CA2008648C - Method for transmitting, via a plurality of asynchronously time-divided transmission channels, a flow of data cells, the state of a counter for each transmission channel being kept up to date in accordance with the number of data cells per unit of time - Google Patents
Method for transmitting, via a plurality of asynchronously time-divided transmission channels, a flow of data cells, the state of a counter for each transmission channel being kept up to date in accordance with the number of data cells per unit of timeInfo
- Publication number
- CA2008648C CA2008648C CA002008648A CA2008648A CA2008648C CA 2008648 C CA2008648 C CA 2008648C CA 002008648 A CA002008648 A CA 002008648A CA 2008648 A CA2008648 A CA 2008648A CA 2008648 C CA2008648 C CA 2008648C
- Authority
- CA
- Canada
- Prior art keywords
- data cell
- counter
- channel
- arrival
- state
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
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Classifications
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L12/00—Data switching networks
- H04L12/54—Store-and-forward switching systems
- H04L12/56—Packet switching systems
- H04L12/5601—Transfer mode dependent, e.g. ATM
- H04L12/5602—Bandwidth control in ATM Networks, e.g. leaky bucket
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L45/00—Routing or path finding of packets in data switching networks
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L12/00—Data switching networks
- H04L12/54—Store-and-forward switching systems
- H04L12/56—Packet switching systems
- H04L12/5601—Transfer mode dependent, e.g. ATM
- H04L2012/5629—Admission control
- H04L2012/5631—Resource management and allocation
- H04L2012/5636—Monitoring or policing, e.g. compliance with allocated rate, corrective actions
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L12/00—Data switching networks
- H04L12/54—Store-and-forward switching systems
- H04L12/56—Packet switching systems
- H04L12/5601—Transfer mode dependent, e.g. ATM
- H04L2012/5629—Admission control
- H04L2012/5631—Resource management and allocation
- H04L2012/5636—Monitoring or policing, e.g. compliance with allocated rate, corrective actions
- H04L2012/5637—Leaky Buckets
Abstract
ABSTRACT
The flow of data cells through a transmission medium with a number of virtual, asynchronously time-divided transmission channels is protected against excessive crowding of data cells in any channel, by means of a counter for each channel and the recording of the time of arrival of data cells in each channel.
At the arrival of each data cell the counter is decreased by a value which is a function of the length of time between the moment of arrival of that data cell and the moment of arrival of a preceding data cell with the same channel designation. The state of the counter is compared with a threshold value and the data cell will be switched through to the downstream portion of the channel if the counter value does not exceed the threshold value.
If the data cell is switched through, the counter is increased with a constant value.
The flow of data cells through a transmission medium with a number of virtual, asynchronously time-divided transmission channels is protected against excessive crowding of data cells in any channel, by means of a counter for each channel and the recording of the time of arrival of data cells in each channel.
At the arrival of each data cell the counter is decreased by a value which is a function of the length of time between the moment of arrival of that data cell and the moment of arrival of a preceding data cell with the same channel designation. The state of the counter is compared with a threshold value and the data cell will be switched through to the downstream portion of the channel if the counter value does not exceed the threshold value.
If the data cell is switched through, the counter is increased with a constant value.
Description
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Method for transmitting, via a plurality of asynchronously time-divided transmission channels, a flow of data cells, , the state of a counter for each transmission channel being - kept up to date in accordance with the number of data -i cells per unit of time : ~, A ~ackground of the lnventlon 1 Field of the invention j The invention relates to a method for transmitting, .jl ~, via a transmisslon médium with a plurality of vlrtual, - asynchronousl~ tlme-divlded transmission channels, a ;' flow of data supplied to that transmi~sion medlum, and conslstlng of data cells which are each transmitted via one of those transmission channels, and each of which comprlses a group of control words wlth one or more control words as well as a group of information words with one or more information words, the group of control .-, words comprising a control word with a channel indication, ~ indlcating via which transmi~sion channel the relevant ; data cell has to be transmitted, and the state of a counter being kept up to date for each tran~mission channel, which ~tate has a certain fixed minimum value, and which is on the one hand decreased proportional to the time, and whlch 18 on the other hand lncrea~ed proportlonal to the number of data cell~ wlth a ohannel ;~ lndloatlon, lndlcatlng ald transmlo~lon channel, whlch ~ state of the counter 1B compared with a threshold i~3 20 value, when a data cell with a channel lndicatlon, i~ lndlcatlng ~aid transmission channel, arrives at the beginning of the trans dssion medium at a certain moment of arrival, after whlch the data cell will be let through to the transmission medium located downstream, when the .~
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Method for transmitting, via a plurality of asynchronously time-divided transmission channels, a flow of data cells, , the state of a counter for each transmission channel being - kept up to date in accordance with the number of data -i cells per unit of time : ~, A ~ackground of the lnventlon 1 Field of the invention j The invention relates to a method for transmitting, .jl ~, via a transmisslon médium with a plurality of vlrtual, - asynchronousl~ tlme-divlded transmission channels, a ;' flow of data supplied to that transmi~sion medlum, and conslstlng of data cells which are each transmitted via one of those transmission channels, and each of which comprlses a group of control words wlth one or more control words as well as a group of information words with one or more information words, the group of control .-, words comprising a control word with a channel indication, ~ indlcating via which transmi~sion channel the relevant ; data cell has to be transmitted, and the state of a counter being kept up to date for each tran~mission channel, which ~tate has a certain fixed minimum value, and which is on the one hand decreased proportional to the time, and whlch 18 on the other hand lncrea~ed proportlonal to the number of data cell~ wlth a ohannel ;~ lndloatlon, lndlcatlng ald transmlo~lon channel, whlch ~ state of the counter 1B compared with a threshold i~3 20 value, when a data cell with a channel lndicatlon, i~ lndlcatlng ~aid transmission channel, arrives at the beginning of the trans dssion medium at a certain moment of arrival, after whlch the data cell will be let through to the transmission medium located downstream, when the .~
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state of the counter i8 leBs than said threshold value, or it will hOt be let through to the transmission medium located downstream, when the state of the counter i8 ~ more than or equal to sald threshold value.
