CA2548943A1

CA2548943A1 - Method, system and apparatus for retrieving location information on behalf of a location-unaware device in a packet-switched environment

Info

Publication number: CA2548943A1
Application number: CA002548943A
Authority: CA
Inventors: William B. Crago; Guy Caron; Jerome Grenier; Calvin C. K. Chow
Original assignee: BCE Inc
Current assignee: BCE Inc
Priority date: 2006-05-08
Filing date: 2006-05-08
Publication date: 2007-11-08

Abstract

According to embodiments of the present invention, a method for retrieving location information on behalf of an endpoint in a packet-switched environment is provided.
The method comprises receiving an indication of a public network address associated with the endpoint; determining a location information database address associated with a location information database responsible for storing emergency addresses for endpoints associated with a range of public network addresses, the range of public network addresses including the public network address of the endpoint. The method further comprises transmitting to the location information database address an emergency address request; the emergency address request comprising the public network address of the endpoint. Responsive to the transmitting, the method further comprises receiving the emergency address from the location information database.

Description

METHOD, SYSTEM AND APPARATUS FOR RETRIEVING LOCATION
INFORMATION ON BEHALF OF A LOCATION-UNAWARE DEVICE IN A
PACKET-SWITCHED ENVIRONMENT

FIELD OF THE INVENTION

The present invention relates generally to communications over packet-switched networks and, in particular, to a method, system and apparatus for retrieving location information on behalf of a location-unaware device in a packet-switched environment.
BACKGROUND OF THE INVENTION

One of the underpinnings of emergency services is the ability to determine the physical location from which an emergency call has been originated. For example, when an emergency call is made in the public switched telephone network (PSTN) using a plain old telephony service (POTS) phone, the emergency call sent through the PSTN specifies the directory number of the POTS phone. Due to the way in which the PSTN is configured, the directory number of each POTS phone corresponds to a fixed physical location (e.g., service address), and this relationship is maintained in an ALI database made available to Public Safety Answering Point (PSAP) operators. Thus, upon handling an emergency call specifying a given directory number, a PSAP operator who queries the ALI database using the given directory number will learn the address from which the emergency call was placed and, consequently, to which an emergency crew needs to be dispatched.

As voice-over-internet-protocol (VoIP) becomes the predominant technology used in the telecommunications industry, customers using VoIP endpoints (hereinafter "VoIP
customers") will expect enhanced emergency services to be delivered when emergency calls are originated from such devices over a broadband network. In other words, customers will expect an emergency address to be made available to an operator who receives the emergency call at the appropriate PSAP, when they make a VoIP call or engage in a communication session via a packet-switched network using other means (such as Instant Messaging and the like). However, some broadband service providers' networks are not natively compatible with the existing emergency infrastructure described above. In order to allow the delivery of emergency services to VoIP customers in a broadband network, the National Emergency Numbering Association (NENA) has proposed various architectures that can interface with the existing emergency infrastructure, thereby allowing existing PSAPs to handle emergency calls placed by VoIP customers.

Compounding the need to address the aforementioned issue of incompatibility with the existing emergency infrastructure is the need to address the issue of determining the physical location of the VoIP device from which an emergency call is originated.
Specifically, because telephone numbers assigned to VoIP devices are not necessarily associated with a fixed address or location, the availability of the directory number of the VoIP device is not sufficient to allow the physical location of the VoIP
device to be determined. In order to resolve this issue in the emergency services context, NENA has proposed a so-called "i2" architecture, which provides a network element known as a location information server (LIS) that serves as a repository for location information. The LIS is configured with a mapping between, on the one hand, location information elements or so-called "emergency addresses" (in the form of civic addresses, geo-spatial location attributes or an appropriate location tag) and, on the other, logical representations of the respective physical locations with which the emergency addresses are associated.

According to the i2 standard, VoIP devices are supposed to receive information on their own physical locations from the LIS, so that this information is conveyed to a network node (such as a soft switch) responsible for handling an emergency call originated from the VoIP device.

However, one significant omission from NENA's proposed i2 architecture is any description of interfaces and required protocols to enable the VoIP device to retrieve the emergency address from the LIS. In fact, document NENA 08-001, Issue 1, December 6, 2005, entitled "Interim VoIP Architecture for Enhanced 9-1-1 Services (i2)", hereby incorporated by reference herein, plainly states that "How the IP

network actually determines the location and the protocol between the LIS and IP
device is outside the scope of this document". Moreover, there is no indication in the industry how a location-unaware device is to locate and contact the LIS.
Actually, the equipment presently available in the industry (such as the VoIP devices, soft switches, etc.) does not have the ability to retrieve such emergency address information from the LIS.

Thus, there remains a need for a solution to the problem of enabling a location-unaware device to retrieve their location information from the LIS.
SUMMARY OF THE INVENTION

According to a first broad aspect of the present invention there is provided a method for retrieving an emergency address on behalf of an endpoint in a packet-switched environment. The method comprises receiving an indication of a public network address associated with the endpoint; determining a location information database address associated with a location information database responsible for storing emergency addresses for endpoints associated with a range of public network addresses, the range of public network addresses including the public network address of the endpoint; transmitting to the location information database using the location information database address an emergency address request; the emergency address request comprising the public network address of the endpoint. The method further comprises responsive to the transmitting, receiving the emergency address from the location information database.

According to a second broad aspect of the present invention there is provided a system for retrieving an emergency address on behalf of an endpoint in a packet-switched environment. The system comprises a computing apparatus conununicatively coupled to a call server responsible for handling an emergency call from the endpoint. The computing apparatus is operable to: receive an indication of a public network address associated with the endpoint from the call server;
determine a location information database address associated with a location information database responsible for storing emergency addresses for endpoints associated with a range of public network addresses, the range of public network addresses including the public network address of the endpoint; transmit to the location information database using the location information database address an emergency address request; the emergency address request comprising the public network address of the endpoint;
receive the emergency address from the location information database.

According to a third broad aspect of the present invention there is provided a computing apparatus for retrieving an emergency address on behalf of an endpoint in a packet-switched environment. The computing apparatus comprises means for receiving an indication of a public network address associated with the endpoint;
means for determining a location information database address associated with a location information database responsible for storing emergency addresses for endpoints associated with a range of public network addresses, the range of public network addresses including the public network address of the endpoint; means for transmitting to the location information database using the location information database address an emergency address request; the emergency address request comprising the public network address of the endpoint; means for receiving the emergency address from the location information database.

According to a fourth broad aspect of the present invention there is provided a call server for handling voice-over-packet-switched-network calls on behalf of an endpoint. The call server is operable to receive an emergency call originated from the endpoint; determine a public network address associated with the endpoint;
transmit the public network address to a computing apparatus, the public network address of the endpoint for enabling the computing apparatus to determine a location information database address based on the public network address of the endpoint;
determine the emergency address based on the location information database address and the public network address of the endpoint. The call server is further operable to receive the emergency address from the computing apparatus; handle the emergency call based on the emergency address.

