Explicit Subscriptions for the REFER Method, August 2015
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The Session Initiation Protocol (SIP) REFER request, as defined by RFC 3515, triggers an implicit SIP-Specific Event Notification framework subscription. Conflating the start of the subscription with handling the REFER request makes negotiating SUBSCRIBE extensions impossible and complicates avoiding SIP dialog sharing. This document defines extensions to REFER that remove the implicit subscription and, if desired, replace it with an explicit one.
For the definition of Status, see RFC 2026.
For the definition of Stream, see RFC 8729.