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2. Problems The above-mentioned, rather new method of data transmission - generally named ATM (= Asynchronous Transfer Mode) - which is particularly ln the making for wlde band ISDN, is applied in quick packet switched networks, in which the information i~ ¢ontained in packets, called (data1 cells, each consisting of one or more informatlon words, and comprising not only those information words, but also a D header~ with (inter alia) a control word indicating the transmission channel via which the cell has to be transmitted to its destination.
The transmission means and the switching means can have a capacity in the range of some Mbit/s up to many Gbit/s. The ATM-technigue enables the network admlnistrator to distribute the available capacity in an extremely flexible way.
A user could, however, try to supply a larger flow of cells to the network than the ¢apa¢ity allo¢ated to him permits. Just because of the flexibility of the ATM-technique this does not yet need to lead immediately to problems at the entrance of the network; an overload can, however, occur somewhere else on the route ln the network due to which also the trafflc of other users could be dl~turbed. In order to avoid su¢h a situation it will be ne¢essary to monitor the entranoe, thus preventing the passage of ¢ells of a ¢ertain u~er whi¢h ex¢eed the ¢apa¢ity allo¢ated to him.
In reference (1) the monitoring of the entran¢e of ATM-networks is dls¢ussed by ¢onsidering two ¢on¢epts, whi¢h are both based on a method whi¢h is known under the name of n leaky bucket~ method or ~leaky integrator~ method.
.
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According to thi~ method the ~tate of a counter i6 kept up to date (with a certain minimum value), which state is on the one hand decreased by a first constant value at set times and on the other hand increased by a second constant value whenever a data cell arrives. Subsequently the state of the counter is compared with a threshold value, after which the relevant data cell will be transmitted only if the state of the coùnter is less than that threshold value. Both the long-term average of the number of cells per unit of time as well as the number of cells which may be transmitted (during a short :;
time) above that average (for example the number of cells which may be supplied immediately following one another) can be monitored by a mechanism of the afore6aid type. Only those data cells which do not exceed the maxima set will be transmitted.
In the aforesaid reference it is suggested to provide a "leaky bucket" device as described above for each network user (in other words, for each virtual ~ 20 transmission channel). The advantage of this is that ;;3 each transmisslon channel will be monitored. A great practical problem i~, however, that slnce the number of virtual transmission channels can be very large, e.g.
2~ 65,5361, the nùmber of monitoring devices has to , 25 be egually large, which i~ from a technical and commercial point of view very unattractive.
~d3 In sald reference lt i8 al~o suggested to provlde for the whole group of network u~ers (ln other words, for the whole group of vlrtual transmi~sion ohannels) a monitoring device as mentloned above for monitorlng the ~olnt users as a group. The advantage of thls 18 that a much smaller number of monitoring device~ have to be provlded, but the dlsadvantage is that the various transmi~sion channels cannot be monitored individually, which causes lnter `~ 35 alla the problem that when the maximally allowed cell freguency is exceeded, it cannot be determined which of ': '.',~.
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; 4 the various users is responsible for this, and consequently of which user the transmission of data cells has to be refused.
B. Summary of the invontlon s The invention provides a method for transmitting via a transmission medium with a plurality of virtual, asynchronously time-divided transmission channels a flow of data supplied to that transmission medium, and more in particular a method for protecting said transmission channels agalnst an exceeding of the respective cell freguencies maximally allowed for said transmission channels, based on the ~leaky bucket~ entrance monitoring method, in whi¢h the aforesaid drawbacks of the methods hitherto suggested for this purpose are outweighed.
According to the invention the state of the counter will be decreased on the arrival of a data cell by a value which is a function of the length of time between the ~ moment of arrival of that data cell and the moment of i~ arrival of a certain preceding data cell with the same channel indication.
The method according to the invention is first of all based on the understandlng that the tlme-dlvlded transmission of data cells also renders it possible to use a monitoring device protecting the transmission channels agalnst an exceeding of the maxlmally allowed (average) oell frequency, in a tlme-divided way. Owlng to thls lt wlll ln prlnclple be pos~lble to monitor all ;; the transmlsslon channels individually by mean~ of only ~ one such a monitoring devioe. Moreover, the method ~~ 30 according to the invention is based on the understanding that the state of the counter for each channel can be brought up to date in a time divlded way only if the decrease of the state of the counter does not take place at set consecutive times (and always with a constant .~
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2008~48 value) as accordlng to the usual way of carrying out the ~leaky bucket~-method, but only at those moments when a data cell arrives at the beginnlng of the transmission medium. According to the invention the ~tate of the counter is not decreased by a constant value at those moments, but by a value which is a function of the time which has passed since the moment of arrival of a certain - data cell preceding the aforesaid (arriving) data cell with an equal channel indication (which consequently makes use of the same transmission channel as the said last arrived data cell). So the decrease of the state of the counter takes place under the same time regime as the - arrival of the data ¢ells at the beginning of the transmisslon medium, which 18 in contrast with what was known 80 far. Also the increase of the state of the counter, the comparison of the state of the counter with a threshold value and the switching through or not, dependent on the re~ult of the comparison, of data cells to the transmis~ion medium located downstream, take place under that same time regime. Thus the monitoring device `~ can function synchronously with the successively arriving data cells in a completely time-divided way, due to which all the virtual channels can be monitored by means of only that one monitoring device.
The value by which the state of the counter is decreased on the arrival of a data cell is preferably the product of a first constant value and the length of time between the moment Or arrlval of that data oell and the moment Or arrival Or a preoedlng data cell with the same channel in~icatlon.
