The Session Refresh feature periodically instructs all INVITE dialog legs to refresh.

  1. On an incoming initial ACK or when the callEstablished session state field is true, a timer is set to the duration specified by the TimerInterval in the feature’s configuration.

  2. On the expiry of the timer, it is reset and Leg.refreshSession is instructed on each leg using the RefreshPeriod from the feature’s configuration.

  3. The RefreshPeriod represents the period of no activity before a refresh request should occur. If no messages have been sent or received on a leg within the RefreshPeriod, a refresh request transaction will be initiated.

Refresh requests are by default re-INVITE requests. The Session Refresh feature can be configured using the RefreshWithUpdateIfAllowed configuration to use UPDATE requests instead. If an endpoint did not include the UPDATE method in it’s Allows header then the RefreshWithUpdateIfAllowed configuration is ignored.

Note RFC 6141 describes this process in SIP INVITE dialogs. The feature is also triggered on receiving a RAR. This will cause all legs to be refreshed immediately.

Details

Feature script name

SessionRefresh

Applicable contexts

SIP service

SAS Support

No

Prerequisite features

N/A

Feature execution points
Pre

SipAccess_SipRequest SipAccess_ChargingReauth SipMidSession_ChargingReauth SipEndSession

Post

SipAccess_SipResponse

Timer usage

Feature-targeted timer triggers feature directly on expiry. Does not need to be registered against SipAccess_ServiceTimer execution point.

Session state inputs and outputs

Inputs

Name Type Format Description Behaviour if null/invalid

SentinelSelectionKey

com.opencloud.sentinel.common.SentinelSelectionKey

selection key
for example, <platform>::::

For selecting configuration data

Increment InputParameterErrors common cleanup actions

CallEstablished

Boolean

true or false

true if the session has been established

Initially set to false

Feature responses

Response Reason

featureHasFinished

feature has finished

Configuration

These parameters configure the Session Refresh feature:

Parameter Type Description

TimerInterval

long

Interval of periodic timer (seconds)

RefreshPeriod

long

Period of no activity for leg to refresh (seconds)

RefreshWithUpdateIfAllowed

boolean

Whether the session should be refreshed using UPDATE requests so long as the endpoint allows UPDATE requests.

Provisioning interfaces

The feature is provisioned using the Sentinel Features REST API or web interface.

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Sentinel Express Version 2.8.0