VoIP i2 Architecture Part II

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VoIP i2 ArchitecturePart II
9-1-1 Call Routing
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• The 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.

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Introduction
VoIP i2 9-1-1 Call Routing is Part 2 in the
9-1-1 VoIP series. It is important that you
review Part 1 VoIP i2 - 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.
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9-1-1 Call Flow
VoIP Domain
SRDB
14. ESQK De-allocation
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Basic Call Routing of a VoIP Emergency Call
GOT IT?
Now the next slide also has the IP Call Flow
graphically depicted. But on this slide you can
click on any of the indicated steps in the call
flow for a closer look at that particular step.
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9-1-1 Call Flow
VoIP Domain
V1
SRDB
11. ESPOSREQ Query
User Agent Endpoint
V0
12. ESPOSREQ Response (CBN, LO)
1. LO and/or LK
LIS
MSAG
14. ESQK De-allocation
MSAG
MSAG
VDB
DBMS
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Step 1 LO and/or LK
User Agent Endpoint
Click on picture to see animation
V0 interface
LO/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.
Click on this button to return to the diagram
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Step 2 Call Initiation
User Agent Endpoint
V1 interface
9-1-1 LO
The VoIP endpoint originates an emergency call by
sending a call initiation request, designating
sos_at_local.domain.name as the target destination,
and including Callback information, and the LO
using the V1 interface.
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Step 3 Query
Routing request
VPC
V2 interface
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.
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Step 4 Query (LK) Step 5 Response (LO)
VPC
Location Key
V3 interface
LIS
Location

• The VPC queries the identified LIS over the V3
  interface, including the received location key.
• The LIS returns to the VPC the LO it has
  associated with the Client-ID.

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Step 6 Response
VPC
Location (LO)
V2 interface
ESQK/ESRN, LO
ERDB
ESQK/ESRN

• 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.
• 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
  callers 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.

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Step 7 Invite (ESRN, ESQK)
ESQK/ESRN
V4 interface

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

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Step 8 - Call Route
9-1-1 ESQK
CAMA/ SS7

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

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Step 9 Deliver Call
ESQK
ESQK
SRDB

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

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Step 10 ALI Query
ALI Database
ESQK
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.
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Step 11 - ESPOSREQ
ALI Database
VPC
ESPOSREQ w/ESQK
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.
For further information on ESPOSREQ, click on the
acronym
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ESPOSREQ

• Emergency Service Position Request from ALI to
  MPC, is used to request the initial, updated, or
  last known position of a wireless handset or
  other device.
• If the requesting entity is authorized, the VPC
  shall use the ESQK contained in the Emergency
  Services Routing Key parameter of the ESPOSREQ
  message to identify the call instance, and to
  look up the associated call and location-related
  information stored at the VPC.

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Step 12 - ALI Query
ALI Database
VPC
ESPOSREQ CBN, LOC, VSP

• 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).
• 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.

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Step 13 - ALI Response
ALI Database
John Smith xxx-xxx-xxxx 1234 W. 6th Ave Eagle
Lake, MO. Fire - xxx xxx -xxxx EMS - xxx-xxx
-xxxx Police - xxx- xxx-xxxx
ALI Response

• The ALI DB receives the ESPOREQ from the VPC (it
  may also extract additional information from the
  shell record for the ESQK).
• The ALI DB returns an ALI response to the PSAP,
  following requirements in NENA 02-010.

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Step 14 ESQK De-allocation
When the VPC receives an indication that a
particular instance of an emergency call is being
cleared, the VPC de-allocates the associated ESQK
and makes it available for subsequent emergency
calls. Note that release of the ESQK may occur
as a result of an indication of call release over
the V2 interface from the Call Server/Routing
Proxy, or the expiration of the ESQK guard timer,
whichever occurs first.
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9-1-1 Call Flow
VoIP Domain
SRDB
14. ESQK De-allocation
SBC Southwest Public Safety Frank Abbenhaus