In a further working-out of the invention a choice can be made from a number of options. For example, as said preceding data cell can be chosen the data cell ~, which precedes the former data cell a number of N data :~ 35 cells arrived at the beginning of the tran~mission~ medium, or the data cell which precedes the former data .
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- 20086~8 cell a number of N data cells let through to the transmission medium located downstream. So in the first case all the data cells whlch have arrived are counted and ln the second case only those data cells which had been let through, in which cases N preferably has the value 1, which implies that said preceding data cell is the last data cell which has arrived but one or the last data cell which ha~ been let through but one, but if desired, N can have a greater value.
The state of the counter can, according to an embodi-ment, be increased by a second constant value preceding the comparison of the state of the counter with the threshold value, in which case after that comparison the state of the counter wlll be decreased again by that second constant value, if the state of the counter turned out to be more than the threshold value. So the second constant value will be subtracted again from the d state of the counter, if the relevant data cell is not let through. According to a preferred embodiment, however, the state of the ¢ounter, after having been compared .. j with the threshold value, wlll be increased by a second .~ constant value only if on that comparison the state of the counter is less than the threshold value. Compared with the preceding embodiment the advantage achieved in this way is that the state of the counter will be increased only if the relevant data cell is let through;
in the preceding embodiment the state of the counter was increased in all the cases, which increase was nullified ~ again ln oa~e the data cell oould not be let through, ;~ 30 which takes more prooesslng tlme than ln the case of the embodlment ~ust mentloned.
; According to a further preferred embodiment of the invention the variables: the last state of the counter but one and the moment of arrival of said preceding data ~i~ 35 cell related to the relevant channel indication have been recorded and they will be read out under the control ,, :"
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of said channel indication on the arrivel of a data . cell, and when the state of the counter ha~ been brought ;' up to date, said variables will moreover be replaced by ~, the updated state of the counter and the moment of arrival of the last arrived data cell, on the understanding, however, that if the data cell i8 not let through (viz. in case the updated state of the counter iB more than the threshold value), a choice can be made either not to replace the last state of the counter but one and the moment of arrival (in which case t.he last values but one remain unchanged) or to replace them; in that latter case the last state of the counter but one wlll be replaced by the state of the counter which ie decrea~ed in the above-mentioned way (the increase has either been nullified or not been carried out because of ~ the fact that the data cell has not been let through -;~ vide the preceding paragraph) and the last moment of ,~ arrival. If the maxlmally allowed average cell frequency, and the maximum spread in cell frequency of all the `~ 20 virtual transmission channels is the same, the first ;.~4 constant value, the second constant value and the threshold value can have been recorded as fixed parameters in the monitoring device. If it is, however, desirable to be able to set for each virtual transmission channel the maximum value for the average cell frequency and/or for the spread in cell frequency (which is preferably the case), said parameters or part of them will, accordlng ~; to a preferred embodiment of the invention, be recorded, related to the relevant channel indication, ~ust like the variables mentioned hereinbefore, and they will be read out under the control of said channel indication on the arrival of a data cell. Preceding the putting into use of the relevant transmission channel the respective channel-specific parameter-values are recorded in the ^~` 35 monitoring device. So with thi~ preferred embodiment it is achieved that whenever a data cell arrives, the state .:
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of the counter of the virtual transmission channel indicated by the channel indication of that data cell will be brought up to date in conformity with the parameters recorded for that channel.
Since said parameters, the first constant value, the second constant value and the threshold value can be increased or decreased proportionally, whereas the working remains unchanged, they are preferably chosen in such a way that the first constant value is equal to 1 or to some other power of 2. If the first constant value is equal to 1, said product by which the state of the counter will be decreased on the arrival of a data cell will be equal to said length of time between the respective data cells, and a ~ultlplication can in fact be dispensed with. If as a first -~ constant value for the respective transmission channels different values are desirable, different powers of 2 will preferably always ,*
be chosen for these values, due to which said product can always ~:~ be obtained in a si~ple way by means of bit shifting.
Besides the above-mentioned parameters also the re~olution with which the respective moments of arrival of the data cells are registered can be set in conformity with the other parameters. Consequently, a low resolution will preferably be chosen for channels with a low maximally allowed cell frequency;
~ in other words, the respective moments are registered with ,~ relatively large discrete time steps. Likewise a high resolution will preferably be chosen for channels with a high cell frequency ~ allowed; because of that high frequency the respective moments are ",r~,, then measured and recorded in small discrete units of time.
~; The present invention provides not only the method indicated hereinabove, but also a device for carrying out that method. Such a device according to the invention comprises first storage means for storing, channel by channel, the last counter value, second storage means for storing, channel by channel, the moment of arrival of a preceding data cell, time lndicating means for determining the moment of arrival of each arriving data cell, computing means for decreasing, after the arrival of such data cell, the counter value of the channel as indicated by the channel indication of that arriving data cell, that counter value being .~ , :
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~ 2008648 read out from said first storage means, by a value which is a function of the calculated length of time between the moment of arrival of said arriving data cell, that moment being determined by said time indicating means, and the moment of arrival of a preceding data cell of the same channel as that arriving data cell, that moment being read out from said second storage means, said comparing means comparing said decreased counter value with said threshold value, stored in said threshold means, said swltchlng means ~witching through said data cell to the transmission medium located downstream, when the decreased counter ~ value ls less than sald threshold value.
.~ C. References l] Kowalk, H.; Lehnert, R.
The ~policlng functionN to control user access in ATH
networks-definition and implementation.
ISSLS 88 5 The International Symposium on Subscriber Loops and Services, Proc., IEEE, pp. 240-5, Sept. 1988.
~;: D. Embodi~ents 1. Flgures Figure 1 shows a dlagrammatic representation of an embodiment of a monitoring device according to the invention, in which the method according to the invention has been carried out.
