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
IP Domain PSAP E9 - 1 - 1 Selective Router(s ) VoIP End Point DBMS IP domain Emergency Services Provider Network Call server/ proxy server LIS SRDB ALI DB MSAG VPC VPC VPC ALI DB ESGW(s ) VDB ESZ RDB v1 v0 v2 v4 v5 v2 v3 v - e2 v7 v8 v4 Routing Proxy & Redirect server(s ) v6 Used for contingency routing v7 PSTN Gateway PSTN RDO v9 v9
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.
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.
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.
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.
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.
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.
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.
Root Discovery Operator The RDO is responsible for m aintaining and making available the identities of the key VDB and ERDB functions in the network.
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.
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.
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.
ERDB (cont.) <ul><li>For each ESZ, the ERDB contains: </li></ul><ul><li>One Emergency Services Routing Number (ESRN) associated with the primary Selective Router (SR) that serves the ESZ and </li></ul><ul><li>One routing Emergency Services Number (ESN) that uniquely identifies the ESZ in the context of that SR. </li></ul>
ERDB (cont.) <ul><li>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: </li></ul><ul><ul><li>ESRN </li></ul></ul><ul><ul><li>the routing ESN </li></ul></ul><ul><ul><li>the Contingency Routing Number (CRN - if available) and optionally, </li></ul></ul><ul><ul><li>the administrative ESN (in Texas the same as routing ESN) </li></ul></ul>
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.
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.
Emergency Services Gateway 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. 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.