CA2281468A1 - A shaping method, a shaper realizing such a shaping method and a communication network including such a shaper - Google Patents
A shaping method, a shaper realizing such a shaping method and a communication network including such a shaper Download PDFInfo
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- CA2281468A1 CA2281468A1 CA002281468A CA2281468A CA2281468A1 CA 2281468 A1 CA2281468 A1 CA 2281468A1 CA 002281468 A CA002281468 A CA 002281468A CA 2281468 A CA2281468 A CA 2281468A CA 2281468 A1 CA2281468 A1 CA 2281468A1
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- 238000000034 method Methods 0.000 title claims abstract description 47
- 238000007493 shaping process Methods 0.000 title claims abstract description 42
- 238000004891 communication Methods 0.000 title claims abstract description 22
- 239000000872 buffer Substances 0.000 claims abstract description 166
- 238000012886 linear function Methods 0.000 claims description 7
- 101100484492 Arabidopsis thaliana VHA-C gene Proteins 0.000 description 21
- 230000011664 signaling Effects 0.000 description 10
- 102000012677 DET1 Human genes 0.000 description 9
- 101150113651 DET1 gene Proteins 0.000 description 9
- 101150066284 DET2 gene Proteins 0.000 description 9
- 230000006870 function Effects 0.000 description 8
- 230000005540 biological transmission Effects 0.000 description 5
- 238000012935 Averaging Methods 0.000 description 4
- 238000009499 grossing Methods 0.000 description 4
- 101150012579 ADSL gene Proteins 0.000 description 2
- 102100020775 Adenylosuccinate lyase Human genes 0.000 description 2
- 108700040193 Adenylosuccinate lyases Proteins 0.000 description 2
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- 230000003044 adaptive effect Effects 0.000 description 1
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- 102220047090 rs6152 Human genes 0.000 description 1
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Classifications
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- 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
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04Q—SELECTING
- H04Q11/00—Selecting arrangements for multiplex systems
- H04Q11/04—Selecting arrangements for multiplex systems for time-division multiplexing
- H04Q11/0428—Integrated services digital network, i.e. systems for transmission of different types of digitised signals, e.g. speech, data, telecentral, television signals
- H04Q11/0478—Provisions for broadband connections
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- 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
- H04L2012/5632—Bandwidth allocation
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- 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
- H04L2012/5678—Traffic aspects, e.g. arbitration, load balancing, smoothing, buffer management
- H04L2012/568—Load balancing, smoothing or shaping
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- 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
- H04L2012/5678—Traffic aspects, e.g. arbitration, load balancing, smoothing, buffer management
- H04L2012/5684—Characteristics of traffic flows
Abstract
The invention relates to a shaping method for use by a shaper in a communication network in order to convert an incoming data flow with an incoming data packet rate into an outgoing data flow with an outgoing data packet rate. The shaper includes a buffer which is leaked with the outgoing data packet rate in order to provide thereby the outgoing data flow.
The shaping method includes the following steps:
- determining a value of a future incoming data packet rate of the incoming data packet rate; and - determining a value of a buffer occupancy related to the number of data packets of the incoming data flow which is received and actual buffered by a buffer included in the shaper; the buffer is leaked with the outgoing data packet rate in order to provide thereby the outgoing data flow; and - determining a value of the outgoing data packet rate in function of the value of the future incoming data packet rate and the value of the buffer occupancy.
The shaping method further includes the step of:
- determining a value of the outgoing data packet rate also in function of a predetermined peak data packet rate and a predetermined minimum data packet rate. Herewith the shaper is enabled to support a service category which provides a service with a predetermined minimum guaranteed bandwidth according to the predetermined minimum data packet rate and which allows use of excess bandwidth over the predetermined minimum guaranteed bandwidth whereby the excess bandwidth is limited according to the predetermined peak data packet rate.
The shaping method includes the following steps:
- determining a value of a future incoming data packet rate of the incoming data packet rate; and - determining a value of a buffer occupancy related to the number of data packets of the incoming data flow which is received and actual buffered by a buffer included in the shaper; the buffer is leaked with the outgoing data packet rate in order to provide thereby the outgoing data flow; and - determining a value of the outgoing data packet rate in function of the value of the future incoming data packet rate and the value of the buffer occupancy.
The shaping method further includes the step of:
- determining a value of the outgoing data packet rate also in function of a predetermined peak data packet rate and a predetermined minimum data packet rate. Herewith the shaper is enabled to support a service category which provides a service with a predetermined minimum guaranteed bandwidth according to the predetermined minimum data packet rate and which allows use of excess bandwidth over the predetermined minimum guaranteed bandwidth whereby the excess bandwidth is limited according to the predetermined peak data packet rate.
Description
A SHAPING METHOD, A SHAPER REALIZING SUCH A SHAPING
METHOD AND A COMMUNICATION NETWORK INCLUDING SUCH A
SHAPER
The present invention relates to a shaping method to convert an incoming data flow with an incoming data packet rate into an outgoing data flow v~ith an outgoing data packet rate as described in the preamble of claim l, to a shaper realizing such a shaping method as described in the preamble of claim 9 and a communication network including such a shaper as described in the preamble of claim 10.
As it is described in the ATM Forum, Technical committee "Traffic Management Specification" Version 4.0 ATM Forum/95-0013810, February 1996, at section 5.5 Traffic Shaping, page 41, traffic shaping is a mechanism that alters the traffic characteristics of a stream of cells on a connection to achieve better network efficiency whilst meeting the Quality Of Service objectives, or to ensure conformance at a subsequent interface. Traffic shaping maintains cell sequence integrity on a connection. Examples of traffic shaping are e.g.
mean cell rate reduction, burst length limiting, reduction of Cell Delay Variation by suitable spacing cells in time and cell scheduling policy.
Shaping methods have also been proposed to reduce the burstiness of video traffic. Indeed, a shaping method realized by a shaper being included in a communication network is already known in the art, e.g. from the article "Adaptive traffic smoothing for live VBR MPEG video service" written by Jin-soo Kim and Jae-kyoon Kim and published in Computer Communications 21 (1998) pages 644 - 653 by Elsevier Science B.V..
Therein, an on-line source traffic smoothing method is proposed that can be effectively used in live video applications such as visual lectures or television news. Through experimental results, it is shown that the proposed scheme, which is designed in such a dynamic way as to smooth maximally the transmission rate, is effective in reducing the peak rate, temporal variations, and effective bandwidth of a given video stream. According to the system model which is described in section 2 of this article, the method converts an incoming data flow with an incoming data packet rate into an outgoing data flow with an outgoing data packet rate. Indeed, the system model includes a buffer, called in the article the sender buffer, wherein the received data packets of the incoming data flow transmitted by the source are buffered. The buffered data packets are leaked with a transmission rate, called hereafter outgoing data packet rate, whereby an outgoing data flow is provided.
In section 3 of the above article it is mentioned that the video smoothing method of the above mentioned article depends on the past information of the outgoing data packet rate as well as the buffer occupancy of the buffer. Furthermore, the system model, called hereafter shaper, includes an Lth order linear predictor in order to efficiently estimate a future incoming data packet rate by using a linear combination of the previous values of the incoming data packet rate.
In this way, the shaping method of the prior art document includes among others the steps of - determining a value of a future incoming data packet rate of the incoming data packet rate; and - determining a value of a buffer occupancy related to the number of data packets of the incoming data flow which are received and are buffered by the buffer; and the step of - determining a value of an outgoing data packet rate in function of among others a value of the future incoming data packet rate and a value of the buffer occupancy.
As it is described in the article, the video smoothing method supports Variable bit Rate VBR MPEG video services.
However, a quality of service category which provides a service with a predetermined minimum guaranteed bandwidth according to a predetermined minimum data packet rate of an incoming data flow and which allows use of excess bandwidth, being limited according to a predetermined peak data packet rate, over this predetermined minimum guaranteed bandwidth, is not supported by the prior art method. Such a service category is e.g. the Guaranteed Frame Rate GFR service category. This service category provides a service with a minimum guaranteed bandv~idth while allowing the users to transmit at a higher rate than this guaranteed bandwidth. The data packets which are part of the minimum guaranteed bandwidth will be delivered to the destination while the data packets which are not part of this guaranteed bandwidth will be delivered to the destination on a best-effort basis depending on the amount of the unreserved bandwidth inside the network. A traffic contract for such a GFR service includes the definition of a Minimum Cell Rate MCR and a Peak Cell Rate for each data flow. Such a minimum cell rate MCR, called hereafter minimum data packet rate, is expressed e.g. in cells per second. The minimum guaranteed bandwidth according to this minimum data packet rate is the minimum bandwidth which is guaranteed at any time for each established data flow following the contract and is determined during connection set-up of the data flow. Such a peak cell rate, called hereafter peak data packet rate, is the maximum transmission rate which is allowed according to the contract.
An object of the present invention is to provide a shaping method and a shaper realizing such a shaping method in a communication network such as the above known one, but which has not the above drawback i.e. which reduces the burstiness of the incoming data packet rate of the incoming data flow while supporting a quality of service category which provides a service with a predetermined minimum guaranteed bandwidth according to a predetermined minimum data packet rate of an incoming data flow and which allows use of excess bandwidth, being limited according to a predetermined peak data packet rate, over this predetermined minimum guaranteed bandwidth.