According to a fifth broad aspect of the present invention there is provided a method for retrieving an emergency address on behalf of an endpoint in a packet-switched environment. The method comprises receiving an indication of a public network address associated with the endpoint; determining a location information database address associated with a location information database responsible for storing emergency addresses for endpoints associated with a range of public network addresses, the range of public network addresses including the public network address of the endpoint; transmitting to the location information database using the location information database address an emergency address request; the emergency address request comprising the public network address of the endpoint; the transmitting being instrumental in causing the location information database to determine the emergency address based on the public network address and to release the emergency address.
According to another broad aspect of the present invention there is provided a system for retrieving an emergency address on behalf of an endpoint in a packet-switched environment. The system comprises a computing apparatus communicatively coupled to a call server responsible for handling an emergency call from the endpoint;
the computing apparatus operable to receive an indication of a public network address associated with the endpoint from the call server; determine a location information database address associated with a location information database responsible for storing emergency addresses for endpoints associated with a range of public network addresses, the range of public network addresses including the public network address of the endpoint; transmit to the location information database using the location information database address an emergency address request; the emergency address request comprising the public network address of the endpoint; the emergency address request being instrumental in causing the location information database to determine the emergency address based on the public network address and to release the emergency address.

According to yet another broad aspect of the present invention there is provided a method for retrieving location information on behalf of an endpoint in a packet-switched environment. The method comprises receiving an indication of a public network address associated with the endpoint; determining a location information database address associated with a location information database responsible for storing location information for endpoints associated with a range of public network addresses, the range of public network addresses including the public network address of the endpoint; transmitting to the location information database using the location information database address a location information request; the location information request comprising the public network address of the endpoint; the transmitting being instrumental in causing the location information database to determine the location information based on the public network address and to release the location information.

According to another broad aspect of the present invention there is provided an apparatus for retrieving location information on behalf of an endpoint in a packet-switched environment. The apparatus comprises means for receiving an indication of a public network address associated with the endpoint; means for determining a location information database address associated with a location information database responsible for storing location information for endpoints associated with a range of public network addresses, the range of public network addresses including the public network address of the endpoint; means for transmitting to the location information database at the location information database address a location information request;
the location information request comprising the public network address of the endpoint; the transmitting being instrumental in causing the location information database to determine the location information based on the public network address and to release the location information.

These and other aspects and features of the present invention will now become apparent to those of ordinary skill in the art upon review of the following description of specific embodiments of the invention in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS
In the drawings:

Fig. 1 is a diagrammatic representation of an infrastructure for the delivery of VoIP
telephony services to a VoIP endpoint, in accordance with an example non-limiting embodiment of the present invention;

Fig. 2 is a diagrammatic representation of an address directory of the infrastructure of Fig. 1;

Fig 3 depicts a block diagram of a method for retrieving an emergency address on behalf of a location-unaware device according to one non-limiting embodiment of the present invention;

Fig. 4 is a diagrammatic representation of an infrastructure for the delivery of VoIP
telephony services to a VoIP endpoint, in accordance with another non-limiting embodiment of the present invention;
Fig. 5 depicts a block diagram of a method for retrieving an emergency address on behalf of a location-unaware device according to another non-limiting embodiment of the present invention.

It is to be expressly understood that the description and drawings are only for the purpose of illustration of certain embodiments of the invention and are an aid for understanding. They are not intended to be a definition of the limits of the invention.
DETAILED DESCRIPTION OF EMBODIMENTS
Fig. 1 shows various components of an infrastructure for delivering VoIP
telephony services, including provisioning of emergency services, to a VoIP device, in accordance with an example non-limiting embodiment of the present invention.
The non-limiting example of the infrastructure comprises an access device 102 connected to a port 106A of an access multiplexer 106 via a physical communication link 108.

In an example non-limiting embodiment, the access device 102 may comprise a broadband modem 110 connected to a router 112 over a home network 114. The router 112 may in turn be connected over the home network 114 to a VoIP phone or, alternatively, to a POTS phone 118 via an analog terminal adapter (ATA) 120.
The ATA 120 and the VoIP phone 116 are just two non-limiting embodiments of a so-called "VoIP endpoint". Another non-limiting example of the VoIP endpoint can be embodied as a computer implementing an IP telephony software.

In another non-limiting embodiment, the functionality of the router 112 and the broadband modem 110 can be embodied in a single device. In an alternative non-limiting embodiment of the present invention, the router 112 can be omitted from the infrastructure of Fig. 1. In yet further non-limiting embodiments of the present invention, the functionality of the ATA 120 can be incorporated into the broadband modem 110. In another non-limiting embodiment of the present invention, the functionality of the ATA 120 can be incorporated into the router 112.
Alternatively, in yet other non-limiting embodiments of the present invention, the functionality of the router 112, the broadband modem 110 and the ATA 120 (or the VoIP phone 116) can be incorporated into a single device.

In an example non-limiting embodiment, the physical communication link 108 can be a copper twisted pair, over which higher-layer protocols allow for the exchange of packets. In an alternative non-limiting embodiment, the physical communication link 108 may comprise an Ethernet link, a fiber optic link (e.g., Fiber-to-the-Home, Fiber-to-the-Curb, etc.), a wireless link (e.g., EV-DO, WiMax, WiFi, CDMA, TDMA, GSM, and the like), a cable, etc., or a combination thereof. In some non-limiting embodiments, the home network 114 can comprise an Ethernet network. In other non-limiting embodiments, the home network 114 can comprise a wireless network (ex. an 802.11 based network, an 802.12 based network and the like) or any other suitable type of home network.

The access multiplexer 106, which in an example non-limiting embodiment can comprise a digital subscriber line access multiplexer (DSLAM), can be connected to a network access server (NAS) 126, which may also be referred to by some in the industry as a broadband remote access server (BRAS), a remote access server (RAS) or a broadband access server (BAS). The NAS 126 provides access to a core packet-switched data network 132, such as the Internet, over which VoIP calls can be established. In an example non-limiting embodiment, communication between the access multiplexer 106 and the NAS 126 may take place over a dedicated logical link (not depicted) between the access multiplexer 106 and the NAS 126. The dedicated logical link can be defined via an access data network 132. In an example non-limiting embodiment, the dedicated logical link can be implemented as an asynchronous transfer mode (ATM) permanent virtual circuit (PVC). In another example non-limiting embodiment, the dedicated logical link can be implemented as a virtual local area network (VLAN). Still other implementations of the dedicated logical link are within the scope of the present invention.

The purpose of the access multiplexer 106 is to multiplex several physical links (such as the link 108) from several access devices (such as access device 102) for communication over the access data network 132 and vice versa.
Also provided in Fig. 1 is a network element 140A, which in some embodiments of the present invention can be provided at an edge of the core packet-switched data network 132. The network element 140A is referred to the industry as a "call server", a "packet switch" or a "soft switch" and comprises circuitry, software andlor control logic for providing various communication services to VoIP endpoints (such as, for example, the aforementioned ATA 120 or VoIP phone 116). Examples of such communication services include (i) connecting incoming calls to the VoIP
endpoint (such as the ATA 120 or the VoIP phone 116); and (ii) handling outgoing calls originated from the VoIP endpoint (such as the ATA 120 or the VoIP phone 116).
Other examples of communication services that can be performed by the network element 140A can include but are not limited to call waiting, call forwarding, voicemail recording, storage and retrieval, and so on.

In addition, the network element 140A can comprise suitable circuitry, software and/or control logic for exchanging calls with entities outside the core packet-switched data network 132. This is particularly convenient, when a call placed by a VoIP customer (i.e. a user of the VoIP phone 116) to a telephone number that is reachable only via the Public Switched Telephone Network (PSTN), which has been omitted from Fig. 1 for the sake of simplicity. A non-limiting example of the network element 140A can be embodied in a MCS 5200 Soft Switch manufactured by Nortel Networks Ltd. of 8200 Dixie Road, Brampton, Ontario L6T 5P6, Canada.

