WO1996042157A1

WO1996042157A1 - Method for establishing a connection in an atm-network using a central control system and distributed agents

Info

Publication number: WO1996042157A1
Application number: PCT/SE1996/000711
Authority: WO
Inventors: Kim Laraqui
Original assignee: Telia Ab
Priority date: 1995-06-08
Filing date: 1996-06-04
Publication date: 1996-12-27
Also published as: SE9502103L; SE514989C2; SE9502103D0

Abstract

The present invention relates to an ATM-network in which a central controlsystem (NMC) and agents controlling the switches interact in order to establish a connection. Information about a second subscriber with whom a first subscriber wishes to establish a connection is transmitted from the first subscriber to the agent of the switch to which the first subscriber is connected. The information is passed on to the central control system, which indicates a path between the subscribers, whereafter the connection between the subscribers is set up by the agents. The connection may involve more than one ATM-switch.

Description

APPLICANT: TELIA AB

Method for establishing a connection in an ATM-network using a central control system and distributed agents.

TECHNICAL FIELD

The present invention relates to ATM (Asynchronous Transmit Mode) where a support system is implemented. The support system uses and coordinates ATM-switches which are controlled by. standard M3 for management of ATM-network. The system solutions furthermore makes possible a powerful interface for customers who want to utilize Internet's SNMP (Simple Network Management Protocol) .

PRIOR ART

ATM-forum has specified an MIB (Management Information Base, i.e. a database where information is stored as ATM-elements) which is called M3 (M = Management, 3 = Management Interface No 3) . M3 IB makes possible for a customer or operator to manage an ATM-switch. The M3-interface which is shown in Figure 1 can for instance be used according to the following:

- The customer's support system (for instance the system administrator in a LAN) uses SNMP (version 1 or 2, M3 allows both) to communicate with the operator^'s support system.

- By SNMP to the operator the customer creates two new lines in atmVplTable (see Figure 2) ifIndex for one is "A" (i.e. port A of the ATM-switch) and for the other "B" . This implies that two new links are created to/from the ATM-switch.

The customer after that asks that one link shall be related to the other. This is performed by the customer creating a new line in atmVplCrossConnectTable and allows pointer in this line refer to link A respective link B. This results in that one now has cross-connected the links. ATM-cells now can move between A and B.

The problem with the interface above is that it is restricted to management of in principle an ATM cross-connector between two customers. A customer must specify exactly how links shall be cross- connected in cascade (from point to point) and cannot for instance indicate two general addresses and then let the network manage the establishing of connection. The customer must know exactly how links shall be created through the network and be cross-connected to each other, from customer interface to customer interface. This is a general problem with Internet's SNMP which, as we know, was specified for point-to-point manipulation and not network management.

As a way to be able to reuse M3-specifications and complete these with a system solution, one in a simple way can go from an M3 for element management to an M3N (N = Network) for network management. Such a modfied M3 can only be offered operators as well as customers who are used to SNMP.

In the American patent document 5185860 is described a method for, in a general way, mapping the existence of nodes (elements) in a network. The method, which implies TCP/IP, utilizes SNMP. Certain nodes in the network are called "Discovery Agent", and these keep count of the existance of other nodes in the network. At mapping of the network these nodes are asked to get information about the topology of the network. This information is then stored in a central memory, at which the system asks each of the discovered nodes if there is also Discovery Agent. The result is stored in a central data base which can be utilized by "Network Manager", among others. The data base is kept updated by periodic mapping.

In the patent document EP 621706 is described a system and a method which allows that a manager in SNMP-environment can collect updatings from agents in the system. This is achieved by providing the tables of the agents with information about current revisions.

In the American patent document 5289468 is described a "Network Management" for local networks (LAN) which are connectod to another network, for instance WAN. The method is based on SNMP. In the American document 5339318 is described "Management" in an ATM-network. The network includes "Network Management Units" which maintains a table over VCI (Virtual Channel Identifier) and VPI (Virtual Path Identifier) . DESCRIPTION OF THE INVENTION

Technical Problem

The present invention is intended to show a solution where central control systems take charge of connection between different users in an ATM-network. The user is at that forced to know connection procedures and current nodes which shall be used at a connection.

