Get documents about "VoIP i2 for ENP Study Group
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This presentation is based on NENA 08-001 Interim VoIP
Architecture for Enhanced 9-1-1 Services (i2)
Prepared for the Texas Emergency Number Association
ENP Study Group
May 10, 2006
June 17, 2012 1
Used for
PSTN contingency routing
IP domain
Routing Proxy & Emergency Services
Redirect server(s) PSTN
Gateway Provider Network
Call server/
v6
proxy server
v4 ESGW(s)
v5
E9-1-1
v4
Selective PSAP
Router(s)
v1
IP Domain v2
VoIP v2
VPC
End SRDB
VPC v-e2
Point v0 VPC
v8 ALI
v3 v9 ALIDB
ESZ DB
LIS v7
RDB
MSAG
v7
VDB DBMS
v9
June 17, 2012 2
RDO
VoIP Endpoint
The term VoIP endpoint is used to refer to the
endpoint IP Device that is used to originate an
emergency call.
In many cases the endpoint is a device provided by
the VoIP Service Provider (VSP) referred to as a
Terminal Adapter (TA) that connects to a standard
telephone instrument.
It may also be a multi-media PC running a VoIP
software program.
June 17, 2012 3
Call Server
The term Call Server is used to refer to the resource
in a private or public IP domain that provides a service
to endpoints in an emergency caller’s home domain.
The Call Server works with other servers and
elements in the IP domain to support emergency
services call routing in the i2 solution.
The Call Server may use SIP (Session Initiated
Protocol) or some other VoIP signaling protocol within
its own serving domain.
June 17, 2012 4
Proxy Server
A proxy server primarily plays the role of routing.
Proxies are also useful for enforcing policy. For
example, making sure a user is permitted by to make a
call.
A proxy interprets and, if necessary, rewrites specific
parts of a request message before forwarding a call.
June 17, 2012 5
Location Information Server
The LIS serves as a repository for location information.
Location information is in the form of civic address or geo-
spatial location attributes correlated to a particular physical
location.
The data in the LIS associating these locations is called a
Wiremap.
June 17, 2012 6
LIS (cont.)
The “wiremap” in the LIS is assumed to be configured
and maintained by the entity that provides/maintains the
physical or logical access facility for endpoint equipment.
This is similar in concept to a private switch provider
being responsible for knowing the location of stations
behind a PBX.
In addition to creating and maintaining this wiremap, the
administrator/owner of the LIS is also responsible for
ensuring that the civic location data is MSAG-validated.
June 17, 2012 7
LIS (cont.)
A given endpoint can be associated with a physical
location that is mapped to a particular address (civic or
geo), and the address is downloaded from the LIS to the
VoIP endpoint.
The LIS may also support assignment of a location query
key, to a particular use of an address, to support
subsequent queries for the address in a more dynamic
process.
June 17, 2012 8
Location Object (LO)
The LO is refers to the current position of a VoIP endpoint
that originates an emergency call.
The i2 standard says the LO may be:
Geo location – latitude, longitude, elevation or floor, and
the datum which identifies the coordinate system used.
Civic location – a set of objects that describe a street
address.
June 17, 2012 9
Root Discovery Operator
The RDO is responsible for maintaining and
making available the identities of the key
VDB and ERDB functions in the network.
June 17, 2012 10
Validation Database
The VDB is a query/response database service that
contains information compiled from the 9-1-1 entities’
Master Street Address Guides (MSAG).
The VDB should have the capability to receive a
validation request from a VSP or LIS containing a civic
address consisting of data elements included in the civic
Location Object (LO) and be able to determine if this civic
address is an MSAG-valid address.
June 17, 2012 11
Validation Database (cont.)
The VDB will return a response indicating that a given
LO is either a valid address or not valid.
The VDB will most likely be distributed across
multiple databases. Although different VDB’s may
serve different regional areas, there will be one
primary source of validation data for any given
geographic area or address.
The Texas 9-1-1 Alliance published an RFP for a
VDB/ERDB service operator for Texas on 4-28-06.
June 17, 2012 12
Emergency Service Zone
Routing Data Base (ERDB)
The ERDB contains routing information associated
with each ESZ (or as we call it in Texas, ESN) in a
serving area. The data are compiled from, and correlate
with, the same data used in the VDB.
The ERDB supports the boundary definitions for ESZs
and the mapping of civic address or geospatial
coordinate location information to a particular ESZ.
June 17, 2012 13
ERDB (cont.)
For each ESZ, the ERDB contains:
1. One Emergency Services Routing Number (ESRN)
associated with the primary Selective Router (SR)
that serves the ESZ and
2. One routing Emergency Services Number (ESN)
that uniquely identifies the ESZ in the context of
that SR.
June 17, 2012 14
ERDB (cont.)
When an emergency call is originated, and a valid
location is received from the VoIP Positioning Center
(VPC), the ERDB will identify the ESZ associated
with the received location information, and will return
the following data elements the to the VPC:
1. ESRN
2. the routing ESN
3. the Contingency Routing Number (CRN - if available) and
optionally,
4. the administrative ESN (in Texas the same as routing ESN)
June 17, 2012 15
The VoIP Positioning Center
VPC is the element that provides information to
support the routing of VoIP emergency calls, and
cooperates in delivering location information to the
PSAP over the existing ALI query infrastructure.
The information provided includes callback
information, when available, and a Location Object
or Location Key.
June 17, 2012 16
VPC (cont.)
The VPC uses the received location information with
other locally stored information that enables it to
determine the appropriate ERDB to query for the
routing instructions.
The VPC uses the received location information to
request routing information from the ERDB that is
associated with the caller’s location.
The VPC may also obtain information from the ERDB
to assist in contingency routing.
June 17, 2012 17
Emergency Services Gateway
The ESGW is the signaling and media interworking
point between the IP domain and dedicated trunks to
the E9-1-1 SR that use either MF or SS7 signaling.
The ESGW uses the ESRN provided by the VPC to
connect the call to the appropriate trunk (group) and
transmits the ESQK to the SR to represent the ANI of
the caller.
June 17, 2012 18
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