Method for setting-up virtual circuits in an ATM (asynchronous transfer mode) switching system.

The invention relates to a method for establishing virtual connections in operating according to an asynchronous transfer mode switching apparatus according to the preamble of claim 1.

Processes of this type are already known by the magazine INTERNATIONAL JOURNAL OF DIGITAL AND ANALOG SYSTEMS CABLED, VOL.1., Articles by KA Lutz on pages 237-243 (1988) and by the conference paper from the International Switching Symposium, 15.-20. March 1987, Proceedings, Phoenix, USA, 3 (1987) pages 602-608. With methods of the known art virtual connections for packet switching are set. For this way of connecting lines as well as ATM (Asynchronous Transfer Mode) -Koppelfelder be searched, selected and determined. Within an ATM switching network paths over ATM switching elements and überATM intermediate lines are set.

When searching, selection and determination of routes (route search) for setting up new virtual connections even free transmission capacity it is important that already occupied by virtual connections paths for more virtual connections can be availed only in so far as these routes available is. For this purpose it is known to store as for each intermediate line in a multistage ATM switch each currently still free, so available for setting up new virtual connections transmission capacity in an ATM intermediate line allocation memory. These are still free, each available ie for setting up new virtual connections transmission capacity can for example be the same as has been utilized transmission capacity of the difference between the total transmission capacity of an intermediate line and set up by this virtual connections. The latter can be, for example, the sum of all the peak bit rates of virtual connections in question.

For the search, selection and determination of routes for setting up new virtual connections, it is now known that each coming into question intermediate line each still free, available thus for setting up new virtual connections transmission capacity is compared in size with the to be established for the new virtual connection required transmission capacity, which may for example correspond to the peak bit rate of the virtual connection.

The invention is directed to simplify the most frequently unwound procedure derWegesuche in the process of the aforementioned kind. If now completed for each path hunt a size moderate comparison of the aforementioned type, so this results in particularly tough requirements for appropriate processing devices, and that is because the processes of setting up new virtual connections one hand numerically many per unit time are thus occur relatively frequently and on the other hand not too long should take. Latency problems connecting are disruptive and undesirable.

It is an object of the invention to provide for a method of the type mentioned appropriate measures that will help the search, selection and determination of routes (route search) for setting up new virtual connections can be handled as easily as possible. The processing operations are to be designed so that all the operations which are to be completed immediately before each and every creation of a new virtual connection, be simplified as possible.

The invention solves this problem in a method according to the preamble of claim 1 by the features specified in the characterizing part of this claim process features.

The invention enables the size moderate comparisons between available transmission capacity and required transmission capacity can be reduced to a simple one-bit comparisons. This way the search for setting up new virtual connections is simplified considerably, which is of particular importance istfür virtual connections over ATM switching networks with multiple switching stages and, accordingly, various groups of ATM intermediate lines. These groups are at various points between the successive switching stages in the ATM switch. For this connection bit rate classes are formed now. A route search uses - starting each of derfür a newly to be established virtual connection authoritative connection bit rate class - of this connection bit rate class corresponding different storage elements and determined on the basis of simple one-bit compare the usable respectively for to be set up new virtual circuit ATM intermediate lines.

Advantageous embodiments of the inventive method result from claims 2 to 4. FIG.

In the drawing aisAusführungsbeispiei is shown a switching device, in which the invention is applied. From this switch only the understanding of the present invention serving components are listed.

An ATM switching matrix K (simply referred to as "switch fabric") of a ATM switch includes three coupling stages K1 to K3 ATM switching elements v11 to v3n (hereinafter referred to only as "coupling element" or "switching elements"), which between lines z111 up zm3n are connected in the manner shown. ATM switches in communication devices with asynchronous transfer mode (ATM) are already known through extensive literature, was what pointed out some prime examples: "International Zurich Seminar on Digital Communications", (March 1986) with the publication "New Directions in Communications" (section A3.1 to A3.8, JB Turner); German Offenlegungsschrift 3,732,937; European Patent Application 89102172.7; Magazine "Telecommunications, Electronics", Berlin, 39 (1989) 1, pp. 3 and 4

