VoIP i2 Architecture Part II 9-1-1 Call Routing SBC – Southwest Public Safety.

VoIP i2 ArchitectureVoIP i2 Architecture

Part IIPart II

9-1-1 Call Routing9-1-1 Call Routing

SBC – Southwest Public SafetySBC – Southwest Public Safety

The Interim VoIP Architecture for Enhanced 9-1-1 Services (i2)Interim VoIP Architecture for Enhanced 9-1-1 Services (i2) document was the primary source of information used to create this presentation.

This NENA STANDARD is published by National Emergency Number Association (NENA) as a guide for the designers and manufacturers of systems that are used for the purpose of processing emergency calls.

IntroductionIntroduction

VoIP i2 ArchitecturePart II 9-1-1 Call Routing is Part II in the 9-1-1

VoIP series. It is important that you have reviewed Part 1: VoIP i2 Architecture - The IP Domain, prior

to viewing this presentation to gain an understanding of the components in the VoIP

architecture and the definitions of the acronyms used.

Now here’s a step-by-step look at a 9-1-1VoIP Call Flow

VoIP Domain Emergency Services Provider Network

V4

7. Invite (ESRN,ESQK)

ESGW

Call Server

2. Call InitiationV1

6. Response (ESRN, ESQK, LRO)

9. Deliver Call(ESQK)

PSAP

9-1-1 Call Flow

V34. Query (LK)

5. Response (LO)

User Agent

Endpoint

1. LO and/or

LK

V0

LIS

11. ESPOSREQ Query

12. ESPOSREQ Response (CBN, LO)

13. ALI response (Callback, LO)

8. Call route(ESQK)

E9-1-1 Selective Router

(ESQK)

10. ALI query

SRDB

V2

3. Query (Callback LIE),

VPC

VDB

ERDB

DBMS

MSAGMSAG

MSAG

14. ESQK De-allocation

Now the next slide also has the IP Call Flow graphically Now the next slide also has the IP Call Flow graphically depicted. But on this slide you can click on any of the depicted. But on this slide you can click on any of the indicated steps in the call flow for a closer look at that indicated steps in the call flow for a closer look at that particular step. particular step.

Basic Call Routing of a VoIP Basic Call Routing of a VoIP Emergency CallEmergency Call

GOT IT?

VoIP Domain Emergency Services Provider Network

14. ESQK De-allocation

DBMS

V4

7. Invite (ESRN,ESQK)

ESGW E9-1-1 Selective Router

8. Call route(ESQK)

MSAGMSAG

MSAG

Call Server

2. Call InitiationV1

6. Response (ESRN, ESQK, LRO)

9. Deliver Call(ESQK)

PSAP

VDB

ERDB

9-1-1 Call Flow

V34. Query (LK)

5. Response (LO)

User Agent

Endpoint

1. LO and/or

LK

V0

LIS

11. ESPOSREQ Query

12. ESPOSREQ Response (CBN, LO)

(ESQK)

10. ALI query

SRDB

V2

3. Query (Callback LIE),

VPC 13. ALI response (Callback, LO)

Step 1 – LO and/or LKStep 1 – LO and/or LK

The LO/LK is downloaded from the Location Information Server (LIS) to the endpoint by the Dynamic Host Configuration Protocol (DHCP) server, using the V0 interface.

User AgentEndpoint

V0 interface

LO/LKLIS

Click on this button to return to the diagram

Click on picture to

see animation

Step 2 – Call InitiationStep 2 – Call Initiation

V1 interface

The VoIP endpoint originates an emergency call by sending a call initiation request, designating [email protected] as the target destination, and including Callback information, and the LO using the V1 interface.

User AgentEndpoint

9-1-

1 +

LO

Call server

Step 3 – QueryStep 3 – Query

The Call Server receives the call initiation request and sends a routing request to the VPC using the information received in the call request over the V2 interface.

V2 interface

Routing request

VPC

Call server

Step 4 – Query Step 4 – Query (LK) (LK)

Step Step 5 – Response 5 – Response (LO)(LO)

4. The VPC queries the identified LIS over the V3 interface, including the received location key.

5. The LIS returns to the VPC the LO it has associated with the Client-ID.

V3 interfaceLocatio

n Key

Location

VPC

LIS

Step 6 – ResponseStep 6 – Response

a. The VPC uses the LO to obtain the ESZ-related routing information from the ERDB (including the, ESRN, ESN, and CRN) that will enable the routing via the ESGW to the SR that serves this ESZ.

b. The VPC uses the received routing information to allocate an available ESQK from the pool of ESQKs appropriate for the SR/ESN associated with the caller’s location/ESZ and sends a response to the routing request for this call, including the allocated ESQK and ESRN, as well as the appropriate LRO.

V2 interface

Loca

tion

(LO

)

ESQK/ESRN

ERDB

ESQK/ESRN,LOVPC

Call server

Step 7 – Invite Step 7 – Invite (ESRN, ESQK)(ESRN, ESQK)

a. The Call Server will take the ESRN received in the response and use it as the basis for selecting the appropriate ESGW with which to route the emergency call.

b. The Call Server routes the call to the ESGW, including the ESRN provided by the VPC and the ESQK.

