Dear all,

SIP overload may block too many calls unnecessarily. "Requirements for Management of Overload in the Session Initiation Protocol. IETF RFC 5390." http://www.ietf.org/rfc/rfc5390.txt Build-in overload mechanism cannot prevent overload effectively. Therefore, IETF SIP Overload Control (soc) Working Group works on IETF RFC "SIP Overload Control" currently. http://tools.ietf.org/html/draft-ietf-soc-overload-control-12 IETF SIP Overload Control discussion archives http://www.ietf.org/mail-archive/web/sip-overload/current/threads.html#00874

We have published a survey on SIP overload control algorithms (including IETF RFC "SIP Overload Control").

http://www.researchgate.net/publication/231609451_A_Comparative_Study_of_SIP... http://arxiv.org/abs/1210.1505 http://www.igi-global.com/chapter/comparative-study-sip-overload-control/674...

We have also used control theorectic approaches to model the interactions between an overloaded SIP server and its upstream servers as a feedback control system in two different scenarios - redundant retransmission ratio control and round trip delay control (IEEE Globecom 2010 and ICC 2011). "Mitigating SIP Overload Using a Control-Theoretic Approach" IEEE Globecom 2010 http://www.researchgate.net/publication/221284946_Mitigating_SIP_Overload_Us... http://ieeexplore.ieee.org/xpl/login.jsp?tp=&arnumber=5683124&url=ht... Implementation of implicit SIP overload control in the real system "An Efficient Earthquake Early Warning Message Delivery Algorithm Using an in Time Control-Theoretic Approach" http://link.springer.com/chapter/10.1007%2F978-3-642-23641-9_15#

"Design Of A PI Rate Controller for Mitigating SIP Overload" IEEE ICC 2011 http://www.researchgate.net/publication/224249824_Design_of_a_PI_Rate_Contro... http://features.rr.com/article/01vBgtc8TR17z?q=Skype http://ieeexplore.ieee.org/xpl/login.jsp?tp=&arnumber=5963029&url=ht...

Best regards,

Winston Hong Software Engineer InBay Technologies Inc. Ottawa, Canada K2K 1Y3 http://www.inbaytech.com/