Bob's Leaky News Service
2006-Apr-28 10:12 UTC
[Asterisk-Users] What is i2 ? 911 Candian Style
NENA i2
The NENA i2 architecture was designed to support the interconnection
of Voice over Internet Protocol (VoIP) domains with the existing
Emergency Services Network infrastructure. This overview will
describe the functional elements and call flow of a VoIP 9-1-1 call
over the i2 architecture.
The NENA i2 architecture was also designed to utilize existing 9-1-1
voice and data links to all existing Public Safety Answering Points
(PSAPs). With the addition of the new network elements described
below, the existing 9-1-1 network can support VoIP Enhanced 9-1-1
calling (including nomadic and non-native).
A traditional 9-1-1 call involves multiple network elements as well as
separate voice and data paths over several different protocols. The
routing of a VoIP call is no different. The delivery of a VoIP 9-1-1
call over an i2 architecture can be broken down into the following
steps which have been separated into 2 categories, pre-9-1-1 call and
during 9-1-1 call.:
Pre-9-1-1 call
STEP -3 Emergency Services Query Key (ESQK) shell record files are
transmitted to targeted Emergency Services Providers so they can
upload these in the designated Selective Router Databases and ALI
(Automatic Location Identification) systems.
Ex. 905-211-9111 + 023 + Ontario +
vpc@operator.ca
ESQK ESN Province VoIP Positioning Centre ID
STEP -2 Location information (civic addresses) are loaded in the
Location Information Server (LIS) and formatted per the Street Address
Guide rules.
Ex. 123.fake.st.west.Mycity.Ontario has an activated broadband service
STEP -1 Location information is validated against the Validation Database (VDB)
Ex. Is 123.fake.st.west.Mycity.Ontario a routable address for 9-1-1?
VDB response: Yes
STEP 0 The VoIP end point (assuming it is location capable) acquires
its location information either by value or by reference from the
Location Information Server.
Ex. LIS, I am this Device running on this Network, please provide me
with my location value and/or reference (key). LIS response: I found
it, here it is: 16612324 (location key in this example)
During 9-1-1 call
STEP 1 The VoIP endpoint/user agent originates an emergency call by
sending a call initiation request to the VoIP Service Provider's Call
Server. The call initiation request will contain call back
information and a Location Key or Value (fully formatted civic
address)
Ex. VoIP subscriber dials 9-1-1
STEP 2 The VoIP Service Provider's Call Server receives the call
initiation request and sends a routing request to a VoIP Positioning
Centre using the information received in the call initiation request.
Ex. 16612324 + 416-NXX-XXXX ? 911
STEP 3 The VoIP Positioning Centre queries the Location Information
Server(s) using the Location Key provided in STEP 1.
Ex. 16612324 = ?? Civic Address
STEP 4 The Location Information Server returns a Location Object to
the VoIP Positioning Centre, based on the Location Key.
Ex. 16612324 = 123.fake.st.west.Mycity.Ontario
STEP 5 The VoIP Positioning Centre uses the Location Object obtained
from the Location Information Server(s) to determine the Emergency
Service Zone routing information from the designated Emergency Routing
Database. The VoIP Positioning Centre receives the Emergency Service
Routing Number, Emergency Service Number and Contingency Routing
Number from the Emergency Routing Database.
Ex. 123.fake.st.west.Mytown.Ontario = 905-123-4567 + 023 + 0-ECRS
ESRN ESN CRN
The VPC uses the received routing information to allocate an available
Emergency Services Query Key from a pool designated for the Selective
Router and Emergency Service Number associated with the caller's
location.
Ex. Ontario + 023 = 905-211-9111
Province ESN ESQK
If no location is found, the call can be default routed using the
Contingency Routing Number.
STEP 6 The VoIP Service Provider's Call Server will use the Emergency
Service Routing Number received in the response from the VoIP
Positioning Centre as the basis for selecting the designated Emergency
Services Gateway. It then sends the call over the facilities to the
Emergency Services Gateway with the Emergency Services Query Key as
the pseudo-ANI (pANI) and the Emergency Services Routing Number as the
called number.
