Understanding MGCP ALG Call Duration and Timeouts

The call duration feature gives you control over Media Gateway Control Protocol (MGCP) call activity and helps you to manage network resources.

Typically a Delete Connection (DLCX) message will be sent out to delete a connection. The MCGP Application Layer Gateway (ALG) intercepts it and removes all media sessions for that connection.

A call can have one or more voice channels. Each voice channel has two sessions (or two media streams), one for Real-Time Transport Protocol (RTP) traffic and one for Real-Time Control Protocol (RTCP) signaling. When managing the sessions, the device considers the sessions in each voice channel as one group. Timeouts and call duration settings apply to a group as opposed to each session.

The following parameters govern MGCP call activity:

• maximum-call-duration—This parameter sets the absolute maximum length of a call. When a call exceeds this parameter setting, the MGCP ALG tears down the call and releases the media sessions. The default setting is 43200 seconds, and the range is from 180 through 432000 seconds. This setting also frees up bandwidth in cases where calls fail to properly terminate.
• inactive-media-timeout—This parameter indicates the maximum length of time (in seconds) a call can remain active without any media (RTP or RTCP) traffic within a group. Each time an RTP or RTCP packet occurs within a call, this timeout resets. When the period of inactivity exceeds this setting, the MGCP ALG gates opened for media are closed. The default setting is 120 seconds, and the range is 10 through 2550 seconds. Note that upon timeout, while resources for media (sessions and pinholes) are removed, the call is not terminated.
• transaction-timeout—A transaction is a signaling message, for example, an NTFY from the gateway to the call agent or a 200 OK from the call agent to the gateway. The Juniper Networks device tracks these transactions and clears them when they time out. The timeout range for MGCP transactions is 3 through 50 seconds and the default is 30 seconds.

Related Topics

• Junos OS Feature Support Reference for SRX Series and J Series Devices
• Understanding MGCP ALGs
• MGCP ALG Configuration Overview
• Example: Setting MGCP ALG Call Duration
• Example: Setting MGCP ALG Inactive Media Timeout
• Example: Setting MGCP ALG Transaction Timeout