Given the components of the infrastructure of Fig. 1 described above, it is possible to deliver VoIP telephony services to the user of the VoIP phone 116 or the POTS
phone 118 equipped with the ATA 120. The VoIP telephony service can be delivered by a service provider which manages the aforementioned access multiplexer 106, the access data network 132, the network access server 126 and the network element 140A. Alternatively, the VoIP telephony service can be delivered by an alternative service provider in which case the VoIP telephony service "runs over" the infrastructure of Fig. 1. This arrangement for delivering the VoIP telephony service is generally referred to as "over-the-top VoIP".

In order to facilitate provisioning of emergency services, the infrastructure of Fig. 1 further comprises an emergency services entity 160. The emergency services entity 160 can comprise several components, such as one or more Public Safety Answering Points (PSAPs), one or more 911 selective routers, one or more emergency services gateways, an Automatic Line Identification (ALI) database and the like. These components are well known to those of skill in the art and, as such, have been omitted from Fig. 1.

In some embodiments of the present invention, the emergency services entity 160 can be connected to the network element 140A via the PSTN (not depicted). In these non-limiting embodiments, the emergency services entity 160 can further comprise one or more media gateways (not depicted), the main purpose of which is to mediate digital communication to analog communication and vice versa.

Also provided in the infrastructure of Fig. 1 is a location information database 150A.
In some non-limiting embodiments, the location information database 150A can be connected directly to the network element 140A. In other non-limiting embodiments of the present invention, the location information database 150A can be integrated with the network element 140A. Yet in further non-limiting embodiments, the network element 140A can access the location information database 150A via the core packet-switched data network 132. In yet other non-limiting embodiments, the location information database 150A may be distributed amongst a plurality of functional elements and/or physical locations. It should be further appreciated that the location information database 150A can be managed, maintained and/or updated by a service provider that may be the same service provider as, or a different service provider from, the service provider that is responsible for providing the access device 102 with access to the core packet-switched data network 132.

In an example non-limiting embodiment, the location information database 150A
can be implemented as a location information server (LIS) described in the document NENA 08-001, Issue 1, December 6, 2005, entitled "Interim VoIP Architecture for Enhanced 9-1-1 Services (i2)", hereby incorporated by reference herein. To this end, the location information database 150A may comprise a plurality of records, each record mapping an emergency address to a logical identifier. In an example non-limiting embodiment, the emergency address can be expressed as a civic address or a set of geo-spatial coordinates (e.g., latitude/longitude) indicative of a physical location of the VoIP telephone 116 or the ATA 120. In various example non-limiting embodiments, the logical identifier may be an IP address in compliance with, e.g., IPv4 or IPv6, or a proprietary address, label or tag. For the purposes of the specific non-limiting example presented herein below, it is assumed that the logical identifier, or in other words, a "public network address" of the VoIP endpoint comprises an IP
address. It is further assumed that the location information database 150A has been populated with the emergency address associated with a location of the VoIP
phone 116.

In some non-limiting embodiments of the present invention, the infrastructure of Fig.
1 can further comprise a network element 140B communicatively coupled to the core packet-switched data network 132. The network element 140B can be managed by a service provider different from the service provider which manages the network element 140A. The network element 140B can be operable to deliver VoIP
telephony services to subscribers (not depicted) of the service provider which manages the network element 140B. These subscribers can use VoIP endpoints that can be substantially similar to the VoIP phone 116 or the ATA 120. The service provider which manages the network element 140B can also provide so-called "roaming services" to the subscribers of the service provider which manages the network element 140A.
The network element 140B can be coupled to a location information database 150B, which can be substantially similar to the location information database 150A.
To that end, the location information database 150B maintains mappings associated with the subscribers of the service provider which manages the network element 140B.
The network element 140B can also be coupled to the emergency services entity 160 for the purposes of provisioning emergency services to its subscribers. In an alternative non-limiting embodiment of the present invention, the network element 140B can be coupled to a separate emergency services entity (not depicted).

Communicatively coupled to the core packet-switched data network 132 is a location retrieving server 145. The function of the location retrieving server 145 will be described in greater detail herein below. For now, suffice it to say, that the location retrieving server 145 is operable to retrieve location information from the location information database 150A or location information database 150B on behalf of a location-unaware device, such the ATA 120, the VoIP phone 116 or the network elements 140A, 140B. In some non-limiting embodiments of the present invention, the location retrieving server 145 can comprise a Ubiquity Application Server, which can be provided by Ubiquity of 515 Legget Drive, Suite 400, Ottawa, Ontario, Canada. It should be noted that in alternative non-limiting embodiments of the present invention, any suitable type of an application server or a suitable computing apparatus can be used.

The location retrieving server 145 can be reached via the core packet-switched data network 132 at a network address, such as but not limited to an IP address. In some non-limiting embodiments, the IP address assigned to the location retrieving server 145 can be a static IP address. The network element 140A and the network element 140B are made aware of this static IP address for the purposes of reaching the location retrieving server 145 via the core packet-switched data network 132. In an alternative non-limiting embodiment, the IP address assigned to the location retrieving server 145 can be a dynamic IP address. In these non-limiting embodiments, the network element 140A and the network element 140B can be dynamically updated with the dynamic IP
address of the location retrieval server 145, as is known to those of skill in the art. In an alternative non-limiting embodiment of the present invention, the location retrieval server 145 can be assigned a Unique Resource Identifier (URI), such as, for example, an URL. The network element 140A and the network element 140B can be made aware of this URL of the location retrieval server 145. The URL enables the network element 140A and network element 140B to contact the location retrieval server via the core packet-switched data network 132 by performing a DNS look-up, as is known to those of skill in the art.

Communicatively coupled to the location retrieving server 145 is an address directory 147. Generally speaking, the purpose of the address directory 147 is to maintain a mapping between an IP address range assigned to a particular service provider and a network address of the location information database maintained by or for the particular service provider. In an alternative non-limiting embodiment of the present invention, the address directory 147 can be integrated with the location retrieving server 145. In another alternative non-limiting embodiment of the present invention, the address directory 147 can be reachable by the location retrieving server 145 via the core packet-switched data network 132. In yet further embodiments, the address directory 147 can be distributed amongst a plurality of functional elements and/or physical locations. The address directory 147 will now be described in greater detail with reference to Fig. 2, which depicts a specific non-limiting embodiment of such an address directory 147.

The address directory 147 can maintain a number of records, such as example records 202, 204 and 206. Each of the records 202, 204 and 206 can map a service provider 210 to a corresponding address range 212 and a corresponding location information database address 214. It should be noted that in some non-limiting embodiments of the present invention, the service provider 210 can be omitted from the records 202, 204 and 206 maintained in the address directory 147.

The record 202 can be maintained for the service provider 210 "A", which can, for example, be the service provider which manages the aforementioned network element 140A. The address range 212 for the service provider 210 "A" contains "151.200Ø0/16" which is indicative of the range of IP addresses allotted to the service provider 210 "A" - from IP address 151.200Ø1 to 151.200.255.255. As will be appreciated by those of skill in the art, the service provider 210 "A" can use these allotted IP addresses, commonly referred to as a pool of available IP
addresses, to assign an IP address to its subscribers, for example to the VoIP phone 116, the ATA
120, the access device 102 and other devices served by the service provider 210"A".
The service provider 210 "A" can also "sublet" a portion of these allotted IP
addresses to another service provider.

The location information database address 214 for the service provider 210 "A"
indicates a network address where a location information database (such as the location information database 150A maintained by or for the service provider 210 "A"
can be reached). In the particular example depicted in record 202, the address maintained in the location information database address 214 comprises an URL
"https://lis.a-isp.net".