When the switching device shown in the drawing so it is a circuit arrangement for communication devices with asynchronous transfer mode. About the multi-stage switching network K virtual connections are established. On this point the ATM intermediate lines z111 to zm3n of switching stage to switching stage. Connect the switching matrices v11 to v3n of three consecutive coupling steps K1 to K3 together. For virtual circuits, which are known to serve for packet-switched transmission of data and messages, connection-specific paths are searched, selected and determined. These virtual connections are known, unlike PCM connections and conventionally-galvanically by switched connections not in such a way that a connecting path (this may therefore be a galvanic or a circuit-switched time division multiplexed way) can only be used for a connection, but virtual compounds are of such that they record information in the form of message packets (cells) are received that these packets (cells) are identified by a header and that all packets (cells) of a virtual connection in each case the same, selected when setting up way over take switching network and transmission paths in the network. About virtual connections to be transmitted message packets or data packets are transmitted in packets, are being transmitted via the connection paths, eg transmission channels of transmission systems and intermediate lines, time-between for that virtual connection to be transmitted data packets more data packets, and indeed of other virtual links concerned. As is known, however, virtual connections are wegmäßig precisely defined. This purpose is served in the exchanges in question corresponding Wegesuch- and selection devices.

When setting up virtual connections over ATM switching devices, it is, among other reasons, that, for example, ATM intermediate lines, just as many virtual connections are routed via corresponding ATM connection ways that this can be considered each of the given transmission capacity here also realized in practice. For this purpose, connection-specific bit rate limit values ​​are determined by storing appropriate data for virtual connections in an ATM switch. This bit rate limit values ​​can be, for example, the peak bit rates of virtual connections in question. Should a subscriber setting up a new virtual connection, he indicates, with which peak bit rate it intends to send (messages, data and. The like.). This peak bit rate may be exceeded by him when sending data packets basically not. In a first ATM switch, arrive at the light emitted by the participant concerned data packets is continuously monitored whether the zoom out ATM message stream in terms of peak bit rate complies with the measures announced by the relevant subscriber rate values ​​or exceed; when exceeding appropriate countermeasures can be initiated in the exchange. This may be that parts of the message packets are suppressed, ie not at all or received mutilated be, and / or that a corresponding signaling to the subscriber in question is transferred out or that a virtual connection is forcibly interrupted. Furthermore, an appropriate countermeasure can also be that corresponding packets are first marked only and only then discarded when the load situation in the network, this actually requires. This countermeasure, therefore means that there can be exceptions to the above prohibition overshoot, which may be authorized if the load situation in the network permits.

As a criterion for a subscriber when sending data packages announced and to be maintained during the life of the virtual circuit in question transmission power can except the peak bit rate and an average bit rate (average over long periods, eg over a time interval of a few minutes) serve. It can also serve as both the peak bit rate and the average bit rate together as a criterion. In this context, attention is drawn to the European Patent Application 90122430.3.

As already mentioned, is reported the required peak bit rate and the average bit rate by a subscriber when setting up a virtual connection. These rate values ​​are determined by appropriate storage in the ATM switch of the message stream that participant whichever comes first. corresponding data so it can be stored in this switching device in association with the respective virtual connection. This peak bit rate and this average bit rate must not be exceeded when transmitting packet-switched messages with that participant. For this purpose, ie bit rate limit values ​​are determined by storing appropriate data (peak bit rate and / or average bitrate) for virtual connections in an ATM switching equipment Vermitt connection-specific.

As already indicated, paths are connection-specific searched, selected and determined by means of a selection device Wegesuch- and to set up new virtual connections. The admissibility of establishing virtual connections is new with respect to each such compound derfüreine each checked against the relevant new virtual connections associated fashion set bit rate limit values ​​in question ATM intermediate lines. This test is done taking into account the currently available on the ATM intermediate lines concerned free bit rate transmission capacities. ATM intermediate lines eligible for new virtual connections initially in accordance with the structure of the relevant switching network principle in question or not. For a virtual connection in the switching network K, which will run through the switching matrices v11 and v32, only the intermediate lines z111 to z11m and Z132 come up ZM32 in question. The remaining intermediate lines are not eligible because they are seen by the switch fabric ago obviously not suitable for the respective virtual connection. From the coming of setting up a new virtual connection in question between lines now all are then überpruft whether the required transmission capacity is on each one of them yet. It is now assumed that this transmission capacity is no longer present in the mentioned example Trap on the ATM intermediate lines Z111 and Z232. In this case, the new virtual connection can not be established through the ATM intermediate lines z111 / Z132 / z112 / Z232. However, the desired virtual connection can be set up via the ATM intermediate lines z11m and ZM32. It must thus be seen that a coincidence condition must be met in terms of transmission capacity each are still available. This coincidence condition is the way search is essential. It is therefore to examine whether this coincidence condition is fulfilled in each case.

