GB2406740A

GB2406740A - Enabling the determination of the location of a terminal in a communications system.

Info

Publication number: GB2406740A
Application number: GB0322836A
Authority: GB
Inventors: Oliver Veits
Original assignee: Siemens AG
Current assignee: Siemens AG
Priority date: 2003-09-30
Filing date: 2003-09-30
Publication date: 2005-04-06
Also published as: WO2005112385A1; GB0322836D0

Abstract

In a telecommunications network utilising in particular soft phones it is sometimes difficult to identify the location of the "phone" making a call. This is particularly significant when the call is one made to an emergency service for urgent assistance. A location manager is included in the network to assign port addresses to certain line identification numbers. Then in order to locate the calling terminal the port location is utilised. Assuming an emergency originates at terminal D, the spanning tree protocol is utilised and the network manager 6 identifies from bridge protocol data units the root node (switch 2) and port 8 connected to the terminal D.

Description

A method and apparatus for enabling the determination of the location of a

terminal in a communications system This invention relates to a method and apparatus for enabling the determination of the location of a terminal used to make a call in an Internet Protocol communications system. The invention is particularly, but not exclusively, applicable to locating a terminal used to make an emergency call.

Voice over IP (VoIP) enabled systems allow the use of computer terminals to act as telephones using their internal speakers and microphones. Socalled soft telephones are an elaboration on this in which the terminal is provided in the usual telephone configuration of microphone speaker and keypad.

Speech picked-up by the microphone is digitised and sent over the network as encoded data. Received data is decoded and output via the speaker. Standards have been developed to govern the way in which such networks operate. These are IEEE Standard for Local and Metropolitan Area Networks: Overview and Architecture 802-2001 and, in particular, ANSI/IEEE Standard 802.1 D Telecommunications and information exchange between systems-local and metropolitan area networks Part 3:Media Access Control (MAC) Bridges and IEEE 802Q Virtual Bridged Local Area Networks.

A problem arises in such systems concerning the location of callers making an emergency call. In normal telephony systems when a call is made to request an emergency service a Location Identification Number (LIN) is transmitted by the network to the emergency service system operator. This indicates to the recipient of the call the location of the caller. This information enables the emergency services to be directed to the correct location.

In a VoIP network this number is not provided since the user can connect to the network from a number of locations. In one proposed attempt at a resolution an Ethernet switch port is established where the telephone or soft client happens to be.

Each switch in a network maintains a table listing the 48 bit MAC (Medium Access Control Layer) address of each machine connected to it.

When data frames traverse the network they include a MAC address and this can be input into the table to determine the origin of the frame.

There may be many switches to consult before the relevant MAC address is found and the location of the caller identified by reference to the known wiring. Thus this approach is no conducive to an emergency situation where a speedy response is required to a request for help.

According to the invention there is provided a port location method to, in a communications network, identify a port receiving a particular call from a network terminal served by that port which method comprising providing a location manager, providing a database managed by the location manager to assign a port address to a line identification number, determining at the network terminal from a spanning tree the port address and informing the location manager.

The preferred port address is a Medium Access Control (MAC) address.

The spanning tree is preferably obtained from a bridge protocol data unit.

In the preferred embodiment the port is a switch port although the invention may also be applicable to other network elements such as bridges or routers.

A specific embodiment of the invention will now be described with reference to and as illustrated by the accompanying drawings in which: Figure 1 shows a communications network operating in accordance with the invention As is shown in figure 1, a communications network 1 comprises a f rst switch 2 serving a number of computer terminals A to D at a particular location, a first gateway 3 connecting the switch 2 to the public switched telephony network 4, a second gateway 4 connected to a second switch 5 serving a number of terminals E to G. The network also includes a network manager 6 linked to a database 7.

The first switch 2 serves terminals A to D in a particular department of an organization. The second switch 5 serves terminals G to F in an emergency services call centre. Both switches are from the Siemens HiPath AM product family.

It will be appreciated that the communications network I is shown in simplified form. It will comprise in reality a large number of network nodes comprising bridges and routers in addition to the switch and gateway nodes depicted in the figure.

Each of the switches will include a plurality of ports to which the terminals are connected and support the use of Voice over IP (VoIP) and operates in accordance with the IEEE 8021D standard and follow the Spanning Tree Protocol STP. s

As will be appreciated by the person skilled in the art the STP is used to prevent loops occurring in a network. Each network node runs an algorithm to prevent the formation of loops by blocking connections that would cause a loop. The protocol establishes a root network node and the lo individual nodes involved in the connection selects ports which offer the least cost path to the root bridge. The selection of the root node and the rest of the nodes to make the connection requires an interchange of management information in a format called Bridge Protocol Data Units (BPDUs).

The BPDUs include two types configuration BPDUs used for bridge and port elections and Topology Change Notification BPDUs which are sent back down to the root where there is a topology change to the tree. As these pass through the links in the network, the nodes monitor these and derive a least cost path to the root node. This process is well known in the art but the important thing to note is that the BPDUs include the following information. an 8 octet root ID which includes a priority figure followed by a MAC address, a bridge ID which includes a priority figure and a MAC address for the bridge and a port ID which is the identification address of the port from which the BPDUs are transmitted.

Thus in establishing a connection a number of network nodes will be interconnected by the use of the BPDUs and the spanning tree protocol.

In doing this the port id of the root node is identifiable.

The operation and maintenance of the communications network 1 is undertaken by the network manager 6. Let us consider the connection of a soft phone to the emergency services. Assuming an emergency occurs to a person using the terminal D. That person dials the emergency number and a call is established in the usual way across the network to the terminal E. in establishing the call, the spanning tree protocol is utilised and the network manager 6 identifies from the BPDUs the root node which will be switch 2 and the port id which will identify the post 8 connected to the terminal D. This information is stored in the memory 7 in a table against a line identification number. The network manager can then return this information to the emergency service operator in order to identify the location of the terminal D.

Claims

Claims 1. A port location method for a communications network to identify

a port receiving a particular call from a network terminal served by that port which method comprising providing a location manager, providing a database managed by the location manager to assign a port address to a line identification number, determining at the network terminal from a spanning tree the port address and informing the location manager.

lo
2. A method as claimed in claim 1 wherein the port address is a Medium Access Control (MAC) address.
3. A method as claimed in claim 1 or claim 2 wherein the address is obtained from a bridge protocol data unit.
4. A method as claimed in claim 1 wherein the particular call is a call to an emergency service.
S. A method substantially as hereinbefore described with reference to and as illustrated by the figure.
6. Apparatus for determining the location of a port in a telecommunications network serving a terminal making a particular type of call comprising: means to identify a call of a predetermined call type; a location manager to assign a port address to a line identification number; means to determine from a spanning tree the port address and to inform the location manager.

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7. Apparatus for determining a location of a port in a communications network substantially as hereinbefore described with reference to and as illustrated by the figure.