THE SOLUTION

The present invention relates to a method at ATM-network in which ATM-network a central control system is arranged. Information from a first subscriber is transmitted to the control system regarding a wanted communication with a second subscriber. The control system receives the information from the first subscriber. The control system communicates with agents in the network. The agents keep count of which ports that exist in one to the agent connected switch. Further the agent keeps count of which ports that are occupied and which connections that are arranged between different switches in the system. The agents decide a communication path in the network between first and second subscriber. The connection is established in the network, at which the subscribers are allowed to communicate with each other.

In a further development of the invention, the agents control connection functions in the network. The agents further inform the control system which paths and connections that are accessible. The control system orders the agents to establish appointed connections and connection of these. Each one of the agents controls an appointed switch in the network. The agents arrange necessary connections in the switches in the network. The control system informs the agents which connections, paths and ports that shall be utilized at connections between the subscribers. The control system orders connection between the subscribers in the network, where a number of the agents respective switches are involved. In the network, switches are arranged, and the switches are controlled by agents. Information from first subscribers can be transmitted to the agents in connection with establishing of communication between the first subscriber and the second subscriber. In the ATM-network a central control system is arranged. Information from the subscriber, regarding wanted communication with a second subscriber, is transmitted to the central control system. The central control system is arranged to indicate a selection of path between the subscribers in the ATM-network. Said selection of path is established between the subscribers, at which communication between them is allowed.

The central control system is arranged to establish a connection between the subscribers over a number of the switches . The central control system is arranged to communicate with the agents. The central control system indicates addresses to/from which communication shall be established. The agents are arranged to order connection for arrangement of communication in the ATM-network. The agents are further arranged to inform the central control system whether concerned switch is capable of establishing a wanted connection or not.

ADVANTAGES

The suggested solution gives the user in an ATM-network the possibility to indicate a subscriber with whom he/she wants to communicate. The network after that takes charge of the connection between respective subscriber. Central control devices in the system take charge of the connection and release the subscriber from the work of finding out addresses and connection paths in the network. Establishing of the connections in the network will in this way become easier and also will be more rapid than if the subscriber him/herself should find his/her way in the network. Further the subscriber need no special knowledge about the structure of the network and the connection procedures in it.

DESCRIPTION OF FIGURES

In Figure 1 is shown a system with M3. With M3 the customer NMS (Network Management System) can ask the operator CNM (Customer Network Management) to cross-connect port A to port B at the ATM- switch. The customer, however, can not ask for a connection through a number of switches in a large ATM-network. With the system solution this is managed by CNM (which constitutes a part of what in the text is called NMC, Network Management Center) . In Figure 2 is shown part of the objects which are defined in RFC1695. Texts to Figure 2 : a) For elements the ifType of which = 37 (ATM) , if Index for other completing ATM-specific tables is also used. The table exemplifies a system with an Ethernet-interface and two ATM-ports. b) The table is used as a complement to the information in If Table . The same ifIndex therefore can be used to get general interface information ( if able) , and more specific ATM-information

(a tmln terfaceConf able) . c) The table is used for storing information about TC (Transmission

Convergence) -resources such as SONET or DS3. d) The table is indexed with regard to 5 attributes which on one hand identify the cross-connection but also in the cross-connection included ports and VPIs . e) Pointers to elements in Table f) for port/VPI which is included in the cross-connection. f) The table contains information about VPL and is indexed by ifIndex (to identify the port of the switch) and VPI. g) Appoints an atmVpCrosεConnect Index in Table d) , and can for instance be used to identify other VPs to which this VP is cross- connected. h) The table contains traffic characteristics which can be appointed to describe a VCL/VPL. Predefined elements exist, but if these are not enough, new descriptions can be added. Figure 3 shows a scenario to illuminate the role of NMC, and how it can use M3N to control a complete ATM-network consisting of standard components.

In Figure 4 is shown tables in NMC for M3N. Texts to Figure 4: a) This table contains information about which direct connections that exist between different ATM-switches in the network. The information in the table is obtained actively by NMC (by contacting an agent and trying to unwind all relations recursively) or is added manually. Under the general structure of the table is given examples of how the table would look in a topology acccording to Figure 3. Directions in the table has no significance (i.e. which switch that is categorized as el64A and which is categorized as el64A) . b) This table contains information about which switches that are controlled by given agents. Agents can be specified by a reference (pointer) to a Party (which contains information about the agent's

IP-address, transport protocol, security arrangements, if any, for authentication and encryption etc) . c) This table contains information about which UNIs that are connected towards each other. Further elements can exist (for instance "status" for creation of new lines) but are not shown here.

