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Overview

The SBC Core supports Application Layer Forking feature to receive a single initial INVITE at the ingress leg and send multiple INVITEs with different Call-IDs to different destinations on the egress leg. The first answered call is considered as active, and the SBC terminates the other calls gracefully by sending a CANCEL message. The SBC exposes a single dialog and a single media stream on the ingress leg while forking to multiple dialogs and exposing multiple media streams on the egress leg.

If different end devices with unique Address of Records (AoRs) in an enterprise exist, the SBC maintains an AoR group to perform Call Forking.

For example, if an enterprise contains three end devices with the following AORs:

tel: +18041774568

sip: +18041774568@mydomain.com

Sip: jack@mydomain.com

All of the above AoRs are grouped under an AoR Group and enabled for call forking. When there is an incoming call to any one of the AoRs, the call is forked to all the AoRs in this group. To support call forking feature, the aorGroupProfile parameter is added to profiles configuration.

Note

In external PSX, the flag Enable Call Forking is used to enable or disable the call forking functionality. However, this flag is not available in the SBC (ERE). The SBC performs VOIP Subscriber dip to determine the AoR Group. If AoRs are found for the VOIP subscriber, the call is forked to different AoR devices.

Note
  • Maximum 10 AoRs are allowed in an AoR group and it is separated by comma ",". These AoRs can be forked at a time with support for up to four Crankback Routes for each forked AoR.
  • The “Preferred Identity" configured for each AoR group is used to populate the originating identity (P-Asserted-Identity, From, Remote-Party-Identity headers) for calls initiated by any of the AoRs in the group.

The SBC supports following timers related to SIP forking:

  • Delay Before Ringing
  • Answer Too Soon
  • Wait for Answer


Note

Native Call Forking does not support GW-GW scenarios.

Perform the following steps to configure call forking feature in the SBC:

Configuring AoR Group Profile

Execute the following command to configure AoR Group Profile:

% set profiles aorGroupProfile AR2 aorDataList sip:123@ss.com;1111;2222;user=phone,sip:456@yy.com;0;0;user=phone aorDialogAttribute useFirst18x
% commit

Configuring the VOIP Subscriber

% set profiles voipSubscriber sip:EXAMPLE@RIBBON.com aorGroupProfile AR2 egressRURIAttribute aorEgress
% commit

Configuring Routing for the AoR Group Profile

To configure routing for the AoR Group Profile, refer to the section Basic Call Flow Using ERE.

Configuring Preferred Identity and Wait for Answer Parameters (Optional)

% set profiles aorGroupProfile AR2 preferredIdentity sip:123@ss.com waitForAnswer 0
% commit

Enabling Preferred Identity in the SIP Trunk Group (Optional)

% set addressContext default zone defaultSigZone sipTrunkGroup TG1 policy preferredIdentity enable
% commit

Viewing the Configuration

To view the AoR Group profile, execute the following command:

% show profiles aorGroupProfile AR2
aorDataList        "sip:123@ss.com;1111;2222;user=phone sip:456@yy.com;0;0;user=phone";
preferredIdentity  sip:123@ss.com;
aorDialogAttribute useFirst18x;
waitForAnswer      0;
[ok]

To view the VOIP Subscriber, execute the following command:

% show profiles voipSubscriber
voipSubscriber sip:EXAMPLE@RIBBON.COM {
    aorGroupProfile     AR1;
    egressRURIAttribute aorEgress;
}
voipSubscriber sip:EXAMPLE@RIBBON.com {
    aorGroupProfile     AR2;
    egressRURIAttribute aorEgress;
}
[ok]

To view the the flag preferredIdentity in the SIP Trunk Group, execute the following command:

> show table addressContext default zone defaultSigZone sipTrunkGroup TG1
carrier               0000;
country               1;
localizationVariant   northAmerica;
tgIPVersionPreference both-ipv4-and-ipv6;
preferredIdentity     enable;
digitParameterHandling {
    numberingPlan NANP_ACCESS;
}
callRouting {
    elementRoutingPriority DEFAULT_IP;
}
media {
    packetServiceProfile DEFAULT;
}
services {
    classOfService DEFAULT_IP;
}
signaling {
    ipSignalingProfile DEFAULT_SIP;
}
featureControlProfile DEFAULT_IP;
ingress {
    flags {
        nonZeroVideoBandwidthBasedRoutingForSip  enable;
        nonZeroVideoBandwidthBasedRoutingForH323 disable;
        hdPreferredRouting                       disable;
        hdSupportedRouting                       disable;
    }
}
[ok]
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