CA2300190A1 - Method for the statistical multiplexing of atm connections - Google Patents
Method for the statistical multiplexing of atm connections Download PDFInfo
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- CA2300190A1 CA2300190A1 CA002300190A CA2300190A CA2300190A1 CA 2300190 A1 CA2300190 A1 CA 2300190A1 CA 002300190 A CA002300190 A CA 002300190A CA 2300190 A CA2300190 A CA 2300190A CA 2300190 A1 CA2300190 A1 CA 2300190A1
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Classifications
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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
-
- 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
-
- 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
-
- 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
- H04L2012/5672—Multiplexing, e.g. coding, scrambling
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- Engineering & Computer Science (AREA)
- Computer Networks & Wireless Communication (AREA)
- Data Exchanges In Wide-Area Networks (AREA)
Abstract
During ATM communications a plurality of communications are transmitted through common link sections. New incoming communications are allowed on the basis of decisions made by acceptance algorithms. However only yes/no decisions are made. It is nevertheless desirable that the reserved band width required for all the communications carried out by said link sections be known. This problem is solved by the invention whereby the band width is evaluated by steps while communications are being set up/switched out, by modifying the sigma rule algorithm.
Description
SPECIFICATION
METHOD FOR THE STATISTICAL MULTIPLEXING OF ATM
CONNECTIONS
The invention is directed to a method according to the preamble of patent claim 1.
A plurality of connection types are defined given connections via which information are transmitted according to the asynchronous transfer mode (ATM). Thus, on the one hand, connections having strict demands made of the cell delay times are distinguished from connections that do not 1 o make strict demands of the cell delay times.
Particularly included among the former are connections with which information are transmitted with a constant bit rate (CBR) as well as connections via which real time information are transmitted with variable bit rate (rt-VBR).
The latter include non-real-time VBR connections (nrt-VBR) or connections via which information are transmitted with a variable bit rate (available bit rate, ABR) or unspecified bit rate connections (UBR).
The information of all five connection types are conducted in ATM
cells in common via virtual paths or, respectively, virtual lines having a 2o predetermined bit rate (bandwidth). In the course of the setup of new connections that have strict demands made of the cell delay times, it is required to calculate the bandwidth that is required for the totality of all connections conducted over a connecting section/connecting line or a virtual path. For calculating an effective bandwidth, it is necessary to determine the 2 5 rate with which the large cell memory offered for this connection type as well as the other connection types (nrt-VBR, ABR, UBR) is allowed to be emptied.
Upon setup of an ATM connection, the transmitting means must generally inform a higher-ranking control means (all acceptance control) of 3 o previously defined parameters. This is required in order to assure the quality ~
of the connection for all subscribers (quality of service). When, for example, too many cells are transmitted and, thus, the transmission capacity is exceeded, too many cells must be discarded. This, however, must be avoided under all circumstances since this all involves a loss of information.
To this end, for example, the demand for a cell loss properly of 10-'° of a connection exists on the part of standardization authorities. For this reason, a calculation is already carried out at the call setup as to whether this new connection can be accepted in addition to the connections already existing.
When the transmission capacity has already been exhausted, the requested to connection is rejected.
A number of transmission parameters are defined for the description of these procedures. These include, for example, the peak cell rate (PCR) defined on a connection. This is thereby a matter of an upper limit for the plurality of ATM cells that can be transmitted per second of this connection.
Further, the control means is informed of a sustainable cell rate (SCR) by the transmitting means given a connection with variable bit rate. This is the upper limit for an average cell rate with which the cells are transmitted during the existence of the connection. As further parameters, the maximally possible transmission capacity of the connecting line (link cell rate, C) as 2 o well as the maximally possible load on the connecting line (p°) are known to the control means. The former is a matter of a quasi material constant of the connecting line, whereas the latter defines a quantity with which the maximally allowable aggregate cell rate on the connecting line is recited.
This is usually 95% of the maximally possible transmission capacity of the connecting line. Based on the measure of these parameters, a decision is then made as to whether new connection requests can be accepted or not.
To this end, an algorithm sequences in the higher-ranking control means with which the parameters received from the transmitting equipment are checked. Further, these are compared to parameters that have already 3 o been calculated and relate to the momentary load on the connecting line.
A decision is then made on the basis of these comparisons as to whether the new connection request is accepted and this connection can still be permitted. Among other things, the peak cell rate that has already been addressed or the sustainable cell rate are employed as critical parameters.
A number of methods have developed in the prior art for handling these procedures. Let the sigma rule algorithm be recited here as a simple method. This algorithm is disclosed in detail in German Patent Application DP 196 49 646.7. A nt" connection is thereby only allowed when the following is valid for the (n - 1 ) connections already existing plus the non connection:
n ( a ) ~ PCRi < pJ ~ C
=I
1 o The connection is likewise allowed when, taking additional properties of the n connections into consideration, as explained later, the following condition (b) is met.