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200~648 D. De~arl~tlon The monitoring device shown in figure I comprises a read-out device 1, a switching device 2, six storage devices 3, S, 7, 9, 12, 14, a time-indicatlng device 4 and a processor, consisting of five computers 6, 8, 10, 11, 15 and a conparison device 13.
Data cells comprising a control word group and an information word group arrive one after the other at an input terminal A of the monitoring device where a read-~ 10 out device 1 is located, which derives the channel 3 number from the control word group. The data cell itself is transmitted on to the switching device 2, where the ~? data cell will be temporarily stored until a decision is made as to whether that data cell can or cannot be let lS through to an output terminal ~ of the switching device 2 to which a transmission network (not shown in the figure) located downstream is connected.
An index is derived from the channel number and by means of that index the storage devices 3, 5, 7, 9, 12, 14 provide the parameters which are speciflc for the relevant channel. The first storage device 3 provides an indication of the resolution with which the time has to be determined by the time indicatlng device 4. The second storage devlce 5 provldes an lndlcatlon for the moment when the last data cell but one wlth the same channel number was let through to the network located ~ downstream by the monitorlng devl¢e. 8ubsequently lt 18 ;~ determined by means of the flr8t oomputer 6 how much tlme has passed between the la8t arrlved data cell (moment tl) and the last data cell but one with the same channel lndicatlon (moment t2).
The second computer 8 multlplles the time passed (~t) by a flrst con~tant value (Cl) provlded by the thlrd ~torage devlce 7. If, however, the flrst constant value (Cl) is chosen egual to 1, the third storage devlce 7 and the second computer 8 can be dispensed wlth. If as . :::~ .
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. ... ,: , . ~ , 2~086~8 . 1 1 , re6pective first con6tant values for the various channels -' only powers of 2 are taken, the multiplication can be ', carried out in a simple way as a bit shift in a shift register.
'~, 5 The value obtained in the aforesaid way i8 subtracted by the third ¢omputer 10 from a value (state of the counter) which is stored for the relevant channel number ,c in the fourth storage device 9. The fourth computer 11 -,~, sees to it that the resulting value will not be less ~,~ 10 than a certain minimum value (e.g.0).
,"~ The result obtained from the above is compared by the ',~ comparison device 13 with a threshold value provided by the fifth storage device 12.
,~ If the comparison device comes to the conclusion that ',,~ lS the result is smaller than the threshold value, the ,~ following actions will be carried out:
- The switching device 2 receives an order to let the ~"~, relevant data cell pass - via its output terminal B -;, to the transmission network located downstream.
, 1 20 - The fifth computer 15 adds a second constant value provided by the sixth storage device 14 for the relevant chann,el number to the result obtalned before , from the fourth computer 11.
,~ - The result obtalned from the flfth computer 15 is recorded ln the fourth storage device 9, in which case the former value in this storage device 9 is ~" overwritten.
- The moment tl determined before is recorded ln the ',' second storage device 5, ln whlch ca~e the former ,', 30 value ln thls storage devlce 5 is overwritten.
`, If the comparison device 13 comes to the conclu6ion ,'i that the result is greater than or egual to the threshold '' value, the following actions will be carrled out:
~' - The switching device-2 receives the order not to let '''$' 35 the relevant data cell pass to the network located :: .:
~ downstream. In many implementations of networks it is . ."
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";' , ' : '. ' '' 200864g required in such a case that the place which hag become vacant iB replaced by a certain bit pattern, which indicates for example an empty data cell; this bit pattern will then be transmitted instead of the S relevant data cell by the switching device 2 via its output terminal B.
In the simplest embodlment it 18 not necessary to ; record in the fourth storage device 9 (~tate of the counter) and in the second storage device 5 (moment t2); the values already recorded in the store are maintained.
~;~ At the initialization of the monitoring device respectively of a transmission channel the first storage ~;~ device 3, the third storage device 7, the fifth storage device 12 and the sixth storage device 14 will be filled from the controlling device (not shown in the figur~) of the network with the parameters specific for the various channel numbers, ~ust like the initial values (start ~ values) for the variables in the second storage device S
;~ 20 and in the fourth storage device 9. For that purpose said storage devices are provided with a setting means which gives the network control access to the storage means without lnterfering with the actual working of the monitorlng circuit.
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2. Problems The above-mentioned, rather new method of data transmission - generally named ATM (= Asynchronous Transfer Mode) - which is particularly ln the making for wlde band ISDN, is applied in quick packet switched networks, in which the information i~ ¢ontained in packets, called (data1 cells, each consisting of one or more informatlon words, and comprising not only those information words, but also a D header~ with (inter alia) a control word indicating the transmission channel via which the cell has to be transmitted to its destination.
The transmission means and the switching means can have a capacity in the range of some Mbit/s up to many Gbit/s. The ATM-technigue enables the network admlnistrator to distribute the available capacity in an extremely flexible way.
A user could, however, try to supply a larger flow of cells to the network than the ¢apa¢ity allo¢ated to him permits. Just because of the flexibility of the ATM-technique this does not yet need to lead immediately to problems at the entrance of the network; an overload can, however, occur somewhere else on the route ln the network due to which also the trafflc of other users could be dl~turbed. In order to avoid su¢h a situation it will be ne¢essary to monitor the entranoe, thus preventing the passage of ¢ells of a ¢ertain u~er whi¢h ex¢eed the ¢apa¢ity allo¢ated to him.
In reference (1) the monitoring of the entran¢e of ATM-networks is dls¢ussed by ¢onsidering two ¢on¢epts, whi¢h are both based on a method whi¢h is known under the name of n leaky bucket~ method or ~leaky integrator~ method.
.
