KR20000037554A - Dynamic routing based call path setup method of asynchronous transfer mode switching system and re-setup method - Google Patents

Abstract

PURPOSE: A dynamic routing based call path setup method of an ATM(Asynchronous Transfer Mode) switching system and a re-setup method are provided to operate a terminal interface and an inter-exchange interface together in a distributed switching system. CONSTITUTION: If a PNNI(Private Network/Network Interface) signaling protocol part(22) receives a call setup message, the PNNI signaling protocol part(22) transmits QOS(Quality of Service) information to a PNNI call path selection part(26) of a central processing system(25). The PNNI call path selection part(26) transmits a call path suitable for a required characteristic to a connection server system(21) in the shape of a DTL(Designated Transit List), referring to a routing information database(27). The PNNI signaling protocol part(22) processes the call through a defined signaling message.

Description

Dynamic routing based call establishment method and re-establishment method of ATM switching system in asynchronous transfer mode switching system

The present invention relates to an asynchronous transmission mode switching system. In particular, a dynamic routing-based call path of an asynchronous transmission mode switching system for interworking a terminal interface and a switching period interface in a distributed switching system that simultaneously accommodates a dynamic routing scheme and a static routing scheme. It relates to a setting method and a reset method.

In an asynchronous transfer mode (ATM) exchange, the interface of the exchange period can use statically set static routing schemes, and also dynamically by sharing information by defining protocols for routing during the exchange period. A dynamic routing scheme can be used that reflects the changing network geometry. This is already known by the Private Network / Network Interface (PNNI) protocol in the ATM Forum, and can be extended to private or public networks.

In the signaling protocol based on such static routing, the relay line and the route are set in advance during the exchange, and then the required service is performed through the established route. However, the dynamic routing method shares the route information between the exchanges by a predetermined protocol, and then processes the required service according to the shape of the network at that time.

In this dynamic routing protocol, PNNI requires a procedure for handling a call failure in terms of network management. This should be addressed in terms of traffic management and quality of service (QoS), which are the biggest features of ATM. In other words, the Call Admission Control (CAC) algorithm is an implementation dependent function and is implemented in various forms by different ATM exchange vendors.

Therefore, from the point of view of the PNNI protocol, it is impossible to predict which call acceptance criteria are adopted by each node of the ATM switching network, and each node in the DTL (Designated Transit List) of the path selected by the source node does not exactly correspond to the physical node. Nor do they correspond to logical nodes represented by summarized information. The PNNI protocol cannot run a very accurate CAC algorithm, but rather only determines which nodes can accept the call.

In response to these limitations, the PNNI adopted the GCAC concept. GCAC is performed to find out which nodes are likely to accept the connection when there is a call establishment request. In other words, it is not completely accurate because it predicts the possibility of call acceptance. Therefore, there may be a case where the source node cannot accept a call among the DTL nodes of the selected path, and in such a case, a crankback procedure is used to effectively reroute. Such crankback may occur due to incompatibility of links between nodes, but may also occur due to an interface error with a corresponding link in a node. Therefore, this must be handled separately in the exchange system.

Accordingly, the present invention has been made to solve the above problems of the prior art, and when the call is not established in the call establishment step of the ATM switching system based on dynamic routing, the call is reestablished according to each cause. An object of the present invention is to provide a dynamic routing based call reconfiguration system and method for an asynchronous transmission mode switching system.

1 is a structural diagram of functions of a PNNI protocol;

2 is a block diagram for implementing a dynamic routing-based call path establishment method of the asynchronous transmission mode switching system according to an embodiment of the present invention;

3 is a diagram illustrating an example in which a call is self routing through a DTL;

4, 5, and 6 are flowcharts illustrating a dynamic routing based call rerouting method of an asynchronous transfer mode switching system according to an embodiment of the present invention.

※ Explanation of code about main part of drawing ※

21: connection subsystem 22: signaling protocol processing unit

23: link resource management unit 24: routing packet processing unit

25 central processing system 26 call path selection unit

27: routing database 28: routing protocol processing unit

In order to achieve the above object, a dynamic routing-based call path setting method of an asynchronous transmission mode switching system according to the present invention is a dynamic routing-based call path setting method of an asynchronous transmission mode switching system consisting of a central processing system and a plurality of connection subsystems. To

A first step of the plurality of access subsystems sharing routing information by exchanging routing packets;

A second step of storing the routing information in a database of a central processing system;

A third step of analyzing a signaling message received by the access subsystem and querying a path of a call; and

And a fourth step in which the central processing system selects a path of a call using routing information stored in the database.