( b ) ~ SCR; .~ ~ r ~ , ~: T:~ ~ ~: s f ~ ( ~ scr~; - c gc~: _ scR; y o'~2 s -V~; f ;_'...~:<;:'~~; s V~; E (.u<3.;>:> rJ
~'o' C - ~ 1~C'Ry vct F a:A~:>::
whereby c - po ~ c - ~ PCR1 is the free capacity for class S.
It can be derived from condition (b) that the pending connections are divided into two classes here. At the beginning of the connection setup, thus, the sigma rule algorithm must make a decision as to which of two classes, namely a class S as well as a class P, the potentially newly added ATM connection is to be assigned to.
All virtual connections are assigned to class S for which a statistical 2 o multiplexing according to the sigma rule algorithm would yield a noticeable gain compared to the peak cell rate reservation algorithm. The following condition must be met as criterion for this type of connection for the peak cell rate and the sustainable cell rate of all connections to be statistically multiplex:
PCRIC < 0.03 and (0.1 s SCRIPCR -< 0.5) All other virtual connections are assigned to the class P. These particularly include the connections with constant bit rate. Further, all connections are assigned here for which the parameters SCR as well as PCR lie very close to one another - or very far from one another or that already exhibit a high peak cell rate PCR compared to the overall capacity of the connecting line. A peak cell rate that is greater then 3% of the maximally possible transmission capacity of the connecting line is valid as criterion for this.
Further, a factor q can be derived from the condition (b). This factor 1 o is dependent both on the class S as well as on the free capacity c of the class S. For a defined class S, the q(c) values must be calculated with a complicated program. In simplifying fashion from dynamics points of view, the dependency of the quantity c is estimated by a hyperbola function q(c)=q,+qz~c.
In this prior art, thus, a n'" virtual connection VC~ having a defined peak cell rate PCR~ as well as a sustainable cell rate SCR is allowed in addition to already existing virtual connections VC; having the parameters SCR; as well as PCR; (1 <_i<n-1 ) on a connecting line when conditions (a) or (b) are met.
2 o According to the condition (a), a check is carried out to see whether the sum of the peak cell rates of all n connections on the connecting line is equal to or less then the maximally possible transmission capacity on the connecting line. When this is the case, then n'" virtual connection can be accepted and the interrogation of condition (b) is superfluous. When this is not the case, then a check is carried in condition (b) to see whether the upper estimate of the average value of the sum of the peak cell rates of all connections of the class S together with a cell rate that is calculated from the burst nature of all connections of the class S is less then or equal to the cell rate that is available currently for class S connections. When this is the 3 o case, then the n~' virtual connection is accepted; otherwise, it is rejected.
In this prior art, the first class S is in turn subdivided into further sub-classes S,, Sz or S3 in order to achieve an even finer classification. In case ~
of the arrival of a new connection request, thus, the sigma rule algorithm must check based on the criterion of determined interrogation criteria to see which of the sub-classes this new connection is to be assigned to.
The most beneficial sub-class SX is then automatically selected. A sub-class SX is thereby defined via a lower limit or, respectively, upper limit of the peak cell rate PCR as well as of the relationship of the transmission parameters SCRIPCR.
Equation (b) thus experiences a modification by the addressed sub-classes Sk_ Pk (c) ~ SCR. + q(c, SK)y ~ 5CRy. (PCRy-SCRi) <_c vc~ ~ sk 1 vc; f 'k 1 o whereby c = py c - ~ pcR is the free capacity for the class S.
v:~z a ~X
The q factor thus derives as q ( c, sk ) - ql n + q2s l c k k This connection acceptance algorithm according to this prior art is thus in the position of deciding whether a predetermined bandwidth, for example the bandwidth of a virtual path or of a line, is adequate overall for a group of connections. Since such acceptance algorithms supply a yeslno decision as a result as to whether a connection is to be accepted or not, they are not directly suited for the calculation of the effective bandwidth for a group of connections.
2 o The effective bandwidth required for a group of connections according to the used sigma rule acceptance algorithm could fundamentally be determined with arbitrary precision by an iterative approximation method. The problem of this method, however, is comprised therein that the acceptance algorithm would have to be multiply run per connection setup and, thus, would require an extremely great amount of processor capacity.
European Patent Application EP 0 673 138 A2 discloses a method of how a plurality of connections can be conducted over a common ~
5a connecting section. Upon arrival of a connection request, a check is thereby carried out to see if adequate bandwidth is still available for accepting this connection. When this is the case, the connection is accepted; otherwise, it is rejected. The calculation of an effective bandwidth, however, is not addressed here.
International Application WO 97101895 likewise discloses a method of how pending connections are conducted via common connecting sections.
The goal of such an algorithm, however, is only to accept or, respectively, to reject the connection based on the criterion of the remaining bandwidth.