According to the invention, this object is achieved by the shaping method as described in claim 1, the shaper realizing such a shaping method as described in claim 9 and the communication network including such a shaper, as described in claim 10.
Indeed, due to the fact that the shaping method further includes determining the value of the outgoing data packet rate also in function of a predetermined peak data packet rate and a predetermined minimum data packet rate. In this way, the minimum data packet rate according to the contract of the incoming data flow is taken into account in order to determine a value for the outgoing data packet rate whereby the shaping method is enabled to guarantee a minimum guaranteed bandwidth according for the data flov~.
Moreover, the shaper is enabled to allow the use of excess bandwidth over the minimum guaranteed bandwidth if this bandwidth is available in the network and to limit the use of excess bandwidth, however, according to the predetermined peak data packet rate.
It has to be remarked that the minimum data packet rate is, as already mentioned above, a data packet rate which is guaranteed to the incoming data flow. This does not mean that the minimum value of incoming data packet rates of the incoming data flow is equal to this minimum data packet rate. Indeed, the incoming data packet rate might be smaller than this minimum data packet rate but the minimum data packet rate is always guaranteed to this incoming data flow.
A possible implementation of the step of determining a value of a future incoming data packet rate is to determine a value of an average incoming data packet rate of the incoming data packet rate. This is described in claim 2.
A simple solution in order to reduce the burstiness of the incoming data packet rate is to use the above mentioned value of an average incoming data packet rate in order to determine a value for the outgoing data packet rate.
Although this solution would limit the burstiness of the incoming data packet rate, it would result in a large and uncontrolled occupancy of the buffer included in the shaper. Therefore two thresholds are predetermined on the occupancy of the buffer : a predetermined minimum buffer occupancy and a predetermined maximum buffer occupancy.
As long as the value of the buffer occupancy is smaller than the predetermined minimum buffer occupancy or substantially equal to the predetermined minimum buffer occupancy, the shaper is allowed to leak the buffer with an outgoing data packet rate which is at least equal to the guaranteed minimum data packet rate. However, in the event when a bigger incoming data packet rate is expected i.e. a bigger value of the future incoming data packet rate is determined, the buffer should b~ leaked according to this future incoming data packet rate. In this way, in the event when a value of the buffer occupancy is smaller than or equal to the predetermined minimum buffer occupancy, the shaping method further includes constituting the step of determining the value of the outgoing data packet rate with the maximum out of the predetermined minimum data packet rate or the future incoming data packet rate. This is described in claim 3.
Furthermore, in the event when the buffer occupancy is between the predetermined minimum buffer occupancy and the predetermined maximum buffer occupancy the shaping method further includes constituting the step of determining the value of the outgoing data packet rate with a function which is directly proportional to the value of the buffer occupancy and which is bounded between the minimum data packet rate and the peak data packet rate. Indeed, in order to keep the buffer occupancy under control, the higher the buffer occupancy becomes, the higher the ou;going data packet rate will be. This is described in claim 4.
In the event when the buffer occupancy is equal to or bigger than the predetermined maximum buffer occupancy the shaping method further includes constituting the step of determining the value of the outgoing data packet rate with the predetermined peak data packet rate which is also predefined in the above mentioned traffic contract during connection set-up of the data flow and which is the maximum data packet rate with which the source of the data flow is allowed to transmit data packets. In order to avoid loss of data packets in the buffer, and in the event when the buffer occupancy is already equal or higher as the predefined maximum buffer occupancy, the shaper can not effort itself to leak the buffer at a too small outgoing data packet rate, whereby it is necessary to leak the buffer with an outgoing data packet rate equal to this predetermined peak data packet rate. This is described in claim 5.
A further characteristic feature of the present invention is that, in the event when the value of the buffer occupancy is between the predetermined minimum buffer occupancy and the predetermined maximum buffer occupancy, the outgoing data packet rate is the maximum of - a value of the future incoming data packet rate; and - a linear function a value of this buffer occupancy with a slope which is equal to a fraction of the difference between the predetermined peak data packet rate and the predetermined minimum data packet rate, over the difference between the predetermined maximum buffer occupancy and the predetermined minimum buffer occupancy.
Indeed, different kind of curves are possible to implement the function in order to be proportional to the buffer occupancy. Furthermore, as long as the value of the future incoming data packet rate is bigger than the value of the function of the buffer occupancy, the buffer will be leaked at this future incoming data packet rate. This is described in claim 6.
However, according to the above paragraph, the buffer will be relieved i.e. the outgoing data packet rate will increase, only at a the point when the average incoming data packet rate and the result of the linear function are crossing each other. This means that the point of relieving the buffer depends on the incoming traffic and not directly on the predetermined minimum buffer occupancy. Therefore a further improvement is provided to the shaper. In the event when value of the buffer occupancy is between a predetermined minimum buffer occupancy and a predetermined maximum buffer occupancy the outgoing data packet rate is determined with a linear function with an interception at a maximum out of the predetermined minimum data packet rate and the average incoming data packet rate and with a slope which is substantially equal to a fraction of the difference between the predetermined peak data packet rate and a maximum out of the predetermined minimum data packet rate and the future incoming data packet rate, over the difference between the predetermined maximum buffer occupancy and the predetermined minimum buffer occupancy.
In this way, once the value of the predetermined minimum buffer occupancy is reached, the buffer will be leaked with an increasing outgoing data packet rate.
This is described in claim 7.
A further characteristic feature of the present invention is that the step of determining a value of a future incoming data packet rate is realized for different group data packet rates whereby the step of determining a value of the outgoing data packet rate is executed by using these different group data packet rates according to different kind of situations. Indeed, in the event when the incoming data packets of the incoming data flow are each part of one of a plurality of predefined group data packets, a future group data packet rate is determined for each group of data packets. The step of determining a value of the outgoing data packet rate in function of a value of the future incoming data packet rate is realized by constituting this future incoming data packet rate by a value of one of the group data packet rates. A possible way to implement the condition of when to use which value of a group data packet rate is e.g.
according to a predefined sequence among the different predefined groups . A
second way to implement this condition is e.g. according to the group data packet whereto an outgoing data packet of the outgoing data flow belongs to.
This is described in claim 8 and will further be explained with the following example. A possible way to predefine different group data packets is e.g.
according to its Cell Loss Priority bit, called hereafter CLP bit, which is included in each Asynchronous Transfer Mode data packet, called ATM cell. In this way, two predefined group of data packets are defined : a first group of ATM cells included in the incoming ATM data flow are the ATM cells having a CLP bit equal to 1 and a second group of ATM cells included in the incoming ATM data flow are the ATM cells having a CLP bit equal to 0. During receiving of the incoming ATM data flow, two future incoming data packet rates are maintained, a first future group data packet rate which is which is associated to the first group and which is based on the total amount of incoming data packets and a second future group data packet rate which is associated to the second group and which is only based on the ATM cells included in the second group of data packets i.e.
CLP bit =0. After being buffered, an incoming ATM cell of the incoming data flow is going to be transmitted at an outgoing data packet rate. In the event when the outgoing data packet includes a CLP bit equal to l, i.e. it belongs to _ $ _ the first group of data packets, the future incoming data packet rate which is used during execution of the step of determining the outgoing data packet rate is constituted by the first future group data packet rate. In the event when the outgoing data packet includes a CLP bit equal to 0, i.e. it belongs to the second group of data packets, the future incoming data packet rate which is used during execution of the step of determining the outgoing data packet rate is constituted by the second future group data packet rate.
It has to be remarked that similar as described in the above paragraph of different kind of future group data packet rates to be used for different kind of groups in order to determine the outgoing data packet rate, also any one of the buffer occupancy, the predefined maximum buffer occupancy and the predefined minimum buffer occupancy can be maintained for the different groups in order to determine the outgoing data packet rate for the outgoing data packets. In this way any one of a value of a group buffer occupancy i.e. a predefined maximum buffer occupancy of a group, a value of a group predetermined maximum buffer occupancy i.e. a predetermined maximum buffer occupancy of a group, and a value of a group predetermined minimum buffer occupancy i.e. a predetermined minimum buffer occupancy of a group, are defined and maintained for one of the plurality of groups. Furthermore, in the event when an outgoing data packet of an outgoing data flow is included in a first group data packet of a plurality of group data packets, the outgoing data packet rate is determined in function of any one of - a value of a first future group data packet rate;
a value of a first group buffer occupancy;
- a value of a first group predetermined maximum buffer occupancy;
- a value of a first group predetermined minimum buffer occupancy.
Furthermore it has to be explained that in the event when such a group parameter is used in order to determine the outgoing data packet rate for a data packet which belongs to a certain group, the outgoing data packet rate for a data packet which belongs to another group does not necessarily be determined by using such group parameters. Indeed, according to the above described example of CLP=1 and CLP=0, the outgoing data packet rate of the group CLP=1 can be put to a constant outgoing data packet rate which is equal to the predetermined peak data packet rate. In this may for the group CLP=1 a faster outgoing data packet rate is determined whereby the ATM cells of this group are faster transmitted into the network and might be discarded later on in the network. However, for the group CLP=0 a slower outgoing data packet rate is determined whereby the ATM cells of this group are slower transmitted into the network and are better protected by the system.