In addition, the dynamic routing based call path resetting method of the asynchronous transmission mode switching system according to the present invention, in the dynamic routing based call path resetting method of the asynchronous transmission mode switching system consisting of a central processing system and a plurality of connection subsystems,

If the crankback occurs because the link resources between input nodes are insufficient or blocked while the call progresses through the link connected to other nodes at the input node, the output terminal analyzes the call release message input through the PNNI link and satisfies the call requirements. A first step of notifying the input terminal that it cannot find;

A second step of the input terminal requesting a new route from the central processing system;

A third step of the central processing system calculating a new route and notifying the input terminal; and

And wherein the input includes a fourth step of resetting the call via the new route.

In addition, the dynamic routing based call path resetting method of the asynchronous transmission mode switching system according to the present invention, in the dynamic routing based call path resetting method of the asynchronous transmission mode switching system consisting of a central processing system and a plurality of connection subsystems,

If the crankback of the call occurs due to the interface error of the other node while the call progresses through the link connected to the other node at the input node, the output end analyzes the call release message input from the other node and notifies the input node of the interface error of the other node. The first step,

A second step of the input end requesting a new local link from the central processing system;

A third step of the central processing system notifying the input terminal by changing a local link; and

And a fourth step in which the input end attempts to reset the call to the access subsystem to which the new local link belongs.

In addition, the dynamic routing based call path resetting method of the asynchronous transmission mode switching system according to the present invention, in the dynamic routing based call path resetting method of the asynchronous transmission mode switching system consisting of a central processing system and a plurality of connection subsystems,

If a call is cranked back due to an interface error of the input node in the course of a call progressing through a link connected to another node in the input node, the output stage transmits the fact to the input terminal through an internal signal,

A second step of the input end requesting a new local link from the central processing system;

A third step of attempting to reset a call using a new local link granted from the central processing system;

A fourth step of transmitting an error occurrence fact to an input terminal when an error of a local link occurs when the output terminal attempts to reset the call;

A fifth step of the input end requesting a new local link from the central processing system;

A sixth step of the input terminal requesting a new route from the central processing system when a local link change failure message is transmitted from the central processing system, and

And a seventh step of being notified of the changed route information from the central processing system.

Hereinafter, exemplary embodiments of the present invention will be described with reference to the accompanying drawings.

In general, the PNNI protocol consists of a routing protocol and a signaling protocol. The PNNI routing protocol is a protocol required for selecting a path between a source node and a destination node that a user requires. Telecommunication networks use a static routing scheme that assigns a preplanned route for the selection of a communication path, but the PNNI routing protocol acts as a dynamic routing protocol.

Source-based dynamic routing is a method in which the source node determines the hierarchical path from the source (or originating) node to the destination node in point-to-point. That is, the intermediate transit node on the routing path must follow the routing instruction selected by the source node. As such, in order to select a reliable path in the source node, information about reachability to each address and topology information about available resources of each node should be periodically advertised in the network.

Since the source-based dynamic routing method has a high burden of periodically exchanging routing information (topology information and reachability information) between communication network nodes, the size of the network to which the source-based dynamic routing method can be applied is practically limited.

The PNNI supports the hierarchical structure using address information and the summarization of information, thereby reducing the routing information that needs to be exchanged in the network, thereby supporting scalability that can be applied to a nationwide network.

In addition, the PNNI signaling protocol proceeds with a call searching for information on a path obtained through the routing protocol. PNNI uses Designated Transit Lists (DTLs) to represent paths through routing domains. This DTL is derived from the PNNI routing topology information, which consists of an array of node identifiers and a pointer to the current node. The DTL information element represents a path through a PNNI routing domain from an ingress node to an egress node, and is carried in a SETUP message. In other words, the DTL represents the exact path that can start from the current local peer group (PG) and pass the logical group nodes (LGNs) of the upper layer PG of the PNNI hierarchy hop-by-hop to the destination node.

1 is a diagram illustrating a functional structure of a PNNI protocol. The routing protocol 1 consists of a topology database for storing information obtained through the exchange of topologies, route generation and calculation functions for calculating routing paths, and network topology exchange functions. This calculates the routing path. The signaling protocol 2 determines a path of a call through UNI signaling and NNI signaling based on higher routing information. The switch module 3 represents the actual switch path when the call is established by the upper routing protocol and the signaling protocol.

2 is a functional diagram of a routing protocol and a signaling protocol of an ATM switching system to which the present invention is applied. A plurality of access subsystems 21 may exist as connection points to which terminals or relay lines are actually connected, and the PNNI routing packet processing function 24 is performed through a link actually connected between nodes on the PNNI protocol. The information of the peripheral nodes obtained by the exchange of routing packets is transferred to the PNNI routing protocol processor 28 of the central processing system 25 and stored in the routing information database 27.