The record 204 can be maintained for the service provider 210 "B", which can, for example, be the service provider which manages the aforementioned network element 140B. The address range 212 for the service provider 210 "B" contains "163.27Ø0/16" which is indicative of the range of IP addresses allotted to the service provider 210 "B" - from IP address 163.27Ø1 to 163.27.255.255. The location information database address 214 for the service provider 210 "B" indicates a network address where a location information database (such as the location information database 150B maintained by or for the service provider 210 "B" can be reached). In the particular example depicted in record 204, the address maintained in the location information database address 214 comprises an URL "https://lisl.b-corp.com".
In substantially the same manner, the record 206 can be maintained for the service provider 210 "C", which can, for example, be the service provider which manages a network element (not depicted) substantially similar to the network elements 140A, 140B. The address range 212 for the service provider 210 "C" contains "201Ø0.0/24' which is indicative of the range of IP addresses allotted to the service provider 210 "C" - from IP address 201Ø0.1 to 201.255.255.255. The location information database address 214 for the service provider 210 "C" indicates a network address where a location information database (such as the location information database substantially similar to the location information databases 150A, 150B
maintained by or for the service provider 210 "C" can be reached.) In the particular example depicted in record 206 the address maintained in the location information database address 214 comprises an IP address "201Ø0.1".
Approaches to populating records 202, 204 and 206 are not particularly limited. In some embodiments of the present invention, the records 202, 204 and 206 can be populated for service providers on the basis of a subscription. For example the service provider associated with the record 204 may subscribe to an emergency retrieval service contemplated in accordance with non-limiting embodiments of the present invention. During the subscription process, the service provider may provide the necessary information to populate the record 204. In another non-limiting embodiment of the present invention, the entity which manages the address directory 147 (for example, the service provider which manages the location retrieval server 145) may populate records 202, 204 and 206 on the basis of publicly available information about the IP ranges assigned to various service providers. An example of such publicly available information can be found at:
http://www.iana.org/assignments/ipv4-address-space. Those of skill in the art will appreciate that yet other approaches to populating records 202, 204 and 206 are possible.

It should be explicitly stated that the above-presented description has used the IP
address for the purposes of illustration and not as a limitation of the embodiments of the present invention. It should be noted that any other network address suitable for the purposes of communication via the core packet-switched data network 132 can be used. A non-limiting example of such network address can comprise a SIP
address, a MAC address, a proprietary network address, a device identifier and the like Of course, it will be apparent to those skilled in the art that numerous modifications and variations of the infrastructure of Fig. 1 are possible. For example, in an alternative non-limiting embodiment, the access multiplexer 106 can be omitted. This is especially true in the case where the access device 102 implements a wireless access point. In an example non-limiting embodiment of this scenario, the connection between the wireless access point and the NAS 126 can be provided by a dedicated point-to-point link. In another non-limiting scenario where the broadband modem 110 implements a cable modem, the access multiplexer 106 can also be omitted. Yet in another non-limiting embodiment, the NAS 126 can be omitted from the infrastructure of Fig. 1.

Given the infrastructure of Fig. 1 and the address directory 147 as more particularly described in Fig. 2, it is possible to perform a method for retrieving an emergency address on behalf of a location-unaware device (such as the VoIP phone 116) according to a non-limiting embodiment of the present invention. With reference to Fig. 3 the method for retrieving an emergency address on behalf of a location-unaware device is now described in greater detail.

Step 310: receive an indication of a public network address The method begins at step 310, where the location retrieving server 145 receives the indication of the public network address from a network element responsible for handling an emergency call from a VoIP endpoint. In a particular non-limiting example being used below, it is assumed that the user of the VoIP phone 116 has originated the emergency call and that the network element 140A is responsible for handling the emergency call.

In some embodiments of the present invention, the association between the VoIP phone 116 and the network element 140A is "hard-coded" into the VoIP
phone 116. More specifically, a network address (such as but not limited to a static IP address) of the network element 140A can be programmed, hard-coded or otherwise made known to the VoIP phone 116. Therefore, all calls originated from and destined to the VoIP phone 116 will be handled by the network element 140A (or another network element, which acts as a fall-back network element for the network element 140A, in case the network element 140A is down, congested or otherwise unavailable).

In an alternative non-limiting embodiment, the IP address assigned to the network element 140A can be a dynamic IP address. In these non-limiting embodiments, the VoIP phone 116 can be dynamically updated with the dynamic IP address of the network element 140A, as is known to those of skill in the art. In an alternative non-limiting embodiment of the present invention, the network element 140A can be assigned a Unique Resource Identifier (URI), such as, for example, an URL. The VoIP phone 116 can be made aware of this URL of the network element 140A. The URL enables the VoIP phone 116 to contact the network element 140A via the core packet-switched data network 132 by performing a DNS look-up, as is known to those of kill in the art.
In a specific non-limiting embodiment of the present invention, the location retrieving server 145 receives a signaling message, such as a SIP invite message, from the network element 140A in response to the network element 140A detecting the emergency call from the VoIP phone 116. In some embodiments of the present invention, the network element 140A can act as a SIP proxy or, in other words, the network element 140A can "forward" a SIP
invite message received from the VoIP phone 116 to the location retrieving server 145. In these non-limiting embodiments, the location retrieving server 145 can extract the indication of the public network address associated with the VoIP phone 116, which can be, but is not limited to, a public IP address, by examining a "via" header of the SIP invite message received from the network element 140A.

In an alternative non-limiting embodiment, the network element 140A can handle the emergency call in a "back-to-back" manner. In other words, upon receiving the emergency call from the VoIP phone 116, the network element 140A can generate a new SIP invite message to establish a VoIP call with the location retrieving server 145. In these embodiments, the network element 140A firstly examines the SIP invite message received from the VoIP phone 116 to retrieve the indication of the public IP address associated with the VoIP
phone 116. Secondly, when generating the SIP message destined to the location retrieving server 145, the network element 140A inserts the indication of the public IP address into the SIP invite message. In a particular non-limiting embodiment, the network element 140A can insert the indication of the public IP address in the SIP invite message into the "via" header.

In some non-limiting embodiments of the present invention, which are particularly applicable when the VoIP phone 116 is assigned a private IP
address for the purposes of communication on the home network 114, the network element 140A can extract and transmit to the location retrieving server 145 the indication of the public IP address associated with the router 112 or the broadband modem 110.
Irrespective of how the network element 140A generates the SIP invite message, the location retrieving server 145 becomes aware of the public network address of the VoIP phone 116 which is in process of establishing the emergency call via the network element 140A.
It should be noted that in other non-limiting embodiments, any other suitable network address of the VoIP phone 116, which is compatible with the location information database 150A, or in other words any network address of the VoIP
phone 116 suitable for performing a lookup into the location information database 150A, can be used. A non-limiting example of such network address of the VoIP phone 116 can comprise a SIP address, a MAC address, a proprietary identifier and the like. Therefore, it should be explicitly understood that the term "public network address" includes any suitable network address of the VoIP phone 116.
For the purposes of a non-limiting example to be presented below, assume that the location retrieving server 145 has received the IP address 151.200.56.101" associated with the VoIP phone 116.

Step 320: determine a location information database address Next, the location retrieving server 145 determines a network address of the location information database responsible for storing location information for the VoIP phone 116.

In a particular non-limiting embodiment, the location retrieving server 145 accesses the address directory 147 to retrieve a record associated with the service provider managing the network element 140A. Specifically, the location retrieving server 145 determines which address range 212 contains the public IP address of the VoIP phone 116 obtained at step 310.

