DE4428349C2 - Method and routing system for traffic control in a communication network - Google Patents

Description

The invention relates to a method and a routing kungs system for traffic control in a communication 7 according to the preamble of claim 1.

In communication networks, for example telephone or Data switching networks, for circuit switched connections The principle of alternative guidance is generally used routing (alternative routing) applied. This is common so pronounced that for a desired connection between a source (calling subscriber facility) and a destination (called subscriber facility) several connection paths in a selection list is available, which is also known as al alternative route selection or routing is referred to. In the simplest case, for example, there is a commu network the connection paths for a network entrance Network output relationship from a direct path between one Input and an output switching device and out a number of alternative routes each over at least another, serving as a transit switch Switching device of this communication network. The The number of alternative routes in the selection list is in the we considerably through the network architecture and through special Specifications of the network operator determined (e.g. number of levels in a hierarchical network and their cross-relationships, Number of switching centers in a full mesh network or by the network operator for a specific ver transport relationship specially selected transit brokerage facilities and bundles).

A connection involving only one, for example Transit switch, d. H. with unavailable  Direct route consists of two sections, namely the Section between the network entrance switch (Originating switch) and the transit ver averaging device and the section between the Tran sit switch and the network exit switch averaging device (destination switching device). With the Selection of the trunk group for the first section the routing system of the network entrance switch direction, the second section is also automatically set sets. Since only in the network input switching device the availability of the first section is checked there is a certain probability that which is implicitly filled with selected second section. In this case, it is known to use an occupied signal (crank back signal) from the transit exchange to transmit the network input switch with which indicates the unavailability of the selected second Ab section is displayed. The network entry switch direction then selects another alternative route. This creates a delay in building one Connection as well as an increased mediation effort in the Communication network. In high load phases for a ver connection establishment repeats the aforementioned busy signal occur, depending on the occupancy of the Communication network and the number of those in question coming network exit switching device provided Alternative routes. So that is a repeated rerouting and an additive call delay connected.

From the European patent EP-B1-0 229 494 is a decentralized procedure for dynamic routing knows that an alternative route as long as overflow traffic points until it is no longer available, d. H. until either the first section of the alternative route is occupied or the originating node receives a busy signal due to blocking of receives a transit node. In this case  the previous alternative route was cyclical or (pseudo) random lig replaced by another alternative route. In one the form of the procedure becomes the overflow traffic distributed over a group of several alternative routes and an alternative route in the event of unavailability replaced by another alternative way.

In addition, an unpublished eu European Patent 0 696 147 A1 a method and a routing system for dynamic traffic control in one Communication network has been proposed, according to which calls between between an originating switching node and a destination Switching node first one or more preferred Because of (planned routes) are offered.

In the event that none of the planned routes are available Call alternative routes that are included in a route fan are offered according to a specific selection scheme. An alternative route previously contained in the route fan will be discontinued the way fan as soon as it is determined that he is no longer available.

The alternative route removed from the route fan will not replaced. However, the path fan is periodically, i.e. H. to certain time intervals, and / or aperiodically, d. H. to Occurrence of at least one event or due to a Commands from a network-central traffic management system or reinitialized by the network operator. Here too an alternative route can be based on a Be removes crankback signal from the way fan will.

The invention has for its object to show a way conditions, such as a method and a routing system stem of the type mentioned at the beginning when occupancy Signals (crankback signals) the control effort for the Path search and thus the delay time for the construction of Connections can be reduced.  

This task is solved with a procedure according to Oberbe handle of claim 1 by the in this patent procedural characteristics listed.

The invention has the advantage that a Accumulation of busy signals for the moment not available Avoid standing sections of the path and thus the time and the effort for the selection of alternative routes in the frame of building connections is reduced. Since also in a high-load phase of the communication network every month about as many connections are triggered as new connection requests (calls) always occur free alternative paths can be found again, in particular if the table of possible alternative routes is relatively large is, d. H. it is appropriate to the unsuccessful age to temporarily block native paths.

Appropriate embodiments of the method according to the lying invention result from the patent claims 2 until 6.

The task outlined above is for a route Steering system according to the preamble of claim 7 by the features specified in this claim ge solves.

In the following the present invention with reference to Drawings, for example, explained in more detail.

Fig. 1 shows in schematic form a communication network to which the present invention is applied, and

Fig. 2 shows a routing table, which will be discussed in more detail below.

Fig. 1 shows in schematic form a communications network which comprises as example, six switching devices A, B, H, K, P and S (switching node). A path section between two switching devices comprises at least one trunk group.

It is assumed below that the mediator a device (originating switching device) Connection request (call) for a connection to the Ver averaging device B (destination switching device) lies, but the initially selected direct route between the currently not available in both switching centers is.

It is also assumed that a plurality of each alternative routes between two route sections between the two switching centers A and B under one hand drawing a transit switching device provided be. These alternative routes are in a routing table (Routing table) of the switching device A captured. Under this condition, the rou includes ting table of alternative routes for the origin-destination Be draw between switch A and switch device B four alternative routes, namely the two Route sections-alternative routes via the switching device H, P, S and K.

Routing chooses under the above conditions kungs system of the switching center A based first an alterna in the available routing table tivweg, which still has at least one verifiable free Line or at least one free channel. Here is a festge in the present embodiment  increased selection order with a fixed starting point based. This selection may be in the order Tran sit switch H, P, S and K take place.