When the PNNI signaling protocol processor 22 receives the call setup message, the PNNI signaling protocol processor 22 transmits the bandwidth and QoS information of the call, together with the corresponding destination number, to the PNNI call path selector 26 of the central processing system 25. The call path selection unit 26 refers to the routing information database 27 and transmits the path of the call that meets the required characteristics to the access subsystem 21 in the form of a DTL. Thereafter, the signaling protocol unit 22 of the connection subsystem 21 advances the call through the defined signaling message. If the UNI processing unit determines that the call should go through the PNNI, it is requested to call path selection unit 26 of the central processing system 25 to be informed of the number of links of which interface module of which connection subsystem of the ATM switching system. This is informed by the PNNI protocol processing unit of the corresponding connection subsystem.

When receiving the information required to set up the call by the method described in FIG. 2, the call is set up by tracking the call. Information required for call establishment is obtained through a form called DTL. For example, as shown in FIG.

That is, the terminal A sends a SETUP message including the called party number to the node 1.1 by the UNI signal. Node 1.1 analyzes the called number and calculates the DTL connected from node 1.1 to the called party. Node 1.1 knows the full path through its PG (1.1 => 1.2 => 1.4) and it is contained within the DTL. In the example of the figure, it is assumed that node 1.3 is not selected because it cannot satisfy the required connection characteristics. The path through the rest of the network is recorded using the next level of PG. For example, the path from node 1 to node 2 is selected.

When node 1.4 receives the SETUP message, the first level hierarchy of that DTL ends. Thus, the node pointer is incremented by one to point to the next level of hierarchy, which in the example picture points to PG 2. Node 1.4 already knows the path to node 2.1 for the Hello packet exchange with node 2.1, the boundary node. Since node 1.4 is the end node of PG 1, it stores the contents of the SETUP message. This content is used for crankback.

Whenever a SETUP message is passed from one PG to another, a new local DTL is obtained using the topology information of the new PG to determine the path of how to pass through that PG. Therefore, the PG 2.1 obtains a new DTL connected to the B terminal through the node 2.2 using the called number and the topology information in the PG.

If the call proceeds normally as shown in FIG. 3, there is no problem. However, if the call fails, the call should be classified according to the cause to determine whether to reset the call again or fail.

The present invention provides a method for rerouting a call in three cases where call rerouting fails. The subject that sets / reroutes the call is an entity that generates a DTL and proceeds with the call and becomes an ingress node of a peer group (PG). One node to which PNNI is applied has both an input point and an output point. That is, if a call connection request (SETUP) comes from another node on a PNNI link that is connected to another node, the link is seen as an input to that call and the PNNI link connected to that node to send the call to another node. If you proceed with the call, the link becomes the output of the call.

In this case, even when the terminal subscriber requests the call, the link of the subscriber may be an input terminal via the PNNI. Therefore, in the case of a system that can have multiple distributed connection subsystems such as an ATM communication system, when a UNI link becomes an input node of an input node, it is possible to select a specific output terminal among multiple output terminals and transmit information to another node. . However, if the output terminal becomes the UNI link in the last destination node, it means that the link has a called number and thus the output terminal cannot be changed.

4 is a flowchart illustrating a dynamic routing based call rerouting method of an asynchronous transmission mode switching system according to an embodiment of the present invention. If a crankback information element is defined on the signaling protocol of the PNNI, and a crankback occurs due to lack of link resources between nodes or blocking, if a release message including a crankback information element is input to an output terminal (step S41). This output stage sends a call release request message to the input stage together with the blocked node / port and blocking node type (step S42). At this time, the input terminal transmits a change route request message including the blocked node / port and the blocking node type included in the crankback information to the path controller of the central processing system (step S43). In addition, the input terminal uses the changed route information provided from the path control unit (step S44) to generate new DTL information to reset the call path (step S45).

5 is a flowchart illustrating a dynamic routing based call rerouting method of the asynchronous transmission mode switching system according to an embodiment of the present invention. When the call fails due to an error in the interface in the destination node, if a release message including a crankback information element is input to the output terminal (step S51), the output terminal transmits a call release request message to the input terminal (step S52). At this time, the blocked transit type is 0x02, which means that the call fails due to an error of the interface in the successive node.

The input end sends a change local link request message to the path control unit in order to find another local link of the destination node before establishing a new route (step S53). Here, the other local link means that the root of the node through which the call passes does not change and the physical link between the nodes is changed. If another local link exists, the call is reset to the changed local link by using the changed local link information provided from the path controller (step S54). However, if it is found that there is no other local link, the call is reset by changing to another new route by the route changing method as shown in FIG.