In the specific non-limiting example being presented here, the location retrieving server 145 attempts to locate a record that contains an address range 212 which includes the IP address "151.200.56.101". The location retrieving server 145 determines that record 202 associated with the service provider 210 "A" contains the address range 212, which includes the IP address "151.200.56.101". The location retrieving server 145 then extracts the content of the location information database address 214, which in this example contains the URL "https://lis.a-isp.net".

Accordingly, the location retrieving server 145 has determined the network address associated with the location information database 150A which maintains the emergency address for the VoIP phone 116.
Step 325: transmit an emergency address request to the location information database Next, the location retrieving server 145 transmits an emergency address request to the location information database 150A at the network address determined at step 320 (i.e. https://lis.a-isp.net). As will be appreciated by those skilled in the art, a DNS query may be performed in some embodiments of the present invention in order to determine an IP address corresponding to the URL obtained in step 320. In some non-limiting embodiments of the present invention, the location retrieving server 145 can transmit the emergency address request using an HTTP enabled location delivery (HELD) with OBO extensions protocol, available from http://www.ietf.org/internet-drafts/draft-winterbottom-http-location-delivery-02.txt. In an alternative non-limiting embodiment of the present invention, the emergency address request can be transmitted using a SIMPLE protocol (SIP IM with Presence Leveraging Extensions), available from http://www.ietf.org/internet-drafts/draft-ietf-simple-presence-data-model-07.txt. It should be noted that in some embodiments of the present invention, a proprietary protocol can be used. One skilled in the art will appreciate that other suitable protocols can also be used.

Irrespective of which protocol is used for transmitting the emergency address request, the emergency address request contains the public network address of the VoIP phone 116 obtained at step 310.

Step 330: receive the emergency address from the location information database Upon receipt of the emergency address request, the location information database 150A performs a look up based on the public network address of the VoIP phone 116 received as part of the emergency address request.

In an event that the location information database 150A fails to locate a record associated with the public network address received as part of the emergency address request, the location information database 150A can execute an exception handling routine, such as but not limited to transmitting an error message to the location retrieving server 145 indicative of the fact that the emergency address for the VoIP phone 116 is not available. If, on the other hand, the location information database 150A successfully locates a record associated with the public network address received as part of the emergency address request, the location information database 150A transmits the associated emergency address back to the location retrieving server 145. In some non-limiting embodiments of the present invention, the location information database 150A can transmit the emergency address by-value (referred to as "The Presence Information Data Format Location Object" or simply PIDF-LO). In alternative non-limiting embodiments, the location information database 150A can transmit the emergency address by reference (referred to as Universal Resource Identifier or simply "URI").
In this manner, the location retrieving server 145 becomes aware of the emergency address associated with the VoIP phone 116.

It should be noted that in some non-limiting embodiments of the present invention, the location information database 150A can transniit the emergency address to another entity, such as but not limited to the network element 140A.
Step 340: release the emergenoy address Next, the location retrieving server 145 releases the emergency address.
Several non-limiting embodiments for how the location retrieving server 145 releases the emergency address are contemplated:

Releasing the emergency address to the network element 140A
In a first non-limiting embodiment of the present invention, the location retrieving server 145 releases the emergency address to the network element 140A. Specifically, the location retrieving server 145 can generate a SIP
invite message directed to the network element 140A and insert an indication of the emergency address into one or more fields of the SIP invite message.

In a particular non-limiting embodiment, the location retrieving server 145 can insert the indication of the emergency address into the SIP invite message using a SIP Location conveyance protocol available from http://www.ietf.org/internet-drafts/draft-ietf-sip-location-conveyance-02.txt.

Upon receipt of the SIP invite message, the network element 140A becomes aware of the emergency address associated with the VoIP phone 116 and can handle the emergency call from the VoIP phone 116 accordingly, as prescribed by the aforementioned NENA i2 standard, for example. These steps are known to those skilled in the art and, therefore, only a non-limiting example is provided herein below for purposes of illustration only.

For example, the network element 140A can transmit a query containing the emergency address to a VoIP positioning center (VPC), which is not depicted on Fig.l for the sake of simplicity, in order to retrieve emergency call routing instructions from the VPC.

Based on the emergency address, the VPC can query an Emergency Routing Data Base (ERDB, not shown) for routing information relating to the emergency call. In an example, the routing information may be in the form of an emergency services query key (ESQK) and an emergency services routing number (ESRN), which are returned to the network element 140A. In addition, the ESQK is pushed to an ALI database (not depicted) in the emergency services entity 160. It should be noted that in some non-limiting embodiments, the ESQK may have been provisioned in the ALI prior to the emergency call being placed. Meanwhile, the VPC stores the ESQK and the aforementioned emergency address along with the callback number of the VoIP phone 116.
Upon receipt of the ESQK and the ESRN from the VPC, network element 140A routes the emergency call based on the ESRN as the routing path identifier and uses the ESQK as the calling number going to an Emergency Services Gateway (not depicted) in the emergency services entity 160. The emergency call with the ESQK is then routed to a PSAP via an appropriate PSTN selective router (not shown). At the PSAP, an operator queries the ALI
database with the ESQK. In turn, the ALI database queries the VPC with the ESQK to obtain the location object that had been stored by the VPC in association with that ESQK. In this way, the PSAP operator learns the physical location of the VoIP phone 116 from which the emergency call was originated. In an alternative non-limiting embodiment, rather than having the operator querying the ALI, the Emergency Services Gateway can send a message containing the ESQK to the ALI, which in turn will send the emergency address to the PSAP.

Acting asa proxy to the network element 140A
In a second non-limiting embodiment of the present invention, the location retrieving server 145 can act as a SIP proxy to the network element 140A for the purposes of handling the emergency call from the VoIP phone 116.
Specifically, the location retrieving server 145 can transmit a query containing the emergency address to the aforementioned VoIP positioning center (VPC) in order to retrieve emergency call routing instructions from the VPC.
Equipped with the routing instructions provided by the VPC, the location retrieving server 145 can dispose of the emergency call in accordance with the routing instructions, as described immediately above.

Acting as a redirect server for the network element 140A
In a third non-limiting embodiment of the present invention, the location retrieving server 145 can act as a redirect server for the network element for the purposes of handling the emergency call from the VoIP phone 116.
Specifically, the location retrieving server 145 can transmit a query containing the emergency address to the aforementioned VoIP positioning center (VPC) in order to retrieve emergency call routing instructions from the VPC.
Equipped with the routing instructions provided by the VPC, the location retrieving server 145 can transmit the routing instructions back to the network element 140A to enable the network element 140A to handle the emergency call in accordance with the routing instructions. In a specific non-limiting example, the location retrieving server 145 can send a SIP redirect message to the network element 140A, the SIP redirect message containing the ESQK and the ESRN.

Releasing the emer eg_ncy address to the VoIP phone 116 In some non-limiting embodiments and as an enhancement, the location retrieving server 145 can also forward a copy of the indication of the emergency address to the VoIP phone 116 for storage thereon. In some non-limiting embodiments of the present invention, the VoIP phone 116 can store the emergency address and forward the emergency address to the network element 140A, for example, during establishment of a future emergency call.

Given steps 310 - 340 described above, the location retrieving server 145 has conveniently obtained the emergency address associated with the VoIP phone 116 from the location information server 150A on behalf of the VoIP phone 116 and the network element 140A.