The invention is based on the object of disclosing a way of how an acceptance algorithm is to be fashioned such that a bandwidth representative for all connections can be calculated in an efficient way.
Proceeding on the basis of the features recited in the preamble of patent claim 1, the invention is achieved by the features of the characterizing part.
What is particularly advantageous for the invention is that the sigma rule algorithm is employed as acceptance algorithm. The bandwidth, proceeding from an initial value, is determined step-by-step with the setuplrelease of connections. The sigma rule algorithm is started at every step and, in addition to supplying a yeslno decision, supplies an estimate of the bandwidth based on the prescription of acceptance criteria, a 1 o conservative traffic parameter value of a class-specific bandwidth is added or, respectively, subtracted. The conservative traffic parameter value is thereby constructed differently in the case of the connection setup than in the case of the connection release. When the sigma rule algorithm determines that the conservative estimate with respect to the bandwidth would be adequate, then a more aggressive traffic parameter value is added to or, respectively, subtracted from the class-specific bandwidth. Here, too, the more aggressive traffic parameter value is fashioned differently in the case of the connection setup than in the case of the connection release.
Advantageous developments of the invention are recited in the 2 o subclaims.
The invention is explained in greater detail below with reference to an exemplary embodiment.
Shown are:
Fig. 1 a flow chart according to the inventive method;
Fig. 2 a flow chart according to the inventive method.
Fig. 1 shows a flow chart of the inventive method. The initially described sigma rule algorithm SR of the prior art is employed as acceptance algorithm. In accord therewith, additional status variables are introduced in addition to the status variable carried in the sigma rule 3 o algorithm SR. What are thereby involved are a matter of the status variables cSk, cPk and Ce~k:
The status variables cSk is a matter of the effective bandwidth of the virtual connections that are to be assigned to one of the classes Sk according to the sigma rule algorithm SR. The status variables cPk indicates the sum of the peak cell rates PCR of all virtual connections in the class Pk, s whereas the status variables ceffk is defined as effective bandwidth of all connections with reference to the classes k. What thus follows is:
( 1 ) Ceffk = CSk -~ CPk Given (n-1 ) existing connections VC; with the parameters PCR;, SCR;, a calculation is then carried out for a connection setup to see whether 1 ) the 1o new connection VC~ can be accepted or not; 2) the effective bandwidth ceffk that are [sic] to be reserved for the (n-1 ) existing connections VC;
including the newly added connection VC~.
In a first step, a check is first carried to see whether the new connection VC~ to be potentially accepted can be assigned to one of the 15 classes Sk or Pk. For example, let it be assumed that this can be assigned to one of the classes Sk. In this case, a check,is carried out to see whether the following condition is met for all virtual connections VC;, including the connection to be potentially added:
(2) ~ SCR;+q(c $H+SCR~,Sk)~ ~ SCR ~(PCR~-SCR,)<C SK+SCR~
VC,E$x VC,ESk In the above equation, Equation (c) is taken as the basis and the 2 o variable c employed therein is replaced by the bandwidth csk reserved for the (n-1 ) connections plus the average sustainable cell rate SCRs that is to be reserved for the nt" connection VC~ to be potentially accepted. As can be seen according to Fig. 1, the method is started with a value csk = 0.
A strict application of condition (2) likewise yields a bandwidth that 25 is greater than the sum of the peak cell rate PCR~ of all connections.
Since the sum of all added, effective bandwidths, however, is never allowed to lie above the sum of its peak cell rates PCR~, condition (2) is modified in such a way that (3) mint ~ SCR;+q(c SK+SCR~,Sk)~ ~ SCR; .(PCR;-SCR;), ~ PCR;
lvcFSk vcFsk vc,~sk Csk+ SCR
is taken. A security in the estimate is thus established.
When the above condition applies, then the effective bandwidth - 5 employed up to then plus the sustainable cell rate SCR allowed for the ntn connection VC~ is taken as new, effective bandwidth cSk. As a result thereof, the following derives:
( 4 ) C SK: =C Sx+SCRn When the condition (3) is not met, the effective bandwidth employed up to 1 o then plus the peak cell rate PCR~ allowed for the n~" connection VC~ is taken as new, effective bandwidth cSk.
(5) c Sk: =C Sk+PCRn When the new connection VCn to be potentially added is to be allocated to one of the classes Sk, a value for the effective bandwidth Ce~k 15 has thus been found.
When the new connection VC~ to be potentially added cannot be assigned to one of the classes Sk, it is automatically assumed that it is to be allocated to one of the classes Pk. The following thus derives:
( 6 ) C pk : - c Pk + PCR
r 2 o Upon employment of Equation (1 ), the effective bandwidth ceffk can then be calculated:
C Pffk - C Sk C Dk t An effective bandwidth has thus been found for the case of a connection setup.
