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SUMMARY:Optimal Gateway Selection in VoIP - Richard Weber\, University of 
 Cambridge
DTSTART:20081029T160000Z
DTEND:20081029T170000Z
UID:TALK14209@talks.cam.ac.uk
CONTACT:Neil Walton
DESCRIPTION:We evaluate strategies by which a VOIP provider might select P
 STN gateways through which to terminate calls. Different gateways may have
  different blocking probabilities and prices for terminating VoIP calls to
  the PSTN. A customer placing a call to a VoIP provider is impatient and m
 ay hang-up if the delay in setting up the call is large. Possible strategi
 es for the VOIP provider are to route each call to the gateway that charge
 s the smallest price\, or to simultaneously route each call to a set of ga
 teways\, a strategy called `forking'. Forking creates a race between gatew
 ays (only one of which ultimately connects the call). It reduces the avera
 ge call setup delay\, but it increases the average price of terminating a 
 call and the load on the system. We investigate some problems of choosing 
 an optimal set of gateways to which to fork a call request. We discuss the
  effects of forking on the overall call blocking probability\, and the inc
 entives for gateways and VoIP providers to deploy it. By analysing a multi
 -player game we see that is can be advantageous for all concerned if gatew
 ays introduce a small signalling charge. Along the way we discuss the foll
 owing problem of "optimal re-dialing". Suppose you are trying to minimize 
 the expected time until you get through to a switchboard. If your first at
 tempt is answered by a busy signal\, should you redial immediately\, or mi
 ght it be better to wait a short time between successive attempts?
LOCATION:MR11\, CMS\, Wilberforce Road\, Cambridge\, CB3 0WB
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