RE: [Ieprep] Diffserv Code Point for Emergency calls

Janet P Gunn <jgunn6@csc.com> Mon, 24 October 2005 12:51 UTC

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In-Reply-To: <4.3.2.7.2.20051023223818.031b77f0@email.cisco.com>
Subject: RE: [Ieprep] Diffserv Code Point for Emergency calls
To: "James M. Polk" <jmpolk@cisco.com>
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From: Janet P Gunn <jgunn6@csc.com>
Date: Mon, 24 Oct 2005 08:50:59 -0400
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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

ieprep-bounces@ietf.org 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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