'.'`~
According to thi~ method the ~tate of a counter i6 kept up to date (with a certain minimum value), which state is on the one hand decreased by a first constant value at set times and on the other hand increased by a second constant value whenever a data cell arrives. Subsequently the state of the counter is compared with a threshold value, after which the relevant data cell will be transmitted only if the state of the coùnter is less than that threshold value. Both the long-term average of the number of cells per unit of time as well as the number of cells which may be transmitted (during a short :;
time) above that average (for example the number of cells which may be supplied immediately following one another) can be monitored by a mechanism of the afore6aid type. Only those data cells which do not exceed the maxima set will be transmitted.
In the aforesaid reference it is suggested to provide a "leaky bucket" device as described above for each network user (in other words, for each virtual ~ 20 transmission channel). The advantage of this is that ;;3 each transmisslon channel will be monitored. A great practical problem i~, however, that slnce the number of virtual transmission channels can be very large, e.g.
2~ 65,5361, the nùmber of monitoring devices has to , 25 be egually large, which i~ from a technical and commercial point of view very unattractive.
~d3 In sald reference lt i8 al~o suggested to provlde for the whole group of network u~ers (ln other words, for the whole group of vlrtual transmi~sion ohannels) a monitoring device as mentloned above for monitorlng the ~olnt users as a group. The advantage of thls 18 that a much smaller number of monitoring device~ have to be provlded, but the dlsadvantage is that the various transmi~sion channels cannot be monitored individually, which causes lnter `~ 35 alla the problem that when the maximally allowed cell freguency is exceeded, it cannot be determined which of ': '.',~.
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; 4 the various users is responsible for this, and consequently of which user the transmission of data cells has to be refused.
B. Summary of the invontlon s The invention provides a method for transmitting via a transmission medium with a plurality of virtual, asynchronously time-divided transmission channels a flow of data supplied to that transmission medium, and more in particular a method for protecting said transmission channels agalnst an exceeding of the respective cell freguencies maximally allowed for said transmission channels, based on the ~leaky bucket~ entrance monitoring method, in whi¢h the aforesaid drawbacks of the methods hitherto suggested for this purpose are outweighed.
According to the invention the state of the counter will be decreased on the arrival of a data cell by a value which is a function of the length of time between the ~ moment of arrival of that data cell and the moment of i~ arrival of a certain preceding data cell with the same channel indication.
The method according to the invention is first of all based on the understandlng that the tlme-dlvlded transmission of data cells also renders it possible to use a monitoring device protecting the transmission channels agalnst an exceeding of the maxlmally allowed (average) oell frequency, in a tlme-divided way. Owlng to thls lt wlll ln prlnclple be pos~lble to monitor all ;; the transmlsslon channels individually by mean~ of only ~ one such a monitoring devioe. Moreover, the method ~~ 30 according to the invention is based on the understanding that the state of the counter for each channel can be brought up to date in a time divlded way only if the decrease of the state of the counter does not take place at set consecutive times (and always with a constant .~
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2008~48 value) as accordlng to the usual way of carrying out the ~leaky bucket~-method, but only at those moments when a data cell arrives at the beginnlng of the transmission medium. According to the invention the ~tate of the counter is not decreased by a constant value at those moments, but by a value which is a function of the time which has passed since the moment of arrival of a certain - data cell preceding the aforesaid (arriving) data cell with an equal channel indication (which consequently makes use of the same transmission channel as the said last arrived data cell). So the decrease of the state of the counter takes place under the same time regime as the - arrival of the data ¢ells at the beginning of the transmisslon medium, which 18 in contrast with what was known 80 far. Also the increase of the state of the counter, the comparison of the state of the counter with a threshold value and the switching through or not, dependent on the re~ult of the comparison, of data cells to the transmis~ion medium located downstream, take place under that same time regime. Thus the monitoring device `~ can function synchronously with the successively arriving data cells in a completely time-divided way, due to which all the virtual channels can be monitored by means of only that one monitoring device.
The value by which the state of the counter is decreased on the arrival of a data cell is preferably the product of a first constant value and the length of time between the moment Or arrlval of that data oell and the moment Or arrival Or a preoedlng data cell with the same channel in~icatlon.
In a further working-out of the invention a choice can be made from a number of options. For example, as said preceding data cell can be chosen the data cell ~, which precedes the former data cell a number of N data :~ 35 cells arrived at the beginning of the tran~mission~ medium, or the data cell which precedes the former data .
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- 20086~8 cell a number of N data cells let through to the transmission medium located downstream. So in the first case all the data cells whlch have arrived are counted and ln the second case only those data cells which had been let through, in which cases N preferably has the value 1, which implies that said preceding data cell is the last data cell which has arrived but one or the last data cell which ha~ been let through but one, but if desired, N can have a greater value.
The state of the counter can, according to an embodi-ment, be increased by a second constant value preceding the comparison of the state of the counter with the threshold value, in which case after that comparison the state of the counter wlll be decreased again by that second constant value, if the state of the counter turned out to be more than the threshold value. So the second constant value will be subtracted again from the d state of the counter, if the relevant data cell is not let through. According to a preferred embodiment, however, the state of the ¢ounter, after having been compared .. j with the threshold value, wlll be increased by a second .~ constant value only if on that comparison the state of the counter is less than the threshold value. Compared with the preceding embodiment the advantage achieved in this way is that the state of the counter will be increased only if the relevant data cell is let through;
in the preceding embodiment the state of the counter was increased in all the cases, which increase was nullified ~ again ln oa~e the data cell oould not be let through, ;~ 30 which takes more prooesslng tlme than ln the case of the embodlment ~ust mentloned.