The embodiment of an ATM switching device contains only a three-stage switching network. The same applies to, but for four-and beyond multistage switching networks.

In the drawing, inter alia, an ATM intermediate line allocation memory is now shown, which consists of the memory sections X1 to xk and y to Yn. Using this assignment memory between line individually each still available to them free bit rate transmission capabilities are stored for the ATM intermediate lines of the switching matrix K. These stored capacity are used for the test has been described above, in which the admissibility of establishing new virtual connections with respect to each derfürsie eligible ATM intermediate lines with reference to the time laid down for that new virtual connections bit rate limit values ​​and on the basis of the respective ATM intermediate lines will each still available free bit rate transmission capacity tested.

It is now provided that the virtual connections to an unlimited number of different possible bit rate limits in contrast, significantly fewer, relating to size ranges of the bit rate limit values ​​connection bit rate classes are summarized. The virtual connections are indeed requested by subscribers using the votes of them dial information first. The desired of them bit rate limit values ​​are individual subscriber. It follows that the number of different possible bit rate limits initially is naturally unlimited. Participants can - as far as their respective terminal technically allows this - choose freely with which the average bit rate and peak bit rate which they intend to send.

Meeting now at the request of a new virtual connection by the subscriber signaling (dial) the freely chosen or determined by the respective existing terminal from the subscriber bit rate limit values, as they are first size ranges of the bit rate limit values ​​assigned. This applies to the average bit rate and the peak bit rate. The relation between the average bit rate and peak bit rate is not fixed. It can be specified connection requests, in which the subscriber in question would send very steadily. In this case, as supplied to peak bit rate is not at all or only slightly higher than the average bit rate indicated by him. In the opposite case, there may be connection requests, where a participant intends to send only sporadically during the existence of his desired virtual connection. In this case it is only a relatively low average bit rate, whereas the time taken up by him peak bit rate may be very much higher. The arguments presented by the participants bit rate limit values ​​are now assigned so specified size ranges of the bit rate values. These size ranges relate both to the limits of the average bit rate and the limits of the peak bit rate.

There are now connection bit rate classes formed, which are characterized by different size ranges of the bit rate limit values. A connection bit rate class is characterized by a size range with respect to the average bit rate and by another size range with respect to the peak bit rate. The various connection bit rate classes may be partially characterized by equal size ranges with respect to the average bit rate and by various size range with respect to the peak bit rate - and vice versa.

In the manner described above, differing from each other by the size ranges of the bit rate limit values ​​connection bit rate classes are numbered expedient. By numbering a connection Bitratenkiasse ie the respective size range of the bit rate limit as regards medium bit rate and the size range of the bit rate limit in terms of peak bit rate are specified.

Should a subscriber to the subscriber station T to establish a virtual connection, it is other than the usual dial information among others, the bit rate limits to medium bit rate and peak bit rate with respect to the relevant switch down from. These limits are, for example, may be included in a subscriber line circuit R and forwarded from there to a central processor P, the verbindingsindividuell controls the establishment of virtual connections and for this purpose per desired virtual connection receives the two said bit rate limit values, among other things, and initially stores.

In like manner, the respective still available on the ATM intermediate lines free transmission capacity in transmission bit rate classes are combined with corresponding transmission bit rate limit values. The ATM intermediate lines have indeed each a specific maximum transfer capacity. By already furnished via an ATM intermediate line virtual connections a part of the transmission capacity of the ATM intermediate line concerned is already claimed. When setting up a new virtual connection can then only the remaining free transmission capacity be availed. Only this is therefore still available for setting up new virtual connection. This applies in general, so from the point of consideration of peak bit rates and / orof average bitrates. - For the detection of per ATM intermediate line free transmission capacity in transmission bit rate classes with corresponding transmission bit rate limits the ATM intermediate line allocation memory which is hereinafter referred to merely as "routing memory" means used. It consists of the memory sections X1 to xk and y1 to yn. The ATM intermediate lines within the matrix K form ATM intermediate line groups. An ATM intermediate line group is always each made of a coupling element or leads towards such a. Such ATM intermediate line group consists for example of the ATM intermediate lines z111 to z11m. It is based on the coupling element v11. Another ATM intermediate line group consists for example of the ATM intermediate lines Z132 to ZM32. It leads toward the ATM switching element v32. The same applies to all other ATM intermediate lines in the switching matrix K.

