Media Inactivity Timers (RTP)

The Media Inactivity feature was added to inform the signaling layers (SIP) when RTP has stopped flowing. The Initial Media Inactivity timer indicates that no RTP was ever received on the IP channel. The Media Inactivity Timer indicates that RTP has stopped flowing. When the signaling layers receive indications that these timers have expired, the signaling releases the channel. This feature resolves the problem where signaling gets out of sync and IP channels remain up with no one on the other side of the call.

Initial Media Inactivity Timer

The Initial Media Inactivity Timer is started when the channel is setup (Outseized). If no RTP packets are received for the configured amount of time, an event is generated to the signaling layers. The Default value for the Initial Media Inactivity Timer field is Disabled. To Enable the Initial Media Inactivity Timer, click in the Initial Media Inactivity Timer field and select Enable. When the Initial Media Inactivity Timer field is set to Enabled, the Initial Media Inactivity Detection Value will appear just below it. This field will allow configuring a value in seconds to this timer.  

Media Inactivity Timer

The Media Inactivity Timer is used to indicate that RTP packets have stopped flowing for a configured amount of time. When RTP packets stop flowing and the timer has elapsed, an event is generated to the signaling layers and the channel is released. The Default value for the Media Inactivity Timer field is set to Disabled. To enable the Media Inactivity Timer, click in the Media Inactivity Timer field and select Enable. After enabling the Media Inactivity Timer field, a second media inactivity field labeled Media Inactivity Detection Value, will appear just below it. This field allows configuring a value in seconds to this timer.

The Initial Media Inactivity Timer and Media Inactivity Timers also take into account if a call is put ON HOLD or if a call is put into a XMT only or RCVonly mode. See table below.

Configuration

• The Initial Media Inactivity Timer and the Media Inactivity Timers are both configured through the IP Profile object. Within this object, the Initial Media Inactivity Timer and Media Inactivity Timer can be enabled. See screen captures below. By default, they are both initially set to Disabled.

Open

• Once either of the timers is set to Enable, the Seconds box under each field will change from being shaded green to shaded white. At this point the value for the timer can be entered into the box The Seconds box lets a user configure the number of seconds required for each timer. Below is a table displaying the default values as well as the range of values that can be configured.

• Once the timers are configured and the profile is committed, both Initial Media Inactivity Timer and Media Inactivity Timers are set for all new calls using this profile.

Call Flows

Below are a few Call Flows and what would happen if the Initial Media Inactivity Timer or Media Inactivity Timer were to expire and send the message to the signaling layer to release the Channel

Call Flow Example  (SIP)

When the Initial Media Inactivity Timer expires it sends a message to Layer 3 Signaling to initiate a tear down of the call. A BYE is sent to the Gateway and a Clear Request is sent to Layer 4 to release call.

Open

Call Trace

Below is and example of a G.723 to G.729 SIP Call. The Initial Media Inactivity Timer expired and sent the information to tear down the channel and any network resources. The Call trace below does not have the complete call. It is a portion of a Call Trace displaying what the Initial Media Inactivity Timer call trace info looks like. The call is initially connected as shown below.