It should be noticed that the term "including", used in the claims, should not be interpreted as being limitative to the means listed thereafter.
Thus, the scope of the expression "a device including means A and B" should not be limited to devices consisting only of components A and B. It means that with respect to the present invention, the only relevant components of the device are A
and B.
Similarly, it is to be noted that the term "coupled", also used in the claims, should not be interpreted as being limitative to direct corinections only.
Thus, the scope of the expression "a device A coupled to a device B" should not be limited to devices or systems wherein an output of device A is directly connected to an input of device B. It means that there exists a path between an output of A and in input of B which may be a path including other devices or means.
The above and other objects and features of the invention will become more apparent and the invention itself will be best understood by referring to the following description of a not limiting embodiment taken in conjunction with the accompanying Figure which illustrates a shaper according to the invention.
First, the working of the method of the present invention will be explained by means of a functional description of the functional blocks shown in the Figure. Based on this description, implementation of the functional blocks will be obvious to a person skilled in the arf and will therefor not be described in further detail. In addition, the principle working of the shaping method will be described.
- ~0 -In order to describe the shaper according to the present invention a shaper is shown in the Figure which is included in a communication netv~ork.
It is considered that the shaper S is coupled to a source which transmits an incoming data flow IN. The object of the shaper is to reduce the burstiness of this incoming data flow but also and not less important to enable the source to benefit from any available unreserved bandwidth inside the network. For this particular embodiment it is presumed that the shaper supports a guaranteed frame rate service category GFR which is provided by the communication network to the source. This means that, in the event when the source is using the GFR
service category, between the source and the communication network a GFR
contract is defined at connection set up of a communication i.e. a data flow.
This contract is defined by the network operator of by means of a signaling protocol between the source and the communication network and includes the definition of a peak cell rate PCR, called herein a peak data packet rate and the definition of a minimum cell rate MCR, called herein minimum data packet rate.
Referring to Figure 1, the shaper S is shown which includes a buffer BUF, a first determiner DET1, a second determiner DET2, a third determiner DET3 and a memory MEM.
The shaper S converts an incoming data packet flow IN with an incoming data packet rate R IN into an outgoing data packet flow OUT with an outgoing data packet rate R-OUT. The incoming data packet rate is received at an input of the shaper S and the outgoing data packet flow is transmitted at an output of the shaper. The input and the output of the shaper are shown with an arrow entering an leaving, respectively, the shaper S.
The buffer BUF is coupled between this input and this output of the shaper S. The buffer BUF is a first in first out buffer and is able to regulate its transmission rate. This means that the buffer BUF receives the incoming data packets of an incoming data flow IN, buffers these incoming data packets if required and transmits these incoming data packets according to an outgoing data packet rate and provides thereby an outgoing data flow OUT.
The buffer BUF includes two predefined buffer occupancy thresholds i.e. a predefined minimum buffer occupancy Mll~l_BO and a predefined maximum buffer occupancy MAX_BO. These t~r~o values are predefined by e.g.
the operator of the communication network. During the further description of the working of the shaper and the shaping method it will become clear how the values for these tv~o thresholds might be determined. The buffer BUF includes a control output in order to provide these predefined thresholds to the memory MEM.
The first determiner DET1 is also coupled to the input of the shaper S
whereto the buffer BUF is coupled. The first determiner DETI determines a value of a future incoming data packet rate. According to the prior art solution an Lth order linear predictor is used to efficiently estimate a future incoming data packet rate whereby a linear combination of the previous values of the incoming data packet rates is used. However, for this embodiment it is preferred to determine an average incoming data packet rate AR in order to estimate a future incoming data packet rate. In order to determine this value of an average incoming data packet rate AR the first determiner DETI includes a counter and a first calculator (both not shown). The counter, coupled to the input of the shaper S is used to measure the average incoming rate of packets. It counts the number of incoming data packets of the incoming data flow IN during every consecutive predetermined period of T seconds and provides this number to the first calculator of the first determiner DETI .
It has to be remarked that for this particular embodiment it is preferred to define the predetermined period of T seconds equal to 10 milliseconds, however the scope of the invention is not limited to a shaper which includes in the first determiner DET1 a counter which determines the number of incoming data packets every 10 milliseconds. Indeed, it is clear to a person skilled in the art that other period times could be determined in order to measure a number of incoming data packets and in order to be used to determine a value of an average incoming data packet rate. The calculator calculates a new average incoming data packet rate AR based upon - the provided number of incoming data packets N(IN)during the predetermined measuring period; and - a predetermined averaging factor F; and - a previous calculated average incoming data packet rate AR(prev).
The first calculator uses the following formulae in order to calculate for each measuring period T of 10 milliseconds AR = AR(prev) + F x {AR(prev) - N(IN)}
For this particular embodiment the averaging factor F is set to 0.05. It is clear to a person skilled in the art that the scope of the invention is not limited to first determiners DET1 which are including an averaging factor of a low pass filter which is set to 0.05 but that this averaging factor could be set to other values e.g. 0.06. Furthermore, it should be clear that the scope of the invention is neither limited to a shaper S which includes a first determiner DET1 which determines the average incoming data packet rate AR according to the above described formulae. Indeed, it is clear to a person skilled in the art that other kind of formulas e.g. more complex solutions could be used in the shaper of the invention in order to determine the average incoming data packet rate AR of the incoming data flow IN.
Upon receiving of the counter the number of data packets N(IN), the first calculator calculates every 10 milliseconds a new average incoming data packet rate. This average incoming data packet rate AR is provided by the first determiner DET1 to the third determiner DET3 which is coupled to an output of this first determiner DET1.
The second determiner DET2 is coupled to an output of the buffer BUF. This output of the buffer BUF provides an increment control signal (see arrow) each time when an incoming data packet enters the buffer BUF and provides a decrement control signal each time when an outgoing data packet of the outgoing data flow leaves the buffer BUF. The second determiner DET2 includes a counter (not shown) which increments with one each time when an increment control signal is recieved and decrements ~«ith one each time when a decrement control signal is received. According to this way a value of a buffer occupancy BO is determined by the second determiner DET2. The second determiner DET2 provides this value of a buffer occupancy BO to the third S determiner DET3 which is also coupled to the second determiner DET2.
It has to be explained that the buffer occupancy, i.e. a number of data packets of the incoming data flow which are actually being buffered by the buffer BUF could be determined according to different kind of ways.
The memory MEM is included in the shaper S in order to store predefined values which must also be provided to the third determiner DET3.
Therefor the memory MEM is coupled to the buffer BUF in order to receive the predefined minimum buffer occupancy MIN-BO and the predefined maximum buffer occupancy MAX-BO and to store these values.
Furthermore the memory MEM is also coupled to a signaling protocol unit (not shown). Such a signaling protocol unit is enabled to understand the signaling protocol between the source of the data flow and the communication network or which is at least enabled to groom out of the information exchanged between the source and the communication network the predetermined peak data packet rate and the predetermined minimum data packet rate according to the established GFR contract. Since a shaper S according to the present invention is used at different places inside the network e.g. inside an asynchronous transfer mode ATM switch of an ATM network, a policing unit, an asymmetric digital subscriber line ADSL modem of an ADSL network, and as a stand-alone device in a communication network, such signaling protocol unit is included in the communication network outside or inside the shaper S. Indeed, in the event when the shaper is included in e.g. the above mentioned ATM
switch, the shaper S takes advantage of the fact that such an ATM switch already includes such a signaling protocol unit, whereby the memory MEM included in the shaper S is coupled to this signaling protocol unit. In the event when the shaper is acting as a stand-alone device in the network it is necessary to include such a signaling protocol unit in the present shaper S. Indeed, the aim of the present paragraph is the fact that the signaling protocol unit is aware of the predefined minimum data packet rate and the peak data packet rate and that this information is provided to the memory MEM of the shaper S in order to be stored in this memory MEM. At predefined time moments the information in the memory MEM i.e. the predefined minimum buffer occupancy, the predefined maximum buffer occupancy, the predefined peak data packet rate and the predefined minimum data packet rate is provided to the third determiner DET3.
A further remark is that a signaling protocol is only required in the event when switched virtual channels are used. However in the event when permanent virtual channels are used, the minimum data packet rate and the peak data packet rate of the virtual channels are directly specified by the network operator for each connection and are known by the switch and consequently by the shaper.
The third determiner DET3 is adapted to determine the value of the outgoing data packet rate in function of the predetermined peak data packet rate, the value of the average incoming data packet rate, the value of the buffer occupancy and the predetermined minimum data packet rate. The determined outgoing data packet rate is provided by the third determiner DET3 to the buffer BUF in order to control the output of the buffer BUF and to enable the buffer BUF
to adapt the actual outgoing data packet rate to this received outgoing data packet rate.
Each time a data packet is transmitted by the shaper S, a new value for the outgoing data packet rate is calculated by the third determiner DET3 according to the received information from the first determiner DETI, the second determiner DET2 and the memory MEM. The initialization of this determining step is provided with an execution signal EXE which is provided by the buffer BUF
to the third determiner DET3 when an outgoing data packet is going to be transmitted by the buffer BUF. It has to be remarked that the shaper according to the invention is not limited to the implementation of determining an outgoing data packet rate for every outgoing data packet, which is in fact upon an irregular base. Indeed, the outgoing data packet rate is in this way changed for every outgoing data packet, but it could be changed also every N outgoing data packets or every S seconds which is upon a regular base.