In order to be able to make a selection, the routing sy stem of switching center A the capacity of the to routes leading individual transit switching centers sections for the individual alternative routes and the An number of lei still available on these sections or channels. Results in a review based on this information that the route section to the transit Switching device H for a new Ver to be set up binding is available, the origin ver averaging device A the connection up to the transit switching facility H is set up. The Rou ting system of the transit switching facility H checks then for the further connection establishment via the way cut the mo to the destination switch B. mental availability of this path section. For this ste hen this routing system the aforementioned capacity gave corresponding capacity information for the concerned Path section available. If according to this information the relevant route section is available, the verb from the transit exchange H to the destination Switching device B built.

If the routing system of the transit switch However, H determines that the path section to the Target switching device B is not available, so triggers the transit switching device H already with the Originating switch A existing sub-connection with a specially defined busy signal (crank back signal). According to the present invention there is provided that the occurrence of such a Signals the alternative route assigned to this, here the Al ternativweg on the transit switch H, for  the further selection of an alternative route is excluded becomes. This alternative route remains so long closed, as well as other alternative routes to the target ver averaging device B are available. With the ange Examples taken are those via the transit broker P, S and K alternative routes.

After excluding the alternative route, here as an example the one running through the transit switching facility H. Alternative route, is in for the currently desired connection an alternative route via the Tran sit switches P, S and K searched. Also for subsequently to be established connections between the original jump switch A and the target switch tion device B are used for the selection of a suitable Connection path only that, via the transit switch P, S and K alternative routes considered.

In a departure from the example shown in FIG. 1, a multiplicity of alternative paths are generally defined for a predetermined origin-target relationship. An alternative route that is initially excluded from the selection is released again if the number of alternative routes still available falls below a predetermined number. In addition, the method described above for selecting an alternative route can also be modified such that an alternative route is only ruled out for the occurrence of a fixed plurality of assigned signals (crankback signals) for an alternative route selection.

For the handling of the previously explained method for selecting an alternative route, in the routing system each of the switching devices of a communication network functioning as the originating switching device for each origin-destination relationship is a routing shown in FIG. 2 using the example of the destination switching device B Table tab led. This contains information regarding all of the proposed alternative routes. As an example, let us assume that this routing table contains information for n.Alternative routes, these information being designated as 1.Alternative route to n.Alternative route. In addition, each alternative route specification is assigned a bit position M, in which a marker bit can always be set if the respective alternative route is to be excluded from the selection due to the occurrence of the specified number of above-mentioned occupancy signals. This routing table is queried sequentially for the selection of an alternative route by skipping a marked alternative route, starting with the alternative route designated in the routing table with the first alternative route. Alternatively, however, the query can also be carried out in a different order.

In the present embodiment is additional provided that even then for the respective alternative route the marker bit assigned to this is set if already from the originating switching device the transit switch in question ver current route section is currently not available.

Finally, it should be pointed out that the present ing invention not only in the commu explained above networks, but rather generally in communication ons networks is applicable, in which in the event of a availability of a path section the transmission of an occupied Signals (crankback signal) is provided and an accumulation such busy signals for the individual alternative routes should be avoided. Among these communication systems hierarchically organized commu also fall, for example nication networks with conventional routing  ("fixed alternated routing") and partially and fully meshed Communication networks with dynamic routing ("dyna mic routing ").

Under the term communication network used above By the way, ze should understand every kind of switching network that will. Examples include telephone, Data switching and ISDN networks. These networks can both for establishing switch-through connections as well trained to establish virtual connections be.

Claims (8)

1. A method for routing traffic in a communication network, in which for the establishment of connections between an originating switching device (A) and a destination switching device (B) pending calls when a direct route is not available from the originating switching device, a plurality of Alternative routes, which each run via at least one transit switching device (H, P, S, K), are offered according to a defined selection scheme and in which of the respective transit switching device in the event that a call received due to the Unavailability of the further route in question cannot be forwarded, a busy signal is transmitted to the originating switching device (A), upon whose occurrence the alternative route assigned to this busy signal is temporarily excluded from the selection, characterized in that that when a specified number occurs l of busy signals for the respective alternative route is excluded from the selection as long as other alternative routes are available for the destination switching facility (B) in question. 2. The method according to claim 1, characterized, that the selection of an alternative route from the plurality of Alternatively, in a fixed order with fe starting point. 3. The method according to claim 1 or 2, characterized, that an alternative route with the first occurrence of this one assigned busy signal excluded from the selection becomes.   4. The method according to claim 1 or 2, characterized, that an alternative way only on the occurrence of a festge placed a plurality of Be assigned to this alternative route sets signals from the selection. 5. The method according to any one of claims 1 to 4, characterized, that an alterna initially excluded from the selection tivweg when falling below a specified number of alternative routes still available for the Aus choice is allowed again. 6. The method according to any one of claims 1 to 5, characterized, that an alternative route is temporarily blocked, if the transit agent in question is already device (e.g. H) towards the moment not available. 7. routing system for traffic control in a com communication network, in which for establishing connections between an originating switch (A < and pending calls to a destination switch (B) if a direct route from the source is not available Switching device forth a plurality of alternatives because of which each have at least one transit broker lungseinrichtung (H, P, S, K) run, according to a specified selection scheme and in which of the respective transit switching device forth for the In the event that one of these incoming calls due to the non-ver Availability of the further path in question a busy signal cannot be forwarded to the Originating switch (A) is transmitted to  the occurrence of that associated with this busy signal Alternative route is excluded from the selection, characterized, that in the originating switch (A) one of the Target switch (B) associated selection table (Tab) for the alternative routes, in which at Occurrence of a specified number of busy signals for the respective alternative way of doing this by setting a Mar is excluded from the selection as long as other alternative routes for the target Switching device are available. 8. routing system according to claim 7, characterized, that in the selection table (tab) in addition to information regarding the Alternative routes one bit for each of these alternative routes is reserved in which a marker bit is set is cash if the respective alternative route from the selection is to be excluded.