; According to a further preferred embodiment of the invention the variables: the last state of the counter but one and the moment of arrival of said preceding data ~i~ 35 cell related to the relevant channel indication have been recorded and they will be read out under the control ,, :"
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of said channel indication on the arrivel of a data . cell, and when the state of the counter ha~ been brought ;' up to date, said variables will moreover be replaced by ~, the updated state of the counter and the moment of arrival of the last arrived data cell, on the understanding, however, that if the data cell i8 not let through (viz. in case the updated state of the counter iB more than the threshold value), a choice can be made either not to replace the last state of the counter but one and the moment of arrival (in which case t.he last values but one remain unchanged) or to replace them; in that latter case the last state of the counter but one wlll be replaced by the state of the counter which ie decrea~ed in the above-mentioned way (the increase has either been nullified or not been carried out because of ~ the fact that the data cell has not been let through -;~ vide the preceding paragraph) and the last moment of ,~ arrival. If the maxlmally allowed average cell frequency, and the maximum spread in cell frequency of all the `~ 20 virtual transmission channels is the same, the first ;.~4 constant value, the second constant value and the threshold value can have been recorded as fixed parameters in the monitoring device. If it is, however, desirable to be able to set for each virtual transmission channel the maximum value for the average cell frequency and/or for the spread in cell frequency (which is preferably the case), said parameters or part of them will, accordlng ~; to a preferred embodiment of the invention, be recorded, related to the relevant channel indication, ~ust like the variables mentioned hereinbefore, and they will be read out under the control of said channel indication on the arrival of a data cell. Preceding the putting into use of the relevant transmission channel the respective channel-specific parameter-values are recorded in the ^~` 35 monitoring device. So with thi~ preferred embodiment it is achieved that whenever a data cell arrives, the state .:
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of the counter of the virtual transmission channel indicated by the channel indication of that data cell will be brought up to date in conformity with the parameters recorded for that channel.
Since said parameters, the first constant value, the second constant value and the threshold value can be increased or decreased proportionally, whereas the working remains unchanged, they are preferably chosen in such a way that the first constant value is equal to 1 or to some other power of 2. If the first constant value is equal to 1, said product by which the state of the counter will be decreased on the arrival of a data cell will be equal to said length of time between the respective data cells, and a ~ultlplication can in fact be dispensed with. If as a first -~ constant value for the respective transmission channels different values are desirable, different powers of 2 will preferably always ,*
be chosen for these values, due to which said product can always ~:~ be obtained in a si~ple way by means of bit shifting.
Besides the above-mentioned parameters also the re~olution with which the respective moments of arrival of the data cells are registered can be set in conformity with the other parameters. Consequently, a low resolution will preferably be chosen for channels with a low maximally allowed cell frequency;
~ in other words, the respective moments are registered with ,~ relatively large discrete time steps. Likewise a high resolution will preferably be chosen for channels with a high cell frequency ~ allowed; because of that high frequency the respective moments are ",r~,, then measured and recorded in small discrete units of time.
~; The present invention provides not only the method indicated hereinabove, but also a device for carrying out that method. Such a device according to the invention comprises first storage means for storing, channel by channel, the last counter value, second storage means for storing, channel by channel, the moment of arrival of a preceding data cell, time lndicating means for determining the moment of arrival of each arriving data cell, computing means for decreasing, after the arrival of such data cell, the counter value of the channel as indicated by the channel indication of that arriving data cell, that counter value being .~ , :
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~ 2008648 read out from said first storage means, by a value which is a function of the calculated length of time between the moment of arrival of said arriving data cell, that moment being determined by said time indicating means, and the moment of arrival of a preceding data cell of the same channel as that arriving data cell, that moment being read out from said second storage means, said comparing means comparing said decreased counter value with said threshold value, stored in said threshold means, said swltchlng means ~witching through said data cell to the transmission medium located downstream, when the decreased counter ~ value ls less than sald threshold value.
.~ C. References l] Kowalk, H.; Lehnert, R.
The ~policlng functionN to control user access in ATH
networks-definition and implementation.
ISSLS 88 5 The International Symposium on Subscriber Loops and Services, Proc., IEEE, pp. 240-5, Sept. 1988.
~;: D. Embodi~ents 1. Flgures Figure 1 shows a dlagrammatic representation of an embodiment of a monitoring device according to the invention, in which the method according to the invention has been carried out.
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200~648 D. De~arl~tlon The monitoring device shown in figure I comprises a read-out device 1, a switching device 2, six storage devices 3, S, 7, 9, 12, 14, a time-indicatlng device 4 and a processor, consisting of five computers 6, 8, 10, 11, 15 and a conparison device 13.
Data cells comprising a control word group and an information word group arrive one after the other at an input terminal A of the monitoring device where a read-~ 10 out device 1 is located, which derives the channel 3 number from the control word group. The data cell itself is transmitted on to the switching device 2, where the ~? data cell will be temporarily stored until a decision is made as to whether that data cell can or cannot be let lS through to an output terminal ~ of the switching device 2 to which a transmission network (not shown in the figure) located downstream is connected.
An index is derived from the channel number and by means of that index the storage devices 3, 5, 7, 9, 12, 14 provide the parameters which are speciflc for the relevant channel. The first storage device 3 provides an indication of the resolution with which the time has to be determined by the time indicatlng device 4. The second storage devlce 5 provldes an lndlcatlon for the moment when the last data cell but one wlth the same channel number was let through to the network located ~ downstream by the monitorlng devl¢e. 8ubsequently lt 18 ;~ determined by means of the flr8t oomputer 6 how much tlme has passed between the la8t arrlved data cell (moment tl) and the last data cell but one with the same channel lndicatlon (moment t2).
The second computer 8 multlplles the time passed (~t) by a flrst con~tant value (Cl) provlded by the thlrd ~torage devlce 7. If, however, the flrst constant value (Cl) is chosen egual to 1, the third storage devlce 7 and the second computer 8 can be dispensed wlth. If as . :::~ .
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. ... ,: , . ~ , 2~086~8 . 1 1 , re6pective first con6tant values for the various channels -' only powers of 2 are taken, the multiplication can be ', carried out in a simple way as a bit shift in a shift register.