Now consider a scenario, whereby the user of the VoIP phone 116 has moved the VoIP phone 116. For example, the user of the VoIP phone 116 may have connected the VoIP phone 116 in a hotel room in another city. Today, high speed access (wired or wireless) is commonly available in most hotels and is offered to hotel guests either at an additional charge or as included in the hotel room price. When accessing the core packet-switched data network 132 from the hotel room, the VoIP phone 116 may be accessing the core packet-switched data network 132 via an access data network which is different from the access data network 132. For example, the VoIP
phone 116 may be accessing the core packet-switched data network 132 via an access data network associated with a service provider "B" which manages the network element 140B and maintains the location information database 150B.

In this non-limiting scenario, when the VoIP phone 116 is connected to the core packet-switched data network 132, an emergency address associated with its location will be provisioned in the location information database 150B. The VoIP phone will also be assigned an IP address from a range of IP addresses of the service provider "B". However, when an emergency call (or any other call) is originated from the VoIP phone 116 in this scenario, it will be routed via a "native network element", such as the network element 140A. In this scenario, by executing the method described above, the location retrieving server 145 is able to retrieve the emergency address from the location information database 150B on behalf of the VoIP
phone 116 to enable emergency call handling, even though the VoIP phone 116, which is location-unaware, accesses the core packet-switched data network 132 via a different access data network and even though the emergency address is stored in the location information database 150B managed by a different service provider from the service provider managing the network element 140A.

An alternative non-limiting embodiment of the infrastructure of Fig. 1 is depicted in Fig. 4. The infrastructure depicted in Fig. 4 is substantially similar to the infrastructure of Fig. 1, but for the specific differences described below.

The infrastructure of Fig. 4 comprises network elements associated with a single service provider, such as the network element 140A-1 and the location information database 150A-1. Naturally, the infrastructure of Fig. 4 can comprise a plurality of other network elements managed by the single service provider, such as a geographically dispersed or "redundant" network element (not depicted). In this non-limiting embodiment, the need for the address directory 147 can be eliminated.
Of course, the address directory 147 can be maintained, for example, where the service provider maintains more than one location information database 150A-1. In that case, the address directory 147 can map a sub-set of IP addresses to the network address of the respective location information database.

Given the infrastructure of Fig. 4, the location retrieving server 145 can execute a method for retrieving an emergency address on behalf of a location-unaware device according to another non-limiting embodiment of the present invention. With reference to Fig. 5 the method for retrieving an emergency address on behalf of a location-unaware device is now described in greater detail.

Step 510: receive an indication of a public network address The method begins at step 510, where the location retrieving server 145 receives the indication of the public network address from the network element 140A-1 in response to the network element 140A-1 detecting an emergency call originating from the VoIP phone 116.
Step 510 can be implemented in substantially the same manner as described above in respect to step 310.

Step 515: transmit an emerizency address rec~uest to the location information database At this step, the location retrieving server 145 transmits the emergency address request to the location information database 150A-1. In these non-limiting embodiments, a network address associated with the location information database 150A-1 can be known to the location retrieving server 145.

How the location retrieving server 145 transmits the emergency address request can be executed in substantially the same manner as described above in reference to step 325.

Step 520: receive the emergency address from the location information database Next, the location retrieving server 145 receives the emergency address associated with the VoIP phone 116 from the location information database 150A-1.

How the location retrieving server 145 receives the emergency address from the location information database 150A-1 can be implemented in substantially the same manner as described above in association with step 330.

Step 530: release the emergency address Next, the location retrieving server 145 releases the emergency address.
Several non-limiting embodiments for how the location retrieving server 145 releases the emergency address are contemplated and these embodiments can be substantially similar to the embodiments contemplated for the step 340 described above.

Effectively, in this non-limiting alternative embodiment of the method for retrieving the emergency address on behalf of a location-unaware device, the location retrieving server 145 can retrieve an emergency address on behalf of a location-unaware device (ex. the VoIP phone 116) used by subscribers to VoIP telephony service of a single service provider, i.e. the service provider, which in these embodiments, manages the network element 140-1 and maintains the location information database 150A-1.

In an alternative embodiment of the present invention, when the location information database 150A receives an emergency address request from the location retrieving server 145, the location information database 150A performs a look up and retrieves the emergency address associated with a network address contained in the emergency address request. The location information database 150A can then transmit the emergency address directly to the network element 140A. In an alternative non-limiting embodiment of the present invention, the location information database 150A
can also transmit the emergency address to the VoIP 116.

In some non-limiting embodiments of the present invention, the functionality of the location retrieving server 145 can be integrated with the functionality of the network element 140A (or the network element 140B) into a single device.

Even though the foregoing description has been presented using an example of retrieving an emergency address on behalf of a location-unaware device in a packet-switched environment, one skilled in the art will appreciate that teachings of the embodiments of this invention can be applied for retrieving other types of location information on behalf of location-unaware devices, such as service addresses and the like. Generally speaking, the teachings of the embodiments of the present invention can be applied for retrieving location information for the purposes of delivering SIP-based services (such as voice calls over packet-switched networks, instant messaging and the like) or location information for the purposes of services delivered to endpoints in a packet-switched network in general.

Those skilled in the art will appreciate that certain functionality of the NAS
126, the location information databases 150A, 150B, the location retrieving server 145 and/or other elements of the infrastructure described herein may be implemented as pre-programmed hardware or firmware elements (e.g., application specific integrated circuits (ASICs), electrically erasable programmable read-only memories (EEPROMs), etc.), or other related components. In other embodiments, certain portions of the NAS 126, the location information databases 150A, 150B, the location retrieving server 145 and/or other elements may be implemented as an arithmetic and logic unit (ALU) having access to a code memory (not shown) which stores program instructions for the operation of the ALU. The program instructions could be stored on a medium which is fixed, tangible and readable directly by the NAS 126, the location information databases 150A, 150B, the location retrieving server 145 and/or other elements, (e.g., removable diskette, CD-ROM, ROM, fixed disk, USB
drive), or the program instructions could be stored remotely but transmittable to the NAS
126, the location information databases 150A, 150B, the location retrieving server and/or other elements via a modem or other interface device.

While specific embodiments of the present invention have been described and illustrated, it will be apparent to those skilled in the art that numerous modifications and variations can be made without departing from the scope of the invention as defined in the appended claims.

Claims

CLAIMS:

1. A method for retrieving an emergency address on behalf of an endpoint in a packet-switched environment, the method comprising:

- receiving an indication of a public network address associated with said endpoint;

- determining a location information database address associated with a location information database responsible for storing emergency addresses for endpoints associated with a range of public network addresses, said range of public network addresses including said public network address of said endpoint;

- transmitting to said location information database using said location information database address an emergency address request; said emergency address request comprising said public network address of said endpoint;

- responsive to said transmitting, receiving said emergency address from said location information database.

2. The method defined in claim 1, further comprising:
releasing said emergency address.

3. The method defined in claim 2, wherein said releasing comprises transmitting said emergency address to said endpoint.

4. The method defined in claim 2, wherein said releasing comprises transmitting said emergency address to a call server responsible for handling an emergency call from said endpoint.

5. The method defined in claim 4, wherein said transmitting said emergency address to a call server is instrumental in causing the call server to determine routing instructions to be applied to the emergency call from said endpoint.

6. The method defined in claim 2, wherein said releasing comprises applying a proxying function to an emergency call originating from said endpoint.

7. The method defined in claim 6, wherein said applying a proxying function comprises transmitting said emergency address to a VPC server in an attempt to determine routing instructions to be applied to the emergency call.