V4 interfaceESQK/ESRN

Call

server

ESGW

Step 8 - Call RouteStep 8 - Call Route

a. The ESGW uses the received ESRN to select an outgoing route (i.e., trunk group) to the appropriate E9‑1‑1 SR.

b. The ESGW signals an emergency call origination to the E9‑1‑1 SR, using outgoing (SS7 or MF) signaling that includes the digits “9-1-1” as the called number and the ESQK as the calling number/ANI.

CAMA/ SS7

9-1-1 + ESQK

E9-1-1 Selective Router ESGW

Step 9 – Deliver CallStep 9 – Deliver Call

a. The SR receives the emergency call, uses the ESQK to query the SRDB for the associated Emergency Service Number (ESN), and uses the ESN to identify the appropriate PSAP for the call.

b. The SR then delivers the call to the appropriate PSAP, signaling the ESQK as the Automatic Number Identification (ANI) information.

ESN

ESQK PSAPESQK

E9-1-1 S/R

SRDB

Step 10 – ALI QueryStep 10 – ALI Query

The PSAP ANI/ALI controller receives the call setup signaling, and sends an ALI query to its serving ALI DB, using the ESQK as the query key.

ESQK

ALI Database

PSAP

Step 11 - ESPOSREQStep 11 - ESPOSREQ

The ALI DB sends an Emergency Services Positioning Request (ESPOSREQ) to the VPC (identified in the shell record for the ESQK in the ALI DB), which includes the ESQK as the query key in the request.

ESPOSREQw/ESQK

VPC ALI Database

For further information on ESPOSREQ, click on the acronym

ESPOSREQESPOSREQ

EEmergency mergency SService ervice PosPosition ition ReqRequestuest from ALI to from ALI to MPC, is used to request the initial, updated, or last MPC, is used to request the initial, updated, or last known position of a wireless handset or other device.known position of a wireless handset or other device.

If the requesting entity is authorized, the VPC shall use If the requesting entity is authorized, the VPC shall use the ESQK contained in the Emergency Services the ESQK contained in the Emergency Services Routing Key parameter of the ESPOSREQ message to Routing Key parameter of the ESPOSREQ message to identify the call instance, and to look up the associated identify the call instance, and to look up the associated call and location-related information stored at the VPC.call and location-related information stored at the VPC.

Step 12 - ALI QueryStep 12 - ALI Query

1. The VPC receives the ESPOSREQ from the ALI DB, and uses the ESQK to retrieve the ALI record information it stored previously (in Step 4).

2. The VPC returns the ESPOSREQ response to the ALI DB to provide the Callback Number, the Location information, and the VSP provided information that can be supported by the V-E2 interface.

ESPOSREQCBN, LOC, VSPVPC

ALI Database

Step 13 - ALI ResponseStep 13 - ALI Response

1. The ALI DB receives the ESPOREQ from the VPC (it may also extract additional information from the shell record for the ESQK).

2. The ALI DB returns an ALI response to the PSAP, following requirements in NENA 02-010.

ALI Response

John Smith xxx-xxx-xxxx1234 W. 6th AveEagle Lake, MO.

Fire - xxx xxx -xxxxEMS - xxx-xxx -xxxxPolice - xxx- xxx-xxxx

ALI Database

Step 14 –Step 14 – ESQK De-allocation ESQK De-allocation

When the VPC receives an indication that a particular When the VPC receives an indication that a particular instance of an emergency call is being cleared, the instance of an emergency call is being cleared, the VPC de-allocates the associated ESQK and makes itVPC de-allocates the associated ESQK and makes itavailable for subsequent emergency calls. available for subsequent emergency calls.

Note that release of the ESQK may occur as a result of Note that release of the ESQK may occur as a result of an indication of call release over the V2 interface from an indication of call release over the V2 interface from the Call Server/Routing Proxy, or the expiration of the the Call Server/Routing Proxy, or the expiration of the ESQK guard timer, whichever occurs first.ESQK guard timer, whichever occurs first.

VoIP Domain Emergency Services Provider Network

V4

7. Invite (ESRN,ESQK)

ESGW

Call Server

2. Call InitiationV1

6. Response (ESRN, ESQK, LRO)

9. Deliver Call(ESQK)

PSAP

9-1-1 Call Flow

V34. Query (LK)

5. Response (LO)

User Agent

Endpoint

1. LO and/or LK

V0

LIS

11. ESPOSREQ Query

12. ESPOSREQ Response (CBN, LO)

13. ALI response (Callback, LO)

8. Call route(ESQK)

E9-1-1 Selective Router

(ESQK)

10. ALI query

SRDB

V2

3. Query (Callback LIE),

VPC

SBC – Southwest

Public Safety

Frank Abbenhaus

VDB

ERDB

DBMS

MSAGMSAG

MSAG

14. ESQK De-allocation

One More Time One More Time Altogether!Altogether!