On the output side are connected to a conventional manner to the coupling elements to v31 v3n ATM interconnections and corresponding subscriber lines in. This lead to other ATM switches. Shown, only two solcherATM interconnection lines G1 and G2.

In the routing memory is now per ATM intermediate line group, for example z111 to z11m, a group of memory elements lines, eg x11 to x18, provided. A respective storage elements line, eg x11 is assigned one of the transmission bit rate classes. The size of the crowd so do not depend on the number of ATM intermediate lines in an ATM intermediate line group, but according to the number of transmission bit rate classes that are provided at all.

As can be seen from the drawing, the memory elements are lines X11 to xk8 and y11 to yn8 divided into columns 111-11 m and 131 to m31. A memory element (memory) is part of a memory row elements, is at the same time in each case also to a particular column, for example, 111th

Within each storage elements line, including x11, the individual memory elements (one memory element per column) assigned to the to the respective ATM coupling element, eg v11, connected ATM intermediate lines, including z111 to z11m individually. These storage elements are binary signifizierbar, that they may take one to logic zero and the logic value. Thus they indicate the availability of information presented on this ATM intermediate lines transmission capacity with respect to the respective transmission bit rate class. This may be characterized signifies that the respective storage element transmits the logic one. Thus, it is for the assigned ATM intermediate line, including z111, the yes z. B. 111 associated column, at that on this ATM intermediate line transmission capacity for the respective transmission bit rate class is still available.

As already mentioned, corresponds to a memory row elements of a transmission bit rate class. This bit rate class can - as has been also explained above - be characterized by two bit rate limit values ​​(of the above size ranges), of which the average rate of a bit and relates to the peak bit rate. By signification therefore is for a particular ATM intermediate line (equivalent of a column) indicates whether transmission capacity at this ATM Zwi rule line still is available with regard to the respective transmission bit rate class, which is characterized by certain size ranges of the bit rate limit values, said bit rate limit values ​​(as already indicated) on the one hand on the average bit rate and on the other hand refer to the peak bit rate.

Will now be given of a subscriber via his subscriber station T of the order to set up a new virtual connection, so has this order except the target information (such as directory number) and information about the desired average bit rate and peak bit rate overthe. Based on this information the desired virtual connection is assigned in accordance with the bit rate limit values ​​his or her size ranges (on average bit rate and peak bit rate); the desired compound is thus assigned to a specific connection bit rate class. For this purpose, the said details of the subscriber line circuit R are supplied to a processor P, which performs, inter alia, these assignments. This processor also receives the destination information (selection information), due to which it directs the device to the desired virtual connection via an interface device E in the ATM switch in the way. This is done in a conventional manner. However, in the way search itself, the processor is going on in the inventive manner.

It is now assumed that the target information (such as long-distance digit plus the area code plus subscriber number) results in a virtual connection is set up via the coupling element v32. It should be assumed that the participants dial the participant is at the subscriber station T. The desired virtual connection is thus among other via the coupling element set v11. The task now is to find a suitable way via the switching network. Hierfürkommen the intermediate line groups z111 to z11m and Z132 to ZM32 in question. A piece of information about the processor from the routing device L, which has the task of finding a suitable free way to find and fix. In that regard, is now available through the information that the routing device L has received already, that a correspondingly clear path in the intermediate line group z111 to z11m one hand and Z132 is to seek to ZM32. These two intermediate line groups corresponding to the two memory parts x1 and y2.