8. The method defined in claim 7, further comprising applying said routing instructions to the emergency call.

9. The method defined in claim 7, further comprising transmitting said routing instructions to a call server responsible for handling the emergency call originating from said endpoint.

10. The method defined in claim 1, wherein said receiving an indication of a public network address associated with said endpoint is executed in response to a call server receiving an emergency call from said endpoint.

11. The method defined in claim 1, wherein said receiving an indication of a public network address associated with said endpoint is executed in response to receiving an emergency call from said endpoint.

12. The method defined in claim 1, wherein said receiving an indication of a public network address associated with said endpoint comprises examining a SIP invite message received from a call server.

13. The method defined in claim 12, wherein said examining a SIP invite message comprises retrieving content of a "via" field of said SIP invite message.

14. The method defined in claim 12, wherein said SIP invite message is generated by the call server in response to receiving an emergency call from said endpoint.

15. The method defined in claim 14, wherein said SIP invite message is generated by the call server based on an initial SIP invite message issued by said endpoint towards the call server to trigger establishment of the emergency call.

16. The method defined in claim 15, wherein said SIP invite message contains at least a portion of said initial SIP invite message.

17. The method defined in claim 1, wherein said determining comprises accessing an address directory mapping a respective range of public network address and a respective location information database address in an attempt to retrieve said location information database address that corresponds to said range of public network addresses based on said public network address of said endpoint.

18. The method defined in claim 1, wherein said transmitting comprises generating a request according to a communication protocol, the communication protocol comprising one of:

an HTTP Enabled Location Delivery (HELD) with OBO extensions protocol;
a SIMPLE protocol; and a proprietary protocol.

19. The method defined in claim 1, wherein said public network address comprises one of:

a public IP address;
a SIP address;

a MAC address;

a proprietary network address.

20. The method defined in claim 1, wherein said endpoint comprises at least one of a VoIP phone, an analog terminal adapter connected to a POTS phone, a computer implementing an IP telephony software, a router and a broadband modem.

21. The method defined in claim 1, wherein said emergency address comprises a civic address.

22. The method defined in claim 1, wherein said emergency address comprises geo-spatial coordinates.

23. The method defined in claim 1, wherein said emergency address comprises a location tag.

24. A system for retrieving an emergency address on behalf of an endpoint in a packet-switched environment, the system comprising:

a computing apparatus communicatively coupled to a call server responsible for handling an emergency call from said endpoint; the computing apparatus operable to:

- receive an indication of a public network address associated with said endpoint from the call server;

- determine a location information database address associated with a location information database responsible for storing emergency addresses for endpoints associated with a range of public network addresses, said range of public network addresses including said public network address of said endpoint;

- transmit to said location information database using said location information database address an emergency address request; said emergency address request comprising said public network address of said endpoint;

- receive said emergency address from said location information database.

25. The system defined in claim 24, wherein said computing apparatus is further operable to release said emergency address.

26. The system defined in claim 25, wherein to release said emergency address, the computing apparatus is operable to transmit said emergency address to the call server responsible for handling the emergency call from said endpoint.

27. The system defined in claim 25, wherein to release said emergency address, the computing apparatus is operable to transmit said emergency address to said endpoint.

28. The system defined in claim 25, wherein to release said emergency address, the computing apparatus is operable to apply a proxying function to the emergency call originating from said endpoint.

29. The system defined in claim 28, wherein to apply a proxying function to the emergency call originating from said endpoint, the computing apparatus is operable to transmit said emergency address to a VPC server in an attempt to determine routing instructions to be applied to the emergency call.

30. The system defined in claim 29, wherein said computing apparatus is further operable to apply said routing instructions to the emergency call.

31. The system defined in claim 30, wherein said computing apparatus is further operable to transmit said routing instructions to the call server.

32. The system defined in claim 24, further comprising an address directory for maintaining a mapping of a location information database address associated with a respective location information database and an indication of a range of public network addresses allotted to a service provider associated with the respective location information database; wherein the computing apparatus is operable to:

consult the address directory to determine the location information database address.

33. The system defined in claim 32, wherein said address directory is integrated with said computing apparatus.

34. The system defined in claim 32, wherein said address directory is coupled directly to said computing apparatus.

35. The system defined in claim 32, wherein said address directory is reachable by said computing apparatus via a packet-switched data network.

36. The system defined in claim 24, wherein said computing apparatus is implemented in an application server.

37. The system defined in claim 24, further comprising said call server responsible for handling an emergency call from said endpoint.

38. The system defined in claim 24, wherein said call server is managed by a first service provider and said computing apparatus is managed by a second service provider.

39. The system defined in claim 37, wherein said call server and said computing apparatus are managed by a single service provider.

40. The system defined in claim 37, said call server being a first call server; wherein the system further comprises a second call server.

41. The system defined in claim 40, wherein:

said first call server and said computing apparatus are managed by a first service provider; and said second call server is managed by a second service provider.

42. The system defined in claim 41, wherein said second service provider subscribes to an emergency address retrieval service provided by said first service provider.

43. The system defined in claim 40, wherein:

said first call server is managed by a first service provider; and said second call server and said computing apparatus are managed by a second service provider.

44. The system defined in claim 40, wherein:

said first call server, said second call server and said computing apparatus are managed by a single service provider.

45. A computing apparatus for retrieving an emergency address on behalf of an endpoint in a packet-switched environment, the computing apparatus comprising:

- means for receiving an indication of a public network address associated with said endpoint;

- means for determining a location information database address associated with a location information database responsible for storing emergency addresses for endpoints associated with a range of public network addresses, said range of public network addresses including said public network address of said endpoint;

- means for transmitting to said location information database using said location information database address an emergency address request; said emergency address request comprising said public network address of said endpoint;

- means for receiving said emergency address from said location information database.

46. The computing apparatus defined in claim 45, further comprising:
means for releasing said emergency address.

47. A method of retrieving an emergency address on behalf of an endpoint in a packet-switched environment, the method comprising:

- receiving from a call server an indication of a public network address associated with said endpoint; the call server being responsible for handling an emergency call originated from said endpoint;

- transmitting to a location information database an emergency address request;
said emergency address request comprising said public network address of said endpoint;

- responsive to said transmitting, receiving said emergency address from said location information database;

- releasing said emergency address.

48. The method defined in claim 47, wherein said releasing comprises transmitting said emergency address to said endpoint.

49. The method defined in claim 47, wherein said releasing comprises transmitting said emergency address to the call server responsible for handling the emergency call from said endpoint.

50. The method defined in claim 49, wherein said transmitting said emergency address to the call server is instrumental in causing the call server to determine routing instructions to be applied to the emergency call from said endpoint.

51. The method defined in claim 47, wherein said releasing comprises applying a proxying function to the emergency call originating from said endpoint.

52. The method defined in claim 51, wherein said applying a proxying function comprises transmitting said emergency address to a VPC server in an attempt to determine routing instructions to be applied to the emergency call.

53. The method defined in claim 52, further comprising applying said routing instructions to the emergency call.

54. The method defined in claim 52, further comprising transmitting said routing instructions to the call server.

55. The method defined in claim 47, wherein said receiving an indication of a public network address associated with said endpoint is executed in response to a call server receiving an emergency call from said endpoint.

56. The method defined in claim 47, wherein said receiving an indication of a public network address associated with said endpoint comprises examining a SIP invite message received from the call server.

57. The method defined in claim 56, wherein said examining a SIP invite message comprises retrieving content of a "via" field of said SIP invite message.

58. The method defined in claim 56, wherein said SIP invite message is generated by the call server in response to receiving an emergency call from said endpoint.