In the event when the value of the buffer occupancy BO is smaller or equal to the predefined minimum buffer occupancy MIN-BO, the outgoing data packet rate is determined by the maximum out of the value of the average incoming data packet rate AR and the minimum data packet rate MCR
BO _< MIN BO ~
R-OUT = MAX {AR , MCR} ~~ ) In this way, during transmission by the source of the incoming data flow, as long as the buffer occupancy is rather small i.e. not bigger than this predefined minimum buffer occupancy, the outgoing data packet rate will be equal to at least the value of the guaranteed minimum data packet rate.
However, when in such a situation the average incoming data packet rate is bigger as the predefined minimum data packet rate, the buffer will be leaked with this bigger value.
In the event when the value of the buffer occupancy BO is between the predefined minimum buffer occupancy MIN-BO and the predefined maximum buffer occupancy MAX-BO, the outgoing data packet rate is determined by the value calculated by the following formulae MIN BO < BO <_ MAX BO
PCR - ~LL4,Y {.~R, I~ICR }
R-OUT=MAX {AR,MCR} + .~~Y BO-.LILY BO x HBO - M!N-BO) ~2) According to this formulae, once the buffer occupancy reaches the predefined minimum threshold i.e. the predefined minimum data packet rate, the buffer must be leaked with an increasing outgoing data packet rate.
The increasing outgoing data packet rate is a linear function which increases with an increasing buffer occupancy. The linear function has an interception at the maximum out of the predetermined minimum data packet rate and the average incoming data packet rate and a slope which is equal to a fraction of the difference between the predetermined peak data packet rate and the maximum out of the predetermined minimum data packet rate and the value of the average incoming data packet rate, over the difference between the predetermined maximum buffer occupancy and the predetermined minimum buffer occupancy.
In the event when the value of the buffer occupancy BO is bigger as the predefined maximum buffer occupancy MAX_BO, the outgoing data packet rate is determined by the value of the predetermined peak data packet rate.
MAX_BO < BO
~ R OUT = PCR
This means that once the value of the buffer occupancy BO is bigger as the predefined maximum buffer occupancy, the buffer is leaked with an outgoing data packet rate which is equal to the maximum allowable incoming data packet rate i.e. the peak data packet rate according to the GFR contract.
Herewith overflow of the buffer BUF is avoided.
Hereafter the principle working of the method of the invention will be described. Presume that incoming data packet was received by the shaper S and has been buffered by the buffer BUF. At the moment when the data packet is going to be transmitted by the shaper S a new value for the outgoing data packet rate has to be determined. A control signal EXE is provided by the buffer BUF
to the third determiner DET3 in order to initiate the determining procedure. In order to be able to calculate a new value for the outgoing data packet rate the buffer BUF requests with a value request control signal (only shown with an arrow) new values for the parameters to the first determiner DET1, the second determiner DET2 ad the memory MEM.
Upon receiving of a value request control signal from the third determiner DET3, the first determiner DET1 provides to the third determiner a value for the future outgoing data packet rate which is a value for the average incoming data packet rate AR and which is updated according to the method S explained above every 10 milliseconds.
Upon receiving of a value request control signal from the third determiner DET3, the second determiner DET2 provides to the third determiner DET3 a value for the buffer occupancy BO which is updated every time a data packet enters or leaves the buffer BUF.
Upon receiving of a value request control signal from the third determiner DET3, the memory MEM provides to the third determiner DET3 a value for the minimum data packet rate MCR, a value for the peak data packet rate PCR, a value for the minimum buffer occupancy MIN_BO and a value for the maximum buffer occupancy MAX_BO. It has to be remarked that these values are not at all updated with the frequency of with which the average rate AR and the buffer occupancy BO are updated. Furthermore, it has to be remarked that other implementations are possible in order to realize this step.
Indeed, another possible implementation is that the third determiner DET3 stores these values and uses these values until the memory MEM provides a warning signal in order to warn the third determiner DET3 that one of the values have been changed. The third determiner DET3 provides than a value request control signal to the memory MEM only upon receiving of such a warning signal.
When the third determiner DET3 has all the needed values of the parameters, it determines a new value for the outgoing data packet rate according to the value of the buffer occupancy. Indeed, upon comparing the value of the buffer occupancy BO with the value of the minimum buffer occupancy MIN-BO and the maximum buffer occupancy MAX_BO the third determiner uses any on of the formulae's (1 ), (2) and (3) mentioned above.
Presume a situation wherein the value of the buffer occupancy BO is between the value of the two thresholds of the buffer BO whereby formulae (2) will be used by the third determiner DET3. A new value for the outgoing data packet rate ROUT is calculated as follows ROUT=MAX AR,MCR + pCR - ~1.I-LY .~1R, :LICR
;LL~LY-BO ~:~II~V BO x (BO - MIN-BO) The new value is provided by the third determiner DET3 to the buffer BO which changes its outgoing data packet rate to this new value.
While the principles of the invention have been described above in connection with specific apparatus, it is to be clearly understood that this description is made only by way of example and not as a limitation on the scope of the invention, as defined in the appended claims.
METHOD AND A COMMUNICATION NETWORK INCLUDING SUCH A
SHAPER
The present invention relates to a shaping method to convert an incoming data flow with an incoming data packet rate into an outgoing data flow v~ith an outgoing data packet rate as described in the preamble of claim l, to a shaper realizing such a shaping method as described in the preamble of claim 9 and a communication network including such a shaper as described in the preamble of claim 10.
As it is described in the ATM Forum, Technical committee "Traffic Management Specification" Version 4.0 ATM Forum/95-0013810, February 1996, at section 5.5 Traffic Shaping, page 41, traffic shaping is a mechanism that alters the traffic characteristics of a stream of cells on a connection to achieve better network efficiency whilst meeting the Quality Of Service objectives, or to ensure conformance at a subsequent interface. Traffic shaping maintains cell sequence integrity on a connection. Examples of traffic shaping are e.g.
mean cell rate reduction, burst length limiting, reduction of Cell Delay Variation by suitable spacing cells in time and cell scheduling policy.
Shaping methods have also been proposed to reduce the burstiness of video traffic. Indeed, a shaping method realized by a shaper being included in a communication network is already known in the art, e.g. from the article "Adaptive traffic smoothing for live VBR MPEG video service" written by Jin-soo Kim and Jae-kyoon Kim and published in Computer Communications 21 (1998) pages 644 - 653 by Elsevier Science B.V..
Therein, an on-line source traffic smoothing method is proposed that can be effectively used in live video applications such as visual lectures or television news. Through experimental results, it is shown that the proposed scheme, which is designed in such a dynamic way as to smooth maximally the transmission rate, is effective in reducing the peak rate, temporal variations, and effective bandwidth of a given video stream. According to the system model which is described in section 2 of this article, the method converts an incoming data flow with an incoming data packet rate into an outgoing data flow with an outgoing data packet rate. Indeed, the system model includes a buffer, called in the article the sender buffer, wherein the received data packets of the incoming data flow transmitted by the source are buffered. The buffered data packets are leaked with a transmission rate, called hereafter outgoing data packet rate, whereby an outgoing data flow is provided.
In section 3 of the above article it is mentioned that the video smoothing method of the above mentioned article depends on the past information of the outgoing data packet rate as well as the buffer occupancy of the buffer. Furthermore, the system model, called hereafter shaper, includes an Lth order linear predictor in order to efficiently estimate a future incoming data packet rate by using a linear combination of the previous values of the incoming data packet rate.
In this way, the shaping method of the prior art document includes among others the steps of - determining a value of a future incoming data packet rate of the incoming data packet rate; and - determining a value of a buffer occupancy related to the number of data packets of the incoming data flow which are received and are buffered by the buffer; and the step of - determining a value of an outgoing data packet rate in function of among others a value of the future incoming data packet rate and a value of the buffer occupancy.
As it is described in the article, the video smoothing method supports Variable bit Rate VBR MPEG video services.
However, a quality of service category which provides a service with a predetermined minimum guaranteed bandwidth according to a predetermined minimum data packet rate of an incoming data flow and which allows use of excess bandwidth, being limited according to a predetermined peak data packet rate, over this predetermined minimum guaranteed bandwidth, is not supported by the prior art method. Such a service category is e.g. the Guaranteed Frame Rate GFR service category. This service category provides a service with a minimum guaranteed bandv~idth while allowing the users to transmit at a higher rate than this guaranteed bandwidth. The data packets which are part of the minimum guaranteed bandwidth will be delivered to the destination while the data packets which are not part of this guaranteed bandwidth will be delivered to the destination on a best-effort basis depending on the amount of the unreserved bandwidth inside the network. A traffic contract for such a GFR service includes the definition of a Minimum Cell Rate MCR and a Peak Cell Rate for each data flow. Such a minimum cell rate MCR, called hereafter minimum data packet rate, is expressed e.g. in cells per second. The minimum guaranteed bandwidth according to this minimum data packet rate is the minimum bandwidth which is guaranteed at any time for each established data flow following the contract and is determined during connection set-up of the data flow. Such a peak cell rate, called hereafter peak data packet rate, is the maximum transmission rate which is allowed according to the contract.