The routing device L controls with the help of their readers Lx and Ly to the memory parts x1 and y1. The processor divides the reading means L also the bit rate class which is the authoritative for the desired virtual connection. On the basis of information about the bit rate class, the route search means L now controlled with the help of their reading means Lx and Ly within the memory parts x1 and y2 those storage elements within these memory line parts that are associated with the bit rate class. The routing means L now searches within the two storage elements rows among those ATM intermediate lines a freely made, which are signified as regards the succession of columns 111 to 11m and 131 coincident to m32 by logic. 1 Of course, the above two logical values ​​are also interchangeable.

The two reading devices Lx and Ly read thus in the respective two memory lines from left to right one column at progressively the contents of each storage elements, in the same memory element for storage element in each of the two memory elements line. In one such Absuchreihenfolge one speaks of a solid with a zero position. Equally also can be used such proceeds or zufallsmä- larly or otherwise changing zeroing. - Once the routing device L is simultaneously receiving each a logical one on its two reading means Lx and Ly, of this is obvious to you that when the two ATM intermediate lines in question each have transmission capacity for the desired bit rate class-free and thus for setting up a new virtual connection is available.

As stated, guaranteed bit rate category concerned that an average bit rate and a peak bit rate can be transmitted via the respective virtual connection that corresponds to the size ranges of the bit rate limit values. It is therefore on the basis of relevant for each setting up new virtual connection bitrate limit or the relevant bit rate limit values ​​(coming expressed by the relevant bit rate class) visited a store elements row whose assigned transmission bit rate class these two bitrate limits and thus provide the desired rate class corresponds in terms of transmission capacity required for the new virtual connection.

Within the relevant memory elements line is one of those intermediate lines whose storage elements are signified selected. This is done for a search for ways provided, the aforementioned selection mode. This may provide that a selection mitfestem zero and constant Absuchreihenfolge comes to fruition. However, other selection modes come into play, for example, with no fixed zero position and / or with non-solid Absuchreihenfolge.

According to the invention in the manner described above in the different switching stages-unequal ATM intermediate line groups corresponding to the candidate storage elements line by line a selection of ATM intermediate lines in response to said coincidence exists within these memory elements lines for mutually corresponding memory elements with respect to their signification. Corresponding memory elements are those that are in the same column, for example, 112 and 231st

The description herein refers to switching networks with stretched grouping terms. When applying the invention in a field with a coupling reversal grouping comprising switching device same shall apply mutatis mutandis.

It has already been noted that the switching network can also be constructed with more than three switching stages. Correspondingly, then the route search is to make, in the inventive way a coincidence education is provided not only between two signifizierten memory elements but between correspondingly more memory elements. Further, the connection bit rate classes and the transmission bit rate classes can be specified instead of in accordance with two limit values ​​(average bit rate and peak bit rate) and in accordance with one or more thresholds.

In the present case (z. B. x1, y1) of eight different memory elements rows are provided per storage part. These correspond to eight connection bit rate classes and eight transmission bit rate classes. These can be characterized by two different size ranges in terms of peak bit rates and four different size ranges in mean bit rates.

The operation of the processor P includes including the writing of Signifizierungen in the individual storage elements of the storage elements for each row of the ATM intermediate lines. For this purpose, starting from the load current state aufeinerATM-Zwischenieitung determined each still free, available for new virtual connections transmission capacity. Then, in those memory elements rows corresponding to transmission bit rate classes with the determined transmission capacity and smaller transmission capacity and the corresponding end transmission bit rate limit values ​​are assigned, signifies the memory element for the respective ATM intermediate line. If eg the still free transmission capacity determined on the ATM intermediate line z112, the writer first P1 on the storage part (x1) is set in connection herewith, the associated z112 the ATM intermediate line. Is that still free, so available for new virtual connections transmission capacity has been determined with respect to the ATM intermediate line z112, writes the writer P1 into the ATM intermediate line corresponding column z112 112 partly logic zeros and partly logical ones a. Here logical ones are written into the storage elements of all those storage elements lines, which transmission bit rate classes are assigned for the transmission capacity on the ATM intermediate line z112 is still plentiful and available. This is subsequently explained in somewhat more detail.

The processor forms and stores in a further memory area for each ATM intermediate line with respect to all of these established connections on the one hand the sum of the mean bit rates of these compounds and on the other hand, a product sum, in which the individual products in each case from the average bit rate and the difference between the peak bit rate and the average bit rate of the virtual connections are formed, ie, the products are formed for individual connections. This particular memory range can for example part of a column, for example 112, in a memory part, for example x1, be. This particular memory area will thus be assigned to the ATM intermediate line z112.

