EP1525756A1

EP1525756A1 - Media gateway for the provision of the pstn/isdn services in next-generation networks

Info

Publication number: EP1525756A1
Application number: EP03766151A
Authority: EP
Inventors: Kathrin Hackl; Walter Held; Hanspeter Ruckstuhl
Original assignee: Siemens AG; Nokia Siemens Networks GmbH and Co KG
Current assignee: Nokia Solutions and Networks GmbH and Co KG
Priority date: 2002-07-29
Filing date: 2003-07-10
Publication date: 2005-04-27
Also published as: JP2006500799A; AU2003246681A1; WO2004014087A1; RU2005105298A; EP1387589A1; RU2326503C2; CN1672433A; US20060031535A1; BR0313465A

Abstract

Packet-based networks of the next generation work on the principle of separation of connection and data channel control. In the above networks, as opposed to current TDM networks, discrete network elements are used for connection control and data channel control, whereby the network element for data channel control is defined as Media Gateway and the network element for connection control is defined as Media Gateway Controller. Problems arise as a result of the physical and positional separation of the connection and data channel control, in particular the problem of performance loss as a result of greatly increased incoming signaling messages and greater distance-related signal delay times. According to the invention, said problems are solved whereby a part of the connection control is integrated in the Media Gateway, whilst the remaining part of the connection control, in particular that concerning the central control and monitoring tasks remains, as before, in the media gateway controller.

Description

description

Media gateway to provide PSTN / ISDN services in next generation networks

1. What technical problem is the invention intended to solve?

In today's voice networks (PSTN / ISDN), which are based on the principle of line switching, they take over

Local and transit exchanges both the connection control and the user channel control (e.g. two-way connection, three-way connection, feeding in tones).

The next generation networks (Next Generation Network, abbreviated NGN) are packet-based (e.g. ATM or IP as a transport level) and are designed for the transport of both voice and data. They work on the principle of separating connection and service channel control. In contrast to today's TDM networks, separate network elements are used in these networks for connection control (call and signaling control) and for user channel control (bearer or media control). The connection control is carried out by media gateway controllers (MGC), which use a media gateway control protocol (MGCP), currently MGCP or H.248 are available, to communicate with the media gateways (MG), which control the user channels. The signaling is terminated in the Media Gateway Controller.

The media gateway controllers in the NGN communicate with each other via a signaling protocol (e.g. BICC protocol) analogous to the switching centers of the PSTN / ISDN (e.g. # 7 signaling).

The network elements (MGC and MG) are physically and normally also physically separated. Spatially separated can mean that an MG and its controlling MGC can carry hundreds of stand meters apart or even communicate with each other via satellite links. A media gateway controller usually takes over the connection control for several media gateways. A media gateway based on today's NGN architecture (master-slave concept) is not able to switch connections independently or make other decisions regarding connection control without a media gateway controller.

Figure 1 shows the principle of today's PSTN / ISDN networks.

Figure 2 shows the example of the principle of voice communication in next-generation networks according to today's NGN understanding.

The physical and spatial separation of the connection and user channel control and their handling by the Media Gateway Controller and the Media Gateway create the following problem points:

- Loss of performance due to a large increase in the number of signaling messages and larger, distance-related signaling delay times

- Limited availability of subscriber or connection lines in the event of a fault in the packet network or the controlling media gateway controller

- Problems with timely charging of connections

1.1 Loss of performance due to a large increase in the number of signaling messages and larger, distance-related signaling delay times

Compared to the * classic telephone architecture, with a separate connection and user channel control for subscriber connections, a significantly larger number of time-critical signaling messages for synchronous control of the user channel must be exchanged between the media gateway controller and media gateway. The signaling received from the terminal In the case of an ISDN subscriber, for example, messages are first sent to the controller using a secure protocol. The media gateway controller then carries out the evaluation of the signaling messages and instructs the media gateway using the control protocol to activate, for example, the ringing tone. When the dialing information is received, it is first transmitted back to the controller until the controller requests that the tone be switched off. In the case of an analog subscriber, an even greater flood of messages is generated when the individual dialing digits are received and passed on.

The large number of messages exchanged between MG and MGC for a call set-up, combined with the transmission of these messages via an external interface over potentially large distances, can lead to considerable noticeable delays in the connection set-up. On the one hand, the delays limit the function when executing time-critical jobs, such as switching on the code receiver, and on the other hand they can lead to the fact that existing time requirements of the external signaling interface in the NGN can no longer be met.