59. The method defined in claim 58, wherein said SIP invite message is generated by the call server based on an initial SIP invite message issued by said endpoint towards the call server to trigger establishment of the emergency call.

60. The method defined in claim 59, wherein said SIP invite message contains at least a portion of said initial SIP invite message.

61. The method defined in claim 47, wherein said transmitting comprises generating a request according to a communication protocol, the communication protocol comprising one of:

an HTTP Enabled Location Delivery (HELD) with OBO extensions protocol;
a SIMPLE protocol; and a proprietary protocol.

62. The method defined in claim 47, wherein said public network address comprises one of:

a public IP address;
a SIP address;

a MAC address;

a proprietary network address.

63. The method defined in claim 47, wherein said endpoint comprises at least one of a VoIP phone, an analog terminal adapter connected to a POTS phone, a computer implementing an IP telephony software, a router and a broadband modem.

64. The method defined in claim 47, wherein said emergency address comprises a civic address.

65. The method defined in claim 47, wherein said emergency address comprises geo-spatial coordinates.

66. The method defined in claim 47, wherein said emergency address comprises a location tag.

67. A call server for handling voice-over-packet-switched-network calls on behalf of an endpoint, the call server operable to:

receive an emergency call originated from said endpoint;
determine a public network address associated with said endpoint;

transmit said public network address to a computing apparatus, said public network address of said endpoint for enabling said computing apparatus to:
determine a location information database address based on said public network address of said endpoint;

determine said emergency address based on said location information database address and said public network address of said endpoint;
receive said emergency address;

handle said emergency call based on said emergency address.

68. The call server defined in claim 67, wherein to transmit said indication of a public network address to a computing apparatus, the call server is operable to forward a SIP invite message received from said endpoint during an establishment of the emergency call to said computing apparatus.

69. The call server defined in claim 67, wherein to transmit said indication of a public network address to a computing apparatus, the call server is operable to generate a SIP invite message destined to said computing apparatus, said SIP invite message comprising at least a portion of an initial SIP invite message received from said endpoint during an establishment of the emergency call.

70. A system comprising the call server defined in claim 67 and said computing apparatus.

71. The system defined in claim 67, wherein said computing apparatus comprises an application server.

72. A method for retrieving an emergency address on behalf of an endpoint in a packet-switched environment, the method comprising:

- receiving an indication of a public network address associated with said endpoint;

- determining a location information database address associated with a location information database responsible for storing emergency addresses for endpoints associated with a range of public network addresses, said range of public network addresses including said public network address of said endpoint;

- transmitting to said location information database using said location information database address an emergency address request; said emergency address request comprising said public network address of said endpoint; said transmitting being instrumental in causing said location information database to determine said emergency address based on said public network address and to release said emergency address.

73. The method defined in claim 72, further comprising:

receiving said emergency address from said location information database.

74. The method defined in claim 73, wherein said receiving is executed by an application server.

75. The method defined in claim 73, wherein said receiving is executed by a call server responsible for handling an emergency call from said endpoint.

76. The method defined in claim 73, further comprising transmitting said emergency address to said endpoint.

77. The method defined in claim 73, further comprising transmitting said emergency address to a call server responsible for handling an emergency call from said endpoint.

78. The method defined in claim 77, wherein said transmitting said emergency address to a call server is instrumental in causing the call server to determine routing instructions to be applied to the emergency call from said endpoint.

79. The method defined in claim 73, further comprising applying a proxying function to an emergency call originating from said endpoint.

80. The method defined in claim 79, wherein said applying a proxying function comprises transmitting said emergency address to a VPC server in an attempt to determine routing instructions to be applied to the emergency call.

81. The method defined in claim 80, further comprising applying said routing instructions to the emergency call.

82. The method defined in claim 80, further comprising transmitting said routing instructions to a call server responsible for handling the emergency call from said endpoint.

83. The method defined in claim 72, wherein said receiving an indication of a public network address associated with said endpoint is executed in response to a call server receiving an emergency call from said endpoint.

84. The method defined in claim 72, wherein said receiving an indication of a public network address associated with said endpoint is executed in response to receiving an emergency call from said endpoint

85. The method defined in claim 72, wherein said receiving an indication of a public network address associated with said endpoint comprises examining a SIP invite message received from a call server.

86. The method defined in claim 85, wherein said examining a SIP invite message comprises retrieving content of a "via" field of said SIP invite message.

87. The method defined in claim 85, wherein said SIP invite message is generated by the call server in response to receiving an emergency call from said endpoint.

88. The method defined in claim 87, wherein said SIP invite message is generated by the call server based on an initial SIP invite message issued by said endpoint towards the call server to trigger establishment of the emergency call.

89. The method defined in claim 88, wherein said SIP invite message contains at least a portion of said initial SIP invite message.

90. The method defined in claim 89, wherein said public network address comprises one of:

a public IP address;
a SIP address;

a MAC address;

a proprietary network address.

91. The method defined in claim 90, wherein said endpoint comprises at least one of a VoIP phone, an analog terminal adapter connected to a POTS phone, a computer implementing an IP telephony software, a router and a broadband modem.

92. The method defined in claim 72, wherein said emergency address comprises a civic address.

93. The method defined in claim 72, wherein said emergency address comprises geo-spatial coordinates.

94. The method defined in claim 72, wherein said emergency address comprises a location tag.

95. A system for retrieving an emergency address on behalf of an endpoint in a packet-switched environment, the system comprising:

a computing apparatus communicatively coupled to a call server responsible for handling an emergency call from said endpoint; the computing apparatus operable to:

- receive an indication of a public network address associated with said endpoint from the call server;

- determine a location information database address associated with a location information database responsible for storing emergency addresses for endpoints associated with a range of public network addresses, said range of public network addresses including said public network address of said endpoint;

- transmit to said location information database using said location information database address an emergency address request; said emergency address request comprising said public network address of said endpoint; said emergency address request being instrumental in causing said location information database to determine said emergency address based on said public network address and to release said emergency address.

96. The system defined in claim 95, further comprising said location information database.

97. The system defined in claim 96, further comprising said call server.

98. The system defined in claim 97, wherein said call server is operable to receive said emergency address from said location information database.

99. The system defined in claim 95, wherein said computing apparatus is further operable to receive said emergency address from said location information database.

100. The system defined in claim 95, wherein said computing apparatus is embodied in an application server.

101. A method for retrieving location information on behalf of an endpoint in a packet-switched environment, the method comprising:

- receiving an indication of a public network address associated with said endpoint;

- determining a location information database address associated with a location information database responsible for storing location information for endpoints associated with a range of public network addresses, said range of public network addresses including said public network address of said endpoint;

- transmitting to said location information database using said location information database address a location information request; said location information request comprising said public network address of said endpoint;
said transmitting being instrumental in causing said location information database to determine said location information based on said public network address and to release said location information.

102. The method defined in claim 101, wherein said location information comprises an emergency address.

103. The method defined in claim 101, wherein said location information comprises a service address.

104. An apparatus for retrieving location information on behalf of an endpoint in a packet-switched environment, the apparatus comprising:

- means for receiving an indication of a public network address associated with said endpoint;

- means for determining a location information database address associated with a location information database responsible for storing location information for endpoints associated with a range of public network addresses, said range of public network addresses including said public network address of said endpoint;

- means for transmitting to said location information database at said location information database address a location information request; said location information request comprising said public network address of said endpoint;
said transmitting being instrumental in causing said location information database to determine said location information based on said public network address and to release said location information.