911 Services
To accept how VoIP networks can accommodate the area and blast cardinal for
911 services, you should accept the action of the basal apparatus of 911 services,
as follows:
■ Automatic Cardinal Identification (ANI): ANI is the calling-party cardinal that is
included with anniversary alarm to analyze area the alarm originated. Often, in a business
environment, the aboriginal ANI ability be afflicted by the account provider at the first
switch to reflect the announcement cardinal of the aggregation instead of absorption the calling
number of the aboriginal party. Discussions with the account provider charge to ensure
that the aboriginal ANI advice is transmitted with all calls. Internal extensions or
private calculation affairs crave mapping or adaptation for outbound ANI.
■ Automatic Area Identification (ALI): The ALI database contains the records
that map blast numbers to geographic locations. The ALI database resides in
the account provider network. Updates to the ALI database are submitted anytime a
move, add, or change accident occurs in a telephony network. Updates can booty up to
48 hours to booty effect, thereby authoritative activating ALI updates clashing in a mobile
environment.
■ Public Safety Answering Point (PSAP): The PSAP is the acknowledgment point area an
emergency alarm is terminated. Calls are directed to specific PSAPs based on the geographic
location of the alarm alpha point.
■ Emergency Response Area (ERL): ERL is the area from which an emergency
call is placed. In a arrangement area VoIP advancement is common, the ANI of the
calling blast does not consistently analyze the area of the emergency because
the callers absorb the aforementioned addendum behindhand of area they are absolutely located.
The ERL is acclimated in advancement environments by advertence ports and accessories to an
ERL group. The advocacy is to ascertain an ERL accumulation for anniversary attic in a building,
each assemblage in a auberge or motel, or anniversary addressee in a multitenant building.
■ Emergency Area Identification Cardinal (ELIN): An ELIN is a NANP telephone
number that is acclimated for acquisition an emergency alarm to the adapted PSAP. In a
mobile ambiance area the ANI is the adaptable addendum of the user, the ELIN is
substituted for the ANI aback the alarm is beatific to the PSAP. This barter enables
the PSAP to almanac the calling cardinal and be able to alarm the cardinal aback if the
need arises. Anniversary ERL has a altered ELIN associated with it. Aback a adaptable caller
logs in to a VoIP phone, the ELIN for the alarm is bent based on the ERL that
the anchorage is associated with.
■ Master Street Address Guide (MSAG): MSAG is a database that is maintained by a
government agency. This database maps geographic locations to the PSAPs that are
responsible for administration emergency calls for those locations.
■ Careful router: A careful router is a committed 911 about-face in a account provider
network that routes 911 calls to an adapted PSAP based on the calling number.
This access is altered from accustomed alarm routing, which routes based on the called
number. Aback a alarm is baffled to the careful router, the router looks at the ANI and
determines which PSAP to accelerate the alarm to.
■ Centralized Automated Message Accounting (CAMA): CAMA is a blazon of analog
trunk that connects a chump about-face anon to the careful router in the service
provider network. A CAMA block carries 911 calls only. It does not backpack added user
calls.
It is analytical that arrangement designers accept and attach to local, municipal, state, and
federal laws apropos acquiescence to 911 requirements.
911 Alarm Processing
To allegorize the alarm breeze of a 911 call, appraise Amount 6-14.
358 Authorized Self-Study Guide: Cisco Voice over IP (CVOICE)
Permanent User Location: 555-1234: 123 N.
Main St, Architecture A, Attic 3, Northwest Corner
“123 N. Capital St.
Building A, Attic 3
Northwest Corner”
911
PRI
CAMA
555-1234, 911
CO
Switch
555-1234
911
911 Selective
Router
PSAP
#001
Route
Database
LEC Network
123 N. Capital St.
123 N. Capital St.
555-1234?
555-1234
“PSAP#
?001”
555-1234?
1
2
3
4
5
6
V PSAP
#002
7
ALI
Database
8
Figure 6-14 911 Alarm Processing in a Nonmobile Environment
The 911 alarm depicted in the amount is candy as follows:
1. The emergency alarm originates from the accessory with the ANI of 555-1234.
2. The alarm is baffled via the capital PSTN aperture at the headquarters.
3. The PSTN aperture either routes the alarm anon to the careful router via the
CAMA block (if present) or routes the alarm via the accustomed PRI affiliation to the CO
switch.
4. The CO about-face retains the aboriginal ANI and does not alter it with the billing
number.
5. The CO about-face routes the alarm to the careful router.
6. The careful router queries the database to actuate which PSAP is amenable for
the area of the ANI.
7. The careful router routes the alarm to the PSAP.
8. The PSAP queries the ALI database to actuate the exact area of the caller.