Ex. 905-123-4567 = Emergency Services Gateway for Ontario Selective
Routers = selective-router-on1@bell.ca, Calling # 905-211-9111, Called
# 905-123-4567
STEP 7 The Emergency Services Gateway uses the received Emergency
Service Routing Number to select an outgoing route (i.e., trunk group)
to the designated 9-1-1 Selective Router using outgoing (SS7 or MF)
signaling. The called number, Emergency Services Routing Number, is
replaced by the digits 9-1-1 by the trunk group options so the call
can now enter the traditional 9-1-1 Network as a 9-1-1 dialed call
originating from the assigned Emergency Services Query Key. The
Emergency Services Query Key acts as a traditional Automatic Number
Identification (ANI) for call routing.
The Selective Router receives the emergency call, uses the Emergency
Services Query Key to query the 9-1-1 Selective Routing Database for
the associated Emergency Service Number (ESN), and uses the ESN to
identify the designated PSAP for the call.
Ex. 905-211-9111 = Selective Router A + ESN 023 Ontario = Primary
Public Safety Answering Point B
STEP 8 The Selective Router then delivers the call to the designated
Primary Public Safety Answering Point, signaling the Emergency Service
Query Key as the Automatic Number Identification (ANI) information.
This causes a "PUSH" of the ANI to the ALI (Automatic Location
Identification) computer. The ALI computer recognizes the ANI as an
Emergency Service Query Key and steers to the VoIP Positioning Centre
so it can build a properly formatted ALI record based on the
information compiled by the VoIP Positioning Centre including the Call
Back Number. Other Enhanced 9-1-1 information such as VoIP Service
Provider will be available in the same way the 9-1-1 service provider
offers it on wireline/wireless 9-1-1 records.
Ex. 905-211-9111 = 123 Fake St West, Mytown Ontario 905-NXX-XXXX
The result of this process is a VoIP 9-1-1 call that is routed to the
designated PSAP with ANI/ALI information delivered in standard form
regardless of caller location (In Canada), with no changes to PSAP
networks, systems or equipment.
NENA i2 Functional Elements
NENA i2 introduces 5 network elements required to support all classes of VoIP:
LIS Location Information Server
The wiremap version will contain the physical address information for
all broadband access service locations. This will provide location
information regardless of the underlying access medium (cable/Digital
Subscriber Line/Fixed Broadband Wireless Access)
? A repository of location information
? Configured with mappings between individual Location Objects and a
logical representation of the physical locations with which they are
associated (i.e. a wiremap)
? Provides mechanisms for either the client or a Network node and the
VoIP Positioning Centre to retrieve location information
? Supports validation of civic location information via a query
interface to the Validation Database
Canadian Consideration for the Location Information Server
Because of Canada's 9-1-1 Service Provider structure, the Street
Address Guide or equivalent data used for 9-1-1 will be required for
Location Information Server development. A close relationship between
the Location Information Server, Validation Database and Street
Address Guide will be required to ensure designated routing, accurate
data and database synchronicity.
ERDB Emergency Routing Database
This will contain Master Street Address Guide (MSAG) data and 9-1-1
routing information associated with the coverage area of the Emergency
services Provider. It will be used by the VoIP Positioning Centre to
find designated routing based on the location information. This will
ensure that any changes to a 9-1-1 Service Provider's Selective
Router, Emergency Service Numbers or Primary Public Safety Answering
Points will be made in real-time.
? Supports storage of the boundary definitions for Emergency Service
Zones and the mapping of civic address or geo location information to
a particular Emergency Service Zone
? Processes routing requests from the VoIP Positioning Centre
? Based on the received Location Object, the Emergency Routing
Database determines the designated Emergency Service Routing Number,
Emergency Service Number and Contingency Routing Number for each VoIP
9-1-1 call.
Canadian Consideration for the Emergency Routing Database
The data in the Emergency Routing Database is dependant upon the
Master Street Address Guide, 9-1-1 Network configuration and the 9-1-1
Service Provider's onboard Selective Routing Database. Coordination
and a close relationship between the Emergency Routing Database,
Selective Routing Database and Master Street Address Guide will be
required to ensure designated routing and database synchronicity.