1.2 Restricted network availability - No possibility of establishing a connection in the event of a network failure or in the event of a failure of the media gateway controller. Due to the complete lack of local connection control and thus the complete dependency on the media gateway controller, * - a media gateway is not able in the event of a failure of the Media Gateway Controller or in the event of an interruption in the signaling between MG and MGC, the user channels connected to it are switched. This means that the failure of a media gateway controller always means the failure of all media gateways controlled by it with all subscriber and connection line connections. In this case, an emergency call is no longer possible. Since one media gateway controller usually has several Controlled media gateways, a large number of connections can be affected by such a failure.

1.3 Precise billing

The separation of the connection and user channel control can lead to problems with the exact recording of the charge, since the user channel is switched in the media gateway, but the time stamp is recorded in the media gateway controller.

2. How has this problem been solved so far?

The technical problems shown are not yet known and result from the use of the standardized function split for the next generation networks to provide the classic telephony services (replica of the PSTN / ISDN).

Restricted comparable problems when using a pure master-slave principle occur for TDM networks when defining classic access networks. Here, the access network is connected to a TDM switch via the V5 interface, with the TDM switch working as the master and the access network as the slave. The problem - when connecting an access network to a TDM switch differs from the problems when using the NGN architecture in the following points,

(a) the spatial separation is usually limited,

(b) the control and signaling messages are exchanged via a securely available message channel, the bandwidth of which is firmly defined,

(c) An access gateway has only a limited useful channel control compared to a media gateway, because the user channel is managed by the TDM switch. The user channel is also routed via the TDM switch and only there is the creation of tones or charging.

The problem of handling time-critical orders was solved there by introducing conditional instructions. The problem of limited availability was not solved there.

3. How does your invention solve the stated technical problem?

The invention provides a new division of functions for NGN, which is shown in Figure 3. Instead of the knitted master-slave division pursued in the NGN concept, a proxy-client approach is chosen, i.e. part of the connection control is integrated into the media gateway, while the remaining part of the connection control, in particular that relating to central control and monitoring tasks, remains in the media gateway controller. The media gateway controller designed according to the invention is referred to below as a network-central control device and the media gateway designed according to the invention is referred to below as an intelligent access gateway.

In contrast to a “master-slave relationship, in which all control over a connection lies with the media gateway controller (= master) and an access gateway (= slave) only reports incentives and events to and from the media gateway controller According to the invention, a client proxy approach is selected to execute commands relating to the connection control. According to this approach, the "Intelligent Access Gateway" (= client) terminates the mentioned incentives or events (signaling) and carries out part of the connection control functions itself, in particular such connections Control functions that do not necessarily have to be provided by a network-central control device (= proxy), but can be provided directly by a client or can be negotiated between the clients involved in a connection.

For the execution of the remaining part, he orders one of the network-central control devices, which either carries out the order himself or controls its further execution instead of the gateway. The connection control functions that the Intelligent Access Gateway (client) performs itself are functions such as for the client of the calling subscriber (A) or client of the called subscriber (B)

- Create dial tone (A) * - Record dial information (A) *

- Display of the calling number of the calling subscriber via FSK for analog subscribers (B) *

- Call repetition for 'subscriber busy' (A and B)

- negotiate between the partners which side pays for the call costs (A and B)

- Fee data collection (A and / or B) *

- Transfer fee information on the billing side to the subscriber terminal (A or B)

- Exchange of the required end point data (IP address, port number, codec information, etc.) for switching connections (A and B) *

- Manage tripartite conference (A or B)

- Autonomous routing of calls to selected, permanently administered destinations (e.g. emergency numbers) if the proxy fails (A or B)

A major advantage of the invention is achieved above all by taking over those connection control functions which are accessible to local processing and are time-critical (in the above-mentioned functions, the time-critical functions are marked with an asterisk (*)). Through the aforementioned takeover of connection control functions by the access gateways, the task of the network-central control devices (media gateway controller, proxy) in the area of connection control is reduced to functions which require a central database, such as, for example, call routing, processing of billing information, and on the coordination of certain features that can be distributed across several clients (eg Centrex). The network-central control device is therefore also referred to below as a feature and route control proxy (see Figure 3).