An object of the present invention is to provide a shaping method and a shaper realizing such a shaping method in a communication network such as the above known one, but which has not the above drawback i.e. which reduces the burstiness of the incoming data packet rate of the incoming data flow while supporting a quality of service category which provides a service with a predetermined minimum guaranteed bandwidth according to a predetermined minimum data packet rate of an incoming data flow and which allows use of excess bandwidth, being limited according to a predetermined peak data packet rate, over this predetermined minimum guaranteed bandwidth.
According to the invention, this object is achieved by the shaping method as described in claim 1, the shaper realizing such a shaping method as described in claim 9 and the communication network including such a shaper, as described in claim 10.
Indeed, due to the fact that the shaping method further includes determining the value of the outgoing data packet rate also in function of a predetermined peak data packet rate and a predetermined minimum data packet rate. In this way, the minimum data packet rate according to the contract of the incoming data flow is taken into account in order to determine a value for the outgoing data packet rate whereby the shaping method is enabled to guarantee a minimum guaranteed bandwidth according for the data flov~.
Moreover, the shaper is enabled to allow the use of excess bandwidth over the minimum guaranteed bandwidth if this bandwidth is available in the network and to limit the use of excess bandwidth, however, according to the predetermined peak data packet rate.
It has to be remarked that the minimum data packet rate is, as already mentioned above, a data packet rate which is guaranteed to the incoming data flow. This does not mean that the minimum value of incoming data packet rates of the incoming data flow is equal to this minimum data packet rate. Indeed, the incoming data packet rate might be smaller than this minimum data packet rate but the minimum data packet rate is always guaranteed to this incoming data flow.
A possible implementation of the step of determining a value of a future incoming data packet rate is to determine a value of an average incoming data packet rate of the incoming data packet rate. This is described in claim 2.
A simple solution in order to reduce the burstiness of the incoming data packet rate is to use the above mentioned value of an average incoming data packet rate in order to determine a value for the outgoing data packet rate.
Although this solution would limit the burstiness of the incoming data packet rate, it would result in a large and uncontrolled occupancy of the buffer included in the shaper. Therefore two thresholds are predetermined on the occupancy of the buffer : a predetermined minimum buffer occupancy and a predetermined maximum buffer occupancy.
As long as the value of the buffer occupancy is smaller than the predetermined minimum buffer occupancy or substantially equal to the predetermined minimum buffer occupancy, the shaper is allowed to leak the buffer with an outgoing data packet rate which is at least equal to the guaranteed minimum data packet rate. However, in the event when a bigger incoming data packet rate is expected i.e. a bigger value of the future incoming data packet rate is determined, the buffer should b~ leaked according to this future incoming data packet rate. In this way, in the event when a value of the buffer occupancy is smaller than or equal to the predetermined minimum buffer occupancy, the shaping method further includes constituting the step of determining the value of the outgoing data packet rate with the maximum out of the predetermined minimum data packet rate or the future incoming data packet rate. This is described in claim 3.
Furthermore, in the event when the buffer occupancy is between the predetermined minimum buffer occupancy and the predetermined maximum buffer occupancy the shaping method further includes constituting the step of determining the value of the outgoing data packet rate with a function which is directly proportional to the value of the buffer occupancy and which is bounded between the minimum data packet rate and the peak data packet rate. Indeed, in order to keep the buffer occupancy under control, the higher the buffer occupancy becomes, the higher the ou;going data packet rate will be. This is described in claim 4.
In the event when the buffer occupancy is equal to or bigger than the predetermined maximum buffer occupancy the shaping method further includes constituting the step of determining the value of the outgoing data packet rate with the predetermined peak data packet rate which is also predefined in the above mentioned traffic contract during connection set-up of the data flow and which is the maximum data packet rate with which the source of the data flow is allowed to transmit data packets. In order to avoid loss of data packets in the buffer, and in the event when the buffer occupancy is already equal or higher as the predefined maximum buffer occupancy, the shaper can not effort itself to leak the buffer at a too small outgoing data packet rate, whereby it is necessary to leak the buffer with an outgoing data packet rate equal to this predetermined peak data packet rate. This is described in claim 5.
A further characteristic feature of the present invention is that, in the event when the value of the buffer occupancy is between the predetermined minimum buffer occupancy and the predetermined maximum buffer occupancy, the outgoing data packet rate is the maximum of - a value of the future incoming data packet rate; and - a linear function a value of this buffer occupancy with a slope which is equal to a fraction of the difference between the predetermined peak data packet rate and the predetermined minimum data packet rate, over the difference between the predetermined maximum buffer occupancy and the predetermined minimum buffer occupancy.
Indeed, different kind of curves are possible to implement the function in order to be proportional to the buffer occupancy. Furthermore, as long as the value of the future incoming data packet rate is bigger than the value of the function of the buffer occupancy, the buffer will be leaked at this future incoming data packet rate. This is described in claim 6.
However, according to the above paragraph, the buffer will be relieved i.e. the outgoing data packet rate will increase, only at a the point when the average incoming data packet rate and the result of the linear function are crossing each other. This means that the point of relieving the buffer depends on the incoming traffic and not directly on the predetermined minimum buffer occupancy. Therefore a further improvement is provided to the shaper. In the event when value of the buffer occupancy is between a predetermined minimum buffer occupancy and a predetermined maximum buffer occupancy the outgoing data packet rate is determined with a linear function with an interception at a maximum out of the predetermined minimum data packet rate and the average incoming data packet rate and with a slope which is substantially equal to a fraction of the difference between the predetermined peak data packet rate and a maximum out of the predetermined minimum data packet rate and the future incoming data packet rate, over the difference between the predetermined maximum buffer occupancy and the predetermined minimum buffer occupancy.
In this way, once the value of the predetermined minimum buffer occupancy is reached, the buffer will be leaked with an increasing outgoing data packet rate.
This is described in claim 7.
A further characteristic feature of the present invention is that the step of determining a value of a future incoming data packet rate is realized for different group data packet rates whereby the step of determining a value of the outgoing data packet rate is executed by using these different group data packet rates according to different kind of situations. Indeed, in the event when the incoming data packets of the incoming data flow are each part of one of a plurality of predefined group data packets, a future group data packet rate is determined for each group of data packets. The step of determining a value of the outgoing data packet rate in function of a value of the future incoming data packet rate is realized by constituting this future incoming data packet rate by a value of one of the group data packet rates. A possible way to implement the condition of when to use which value of a group data packet rate is e.g.
according to a predefined sequence among the different predefined groups . A
second way to implement this condition is e.g. according to the group data packet whereto an outgoing data packet of the outgoing data flow belongs to.
This is described in claim 8 and will further be explained with the following example. A possible way to predefine different group data packets is e.g.
according to its Cell Loss Priority bit, called hereafter CLP bit, which is included in each Asynchronous Transfer Mode data packet, called ATM cell. In this way, two predefined group of data packets are defined : a first group of ATM cells included in the incoming ATM data flow are the ATM cells having a CLP bit equal to 1 and a second group of ATM cells included in the incoming ATM data flow are the ATM cells having a CLP bit equal to 0. During receiving of the incoming ATM data flow, two future incoming data packet rates are maintained, a first future group data packet rate which is which is associated to the first group and which is based on the total amount of incoming data packets and a second future group data packet rate which is associated to the second group and which is only based on the ATM cells included in the second group of data packets i.e.
CLP bit =0. After being buffered, an incoming ATM cell of the incoming data flow is going to be transmitted at an outgoing data packet rate. In the event when the outgoing data packet includes a CLP bit equal to l, i.e. it belongs to _ $ _ the first group of data packets, the future incoming data packet rate which is used during execution of the step of determining the outgoing data packet rate is constituted by the first future group data packet rate. In the event when the outgoing data packet includes a CLP bit equal to 0, i.e. it belongs to the second group of data packets, the future incoming data packet rate which is used during execution of the step of determining the outgoing data packet rate is constituted by the second future group data packet rate.
It has to be remarked that similar as described in the above paragraph of different kind of future group data packet rates to be used for different kind of groups in order to determine the outgoing data packet rate, also any one of the buffer occupancy, the predefined maximum buffer occupancy and the predefined minimum buffer occupancy can be maintained for the different groups in order to determine the outgoing data packet rate for the outgoing data packets. In this way any one of a value of a group buffer occupancy i.e. a predefined maximum buffer occupancy of a group, a value of a group predetermined maximum buffer occupancy i.e. a predetermined maximum buffer occupancy of a group, and a value of a group predetermined minimum buffer occupancy i.e. a predetermined minimum buffer occupancy of a group, are defined and maintained for one of the plurality of groups. Furthermore, in the event when an outgoing data packet of an outgoing data flow is included in a first group data packet of a plurality of group data packets, the outgoing data packet rate is determined in function of any one of - a value of a first future group data packet rate;
a value of a first group buffer occupancy;
- a value of a first group predetermined maximum buffer occupancy;
- a value of a first group predetermined minimum buffer occupancy.
Furthermore it has to be explained that in the event when such a group parameter is used in order to determine the outgoing data packet rate for a data packet which belongs to a certain group, the outgoing data packet rate for a data packet which belongs to another group does not necessarily be determined by using such group parameters. Indeed, according to the above described example of CLP=1 and CLP=0, the outgoing data packet rate of the group CLP=1 can be put to a constant outgoing data packet rate which is equal to the predetermined peak data packet rate. In this may for the group CLP=1 a faster outgoing data packet rate is determined whereby the ATM cells of this group are faster transmitted into the network and might be discarded later on in the network. However, for the group CLP=0 a slower outgoing data packet rate is determined whereby the ATM cells of this group are slower transmitted into the network and are better protected by the system.