ESGW Emergency Services Gateway
This will provide IP access to the existing 9-1-1 selective routers
for 9-1-1 call delivery to the designated Public Safety Answering
Point. By connecting through an Emergency Services Gateway, the VoIP
9-1-1 call will follow any network changes or activity made by the
9-1-1 service provider (reroute, outage). This will also allow VoIP
9-1-1 calls the same treatment, including diversity, offered to
wireline and wireless 9-1-1.
? Converts between VoIP signalling and traditional signalling (SS7 or CAMA/MF)
? Determines the designated dedicated 9-1-1 outgoing trunk group based
on the received Emergency Services Routing Number
? Transmits the received Emergency Services Query Key to the Selective
Router over the designated trunk group
Canadian Consideration for the Emergency Services Gateway
Because of Canada's 9-1-1 Service Provider structure, gateways to the
9-1-1 Selective Routers can be provisioned per province or per 9-1-1
service provider. A relationship between the VoIP Service Provider
and Emergency Services Gateway provider will be required in order to
have a voice path to 9-1-1.
VDB Validation Database
This will provide a means of civic address validation for addresses
stored in the Location Information Server(s). The Validation Database
requires that daily changes to civic addresses are synchronized with
the existing 9-1-1 routing schemes (boundary changes, new streets,
street name change, municipal amalgamation).
? Validates received civic address against the Master Street Address Guide
? Provides error responses
? Supports a web services interface to enable civic address validation
from the Location Information Server(s)
Canadian Consideration for the Validation Database
The data in the Validation Database is only as accurate as it is
current. Due to the different provisioning and update processes
across 9-1-1 Service Providers in Canada, the Validation Database
function will require almost real-time synchronicity with numerous
Street Address Guides or equivalent across Canada. A mismatch in the
Validation Database will cause a validation error and record rejection
in the Location Information Server. This process is simplified in the
wireline/wireless world by deriving all pertinent data from one
dynamic source, the Master Street Address Guide.
VPC VoIP Positioning Centre
This is the mechanism which will provide a VoIP Service Provider with
IP selective routing functions through multiple Emergency Routing
Databases for national 9-1-1 routing and thus, facilitate the delivery
of Enhanced 9-1-1 data to the designated Public Safety Answering
Points.
? Processes routing requests from call server/routing proxy/redirect server
? If location by reference has been used, query the designated
Location Information Server to retrieve the Location Object
? Determines the designated Emergency Routing Database based on the
received Location Object
? Receives Emergency Service Routing Number, Emergency Service Number,
Contingency Routing Number from the Emergency Routing Database
? Allocates designated Emergency Services Query Key for the call
? Responds to queries from ALI with Call Back Number and Master Street
Address Guide formatted location
? De-allocates Emergency Services Query Key when the call is terminated
Other Canadian Considerations for i2
Civic vs Postal Address
? I2 allows for Postal address format in Location Information Servers
? Since Canadian Master Street Address Guides use Geo-Civic data,
there is no need to develop postal translation (saving time, money and
reducing complexity)
Push vs Pull
? In the U.S., most 9-1-1 systems are in a PULL arrangement
? In Canada, most 9-1-1 systems are in a PUSH arrangement
? i2 can support both PUSH or PULL arrangements as well as hybrid
networks that use both.
RDO (Root Directory Operator)
? Because of loosely coupled U.S. 9-1-1 implementation, a Root
Directory Operator is required in order to discover who can provide
Validation Database services
? In a Canadian implementation, this would not be required because of
direct relationship between various Operators
VoIP Location Awareness
? In i2, a VoIP end point/user agent provides its civic location to
the VoIP Positioning Centre from data it collects from the Location
Information Server. VoIP end points do not presently support this
feature, therefore a mechanism is required to gather location data
from the Location Information Server (on behalf of the VoIP end
point/user agent).
? An example of the On-Behalf-Of (OBO) function was presented to CISC
ESWG (ESCO0249).
? Standards being drafted by IETF (Internet Engineering Task Force)
and Industry to allow VoIP end points/user agents to support this
function without assistance as the devices evolve.
? The unique Canadian 9-1-1 landscape allows VoIP end points/user
agents to overcome their location unaware limitation by incorporating
an On-Behalf-Of Engine as part of the 9-1-1 network. Alternatively,
VoIP Service providers could each implement their own OBO ? type
function (subject to further technical investigations).
Reasonably Related Threads
Wisdom of the Ancients