In addition to the connection control functions mentioned, the intelligent access gateway also carries out the termination of the signaling (subscriber line signaling and connection line signaling) and carries out the user channel control as before.

With the division of labor mentioned, the subscriber data are advantageously stored and managed in the Intelligent Access Gateway.

The invention solves all three problem areas already mentioned equally.

3.1 Problem of loss of performance

The local parts of the connection control signal all user channel settings directly in the intelligent access gateway via an internal interface between the connection and user channel control. The evaluation of the

Signaling messages can be sent without delay and the required resources can be requested immediately. This means there are no time-critical delays. The number of messages relating to feature control is smaller and not comparable in terms of time. The same applies to call routing. 3.2 Problem of restricted network availability

Due to the local connection control and the knowledge of the existing subscriber connections in the intelligent access gateway, the gateway is able to perform at least a limited connection control for all existing subscriber connections without having to communicate with the feature and route proxy if an alternative route proxy is in the Network is available, which does not have to have any knowledge of existing participants.

The local establishment of a fixed route for emergency operation enables calls to connected emergency call centers without an existing route proxy.

3.3 Problem of accurate billing

The necessary charging data is recorded immediately and precisely in the intelligent access gateway, since both the time stamp and the switching of the user channel are carried out in the intelligent access gateway without delays occurring via an external transport network.

For further processing of the collected charge data, these connection-related data are then sent either directly or via the feature and route proxy to a higher-level postprocessing system.

4. Comparison of the invention with a traditional functional approach

The NGN structure according to the invention is created by adopting elements of the traditional functional approach of the combined user channel and connection control. The elements of the traditional function control allow precise control All time-critical processes of connection and user channel control, while maintaining the approach of a central call server for controlling access gateways. The possibility of using a large central call server, which can be locally separated from the access gateways distributed in the network, is greatly favored with this architecture, since runtime delays in the transport network are no longer a dimensioning criterion.

5. Embodiment (s) of the invention

The hallmark of an intelligent access gateway (IAGW) is the existence of a comprehensive call control function on the access gateway. After the partners are known, there are basically two ways of communication between 2 IAGWs for connection control:

- All messages between one IAGW (client A) and the other IAGW (client B) are always routed through the proxy and forwarded to the destination without interpretation of the content. - After client A has been informed of the destination address of client B by the proxy, these communicate directly with one another. Only when special central features are required for the connection in the further course is the proxy temporarily included in the communication relationship.

These basic communication relationships are shown in Figure 4.

5.1 Intelligent Access Gateway The approach of an intelligent access gateway is realized for the first time in the SURPASS product line with the development of the hiA 7600. Here, the function of the Connection Agent (CoX), which controls the connection setup and cleardown processes on the Media Gateway, moves from the Media Gateway Controller to the Media Gateway itself.

The Intelligent Access Gateway hiA 7600 is controlled by the Feature and Route Control Proxy hiQ 9200. The messages are exchanged between the MGC and the MG using a proprietary Access Gateway Control protocol, since the standardized MGCP and H.248 protocols have not been standardized for the intended function split and are used purely for the control of the service channel. In future versions, however, the SIP protocol can also be used as the client proxy protocol.

Figure 5 shows a comparison of the architectures with the conventional NGN approach and the approach. he hiA 7600 realizes:

Figure 5 clearly shows how in the new NGN approach the call control function is shifted to the media gateway and the external H.248 / MGCP interface becomes an internal system interface with all the associated advantages, which are described in the above chapters have been described. At the heart of the hiA 7600 is a call control processor, which controls and executes the IP-TDM mediation. The call control processor simultaneously contains the control software for the basic connection and the user channel control. The access control protocol is used to exchange messages with the HiQ 9200 feature and route control proxy, which carries out the routing and feature handling. In addition, the control proxy controls all actions that have to be carried out for additional feature control proxies for feature handling or the communication between two control proxies for handling the call if the connections are assigned to different control proxies (for routing, each hiA 7600 with its connections is assigned to a controller via which it can be reached and who has knowledge of the assignment status).

Figure 6 shows the network image for such a basic call, in which both connections are assigned to the control proxy.

Figure 7 shows the flow of signaling messages associated with Figure 6 for the basic call mentioned.

For the communication between the intelligent access gateways, as previously mentioned, the following two variants are possible.