It should be noticed that the term "including", used in the claims, should not be interpreted as being limitative to the means listed thereafter.
Thus, the scope of the expression "a device including means A and B" should not be limited to devices consisting only of components A and B. It means that with respect to the present invention, the only relevant components of the device are A
and B.
Similarly, it is to be noted that the term "coupled", also used in the claims, should not be interpreted as being limitative to direct corinections only.
Thus, the scope of the expression "a device A coupled to a device B" should not be limited to devices or systems wherein an output of device A is directly connected to an input of device B. It means that there exists a path between an output of A and in input of B which may be a path including other devices or means.
The above and other objects and features of the invention will become more apparent and the invention itself will be best understood by referring to the following description of a not limiting embodiment taken in conjunction with the accompanying Figure which illustrates a shaper according to the invention.
First, the working of the method of the present invention will be explained by means of a functional description of the functional blocks shown in the Figure. Based on this description, implementation of the functional blocks will be obvious to a person skilled in the arf and will therefor not be described in further detail. In addition, the principle working of the shaping method will be described.
- ~0 -In order to describe the shaper according to the present invention a shaper is shown in the Figure which is included in a communication netv~ork.
It is considered that the shaper S is coupled to a source which transmits an incoming data flow IN. The object of the shaper is to reduce the burstiness of this incoming data flow but also and not less important to enable the source to benefit from any available unreserved bandwidth inside the network. For this particular embodiment it is presumed that the shaper supports a guaranteed frame rate service category GFR which is provided by the communication network to the source. This means that, in the event when the source is using the GFR
service category, between the source and the communication network a GFR
contract is defined at connection set up of a communication i.e. a data flow.
This contract is defined by the network operator of by means of a signaling protocol between the source and the communication network and includes the definition of a peak cell rate PCR, called herein a peak data packet rate and the definition of a minimum cell rate MCR, called herein minimum data packet rate.
Referring to Figure 1, the shaper S is shown which includes a buffer BUF, a first determiner DET1, a second determiner DET2, a third determiner DET3 and a memory MEM.
The shaper S converts an incoming data packet flow IN with an incoming data packet rate R IN into an outgoing data packet flow OUT with an outgoing data packet rate R-OUT. The incoming data packet rate is received at an input of the shaper S and the outgoing data packet flow is transmitted at an output of the shaper. The input and the output of the shaper are shown with an arrow entering an leaving, respectively, the shaper S.
The buffer BUF is coupled between this input and this output of the shaper S. The buffer BUF is a first in first out buffer and is able to regulate its transmission rate. This means that the buffer BUF receives the incoming data packets of an incoming data flow IN, buffers these incoming data packets if required and transmits these incoming data packets according to an outgoing data packet rate and provides thereby an outgoing data flow OUT.
The buffer BUF includes two predefined buffer occupancy thresholds i.e. a predefined minimum buffer occupancy Mll~l_BO and a predefined maximum buffer occupancy MAX_BO. These t~r~o values are predefined by e.g.
the operator of the communication network. During the further description of the working of the shaper and the shaping method it will become clear how the values for these tv~o thresholds might be determined. The buffer BUF includes a control output in order to provide these predefined thresholds to the memory MEM.
The first determiner DET1 is also coupled to the input of the shaper S
whereto the buffer BUF is coupled. The first determiner DETI determines a value of a future incoming data packet rate. According to the prior art solution an Lth order linear predictor is used to efficiently estimate a future incoming data packet rate whereby a linear combination of the previous values of the incoming data packet rates is used. However, for this embodiment it is preferred to determine an average incoming data packet rate AR in order to estimate a future incoming data packet rate. In order to determine this value of an average incoming data packet rate AR the first determiner DETI includes a counter and a first calculator (both not shown). The counter, coupled to the input of the shaper S is used to measure the average incoming rate of packets. It counts the number of incoming data packets of the incoming data flow IN during every consecutive predetermined period of T seconds and provides this number to the first calculator of the first determiner DETI .
It has to be remarked that for this particular embodiment it is preferred to define the predetermined period of T seconds equal to 10 milliseconds, however the scope of the invention is not limited to a shaper which includes in the first determiner DET1 a counter which determines the number of incoming data packets every 10 milliseconds. Indeed, it is clear to a person skilled in the art that other period times could be determined in order to measure a number of incoming data packets and in order to be used to determine a value of an average incoming data packet rate. The calculator calculates a new average incoming data packet rate AR based upon - the provided number of incoming data packets N(IN)during the predetermined measuring period; and - a predetermined averaging factor F; and - a previous calculated average incoming data packet rate AR(prev).
The first calculator uses the following formulae in order to calculate for each measuring period T of 10 milliseconds AR = AR(prev) + F x {AR(prev) - N(IN)}
For this particular embodiment the averaging factor F is set to 0.05. It is clear to a person skilled in the art that the scope of the invention is not limited to first determiners DET1 which are including an averaging factor of a low pass filter which is set to 0.05 but that this averaging factor could be set to other values e.g. 0.06. Furthermore, it should be clear that the scope of the invention is neither limited to a shaper S which includes a first determiner DET1 which determines the average incoming data packet rate AR according to the above described formulae. Indeed, it is clear to a person skilled in the art that other kind of formulas e.g. more complex solutions could be used in the shaper of the invention in order to determine the average incoming data packet rate AR of the incoming data flow IN.
Upon receiving of the counter the number of data packets N(IN), the first calculator calculates every 10 milliseconds a new average incoming data packet rate. This average incoming data packet rate AR is provided by the first determiner DET1 to the third determiner DET3 which is coupled to an output of this first determiner DET1.
The second determiner DET2 is coupled to an output of the buffer BUF. This output of the buffer BUF provides an increment control signal (see arrow) each time when an incoming data packet enters the buffer BUF and provides a decrement control signal each time when an outgoing data packet of the outgoing data flow leaves the buffer BUF. The second determiner DET2 includes a counter (not shown) which increments with one each time when an increment control signal is recieved and decrements ~«ith one each time when a decrement control signal is received. According to this way a value of a buffer occupancy BO is determined by the second determiner DET2. The second determiner DET2 provides this value of a buffer occupancy BO to the third S determiner DET3 which is also coupled to the second determiner DET2.
It has to be explained that the buffer occupancy, i.e. a number of data packets of the incoming data flow which are actually being buffered by the buffer BUF could be determined according to different kind of ways.
The memory MEM is included in the shaper S in order to store predefined values which must also be provided to the third determiner DET3.
Therefor the memory MEM is coupled to the buffer BUF in order to receive the predefined minimum buffer occupancy MIN-BO and the predefined maximum buffer occupancy MAX-BO and to store these values.
Furthermore the memory MEM is also coupled to a signaling protocol unit (not shown). Such a signaling protocol unit is enabled to understand the signaling protocol between the source of the data flow and the communication network or which is at least enabled to groom out of the information exchanged between the source and the communication network the predetermined peak data packet rate and the predetermined minimum data packet rate according to the established GFR contract. Since a shaper S according to the present invention is used at different places inside the network e.g. inside an asynchronous transfer mode ATM switch of an ATM network, a policing unit, an asymmetric digital subscriber line ADSL modem of an ADSL network, and as a stand-alone device in a communication network, such signaling protocol unit is included in the communication network outside or inside the shaper S. Indeed, in the event when the shaper is included in e.g. the above mentioned ATM
switch, the shaper S takes advantage of the fact that such an ATM switch already includes such a signaling protocol unit, whereby the memory MEM included in the shaper S is coupled to this signaling protocol unit. In the event when the shaper is acting as a stand-alone device in the network it is necessary to include such a signaling protocol unit in the present shaper S. Indeed, the aim of the present paragraph is the fact that the signaling protocol unit is aware of the predefined minimum data packet rate and the peak data packet rate and that this information is provided to the memory MEM of the shaper S in order to be stored in this memory MEM. At predefined time moments the information in the memory MEM i.e. the predefined minimum buffer occupancy, the predefined maximum buffer occupancy, the predefined peak data packet rate and the predefined minimum data packet rate is provided to the third determiner DET3.
A further remark is that a signaling protocol is only required in the event when switched virtual channels are used. However in the event when permanent virtual channels are used, the minimum data packet rate and the peak data packet rate of the virtual channels are directly specified by the network operator for each connection and are known by the switch and consequently by the shaper.
The third determiner DET3 is adapted to determine the value of the outgoing data packet rate in function of the predetermined peak data packet rate, the value of the average incoming data packet rate, the value of the buffer occupancy and the predetermined minimum data packet rate. The determined outgoing data packet rate is provided by the third determiner DET3 to the buffer BUF in order to control the output of the buffer BUF and to enable the buffer BUF
to adapt the actual outgoing data packet rate to this received outgoing data packet rate.