Subsequently, it then must also be determined whether the new connection VC~ can be accepted. To this end, the condition effk c <_ Po~C
must be met.
It is assumed below according to Fig. 1 that a connection release is to be implemented. It is thereby assumed that a connection VC~ is released given n existing connections VC; having the parameters PCR;, SCR;.
Given release of the connection, a check is first carried out to see to whether this appertaining connection VC~ was allocated to one of the classes Sk. In this case, an interrogation criterion is applied to all remaining virtual connections VC; (accept the connection VC~) according to condition (7):
;,SC~t,; + q#c~ ~- t~'R.o,;':,~,), ~GR;.(PCR; -- ~'GR; ) 5 c~' - R*
('31 v~c,es, ~~r.
A strict application of condition (7) now potentially yields a bandwidth for the remaining (n-1 ) connections that is greater than the sum of the peak cell rates of the connections. Condition (7) is therefore to be modified in such a way that uc,~ xe,~ u~,~r S,a~ - PAR;
derives.
When the above condition applies, then the effective bandwidth applied up to then minus the peak cell rate PCR~ allowed for the ntn connection VC~ is taken as new, effective bandwidth csk. Deriving therefrom 5 IS:
(9) csk:=cSK-PCR
r;
When condition (8) is not met, then the effective bandwidth employed up to then minus the sustainable cell rate SCR for the nt" connection VC~ is taken as new effective bandwidth csk.
( 10 ) c Jk: =c ~k-S'CRn A value for the effective bandwidth ceffk has been found for the 1 o released connection VC~ that was allocated to one of the classes Sk.
When the r~l~ased connection VC~ was not allocated to one of the classes Sk, it is automatically assumed that it was allocated to one of the classes Pk. The following thus derives:
( 11 ) C ~k : = C Pk - PCRr Upon application of Equation (1 ), the effective bandwidth ceffk can then be calculated:
C effk _ C Sk C rx ' CA 02300190 2000-02-11 An effective bandwidth has thus been found for the case of a connection release.
In one development of the invention, it is provided to replace Equation ( 10) with f ~.2 ? c~' : = mitt c~ - SCRs, ~CR~
s Upon release of connections that were allocated to one of the classes Sk, the value of the class-specific bandwidth csk is thus upwardly limited by the sum of the peak cell rate of all connections allocated to the classes Sk. The corresponding conditions are shown in Fig. 2
METHOD FOR THE STATISTICAL MULTIPLEXING OF ATM
CONNECTIONS
The invention is directed to a method according to the preamble of patent claim 1.
A plurality of connection types are defined given connections via which information are transmitted according to the asynchronous transfer mode (ATM). Thus, on the one hand, connections having strict demands made of the cell delay times are distinguished from connections that do not 1 o make strict demands of the cell delay times.
Particularly included among the former are connections with which information are transmitted with a constant bit rate (CBR) as well as connections via which real time information are transmitted with variable bit rate (rt-VBR).
The latter include non-real-time VBR connections (nrt-VBR) or connections via which information are transmitted with a variable bit rate (available bit rate, ABR) or unspecified bit rate connections (UBR).
The information of all five connection types are conducted in ATM
cells in common via virtual paths or, respectively, virtual lines having a 2o predetermined bit rate (bandwidth). In the course of the setup of new connections that have strict demands made of the cell delay times, it is required to calculate the bandwidth that is required for the totality of all connections conducted over a connecting section/connecting line or a virtual path. For calculating an effective bandwidth, it is necessary to determine the 2 5 rate with which the large cell memory offered for this connection type as well as the other connection types (nrt-VBR, ABR, UBR) is allowed to be emptied.
Upon setup of an ATM connection, the transmitting means must generally inform a higher-ranking control means (all acceptance control) of 3 o previously defined parameters. This is required in order to assure the quality ~
of the connection for all subscribers (quality of service). When, for example, too many cells are transmitted and, thus, the transmission capacity is exceeded, too many cells must be discarded. This, however, must be avoided under all circumstances since this all involves a loss of information.
To this end, for example, the demand for a cell loss properly of 10-'° of a connection exists on the part of standardization authorities. For this reason, a calculation is already carried out at the call setup as to whether this new connection can be accepted in addition to the connections already existing.
When the transmission capacity has already been exhausted, the requested to connection is rejected.
A number of transmission parameters are defined for the description of these procedures. These include, for example, the peak cell rate (PCR) defined on a connection. This is thereby a matter of an upper limit for the plurality of ATM cells that can be transmitted per second of this connection.
Further, the control means is informed of a sustainable cell rate (SCR) by the transmitting means given a connection with variable bit rate. This is the upper limit for an average cell rate with which the cells are transmitted during the existence of the connection. As further parameters, the maximally possible transmission capacity of the connecting line (link cell rate, C) as 2 o well as the maximally possible load on the connecting line (p°) are known to the control means. The former is a matter of a quasi material constant of the connecting line, whereas the latter defines a quantity with which the maximally allowable aggregate cell rate on the connecting line is recited.
