RE: Diffserv Code Point for Emergency calls

James,

There are additional Switch call processing requirements.

Cheers,

Martin



> -----Original Message-----
> From: [email protected] 
> [mailto:[email protected]]On Behalf
> Of Janet P Gunn
> Sent: Monday, October 24, 2005 5:51 AM
> To: James M. Polk
> Cc: [email protected]; [email protected]; ken carlberg
> Subject: RE: [Ieprep] Diffserv Code Point for Emergency calls
> 
> 
> 
> 
> 
> 
> James,
> 
> The PSTN DOES give emergency (911) calls priority in a small way.
> 
> The SS7 signaling messages have an associated priority, 
> called MTP.  When
> an SS7 "server" is congested, it will shed MTP 0 messages 
> before it sheds
> MTP 1 messages.
> 
> Normal call request messages ( ISUP IAMs) are MTP 0.
> Emergency (911), NS/EP. and MLPP call request messages are MTP 1.
> 
> Janet
> 
> [email protected] wrote on 10/23/2005 11:42:34 PM:
> 
> > Reinaldo
> >
> > Actually, the PSTN does not give better priority to 911 
> calls (vs. normal
> 
> > calls), they just use separate cirucuits once the 911 call 
> gets to the
> > first Class-5 switch.  Typically, a Class-5 Switch will have a small
> number
> > of dedicated circuits that connect directly to a 911 
> Selective Router
> > (which is a special instance of a Class-5 switch). 911 
> calls are routed
> > over these dedicated circuits towards the SR to then be 
> routed to the
> > appropriate PSAP. This isn't really anything special - 
> since the circuit
> > world is not bandwidth contending, they are circuit contending.
> 
> 
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