In the example there exists a connection between switch 1/port 2, up to switch 4/port 1. This connection has the VPI-value 88 for customer

A, and 77 for customer B. d) This table contains information about which point-to-point connections that exist. The value of pathlndex is the same as for xclndex, so it is easy to relate an amount of elements in uniNNIPathTable to an element in uniUNITable.

In the example we suppose that NMC chooses to use the following path for establishing of a VP between customer A and customer B:

1 <->3<-> 4.

The for the example specific lines can all easily be related to a

UNI-UNI-connection pathlndex/xcIndex. uniUNITable is in fact a modified variant of atmVpCrossConnectTable according to M3 (see previous figure) . uniUNITable is used as reference to the real M3- tables where the information is stored.

DETAILED EMBODIMENT

In the following the invention is described with references to the figures and the terms therein.

In Figure 1 is shown how, by means of M3 (M = Management, 3 = Management Interface No 3), the customer NMS (Network Management System) can ask the operator CNM (Customer Network Management) to cross-connect port A to port B of the ATM-switch (ATM = Asynchronous Transmit Mode) . In the traditional case, however, the customer cannot ask for a connection over a number of switches in an ATM-network. The arrangement of connections over one or more switches is in this case managed by an CNM-agent. CNM consists of a part of NMC (Network Management Center) . A user who wants to establish a connection gives the address/addresses to the wanted party/parties in a communication. The information is received by the control system, which after that contacts agents in question in the system. The agents after that inform the control system whether wanted connections can be performed or not in the network. With the suggested solution no changes in network elements are required other than in the central support system (NMC) where the system solution shall be implemented.

M3N (M = Management, 3 = Management Interface No 3, N = Network) has to start with references to at least one SNMP-agent (SNMP = Simple Network Management Protocol which implements M3, i.e. ATM- forum's standard M3) . By the agent M3N can obtain information about which other agents there exist that control neighbouring switches of the switch which is controlled by the agent. The M3N-system can for instance contact agents and read its atmlnterfaceConfTable (see Figure 2) .

EXAMPLE

See Figure 3. NMC has the address to agent 1 who controls ATM- switch 1. It contacts agent 1 (with SNMP) and reads all elements in its atmlnterfaceConfTable (Fig.2) . NMC then sees that switch 1 has a direct connection to

- ATM-switch 2 which is controlled by agent 2. ATM-switch 3 which is controlled by agent 3. NMC now stores this fact in atmTopologyTable (Fig.4) and repeates the procedure with agent 2 and agent 3 until it will find no new ATM- switches.

This procedure to map all agents, and indirectly also the topology of ATM-switches, consequently can be performed by the M3N-platform (NMC) or manually. In the latter case the operator him/herself adds information about which switches the ATM-network consists of, which SNMP-agents the switches are controlled by, and how they are connected to each other. The system solution amounts to specification of four tables in NMC, which NMC can use to keep count of the interrelation between agents in the network which is controlled by M3. From these tables the customer gets access to one, by which he/she can require that a VP shall be connected between UNI (User Network Interface), i.e. two customers. The customer who asks for connection and the customers who are connected need not be the same, so the M3N-method can be utilized as service at different operators (for instance to allow an organisation to subscribe to resources in an ATM network provided by an operator) . The customer is hereby himself/herself given possibility to control how these resources shall be used. The organisation can for instance choose to let a central administrator establish switching trains between members in the organisation.

Suppose that customer A wants to establish a connection to customer B. By the operator the customer need not find out what happens in switches along the path between A and B. Instead the customer transmits SNM-inquiries to NMC with request according to the following. [Customer A - >NMC] Get Request (Next xclndex) to, in accordance to the standard performance in SNM, find out next free index in uniUNITable. The answer is obtained from NMC, i.e. xclndex (in the example xclndex = 3), is then used to create a new line in uniUNITable.

[Customer A - > NMC] Set Request (3, 1.2, 4.1),. i.e. create a new connection between port 2 of switch 1 and port 1 of switch 4. The combination port/switch i expressed by ITU E.164-addresses (ISDN- number) .