Each time a data packet is transmitted by the shaper S, a new value for the outgoing data packet rate is calculated by the third determiner DET3 according to the received information from the first determiner DETI, the second determiner DET2 and the memory MEM. The initialization of this determining step is provided with an execution signal EXE which is provided by the buffer BUF
to the third determiner DET3 when an outgoing data packet is going to be transmitted by the buffer BUF. It has to be remarked that the shaper according to the invention is not limited to the implementation of determining an outgoing data packet rate for every outgoing data packet, which is in fact upon an irregular base. Indeed, the outgoing data packet rate is in this way changed for every outgoing data packet, but it could be changed also every N outgoing data packets or every S seconds which is upon a regular base.
In the event when the value of the buffer occupancy BO is smaller or equal to the predefined minimum buffer occupancy MIN-BO, the outgoing data packet rate is determined by the maximum out of the value of the average incoming data packet rate AR and the minimum data packet rate MCR
BO _< MIN BO ~
R-OUT = MAX {AR , MCR} ~~ ) In this way, during transmission by the source of the incoming data flow, as long as the buffer occupancy is rather small i.e. not bigger than this predefined minimum buffer occupancy, the outgoing data packet rate will be equal to at least the value of the guaranteed minimum data packet rate.
However, when in such a situation the average incoming data packet rate is bigger as the predefined minimum data packet rate, the buffer will be leaked with this bigger value.
In the event when the value of the buffer occupancy BO is between the predefined minimum buffer occupancy MIN-BO and the predefined maximum buffer occupancy MAX-BO, the outgoing data packet rate is determined by the value calculated by the following formulae MIN BO < BO <_ MAX BO
PCR - ~LL4,Y {.~R, I~ICR }
R-OUT=MAX {AR,MCR} + .~~Y BO-.LILY BO x HBO - M!N-BO) ~2) According to this formulae, once the buffer occupancy reaches the predefined minimum threshold i.e. the predefined minimum data packet rate, the buffer must be leaked with an increasing outgoing data packet rate.
The increasing outgoing data packet rate is a linear function which increases with an increasing buffer occupancy. The linear function has an interception at the maximum out of the predetermined minimum data packet rate and the average incoming data packet rate and a slope which is equal to a fraction of the difference between the predetermined peak data packet rate and the maximum out of the predetermined minimum data packet rate and the value of the average incoming data packet rate, over the difference between the predetermined maximum buffer occupancy and the predetermined minimum buffer occupancy.
In the event when the value of the buffer occupancy BO is bigger as the predefined maximum buffer occupancy MAX_BO, the outgoing data packet rate is determined by the value of the predetermined peak data packet rate.
MAX_BO < BO
~ R OUT = PCR
This means that once the value of the buffer occupancy BO is bigger as the predefined maximum buffer occupancy, the buffer is leaked with an outgoing data packet rate which is equal to the maximum allowable incoming data packet rate i.e. the peak data packet rate according to the GFR contract.
Herewith overflow of the buffer BUF is avoided.
Hereafter the principle working of the method of the invention will be described. Presume that incoming data packet was received by the shaper S and has been buffered by the buffer BUF. At the moment when the data packet is going to be transmitted by the shaper S a new value for the outgoing data packet rate has to be determined. A control signal EXE is provided by the buffer BUF
to the third determiner DET3 in order to initiate the determining procedure. In order to be able to calculate a new value for the outgoing data packet rate the buffer BUF requests with a value request control signal (only shown with an arrow) new values for the parameters to the first determiner DET1, the second determiner DET2 ad the memory MEM.
Upon receiving of a value request control signal from the third determiner DET3, the first determiner DET1 provides to the third determiner a value for the future outgoing data packet rate which is a value for the average incoming data packet rate AR and which is updated according to the method S explained above every 10 milliseconds.
Upon receiving of a value request control signal from the third determiner DET3, the second determiner DET2 provides to the third determiner DET3 a value for the buffer occupancy BO which is updated every time a data packet enters or leaves the buffer BUF.
Upon receiving of a value request control signal from the third determiner DET3, the memory MEM provides to the third determiner DET3 a value for the minimum data packet rate MCR, a value for the peak data packet rate PCR, a value for the minimum buffer occupancy MIN_BO and a value for the maximum buffer occupancy MAX_BO. It has to be remarked that these values are not at all updated with the frequency of with which the average rate AR and the buffer occupancy BO are updated. Furthermore, it has to be remarked that other implementations are possible in order to realize this step.
Indeed, another possible implementation is that the third determiner DET3 stores these values and uses these values until the memory MEM provides a warning signal in order to warn the third determiner DET3 that one of the values have been changed. The third determiner DET3 provides than a value request control signal to the memory MEM only upon receiving of such a warning signal.
When the third determiner DET3 has all the needed values of the parameters, it determines a new value for the outgoing data packet rate according to the value of the buffer occupancy. Indeed, upon comparing the value of the buffer occupancy BO with the value of the minimum buffer occupancy MIN-BO and the maximum buffer occupancy MAX_BO the third determiner uses any on of the formulae's (1 ), (2) and (3) mentioned above.
Presume a situation wherein the value of the buffer occupancy BO is between the value of the two thresholds of the buffer BO whereby formulae (2) will be used by the third determiner DET3. A new value for the outgoing data packet rate ROUT is calculated as follows ROUT=MAX AR,MCR + pCR - ~1.I-LY .~1R, :LICR
;LL~LY-BO ~:~II~V BO x (BO - MIN-BO) The new value is provided by the third determiner DET3 to the buffer BO which changes its outgoing data packet rate to this new value.
While the principles of the invention have been described above in connection with specific apparatus, it is to be clearly understood that this description is made only by way of example and not as a limitation on the scope of the invention, as defined in the appended claims.
Claims (10)
1. A shaping method for use by a shaper (S) in a communication network to convert an incoming data flow (IN) with an incoming data packet rate R-IN) into an outgoing data flow (OUT) with an outgoing data packet rate (R_OUT), said shaping method includes the steps of determining a value of a future incoming data packet rate (AR) of said incoming data packet rate, determining a value of a buffer occupancy (BO) related to the number of data packets of said incoming data flow (IN) being received and actual being buffered by a buffer (BUF) included in said shaper (S), said buffer (BUF) being leaked with said outgoing data packet rate (R_OUT) in order to provide thereby said outgoing data flow (OUT), and the step of determining a value of said outgoing data packet rate (R-OUT) in function of said value of said future incoming data packet rate (AR) and said value of said buffer occupancy (BO), characterized in that said shaping method includes the step of determining said value of said outgoing data packet rate (R_OUT) also in function of a predetermined peak data packet rate (PCR) and a predetermined minimum data packet rate (MCR) in order to enable said shaper (S) to support a service category providing a service with a predetermined minimum guaranteed bandwidth according to said predetermined minimum data packet rate (MCR) and allowing use of excess bandwidth over said predetermined minimum guaranteed bandwidth, said excess bandwidth being limited according to said predetermined peak data packet rate (PCR).
2. The shaping method according to claim 1, characterized in that said shaping method includes constituting said step of determining a value of a future incoming data packet rate by determining a value of an average incoming data packet rate (AR) of said incoming data packet rate.
3. The shaping method according to any one of claim 1 and claim 2, characterized in that in the event when a value of said buffer occupancy (BO) is any one of being smaller than a predetermined minimum buffer occupancy (MIN_BO) and being substantially equal to said predetermined minimum buffer occupancy (MIN_BO), said shaping method includes constituting said step of determining said value of said outgoing data packet rate (R-OUT) with a maximum of any one of said predetermined minimum data packet rate and said future incoming data packet rate (MAX{MCR,AR)}).
4. The shaping method according to any one of claim 1 and claim 2, characterized in that in the event when a value of said buffer occupancy (BO) lays between a predetermined minimum buffer occupancy (BO_MIN) and a predetermined maximum buffer occupancy (MAX_BO) said shaping method includes constituting said step of determining said value of said outgoing data packet rate (R_OUT) with a function being directly proportional to said value of said buffer occupancy (BO) and being bounded between said predetermined minimum data packet rate (MCR) and said predetermined peak data packet rate (PCR).
5. The shaping method according to any one of claim 1 and claim 2, characterized in that in the event when a value of said buffer occupancy is any one of being substantially equal to a predetermined maximum buffer occupancy (MAX-BO) and being bigger than said predetermined maximum buffer occupancy (MAX_BO) said shaping method includes constituting said step of determining said value of said outgoing data packet rate (R_OUT) with said predetermined peak data packet rate (PCR).
6. The shaping method according to claim 4, characterized in that said function is a maximum of any one of said future incoming data packet rate and a linear function of said value of said buffer occupancy with a slope being substantially equal to a fraction of the difference between said predetermined peak data packet rate and said predetermined minimum data packet rate, over the difference between said predetermined maximum buffer occupancy and said predetermined minimum buffer occupancy.
7. The shaping method according to claim 4, characterized in that said function is a linear function with an interception at a maximum of any one of said predetermined minimum data packet rate and said future incoming data packet rate and with a slope being substantially equal to a fraction of the difference between said predetermined peak data packet rate and a maximum of any one of said predetermined minimum data packet rate and said average incoming data packet rate, over the difference between said predetermined maximum buffer occupancy and said predetermined minimum buffer occupancy.