When setting up a new virtual connection, and when picked up one in courts virtual connection and the sum of the products sum of the processor P makes new. This can be done in such a way that the occupancy situation each changing virtual connection the average bit rate and the product of this virtual connection corresponding be used to increase the said sum and the said products sum or smaller, ie, at each date bring.

As already pointed out, the central processor for each ATM intermediate line on the basis of the mean bit rate and peak bit rates of the established already have this intermediate line virtual circuits determined on the basis of average bit rate and peak bit rate of each of the transmission bit rate classes, if in each case at least one new virtual connection the corresponding one of the respective transmission bit rate class connection bit rate class can be established. These arithmetic operations are carried out in time to the way search operations by the processor. Thereby, the path search processes are both very defused with respect to their temporal urgency and simplified, in that they are reduced to simple one-bit compare operations. In particular, however it affects respect is very positive that the calculation operations may be limited to those ATM intermediate lines currently directly affected by the setting or triggering of a virtual connection.

Thus, the processor calculates for each ATM intermediate line, has in itself changed in the assignment situation somewhat (ie not only when setting up a new virtual connection, but in the mutatis mutandis appropriate manner after each trigger such) successively the possibilities of virtual connections in the various rate classes by. Here he sets based on the average bit rate and the peak bit rate of each of the established already this ATM intermediate line virtual connections. Appropriately, he used this sum and product sum already formed. Starting from medium bit rate and peak rate of each of the possible transmission bit rate classes the processor calculates whether each at least one new virtual connection corresponding to the respective transmission bit rate class rate class in terms of transmission capacity Outfitted Are still available may. For this purpose, it pulls both the products mentioned sum and said sum of the mean bit rates for the established virtual connections zoom and added to the product sum and the sum of the mean bit rates, also the corresponding product and the corresponding average bit rate for a virtual connection of the various rate classes. Thus, the processor forms a product sum and a sum of the average bit rates for the in courts virtual connections and for a virtual connection of the various rate classes. This is handled by the processor per rate class. He then forms the products sum thus obtained a square root value and multiplies it by a magnification factor. It then adds to this, the sum of the mean bit rates and thus forms a comparison value, that is the result of this addition. Now, if this comparison value does not exceed the maximum transmission bit rate of the possible ATM intermediate line in the memory line corresponding to the respective transmission bit rate class, this ATM intermediate line is signified, that is, it is written a logic one. In the other case a logic zero is written.

It should also be drawn to the comparator V. This is used for performing the coincidence check already described. With its help is so determined that corresponding intermediate lines are signified coincident.

It has already been referred to the European Patent Application 90122430.3. Herein is described, inter alia, that the comparison process described can also be modified. This naturally also applies when using the content of this prior application in the case of the present invention. So it is also possible that the processor said comparative value for about clarified. Accordingly, it is provided that it selects from the peak bit rates of already established over the respective ATM intermediate line virtual connections, the largest peak bit rate and the amount of which adds even the comparison value and then performs the comparison described.

Earlier a magnification factor has been mentioned, to be subsequently explained in somewhat more detail. the case does not occur with a high degree of probability that bit rates occur on an ATM line in practical operation to such an extent that the transmission capacity of an ATM line is exceeded. It is assumed that this probability with 10-⁹ is required. Essentially resulted from this exponent (- 9) the size of the enlargement factor. This is at a probability (the so enters a loss of cells) of 10-⁹ until 10-¹⁰ about 8 to 9. boundary conditions here are that a) an ATM line with a gross transport capacity ( "gross" means including the header of the ATM cells) of about 150 Mbit / s is operated, b) the peak bit rates of virtual connections managed this ATM line, not exceed 2 Mbit / s and c) is the ratio of average bit rate to peak bit rate at each of the connections between 0.1 and 0.9.

Finally it should be noted that the switching device described above can be modified to also, on the one hand, instead of an ATM intermediate line allocation memory (routing memory) forthe ATM intermediate line groups, a number of ATM intermediate line groups provided corresponding number of ATM intermediate line occupancy Save may be, which are controlled in parallel in the route search described above, and the above-described functions of the route search device L can also be implemented by the processor P on the other hand.