This is usually 95% of the maximally possible transmission capacity of the connecting line. Based on the measure of these parameters, a decision is then made as to whether new connection requests can be accepted or not.
To this end, an algorithm sequences in the higher-ranking control means with which the parameters received from the transmitting equipment are checked. Further, these are compared to parameters that have already 3 o been calculated and relate to the momentary load on the connecting line.
A decision is then made on the basis of these comparisons as to whether the new connection request is accepted and this connection can still be permitted. Among other things, the peak cell rate that has already been addressed or the sustainable cell rate are employed as critical parameters.
A number of methods have developed in the prior art for handling these procedures. Let the sigma rule algorithm be recited here as a simple method. This algorithm is disclosed in detail in German Patent Application DP 196 49 646.7. A nt" connection is thereby only allowed when the following is valid for the (n - 1 ) connections already existing plus the non connection:
n ( a ) ~ PCRi < pJ ~ C
=I
1 o The connection is likewise allowed when, taking additional properties of the n connections into consideration, as explained later, the following condition (b) is met.
( b ) ~ SCR; .~ ~ r ~ , ~: T:~ ~ ~: s f ~ ( ~ scr~; - c gc~: _ scR; y o'~2 s -V~; f ;_'...~:<;:'~~; s V~; E (.u<3.;>:> rJ
~'o' C - ~ 1~C'Ry vct F a:A~:>::
whereby c - po ~ c - ~ PCR1 is the free capacity for class S.
It can be derived from condition (b) that the pending connections are divided into two classes here. At the beginning of the connection setup, thus, the sigma rule algorithm must make a decision as to which of two classes, namely a class S as well as a class P, the potentially newly added ATM connection is to be assigned to.
All virtual connections are assigned to class S for which a statistical 2 o multiplexing according to the sigma rule algorithm would yield a noticeable gain compared to the peak cell rate reservation algorithm. The following condition must be met as criterion for this type of connection for the peak cell rate and the sustainable cell rate of all connections to be statistically multiplex:
PCRIC < 0.03 and (0.1 s SCRIPCR -< 0.5) All other virtual connections are assigned to the class P. These particularly include the connections with constant bit rate. Further, all connections are assigned here for which the parameters SCR as well as PCR lie very close to one another - or very far from one another or that already exhibit a high peak cell rate PCR compared to the overall capacity of the connecting line. A peak cell rate that is greater then 3% of the maximally possible transmission capacity of the connecting line is valid as criterion for this.
Further, a factor q can be derived from the condition (b). This factor 1 o is dependent both on the class S as well as on the free capacity c of the class S. For a defined class S, the q(c) values must be calculated with a complicated program. In simplifying fashion from dynamics points of view, the dependency of the quantity c is estimated by a hyperbola function q(c)=q,+qz~c.
In this prior art, thus, a n'" virtual connection VC~ having a defined peak cell rate PCR~ as well as a sustainable cell rate SCR is allowed in addition to already existing virtual connections VC; having the parameters SCR; as well as PCR; (1 <_i<n-1 ) on a connecting line when conditions (a) or (b) are met.
2 o According to the condition (a), a check is carried out to see whether the sum of the peak cell rates of all n connections on the connecting line is equal to or less then the maximally possible transmission capacity on the connecting line. When this is the case, then n'" virtual connection can be accepted and the interrogation of condition (b) is superfluous. When this is not the case, then a check is carried in condition (b) to see whether the upper estimate of the average value of the sum of the peak cell rates of all connections of the class S together with a cell rate that is calculated from the burst nature of all connections of the class S is less then or equal to the cell rate that is available currently for class S connections. When this is the 3 o case, then the n~' virtual connection is accepted; otherwise, it is rejected.
In this prior art, the first class S is in turn subdivided into further sub-classes S,, Sz or S3 in order to achieve an even finer classification. In case ~
of the arrival of a new connection request, thus, the sigma rule algorithm must check based on the criterion of determined interrogation criteria to see which of the sub-classes this new connection is to be assigned to.
The most beneficial sub-class SX is then automatically selected. A sub-class SX is thereby defined via a lower limit or, respectively, upper limit of the peak cell rate PCR as well as of the relationship of the transmission parameters SCRIPCR.
Equation (b) thus experiences a modification by the addressed sub-classes Sk_ Pk (c) ~ SCR. + q(c, SK)y ~ 5CRy. (PCRy-SCRi) <_c vc~ ~ sk 1 vc; f 'k 1 o whereby c = py c - ~ pcR is the free capacity for the class S.
v:~z a ~X
The q factor thus derives as q ( c, sk ) - ql n + q2s l c k k This connection acceptance algorithm according to this prior art is thus in the position of deciding whether a predetermined bandwidth, for example the bandwidth of a virtual path or of a line, is adequate overall for a group of connections. Since such acceptance algorithms supply a yeslno decision as a result as to whether a connection is to be accepted or not, they are not directly suited for the calculation of the effective bandwidth for a group of connections.