'~, 5 The value obtained in the aforesaid way i8 subtracted by the third ¢omputer 10 from a value (state of the counter) which is stored for the relevant channel number ,c in the fourth storage device 9. The fourth computer 11 -,~, sees to it that the resulting value will not be less ~,~ 10 than a certain minimum value (e.g.0).
,"~ The result obtained from the above is compared by the ',~ comparison device 13 with a threshold value provided by the fifth storage device 12.
,~ If the comparison device comes to the conclusion that ',,~ lS the result is smaller than the threshold value, the ,~ following actions will be carried out:
- The switching device 2 receives an order to let the ~"~, relevant data cell pass - via its output terminal B -;, to the transmission network located downstream.
, 1 20 - The fifth computer 15 adds a second constant value provided by the sixth storage device 14 for the relevant chann,el number to the result obtalned before , from the fourth computer 11.
,~ - The result obtalned from the flfth computer 15 is recorded ln the fourth storage device 9, in which case the former value in this storage device 9 is ~" overwritten.
- The moment tl determined before is recorded ln the ',' second storage device 5, ln whlch ca~e the former ,', 30 value ln thls storage devlce 5 is overwritten.
`, If the comparison device 13 comes to the conclu6ion ,'i that the result is greater than or egual to the threshold '' value, the following actions will be carrled out:
~' - The switching device-2 receives the order not to let '''$' 35 the relevant data cell pass to the network located :: .:
~ downstream. In many implementations of networks it is . ."
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";' , ' : '. ' '' 200864g required in such a case that the place which hag become vacant iB replaced by a certain bit pattern, which indicates for example an empty data cell; this bit pattern will then be transmitted instead of the S relevant data cell by the switching device 2 via its output terminal B.
In the simplest embodlment it 18 not necessary to ; record in the fourth storage device 9 (~tate of the counter) and in the second storage device 5 (moment t2); the values already recorded in the store are maintained.
~;~ At the initialization of the monitoring device respectively of a transmission channel the first storage ~;~ device 3, the third storage device 7, the fifth storage device 12 and the sixth storage device 14 will be filled from the controlling device (not shown in the figur~) of the network with the parameters specific for the various channel numbers, ~ust like the initial values (start ~ values) for the variables in the second storage device S
;~ 20 and in the fourth storage device 9. For that purpose said storage devices are provided with a setting means which gives the network control access to the storage means without lnterfering with the actual working of the monitorlng circuit.
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Claims (14)
1. A method for transmitting, via a transmission medium with a plurality of virtual, asynchronously time-divided transmission channels, a flow of data supplied to that transmission medium, and consisting of data cells which are each transmitted via one of those transmission channels, and each of which comprises a group of control words with one or more control words as well as a group of information words with one or more information words, the group of control words comprising a control word with a channel indication indicating via which transmission channel the relevant data cell has to be transmitted, and the state of a counter being kept up to date for each transmission channel, which state has a certain fixed minimum value, and which is on the one hand decreased proportional to the time, and which is on the other hand increased proportional to the number of data cells with a channel indication, indicating said transmission channel, which state of the counter is compared with a threshold value, when a data cell with a channel indication indicating said transmission channel arrives at the beginning of the transmission medium at a certain moment of arrival, after which the data cell will be let through to the transmission medium located downstream, when the state of the counter is less than said threshold value, or it will not be let through to the transmission medium located downstream, when the state of the counter is more than or equal to said threshold value, characterized in that the state of the counter will be decreased on the arrival of said data cell by a value which is a function of the length of time between the moment of arrival of that data cell and the moment of arrival of a certain preceding data cell with the same channel indication.
2. A method in accordance with claim 1, characterized in that the value by which the state of the counter is decreased on the arrival of the data cell is the product of a first constant value and said length of time between the moment of arrival of that data cell and the moment of arrival of said preceding data cell with the same channel indication.
3. A method in accordance with claim 1, characterized in that said preceding data cell precedes the data cell mentioned first a number of N data cells arrived at the beginning of the transmission medium.
4. A method in accordance with claim 1, characterized in that said preceding data cell precedes the data cell mentioned first a number of N data cells let through to the transmission medium located downstream.
5. A method in accordance with claim 3 or 4, characterized in that said number of N is equal to 1.
6. A method in accordance with claim 1, characterized in that the state of the counter is increased by a second constant value, preceding the comparison of the state of the counter with the threshold value, and in that after that comparison the state of the counter will be decreased again by the second constant value, if on that comparison the state of the counter turned out to be more than the threshold value.
7. A method in accordance with claim 1, characterized in that the state of the counter will be increased by a second constant value after the state of the counter has been compared with the threshold value, notably only if on that comparison the state of the counter turned out to be less than the threshold value.
8. A method in accordance with claim 1, characterized in that the variables, the penultimate state of the counter and the moment of arrival of said preceding data cell, related to the relevant channel indication of the respective transmission channels are recorded, in that on the arrival of a data cell said variables will be read out under the control of said channel indication in the control word of that data cell, and in that said variables will be replaced by respectively the updated state of the counter and the moment of arrival of the data cell mentioned first, at least if the state of the counter is less than the threshold value.
9. A method in accordance with claim 8, characterized in that the parameters: the first constant value, the second constant value, the threshold value and the resolution with which the respective moments of arrival of the data cells are registered -at any rate at least part of those parameters - have been recorded, related to the channel indication of the respective transmission channels, and in that on the arrival of a data cell these parameters will be read out under the control of said channel indication in the control word of that data cell.
10. A method in accordance with claim 2, characterized in that the first constant value is equal to a power of 2.
11. A method in accordance with claim 10, characterized in that the first constant value is equal to 1.
12. A method in accordance with claim 9, characterized in that the first constant value of the respective transmission channels are powers of 2.