8. The shaping method according to any one of claim 1 and claim 2, characterized in that said step of determining a value of a future incoming data packet rate (AR) is realized for a first one of a plurality of group data packet rates whereby a value of a first future group data packet rate is provided, each one of said plurality of group data packet rates being an incoming data packet rate of one of a plurality of group data packets, each one of said plurality of group data packets including data packets of said incoming data flow, and that in the event when an outgoing data packet included in said outgoing data flow is included in a first group data packet of said plurality of group data packets, said future incoming data packet rate is constituted by said value of said first future group data packet rate in order to execute said step of determining said value of said outgoing data packet rate (R_OUT), said value of said first future group data packet rate being an incoming data packet rate of said first group data packets.
9. A shaper (S) for use in a communication network to convert an incoming data flow (IN) with an incoming data packet rate (R_IN) into an outgoing data flow (OUT) with an outgoing data packet rate (R_OUT) according to a predetermined shaping method, said shaper (S) including a buffer (BUF) coupled to an input of said shaper in order to receive and to buffer data packets of said incoming data flow and in order to be leaked via an output of said shaper with a value of said outgoing data packet rate and to provide thereby said outgoing data flow (OUT), first determining means (DET1) coupled to an input of said shaper in order to determine a future incoming data packet rate of said incoming data packet rate and to provide thereby a value of said average incoming data packet rate (AR), second determining means (DET2) coupled to said buffer (BUF) in order to determine a buffer occupancy related to a number of data packets actual being buffered by said buffer and to provide thereby a value of said buffer occupancy (BO), third determining means (DET3) coupled to said first determining means (DET1), to said second determining means (DET2), and to said buffer (BUF) in order to determine a value of said outgoing data packet rate {R_OUT) in function of said value of said future incoming data packet rate (AR) and said value of said buffer occupancy (BO) and in order to provide said value of said outgoing data packet rate to said buffer (BUF), characterized in that said third determining means (DET3) is adapted to determine said value of said outgoing data packet rate also in function of a predetermined peak data packet rate (PCR) and a predetermined minimum data packet rate (MCR) in order to enable said shaper (S) to support a service category providing a service with a predetermined minimum guaranteed bandwidth according to said predetermined minimum data packet rate (MCR) and allowing use of excess bandwidth over said predetermined minimum guaranteed bandwidth, said excess bandwidth being limited according to said predetermined peak data packet rate (PCR).
10. A communication network characterized in that said communication network includes at least one shaper as described in claim 9.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| EP98402245A EP0986218A1 (en) | 1998-09-11 | 1998-09-11 | A shaping method, a shaper realizing such a shaping method and a communication network including such a shaper |
| EP98402245.9 | 1998-09-11 |
Publications (1)
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| CA2281468A1 true CA2281468A1 (en) | 2000-03-11 |
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| CA002281468A Abandoned CA2281468A1 (en) | 1998-09-11 | 1999-08-26 | A shaping method, a shaper realizing such a shaping method and a communication network including such a shaper |
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| EP (1) | EP0986218A1 (en) |
| JP (1) | JP2000101608A (en) |
| CA (1) | CA2281468A1 (en) |
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| JP3512152B2 (en) | 1998-10-14 | 2004-03-29 | 松下電器産業株式会社 | Amplification type solid-state imaging device and driving method thereof |
| JP3578648B2 (en) * | 1998-11-16 | 2004-10-20 | 松下電器産業株式会社 | Amplification type solid-state imaging device and driving method thereof |
| JP2001111619A (en) * | 1999-10-12 | 2001-04-20 | Sony Corp | Transmitter, communication system and its communication method |
| JP3570501B2 (en) * | 2000-06-15 | 2004-09-29 | 日本電気株式会社 | Network system and packet data transmission method |
| JP2002009778A (en) * | 2000-06-26 | 2002-01-11 | Fujitsu Ltd | Packet switch device |
| US6839321B1 (en) * | 2000-07-18 | 2005-01-04 | Alcatel | Domain based congestion management |
| US7502317B2 (en) * | 2002-05-17 | 2009-03-10 | Alcatel-Lucent Usa Inc. | Method for differentiating services and users in communication networks |
| JP2006528861A (en) * | 2003-07-24 | 2006-12-21 | コーニンクレッカ フィリップス エレクトロニクス エヌ ヴィ | Admission control method for wireless network based on guaranteed transmission rate |
| US7420919B1 (en) * | 2003-11-10 | 2008-09-02 | Cisco Technology, Inc. | Self converging communication fair rate control system and method |
| KR100584381B1 (en) * | 2004-02-04 | 2006-05-26 | 삼성전자주식회사 | Method for adjusting transmission rate of mpeg-2 data and apparatus therefor |
| US8788640B1 (en) | 2005-08-16 | 2014-07-22 | F5 Networks, Inc. | Employing rate shaping class capacities and metrics to balance connections |
| US8411566B2 (en) * | 2007-10-31 | 2013-04-02 | Smart Share Systems APS | Apparatus and a method for distributing bandwidth |
| EP3490322A1 (en) | 2010-06-04 | 2019-05-29 | Board of Regents, The University of Texas System | Wireless communication methods, systems, and computer program products |
| WO2012016187A2 (en) * | 2010-07-30 | 2012-02-02 | Board Of Regents | Distributed rate allocation and collision detection in wireless networks |
| WO2012122508A2 (en) | 2011-03-09 | 2012-09-13 | Board Of Regents | Network routing system, method, and computer program product |
| US20120250694A1 (en) * | 2011-03-28 | 2012-10-04 | Tttech Computertechnik Ag | Centralized traffic shaping for data networks |
| US20130003543A1 (en) * | 2011-06-30 | 2013-01-03 | Avistar Communications Corporation | NEXT-GENERATION BANDWIDTH MANAGEMENT CONTROL SYSTEMS FOR MULTIPLE-SERVICE CALLS, SESSIONS, PACKET-LEVEL PROCESSES, AND QoS PARAMETERS - PART 1: STRUCTURAL AND FUNCTIONAL ARCHITECTURES |
| WO2013070232A1 (en) | 2011-11-10 | 2013-05-16 | Assia, Inc. | Method, apparatus, and system for optimizing performance of a communication unit by a remote server |
| US9819595B2 (en) | 2011-12-05 | 2017-11-14 | John Cioffi | Systems and methods for traffic aggregation on multiple WAN backhauls and multiple distinct LAN networks |
| WO2013085486A1 (en) | 2011-12-05 | 2013-06-13 | Adaptive Spectrum And Signal Alignment, Inc. | Systems and methods for traffic load balancing on multiple wan backhauls and multiple distinct lan networks |
| US20130282868A1 (en) * | 2012-04-23 | 2013-10-24 | Jae Chung | Integral Controller Based Pacing for HTTP Pseudo-streaming |
| US8743758B1 (en) | 2013-11-27 | 2014-06-03 | M87, Inc. | Concurrent uses of non-cellular interfaces for participating in hybrid cellular and non-cellular networks |
| EP3611951A1 (en) | 2013-12-13 | 2020-02-19 | M87, Inc. | Methods and systems of secure connections for joining hybrid cellular and non-cellular networks |
| EP3806397B1 (en) | 2014-12-04 | 2023-11-22 | Assia Spe, Llc | Method and apparatus for predicting successful dsl line optimization |
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| CA2012868C (en) * | 1989-03-23 | 1994-03-22 | Shin-Ichiro Hayano | Call control with transmission priority in a packet communication network of an atm type |
| US5623492A (en) * | 1995-03-24 | 1997-04-22 | U S West Technologies, Inc. | Methods and systems for managing bandwidth resources in a fast packet switching network |
| US6327246B1 (en) * | 1995-11-29 | 2001-12-04 | Ahead Communications Systems, Inc. | Controlled available bit rate service in an ATM switch |
| US5793747A (en) * | 1996-03-14 | 1998-08-11 | Motorola, Inc. | Event-driven cell scheduler and method for supporting multiple service categories in a communication network |
| US5949795A (en) * | 1997-02-14 | 1999-09-07 | General Instrument Corporation | Processing asynchronous data within a set-top decoder |
| US6081843A (en) * | 1997-03-20 | 2000-06-27 | Nokia Telecommunications | System using simulation cell and simulation buffer for regulating cell transfer rate according to occupancy level of the simulation buffer |
| US6198724B1 (en) * | 1997-10-02 | 2001-03-06 | Vertex Networks, Inc. | ATM cell scheduling method and apparatus |
| US6247072B1 (en) * | 1998-01-27 | 2001-06-12 | Cisco Technology, Inc. | Real-time data rate matching across a medium |
| US6404767B1 (en) * | 1998-06-17 | 2002-06-11 | Nortel Networks Corporation | Architecture for ABR processing within an ATM switch |
| US6333917B1 (en) * | 1998-08-19 | 2001-12-25 | Nortel Networks Limited | Method and apparatus for red (random early detection) and enhancements. |
| CA2245367A1 (en) * | 1998-08-19 | 2000-02-19 | Newbridge Networks Corporation | Two-component bandwidth scheduler having application in multi-class digital communication systems |
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- 1999-08-26 CA CA002281468A patent/CA2281468A1/en not_active Abandoned
- 1999-09-08 US US09/392,336 patent/US6680907B1/en not_active Expired - Fee Related
Also Published As
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| JP2000101608A (en) | 2000-04-07 |
| EP0986218A1 (en) | 2000-03-15 |
| US6680907B1 (en) | 2004-01-20 |
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