Cisco Emergency Responder

Before we delve into the details of Cisco Emergency Responder (CER), let’s discuss the type of interfaces to route calls to the Public Safety Answering Point (PSAP). Calls can be routed to the PSAP via the following three mechanisms depending on the requirements of the local PSAP: • Primary Rate Interface (PRI) • Centralized Automatic Message Accounting (CAMA) • Plain Old Telephony Service (PoTS) Foreign Exchange Office (FXO) interface PRI interfaces can be used for the call routing of all phone calls to the PSTN including 911 calls. Some local exchange carriers (LEC) do not support PRI routing of 911 calls to the PSAP and some LECs charge for 911 call routing over PRI interfaces. Some providers support emergency call routing over T1-CAS and/or E1 interfaces as well. CAMA trunks are dedicated analog connections that provide calling party information over wink start signaling and battery reversal. Calling party information is provided over dual tone multi-frequency (DTMF). Some LEC carriers require CAMA trunk connectivity for the routing of 911 calls. CAMA functionality can be enabled in all second generation FXO voice interface cards (VIC). The VIC2-2FXO and VIC2-4FXO interfaces support the software configuration of CAMA facilities. The references section of this blog includes a link to the configuration details of these voice interfaces if CAMA functionality is required. A site specific analog circuit (FXO) is a good backup option to the primary method of PSAP connectivity, but has the limitation of providing ANI information that will identify the site, not the specific location of the user initiating the emergency call. Cisco Emergency Responder (CER) is a database server that automatically tracks mobile users throughout the network and routes 911 calls to the local gateway at the site. Cisco Emergency Responder provides caller ID (ANI) information to the PSAP that maps to an emergency line identification number (ELIN) that the PSAP recognizes as an emergency response location (ERL). The ELIN that CER routes to the PSAP is usually a phone number that is associated with an address location in the master street address guide (MSAG), not the caller’s real caller ID. CER maintains a mapping between the ELIN and original caller to facilitate PSAP callbacks for a configurable interval. CER also allows on-site emergency responders to be notified of the emergency call in real time through E-Mail, pager, phone, or web page. Cisco Emergency Responder (CER) integrates with Cisco Unified Communications Manager over CTI ports (JTAPI). When a phone registration event occurs, CUCM notifies CER of the new registration. CER then discovers the devices location in the network through a dynamic process in which the phone inspects the routing tables, arp caches, and MAC address tables of the routers and switches. CER discovers the MAC address of the Cisco phone to the port on the switch. Each switch port is associated with an ERL in CER which is mapped to a unique ELIN if a 911 call is made from the phone. CUCM routes all 911 calls to CER allowing CER to change the calling party field (ANI) of the phone call and before the call is routed to the PSTN. CER notified local emergency responders while the call is routed to the PSAP. The network discovery phase associated with phone registrations procedure requires the CER server to be configured with the IP address and simple network management protocol (SNMP) information of all the routers and switches in the network. The CER server uses SNMP get messages to obtain the MAC address of newly registered phones and to discover the MAC address tables and Cisco Discovery Protocol (CDP) neighbor information in the switches. It is imperative that all cabling changes involve the re-configuration of the CER database or the integrity of the ERL information will be compromised. REFERENCES CAMA Trunk Configuration National Emergency Number Association (NENA) Wikipedia E-911 Definition Cisco Emergency Responder Literature

Join the Network World communities on Facebook and LinkedIn to comment on topics that are top of mind.

Copyright © 2009 IDG Communications, Inc.

SD-WAN buyers guide: Key questions to ask vendors (and yourself)