2 o The effective bandwidth required for a group of connections according to the used sigma rule acceptance algorithm could fundamentally be determined with arbitrary precision by an iterative approximation method. The problem of this method, however, is comprised therein that the acceptance algorithm would have to be multiply run per connection setup and, thus, would require an extremely great amount of processor capacity.
European Patent Application EP 0 673 138 A2 discloses a method of how a plurality of connections can be conducted over a common ~
5a connecting section. Upon arrival of a connection request, a check is thereby carried out to see if adequate bandwidth is still available for accepting this connection. When this is the case, the connection is accepted; otherwise, it is rejected. The calculation of an effective bandwidth, however, is not addressed here.
International Application WO 97101895 likewise discloses a method of how pending connections are conducted via common connecting sections.
The goal of such an algorithm, however, is only to accept or, respectively, to reject the connection based on the criterion of the remaining bandwidth.
The invention is based on the object of disclosing a way of how an acceptance algorithm is to be fashioned such that a bandwidth representative for all connections can be calculated in an efficient way.
Proceeding on the basis of the features recited in the preamble of patent claim 1, the invention is achieved by the features of the characterizing part.
What is particularly advantageous for the invention is that the sigma rule algorithm is employed as acceptance algorithm. The bandwidth, proceeding from an initial value, is determined step-by-step with the setuplrelease of connections. The sigma rule algorithm is started at every step and, in addition to supplying a yeslno decision, supplies an estimate of the bandwidth based on the prescription of acceptance criteria, a 1 o conservative traffic parameter value of a class-specific bandwidth is added or, respectively, subtracted. The conservative traffic parameter value is thereby constructed differently in the case of the connection setup than in the case of the connection release. When the sigma rule algorithm determines that the conservative estimate with respect to the bandwidth would be adequate, then a more aggressive traffic parameter value is added to or, respectively, subtracted from the class-specific bandwidth. Here, too, the more aggressive traffic parameter value is fashioned differently in the case of the connection setup than in the case of the connection release.
Advantageous developments of the invention are recited in the 2 o subclaims.
The invention is explained in greater detail below with reference to an exemplary embodiment.
Shown are:
Fig. 1 a flow chart according to the inventive method;
Fig. 2 a flow chart according to the inventive method.
Fig. 1 shows a flow chart of the inventive method. The initially described sigma rule algorithm SR of the prior art is employed as acceptance algorithm. In accord therewith, additional status variables are introduced in addition to the status variable carried in the sigma rule 3 o algorithm SR. What are thereby involved are a matter of the status variables cSk, cPk and Ce~k:
The status variables cSk is a matter of the effective bandwidth of the virtual connections that are to be assigned to one of the classes Sk according to the sigma rule algorithm SR. The status variables cPk indicates the sum of the peak cell rates PCR of all virtual connections in the class Pk, s whereas the status variables ceffk is defined as effective bandwidth of all connections with reference to the classes k. What thus follows is:
( 1 ) Ceffk = CSk -~ CPk Given (n-1 ) existing connections VC; with the parameters PCR;, SCR;, a calculation is then carried out for a connection setup to see whether 1 ) the 1o new connection VC~ can be accepted or not; 2) the effective bandwidth ceffk that are [sic] to be reserved for the (n-1 ) existing connections VC;
including the newly added connection VC~.
In a first step, a check is first carried to see whether the new connection VC~ to be potentially accepted can be assigned to one of the 15 classes Sk or Pk. For example, let it be assumed that this can be assigned to one of the classes Sk. In this case, a check,is carried out to see whether the following condition is met for all virtual connections VC;, including the connection to be potentially added:
(2) ~ SCR;+q(c $H+SCR~,Sk)~ ~ SCR ~(PCR~-SCR,)<C SK+SCR~
VC,E$x VC,ESk In the above equation, Equation (c) is taken as the basis and the 2 o variable c employed therein is replaced by the bandwidth csk reserved for the (n-1 ) connections plus the average sustainable cell rate SCRs that is to be reserved for the nt" connection VC~ to be potentially accepted. As can be seen according to Fig. 1, the method is started with a value csk = 0.
A strict application of condition (2) likewise yields a bandwidth that 25 is greater than the sum of the peak cell rate PCR~ of all connections.
Since the sum of all added, effective bandwidths, however, is never allowed to lie above the sum of its peak cell rates PCR~, condition (2) is modified in such a way that (3) mint ~ SCR;+q(c SK+SCR~,Sk)~ ~ SCR; .(PCR;-SCR;), ~ PCR;
lvcFSk vcFsk vc,~sk Csk+ SCR
is taken. A security in the estimate is thus established.