- Proxy variant a): All messages between two intelligent access gateways (clients) are always routed via the proxy

- Proxy variant b): Only feature and routing-related requests are sent from an intelligent access gateway (client) to the proxy. The rest of the communication for connection control runs directly between the clients involved.

In the present example (hiA 7600) the proxy variant a) is used. All signaling messages - including those that could be exchanged directly between the access gateways - therefore run via the proxy, but are not processed on the proxy (see Figure 7).

The following can also be seen from the message flow in Figure 7: The subscriber signaling (MFC, DSSl, etc) is terminated at the Intelligent Access Gateway. The one for performing Digit processing and routing, as well as information required for feature handling, are sent to the proxy via the proxy client protocol, in the case of the hiA 7600 via ACP. In the case of SS7-signaled connection lines, in which the signaling channels are terminated together with the connection lines on the Intelligent Access Gateway, MTP and SCCP are not processed by the Intelligent Access Gateway. Only the higher SS7 user parts (e.g. ISUP) are processed on the Intelligent Access Gateway. In the case of the hiQ 9200, processing the lower layers of the SS7 protocol is the task of the signaling gateway integrated in the HiQ 9200 control proxy.

Figure 8 shows the network image for such a basic call, in which only the input-side access is controlled by the control proxy.

Figure 9 shows the signaling flow associated with Figure 8. The connection on the output side can be controlled by another control proxy, but also by a media gateway controller. Communication between the controllers takes place using BICC, as shown here, or SIP-T.

Since the control proxy contains the functionality of the interworking and supports two standardized network network interface protocols by means of BICC and SIP-T, the different NGN architectures for the access control can work together within a network.

5.2 SIP Access Client

The approach of an intelligent access gateway corresponds to the division of functions pursued by SIP and thus enables the integration of the access gateway into the SIP world. The Ac The cess control protocol is replaced by the standardized SIP protocol (see Figure 10). A session to a SIP proxy is established using SIP signaling. The SIP proxy provides the information needed to locate the B subscriber. The supported range of features for the

Participant depends on the supported features within the SIP domain.

Figure 11 shows the flow of messages between clients and proxy using SIP.

All conventional subscriber connections (PSTN, ISDN) can be connected to a SIP domain via the intelligent access gateway. This results in an inexpensive and highly available solution for the PSTN / ISDN connection.

Claims

claims

1. Media gateway of a packet-based communication network, with - a user channel control means that controls the user channel of a communication connection, characterized by

a termination means which terminates signaling messages of a communication connection, a connection control means which itself carries out part of the connection control of a communication connection and commissions a network-central control device for carrying out the other part.

2. Media gateway according to claim 1, characterized in that said connection control means performs all connection control functions that do not necessarily have to be carried out centrally.

3rd Media gateway according to claim 1 d a d u r c h g e k e n n z e i c h n e t that said connection control means performs all connection control functions that do not necessarily have to be carried out centrally and that are time-critical.

4. Media gateway according to one of claims 1 to 4, characterized in that it contains an administration means which stores and manages the subscriber data.

5. Media gateway according to one of claims 1 to 4, characterized in that it carries out the charge data acquisition to a communication link.

6. Media gateway according to one of claims 1 to 5, characterized in that it uses the access control protocol for communication with said network-central control device,

7. Media gateway according to one of claims 1 to 5, characterized in that it uses the SIP protocol for communication with said network-central control device.

8. Media gateway according to one of claims 1 to 7, characterized in that it sends the messages for connection control, which are intended for another gateway, via a network-central control device to the ^" other gateway ^" .

9. Control device in a packet-based network, with a connection control means which carries out connection control functions central to the network for communication connections, characterized in that it accepts orders for carrying out the said connection control functions from media gateways and either carries them out itself or carries them out further instead of Controls media gateways.

10. A method for handling communication connections in a packet-based network, accordingly

- Signaling messages from a media coming from a subscriber line and / or a connecting line

Gateway are received and evaluated,

- Part of the connection control is then carried out by the media gateway itself and a network-central control device is commissioned to carry out the other part.

11. A method for handling communication connections in a packet-based network, accordingly

signaling messages coming from a subscriber line and / or a non-SS7 signaled connecting line are received and evaluated by a media gateway,

in the case of signaling messages coming from an SS7-signaled connecting line, the user part is received and evaluated by a media gateway after the underlying protocol layers have been processed by a network-central control device which comprises a central signaling gateway function,