13. A device for controlling, in a system for transmitting, via a transmission medium comprising a plurality of virtual, asynchronously time-divided transmission channels, a flow of data channel by channel, said flow of data consisting of data cells which are each transmitted via one of those transmission channels, and each of which comprises a group of control words with one or more control words as well as a group of information words with one or more information words, the group of control words comprising a control word with a channel indication, indicating via which transmission channel the relevant data cell has to be transmitted, said device comprising read-out means for reading out from the control word group of an arriving data cell its channel indication, said device comprising a counter, keeping up to date, for each transmission channel, a counter value, having a certain fixed minimum, and which is on the one hand decreased proportional to the time and which is on the other hand increased proportional to the number of data cells with a channel indication, indicating said transmission channel, said device comprising comparing means, for comparing said counter value with a threshold value, supplied by a threshold means, when a data cell with a channel indication, indicating said transmission channel, arrives at the beginning of the transmission medium, said device comprising switching means for switching through said data cell to the transmission medium located downstream, when the counter value is less than said threshold value, characterized by first storage means for storing, channel by channel, the last counter value, second storage means for storing, channel by channel, the moment of arrival of a preceding data cell, time indicating means for determining the moment of arrival of each arriving data cell, computing means for decreasing, after the arrival of such data cell, the counter value of the channel as indicated by the channel indication of that arriving data cell, that counter value being read out from said first storage means, by a value which is a function of the calculated length of time between the moment of arrival of said arriving data cell, that moment being determined by said time indicating means, and the moment of arrival of a preceding data cell of the same channel as that arriving data cell, that moment being read out from said second storage means, said comparing means comparing said decreased counter value with said threshold value, stored in said threshold means, said switching means switching through said data cell to the transmission medium located downstream, when the decreased counter value is less than said threshold value.
14. A system according to claim 13, characterized by third storage means for storing, channel by channel, the time resolution with which said time indicating means determines the moment of arrival such arriving data cell.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| NL8900269A NL8900269A (en) | 1989-02-03 | 1989-02-03 | METHOD FOR TRANSMISSION OF TIME-DISTRIBUTED TRANSMISSION CHANNELS OVER A STAGE OF DATA CELLS THROUGH A MULTIPLE OF ASYNCHRONOUS Maintaining a counter reading per transmission channel, which depends on the number of data cells per time. |
| NL8900269 | 1989-02-03 |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA2008648A1 CA2008648A1 (en) | 1990-08-03 |
| CA2008648C true CA2008648C (en) | 1994-05-31 |
Family
ID=19854069
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002008648A Expired - Lifetime CA2008648C (en) | 1989-02-03 | 1990-01-26 | Method for transmitting, via a plurality of asynchronously time-divided transmission channels, a flow of data cells, the state of a counter for each transmission channel being kept up to date in accordance with the number of data cells per unit of time |
Country Status (9)
| Country | Link |
|---|---|
| US (1) | US5007043A (en) |
| EP (1) | EP0381275B1 (en) |
| JP (1) | JPH0748729B2 (en) |
| AT (1) | ATE103746T1 (en) |
| CA (1) | CA2008648C (en) |
| DE (2) | DE381275T1 (en) |
| DK (1) | DK0381275T3 (en) |
| ES (1) | ES2016922T3 (en) |
| NL (1) | NL8900269A (en) |
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| JP4080911B2 (en) * | 2003-02-21 | 2008-04-23 | 株式会社日立製作所 | Bandwidth monitoring device |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4769811A (en) * | 1986-12-31 | 1988-09-06 | American Telephone And Telegraph Company, At&T Bell Laboratories | Packet switching system arranged for congestion control |
| US4769810A (en) * | 1986-12-31 | 1988-09-06 | American Telephone And Telegraph Company, At&T Bell Laboratories | Packet switching system arranged for congestion control through bandwidth management |
| FR2616025B1 (en) * | 1987-05-26 | 1989-07-21 | Lespagnol Albert | METHOD AND SYSTEM FOR PACKET FLOW CONTROL |
| FR2616024B1 (en) * | 1987-05-26 | 1989-07-21 | Quinquis Jean Paul | SYSTEM AND METHOD FOR PACKET FLOW CONTROL |
-
1989
- 1989-02-03 NL NL8900269A patent/NL8900269A/en not_active Application Discontinuation
-
1990
- 1990-01-26 CA CA002008648A patent/CA2008648C/en not_active Expired - Lifetime
- 1990-01-29 ES ES90200189T patent/ES2016922T3/en not_active Expired - Lifetime
- 1990-01-29 EP EP90200189A patent/EP0381275B1/en not_active Revoked
- 1990-01-29 DE DE199090200189T patent/DE381275T1/en active Pending
- 1990-01-29 DK DK90200189.0T patent/DK0381275T3/en active
- 1990-01-29 AT AT90200189T patent/ATE103746T1/en not_active IP Right Cessation
- 1990-01-29 DE DE69007644T patent/DE69007644T2/en not_active Expired - Fee Related
- 1990-01-30 US US07/472,349 patent/US5007043A/en not_active Expired - Lifetime
- 1990-02-02 JP JP2233390A patent/JPH0748729B2/en not_active Expired - Lifetime
Also Published As
| Publication number | Publication date |
|---|---|
| EP0381275B1 (en) | 1994-03-30 |
| DK0381275T3 (en) | 1994-08-08 |
| US5007043A (en) | 1991-04-09 |
| EP0381275A1 (en) | 1990-08-08 |
| CA2008648A1 (en) | 1990-08-03 |
| ATE103746T1 (en) | 1994-04-15 |
| ES2016922T3 (en) | 1994-06-16 |
| DE69007644D1 (en) | 1994-05-05 |
| JPH02239748A (en) | 1990-09-21 |
| NL8900269A (en) | 1990-09-03 |
| ES2016922A4 (en) | 1990-12-16 |
| DE69007644T2 (en) | 1994-08-25 |
| DE381275T1 (en) | 1990-10-18 |
| JPH0748729B2 (en) | 1995-05-24 |
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