General Registration Request Processing

The device's general handling of registration requests (REGISTER messages) for unregistered users is as follows:

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The device routes REGISTER requests according to the IP-to-IP Routing table. If the destination is a User-type IP Group, the device doesn't forward the registration; instead, it accepts (replies with a SIP 200 OK response) or rejects (replies with a SIP 4xx) the request according to the user's IP Group configuration.

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Alternative routing can be configured for REGISTER requests in the IP-to-IP Routing table.

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By default, the SIP Expires header has the same value in incoming and outgoing REGISTER messages. However, you can modify the its value using the following parameters: [SBCUserRegistrationTime], [SBCProxyRegistrationTime], [SBCRandomizeExpires], and [SBCSurvivabilityRegistrationTime]. You can also modify the Expires value of REGISTER requests received from users located behind NAT, using the IP Profile parameters 'NAT UDP Registration Time' and 'NAT TCP Registration Time'.

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By default, the SIP Contact header in the outgoing REGISTER message is different than the Contact header in the incoming REGISTER. The user part of the Contact header is populated with a unique contact generated by the device and associated with the specific registration. The IP address in the host part is changed to the address of the device. Alternatively, the original user can be retained in the Contact header and used in the outgoing REGISTER request, using the [SBCKeepContactUserinRegister] parameter.