Hi, One of the use-cases for the keep parameter is non-registration emergency calls, where Outbound can't be used even if supported.
However, a question has come up whether it could also be useful in certain emergency use-cases WITH registration. At least in 3GPP, when a UA performs an emergency registration, the S-CSCF/registrar does not insert itself in the "path" (it does not insert Service-Route), which means that the INVITE for the emergency call will not traverse the S-CSCF. And, therefor the usage of Outbound is not needed, since there is no idea of establishing multiple flows between the UA and the S-CSCF/registrar. So, in this case the keep parameter could be used by the UA and P-CSCF/edge proxy to indicate support of keep-alive also for registration emergency calls. Regards, Christer
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