When the above condition applies, then the effective bandwidth - 5 employed up to then plus the sustainable cell rate SCR allowed for the ntn connection VC~ is taken as new, effective bandwidth cSk. As a result thereof, the following derives:
( 4 ) C SK: =C Sx+SCRn When the condition (3) is not met, the effective bandwidth employed up to 1 o then plus the peak cell rate PCR~ allowed for the n~" connection VC~ is taken as new, effective bandwidth cSk.
(5) c Sk: =C Sk+PCRn When the new connection VCn to be potentially added is to be allocated to one of the classes Sk, a value for the effective bandwidth Ce~k 15 has thus been found.
When the new connection VC~ to be potentially added cannot be assigned to one of the classes Sk, it is automatically assumed that it is to be allocated to one of the classes Pk. The following thus derives:
( 6 ) C pk : - c Pk + PCR
r 2 o Upon employment of Equation (1 ), the effective bandwidth ceffk can then be calculated:
C Pffk - C Sk C Dk t An effective bandwidth has thus been found for the case of a connection setup.
Subsequently, it then must also be determined whether the new connection VC~ can be accepted. To this end, the condition effk c <_ Po~C
must be met.
It is assumed below according to Fig. 1 that a connection release is to be implemented. It is thereby assumed that a connection VC~ is released given n existing connections VC; having the parameters PCR;, SCR;.
Given release of the connection, a check is first carried out to see to whether this appertaining connection VC~ was allocated to one of the classes Sk. In this case, an interrogation criterion is applied to all remaining virtual connections VC; (accept the connection VC~) according to condition (7):
;,SC~t,; + q#c~ ~- t~'R.o,;':,~,), ~GR;.(PCR; -- ~'GR; ) 5 c~' - R*
('31 v~c,es, ~~r.
A strict application of condition (7) now potentially yields a bandwidth for the remaining (n-1 ) connections that is greater than the sum of the peak cell rates of the connections. Condition (7) is therefore to be modified in such a way that uc,~ xe,~ u~,~r S,a~ - PAR;
derives.
When the above condition applies, then the effective bandwidth applied up to then minus the peak cell rate PCR~ allowed for the ntn connection VC~ is taken as new, effective bandwidth csk. Deriving therefrom 5 IS:
(9) csk:=cSK-PCR
r;
When condition (8) is not met, then the effective bandwidth employed up to then minus the sustainable cell rate SCR for the nt" connection VC~ is taken as new effective bandwidth csk.
( 10 ) c Jk: =c ~k-S'CRn A value for the effective bandwidth ceffk has been found for the 1 o released connection VC~ that was allocated to one of the classes Sk.
When the r~l~ased connection VC~ was not allocated to one of the classes Sk, it is automatically assumed that it was allocated to one of the classes Pk. The following thus derives:
( 11 ) C ~k : = C Pk - PCRr Upon application of Equation (1 ), the effective bandwidth ceffk can then be calculated:
C effk _ C Sk C rx ' CA 02300190 2000-02-11 An effective bandwidth has thus been found for the case of a connection release.
In one development of the invention, it is provided to replace Equation ( 10) with f ~.2 ? c~' : = mitt c~ - SCRs, ~CR~
s Upon release of connections that were allocated to one of the classes Sk, the value of the class-specific bandwidth csk is thus upwardly limited by the sum of the peak cell rate of all connections allocated to the classes Sk. The corresponding conditions are shown in Fig. 2
Claims (9)
1. Method for statistical multiplexing of ATM connections, comprising a plurality of ATM connections that are conducted over a common connecting line and for which an effective bandwidth (C eff k) is reserved in aggregate on this connecting line for this purpose, as well as with an acceptance algorithm (SR) by which, given arrival of a connection request of a further connection to be potentially added, this is allocated to a first (S k) or second class (P k) and by which, in conjunction with acceptance criteria plus a bandwidth to be adhered to, a decision is made as to whether this further connection to be potentially added can still be accepted on the common connecting line, characterized in that, proceeding from an initial value, the effective bandwidth (C eff k) is identified step-by-step with the setup/release of connections in that the acceptance algorithm (SR) is started at every step, and a first bandwidth (c s k) representative of the first class (S k) and a second bandwidth (c P k) representative of the second class (P k) is defined, and, based on the measure of the allocation of the connection, into consideration to one of the two classes (S k, P k) as well as of at least one acceptance criterion (c eff k), the first or second bandwidth (c s k, c P k) is modified by a first (SCR) or by a second traffic parameter value (PCR).
2. Method according to claim 1, characterized in that the first traffic parameter value is the sustainable cell rate (SCR) and the second traffic parameter value is the peak cell rate (PCR) of the appertaining connection.