By the solution in NMC, M3N will then see to it that right cross- connections are performed in the network, at which customer A receives the answer.

Response (3, 1.2, 88, 4.1, 77) (i.e. VP No 88 can be used by customer A to communicate with customer B) .

Before the answer is transmitted, however, NMC must see to it that the connection between the customers is established. First they look into atmTopologyTable to find a path (for instance the shortest or the cheapest, or the one with most bandwidth) . In the example we suppose that NMC choses the path 1-3-4. NMC after that contacts the agents 1, 3 and 4 and cross-connects each ATM-switch in cascade or parallell.

It first asks agent 1 to find a port on switch 1 which leads to switch 3. NMC after that reserves this VP and cross-connects it with a VP which is reserved for customer A. If the cross-connection is accepted by agent 1, NMC creates a new line in the table uniUNITable (NNI = Network-to-Network Interface) which contains information about one of the cross-connections for xclndex = 3) . The procedure is repeated at which the tables for NM3 will have a look according to Figure 4.

A device according to the invention is utilized in an NMC for control of ATM-networks. Because the number of NMC with M3N becomes small, an operator can go in for implementing the system solution himself/herself. Additional costs, if any, will be balanced by the possibility to buy standard components without the requirement of special solutions from contractors. One at that will be more independent at selection of contractor.

The invention will also be possible to use as LAN-managers which in a simple way can establish switching trains without worrying about the internal structure of the network.

The system solution consequently is based on a combination of M3- elements and management of simple tables at the telecommunications administrator. The invention is not restricted to what has been described above, or by the patent claims, but may be subject to modifications within the frame of the idea of invention.

Claims

PATENT CLAIMS

1. Device at ATM-network, in which network switches are arranged and the switches are controlled by agents, and information can be transmitted to the agents i connection with establishment of communication between the first subscriber and a second subscriber, c h a r a c t e r i z e d in that in the ATM-network a central control system is arranged, that information from the first subscriber, regarding wanted communication with one of the other subscribers, is transmitted to the central control system, that the central control system is arranged to indicate a selection of path between the subscribers in the ATM-network, and that said selection of path is connected between the subscribers, at which communication between them is allowed.

2. Device according to patent claim 1, c h a r a c t e r i z e d in that the central control system is arranged to establish a connection between the subscribers over a number of the switches.

3. Device according to any of the previous patent claims, c h a r a c t e r i z e d in that the central control system is arranged to communicate with the agents.

4. Device according to any of the previous patent claims, c h a r a c t e r i z e d in that the central control system indicates addresses to/from which communication shall be established.

5. Device according to any of the previous patent claims, c h a r a c t e r i z e d in that the agents are arranged to order connection for the establishing of communication in the ATM-network.

6. Device according to any of the previous patent claims, c h a r a c t e r i z e d in that the agents are arranged to inform the central control system whether concerned switch is capable of establishing a wanted connection or not.

7. Method at ATM-network, in which ATM-network central control system is arranged, and information, from first subscriber, is transmitted to the control system, regarding wanted communication with a second subscriber, c h a r a c t e r i z e d in that the control system receives information from the first subscriber, that the control system communicates with agents in the network and decides a communication path between first and second subscriber, and that the connection is established in the network, at which the subscribers are allowed to communicate with each other.

8. Method according to patent claim 7, c h a r a c t e r i z e d in that the agents control switching functions in the network.

9. Method according to any of the patent claims 7 or 8, c h a r a c t e r i z e d in that the agents inform the control system which paths and connections that are accessible.

10. Method according to any of the patent claims 7-10, c h a r a c t e r i z e d in that the control system orders the agents to establish appointed calls and connections.

11. Method according to any of the patent claims 9-10, c h a r a c t e r i z e d in that each of the agents controls an appointed switch in the network.

12. Method according to any of the patent claims 9, 10 and 11, c h a r a c t e r i z e d in that the agents arrange necessary connections in the switches in the network.

13. Method according to any of the patent claims 9-12, c h a r a c t e r i z e d in that the control system informs the agents which connections, paths and ports that shall be utilized at a connection between the subscribers.

14. Method according to any of the patent claims 9-13, c h a r a c t e r i z e d in that the control system orders connection between the subscribers in the network, where a number of the agents respective switches are involved.