5 is a flowchart illustrating a dynamic routing based call rerouting method of the asynchronous transmission mode switching system according to an embodiment of the present invention. This is a case where the call fails due to an interface error at the output of the input node during the call progressing through a link connected to another node at the input node.

In this case, since the call is not a failure due to the signaling message between the nodes, it is notified to the input node of the input node using the internal signal (step S61). At this time, the input node of the input node searches for another local link connected to the destination node. That is, the change local link request message is transmitted from the input terminal to the path controller (step S62), and if the change local link information message is input from the path controller (step S63), the call setup request message is transmitted to the output terminal (step S64). Even if a call reset is requested using the changed local link, if the call fails, the output stage sends a crankback request message to the input stage (step S65).

When the change local link request message is transmitted to the path control unit at the input terminal (step S66), but a change local link failure message is input from the path control unit because no other local link exists (step S67), the input terminal searches for a new route. The change route request message is transmitted to the path control unit (step S68). If a new route exists and a change route information message is input from the path controller (step S69), the call is reset using the changed route, and if the new route does not exist, the call is finally rejected and a call release message is sent to the other node or terminal. Send it.

As described above, according to the present invention, even when the node is frequently added or deleted in the ATM switching network or when the topology changes frequently, the dynamic network shape can be automatically reflected through the interface between the nodes. Add / Remove can be applied with the concept of plug and play, which improves the quality of service of ATM switching system.

In such a dynamic routing-based ATM switching system, if call setup fails due to a link error between networks, a new route is generated and processed to increase the reliability of the network. In addition, if call setup fails due to an interface error in the network, cost savings can be obtained by finding and processing a new local link.

Claims (7)

In the method of dynamic routing based call routing in an asynchronous transmission mode switching system consisting of a central processing system and a plurality of connection subsystems, A first step of the plurality of access subsystems sharing routing information by exchanging routing packets; A second step of storing the routing information in a database of a central processing system; A third step of analyzing a signaling message received by the access subsystem and querying a path of a call; and And a fourth step in which the central processing system selects a path of a call by using routing information stored in the database. A dynamic routing based call rerouting method of an asynchronous transmission mode switching system consisting of a central processing system and a plurality of connection subsystems, If the crankback occurs because the link resources between input nodes are insufficient or blocked while the call progresses through the link connected to other nodes at the input node, the output terminal analyzes the call release message input through the PNNI link and satisfies the call requirements. A first step of notifying the input terminal that it cannot find; A second step of the input terminal requesting a new route from the central processing system; A third step of the central processing system calculating a new route and notifying the input terminal; and And a fourth step of the input terminal resetting a call through a new route. A dynamic routing based call rerouting method of an asynchronous transmission mode switching system consisting of a central processing system and a plurality of connection subsystems, If the crankback of the call occurs due to the interface error of the other node while the call progresses through the link connected to the other node at the input node, the output end analyzes the call release message input from the other node and notifies the input node of the interface error of the other node. The first step, A second step of the input end requesting a new local link from the central processing system; A third step of the central processing system notifying the input terminal by changing a local link; and And a fourth step in which the input end attempts to reset the call to the access subsystem to which the new local link belongs. The method of claim 3, If there is no other local link to change, the central processing system notifies the input end of the fifth step; A sixth step in which the input terminal requests a new route from the central processing system; A seventh step in which the central processing system calculates a new route and notifies the input terminal; and And an eighth step of the input terminal resetting the call through the new route. A dynamic routing based call rerouting method of an asynchronous transmission mode switching system consisting of a central processing system and a plurality of connection subsystems, If a call is cranked back due to an interface error of the input node in the course of a call progressing through a link connected to another node in the input node, the output stage transmits the fact to the input terminal through an internal signal, A second step of the input end requesting a new local link from the central processing system; A third step of attempting to reset a call using a new local link granted from the central processing system; A fourth step of transmitting an error occurrence fact to an input terminal when an error of a local link occurs when the output terminal attempts to reset the call; A fifth step of the input end requesting a new local link from the central processing system; A sixth step of the input terminal requesting a new route from the central processing system when a local link change failure message is transmitted from the central processing system, and And a seventh step of being informed of the changed route information from the central processing system. The method of claim 5, wherein in the seventh step, And the input end further comprises an eighth step of attempting to reestablish a call using the changed route. The method of claim 5, wherein in the seventh step, If the new route does not exist, the call is finally rejected, and the input end further comprises a ninth step of transmitting a call release message to the counterpart node.