitions

Start Port

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

Number of Port Pairs

The number of media port pairs used by the SBC system. 

To determine the last port number:

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


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



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

This is used whenever the SBC 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 SBC 1000: 1MiB
  • For SBC 2000: 4MiB
  • For SWe Lite: 1MiB

Music files must be one of the following formats:

  • WAV
  • PCMA (not supported in SWe Lite)
  • PCMU (not supported in SWe Lite)
  • PCM (not supported in SWe Lite)

For detailed information about how to upload a Music on Hold file, see Uploading Music on Hold Files - SBC SWe Lite or Uploading Music on Hold Files - SBC Edge.

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

Note: Field applies to SBC 1000/2000 only.

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

Note: Field applies to SBC 1000/2000 only.

Specifies the level of echo cancellation employed by the SBC 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 SBC. The SBC sends STUN packets on the RTP and RTCP ports on all outbound IP call legs to open ports in the firewall (between the SBC 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 SBC) or Disable (STUN packets are not generated). Default option: Enable.