IEEE ICC 2012 - COMMUNICATION QOS, RELIABILITY AND MODELING SYMPOSIUM

ARTHUR: SEYED VAHID AZHARI , HANI NEMATI

PRESENTER: 侯宗佑

Stability Analysis of Tandem SIP Proxies

Outline

IntroductionFluid Flow ModelLyapunov stabilityStabilizing AlgorithmConclusion

SIP protocol

Signaling Communications ProtocolIETF,RFC 2543, latest RFC 3261Setup, modify, tear down multimedia sessionsText-based protocol (like http, smtp)Media stream use RTP protocol

SIP protocol(cont’d)

Lyapunov Stability

Mostly used for non-linear dynamic systemStay near Equilibrium point

Fluid Flow Model

Fluid Flow Model(Cont’d)

Assumption: Infinite queues, negligible packet loss and processing time, only Invite and OK message

State variable: weighted number of Invite message queues on proxy

Fluid Flow Model(Cont’d)

Fluid Flow Model

Lyapunov Stability

Equilibrium : (x1,x2) = (0,0)

Lyapunov Stability(Cont’d)

Lyapunov Stability(Cont’d)

Optimal rejection policy

P2,rej = 0 has max value

All rejection burden at upstream proxy

Stabilizing Algorithm

Idetical:

P1 >= 1:

Stabilizing Algorithm(Cont’d)

Stabilizing Algorithm(Cont’d)

Stabilizing Algorithm(Cont’d)

Maximum Withstand-able Overload

Conslusion

Modeled SIP topologyDerive Lyapunov stability conditionProposed a simple overload control algorithmOptimal rejection policy