Avaya BCM Emergency Services Access (ESA) User Manual download pdf (Page 8)

Technical Solution Guide for BCM ESA v2.2 November 2006

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7 Nortel Confidential

1.1.3 IP Trunking

The introduction of VoIP heralds a new phase in the evolution of telecommunications; users can now leverage the

ubiquity of IP networks to be connected almost anywhere and at any time.

This mobility of IP telephone and softclients, create a new set of challenges for ESA as a user’s location can

change as dynamically as their IP address. This is an industry wide issue, and suppliers are adapting an evolving

their approach to ESA. BCM specific recommendations are contained within this document.

1.2 Reference ESA Call Flow

This section explains a general emergency services model as it relates to PBX systems and emergency calls.

The following steps explain the progress of a 911 call from initiation through to PSAP answering.

1. A PBX station initiates a 911 call.

2. The PBX will initiate the call on a trunk to the Telco central office. In the case of analog trunks, the calling

number is the line associated with the analog trunk that was seized for the 911 call. In the case of digital

trunks, the calling number may be passed along by the PBX to the central office.

3. The central office will route the call to the PSAP. A Caller’s Emergency Service Identification number

(CESID) will be passed along with the call to the PSAP. The CESID sent to the PSAP will depend upon

how the methodology the Telco uses to pass this information over to the PSAP:

a. In the case of analog trunk call from the PBX, this will be the calling number of the trunk.

b. In the case of digital trunk call from the PBX with direct inward dial (DID) numbers, this may be

the calling number signaled over the trunk from the PBX

c. In the case where a PBX passes non-DID extension numbers to the central office, this may be a

mapping of extension numbers to a DID number on the PBX. Or, the PBX will provide a CLI

number which represents an externally dialable number that is in close proximity to the calling

non-DID number.

4. The PSAP receives the call and an Automatic Location Identification (ALI) lookup is performed which

maps the CESID to a physical location.

Note that the CESID is not only used to provide a physical location of the emergency for dispatching emergency

crews but also provides the call back number for the 911 agent in the case of emergency call disconnection.

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Avaya BCM Emergency Services Access (ESA) User Manual Page 8