scope:

The prevalent use of the Session Initiation Protocol (SIP) in Next Generation Networks necessitates that SIP networks provide adequate control mechanisms to maintain transaction throughput by preventing congestion collapse during traffic overloads. A loss-based solution to remedy known vulnerabilities of the SIP 503 (Service Unavailable) overload control mechanism has already been proposed. Using the same signaling, this document proposes a rate-based control scheme to complement the loss-based control scheme.