3. Method according to claim 1 or 2, characterized in that one of the acceptance criteria is fashioned such in the case of the connection setup that, when the connection to be potentially newly added can be allocated to the first class (S k), a calculation is carried out to see whether the first bandwidth (c s k) identified in the preceding step is adequate including this connection, whereby it is assured that the calculated, first bandwidth dare not exceed the sum of the peak cell rates of all connections; and in that, when the acceptance criterion is met, the first bandwidth (c S k) is incremented by the first traffic parameter value (SCR n) and is otherwise incremented by the second traffic parameter value (PCR n).
4. Method according to claim 3, characterized in that, when the connection to be potentially newly added cannot be allocated to the first class (S k), this is automatically allocated to the second class (P k) and the second bandwidth (c P k ) is incremented by the second traffic parameter value (PCR n).
5. Method according to claim 1, 2, characterized in that the acceptance criterion is fashioned such in the case of a connection release that, when the connection to be released was allocated to the first class (S
k), a calculation is carried out to see whether the first bandwidth (c S k) calculated in the previous step and exclusive of this connection is adequate for the remaining connections, whereby it is assured that the calculated, first bandwidth dare not exceed the sum of the peak cell rates of all connections;
and in that, when the acceptance criterion is met, the first bandwidth (c S k) is diminished by the second traffic parameter value (PCR n) or is otherwise diminished by the first traffic parameter value (SCR n).
k), a calculation is carried out to see whether the first bandwidth (c S k) calculated in the previous step and exclusive of this connection is adequate for the remaining connections, whereby it is assured that the calculated, first bandwidth dare not exceed the sum of the peak cell rates of all connections;
and in that, when the acceptance criterion is met, the first bandwidth (c S k) is diminished by the second traffic parameter value (PCR n) or is otherwise diminished by the first traffic parameter value (SCR n).
6. Method according to claim 5, characterized in that, when the connection to be released was not allocated to the first class (S k), it is automatically assumed that this was allocated to the second class (P k) and, in this case, the second bandwidth (c P k) is diminished by the second traffic parameter value (PCR n).
7. Method according to claim 5, characterized in that the acceptance criterion is fashioned such in the case of a connection release that, when the connection to be released was allocated to the first class (S
k), a calculation was carried out to see whether the first bandwidth (c S k) determined in the previous step and minus this connection is adequate for the remaining connections; and in that, when the acceptance criterion is met, the first bandwidth (c S k) is diminished by the second traffic parameter value (PCR n) or, otherwise, the value of the identified first bandwidth (c S k) is upwardly limited by the sum of the peak cell rates of the first class (S k).
k), a calculation was carried out to see whether the first bandwidth (c S k) determined in the previous step and minus this connection is adequate for the remaining connections; and in that, when the acceptance criterion is met, the first bandwidth (c S k) is diminished by the second traffic parameter value (PCR n) or, otherwise, the value of the identified first bandwidth (c S k) is upwardly limited by the sum of the peak cell rates of the first class (S k).
8. Method according to one of the preceding claims, characterized in that the effective bandwidth (C eff k) derives from the sum of the first (c S k) and second (c P k) bandwidth.
9. Method according to one of the preceding claims, characterized in that the acceptance algorithm (SR) is started only once per connection to be potentially added or, respectively, released.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE19735166 | 1997-08-13 | ||
| DE19735166.2 | 1997-08-13 | ||
| PCT/DE1998/002109 WO1999009782A1 (en) | 1997-08-13 | 1998-07-27 | Method for atm communication statistical multiplexing |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2300190A1 true CA2300190A1 (en) | 1999-02-25 |
Family
ID=7838901
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002300190A Abandoned CA2300190A1 (en) | 1997-08-13 | 1998-07-27 | Method for the statistical multiplexing of atm connections |
Country Status (3)
| Country | Link |
|---|---|
| EP (1) | EP1004221A1 (en) |
| CA (1) | CA2300190A1 (en) |
| WO (1) | WO1999009782A1 (en) |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2928452B2 (en) * | 1994-03-17 | 1999-08-03 | 富士通株式会社 | ATM switch and call receiving apparatus and method in ATM switch |
| GB9513024D0 (en) * | 1995-06-27 | 1995-08-30 | Newbridge Networks Corp | Connection admission control system (cac) for atm networks |
-
1998
- 1998-07-27 CA CA002300190A patent/CA2300190A1/en not_active Abandoned
- 1998-07-27 EP EP98947344A patent/EP1004221A1/en not_active Withdrawn
- 1998-07-27 WO PCT/DE1998/002109 patent/WO1999009782A1/en not_active Application Discontinuation
Also Published As
| Publication number | Publication date |
|---|---|
| EP1004221A1 (en) | 2000-05-31 |
| WO1999009782A1 (en) | 1999-02-25 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| EEER | Examination request | ||
| FZDE | Discontinued |