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A Mechanism for Session Initiation Protocol (SIP) Avalanche Restart Overload Control

Document type: Expired Internet-Draft (individual)
Document stream: No stream defined
Last updated: 2014-08-14 (latest revision 2014-02-10)
Intended RFC status: Unknown
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IESG State: Expired
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This Internet-Draft is no longer active. A copy of the expired Internet-Draft can be found here:


When a large number of clients register with a SIP registrar server at approximately the same time, the server may become overloaded. Near-simultaneous floods of SIP SUBSCRIBE and PUBLISH requests may have similar effects. Such request avalanches can occur, for example, after a power failure and recovery in a metropolitan area. This document describes how to avoid such overload situations. Under this mechanism, a server estimates an avalanche restart backoff interval during its normal operation and conveys this interval to its clients through a new Restart-Timer header in normal response messages. Once an avalanche restart actually occurs, the clients perform backoff based on the previously received Restart-Timer header value before sending out the first request attempt. Thus, the mechanism spreads all the initial client requests and prevents them from overloading the server.


Charles Shen <>
Henning Schulzrinne <>
Arata Koike <>

(Note: The e-mail addresses provided for the authors of this Internet-Draft may no longer be valid)