CA2119205C - Improvements in or relating to asynchronous transfer mode communication systems - Google Patents
Improvements in or relating to asynchronous transfer mode communication systems Download PDFInfo
- Publication number
- CA2119205C CA2119205C CA002119205A CA2119205A CA2119205C CA 2119205 C CA2119205 C CA 2119205C CA 002119205 A CA002119205 A CA 002119205A CA 2119205 A CA2119205 A CA 2119205A CA 2119205 C CA2119205 C CA 2119205C
- Authority
- CA
- Canada
- Prior art keywords
- data
- bandwidth
- output port
- request
- switch
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Fee Related
Links
Classifications
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L49/00—Packet switching elements
- H04L49/50—Overload detection or protection within a single switching element
- H04L49/505—Corrective measures
- H04L49/508—Head of Line Blocking Avoidance
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L12/00—Data switching networks
- H04L12/54—Store-and-forward switching systems
- H04L12/56—Packet switching systems
- H04L12/5601—Transfer mode dependent, e.g. ATM
- H04L12/5602—Bandwidth control in ATM Networks, e.g. leaky bucket
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L49/00—Packet switching elements
- H04L49/30—Peripheral units, e.g. input or output ports
- H04L49/3018—Input queuing
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L49/00—Packet switching elements
- H04L49/30—Peripheral units, e.g. input or output ports
- H04L49/3081—ATM peripheral units, e.g. policing, insertion or extraction
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L49/00—Packet switching elements
- H04L49/50—Overload detection or protection within a single switching element
- H04L49/501—Overload detection
- H04L49/503—Policing
-
- 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
- H04L2012/5631—Resource management and allocation
- H04L2012/5632—Bandwidth allocation
- H04L2012/5635—Backpressure, e.g. for ABR
-
- 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
- H04L2012/5638—Services, e.g. multimedia, GOS, QOS
- H04L2012/5646—Cell characteristics, e.g. loss, delay, jitter, sequence integrity
- H04L2012/5651—Priority, marking, classes
-
- 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
- H04L2012/5679—Arbitration or scheduling
-
- 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
- H04L2012/5681—Buffer or queue management
- H04L2012/5682—Threshold; Watermark
-
- 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
- H04L2012/5681—Buffer or queue management
- H04L2012/5683—Buffer or queue management for avoiding head of line blocking
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L49/00—Packet switching elements
- H04L49/30—Peripheral units, e.g. input or output ports
Abstract
An ATM communication system comprising an ATM switch having a plurality of input ports and a plurality of output ports, each of the said input ports being fed from an input port server and each of the said output ports being arranged to feed an output port server. The input port servers each have a plurality of buffer stores one for each of the output ports to which said output port data is transmitted through the switch. Each buffer store in the input port servers is arranged to interrogate the output port server with which it communicates by means of a bandwidth request before the transmission of data, thereby to determine whether output port server data handling capacity is available, whereby ATM switch operation during periods of peak traffic is facilitated. The system includes a queuing arrangement for bandwidth requests received during periods when there is no available bandwidth capacity, the arrangement being such that requests are released in a predetermined order when capacity becomes available.
Description
IMPROVEMENTS IN OR RELATING TO ASYNCHRONOUS
TRANSFER MODE COMMUNICATION SYSTEMS
This invention relates to asynchronous transfer mode (ATM) communication systems.
More especially the invention relates to apparatus operative to facilitate ATM switch operation during periods of peak data traffic, and to the problem of efficiently allocating bandwidth resources in a situation where a multiplexed stream of ATM cells are to be individually switched to different ports.
The above problem has already been addressed and discussed in Great Britain published patent application GB 2288372, to which attention is hereby directed and is further discussed hereafter.
ATM data traffic is predominantly bursty data traffic. By its nature, bursty traffic requires high bandwidths for a part of the time and little or no bandwidth for the rest of the time. In order to efficiently use available bandwidth it is necessary to allocate the bandwidth using the mean bandwidth requirement of each data source and not the peak bandwidth. Thus it will be appreciated that if mean bandwidth allocation is used, the total peak bandwidth may thus be greater than the bandwidth available. Thus in operation of an ATM switch, a problem occurs when a number of data sources burst at the same time causing a peak overload condition to occur inside an ATM
switch/multiplexer. If not controlled or limited this condition will ~11~~~j cause data overflow in one or many of the switch/multiplexer internal data buffers, and this will result in data being lost.
Data destined for a particular output port will enter a switch from many different input ports. The total instantaneous data rate across a switch may be greater than an output port can sustain, and therefore buffering is required. However, even with the provision of buffering, eventual loss of data due to buffer overflow may occur. To reduce this probability to an operationally acceptable level by simply increasing peak capability, results in a low utilisation of the switch for much of the time, which is clearly unacceptable. A dynamic bandwidth allocation protocol, as described hereafter, provides a method of allocating bandwidth by sending requests for bandwidth to a designated output port and sending data thereafter only when bandwidth has been allocated as indicated by a return acknowledgement message.
In ATM systems, request messages for increases in bandwidth are sent by an input port server to an output port bandwidth allocation mechanism for initial processing. When a switch is heavily loaded, bandwidth is only available from an output port when a bandwidth cleardown message arrives which serves to release some bandwidth. Therefore, bandwidth request messages will always be y-ejected until after a cleardown. Under these circumstances the first request to be received after a cleardown will be allocated the recently cleared down bandwidth.
This is clearly unfair to request messages which may have been ~~.J.~20:1 _~_ rejected just before the bandwidth cleardown message arrived.
Requests rejected by an output port are re-sent after a suitable backoff delay. 'This may lead to unacceptable delays and perhaps to periods during backoff delays when there is bandwidth.
It is an object of the present invention to provide for A'TM
switch operation during periods of peak data traffic so that data is not lost.
It is a further object of the present invention to provide a system wherein this problem is substantially eliminated.
According to the present invention an ATM communication - system comprises an ATM switch having a plurality of input ports and a plurality of output ports, each of the input ports being fed from an input port server and each of the output ports being arranged to feed an output port server, the input port servers each having a plurality of buffer stores, one for each of the output ports, to which said output ports data is transmitted through the switch, each buffer store in the input port servers being arranged to interrogate the output port server with which it communicates before the transmission of data, thereby to determine whether output port server data handling capacity is available, whereby ATM switch operation during periods of peak data traffic is facilitated.
'The interrogation may take the form of a bandwidth request signal fiom an input port server in respect of an associated buffer stoa-e, the request signal being directed to an output port server 4vith which that buffer store communicates via the switch, and an ~~l~~Oa _~_ acknowledgement signal from this output port server in the presence of available capacity, in response to which acknowledgement signal data is thereafter transmitted from the buffer store to the output port via the switch.
It will be appreciated that by the expedient of providing in each input port server a buffer store for each output port server and by ensuring that no transmission takes place across the switch if output port server capacity is not available to accept it, data loss through output port server overload is obviated and ATM
operation during peaks of data traffic without loss of data is facilitated.
ATM data traffic is transmitted in frames, wherein each fa-ame camprises a plurality of cells, an end of frame marking being transmitted in the final cell of each frame.
In one contemplated embodiment of the invention the request signal is sent in the first cell of each frame, ie. a cell following a cell which includes an end of frame marker.
In this case the request cell may be arranged to request a bandwidth allotment which is based on mean frame size, ie. the mean data capacity of a frame.
According to an alternative embodiment of the invention the request signal may be sent in dependence upon the data stored from time to time in a buffer store.
In accordance with this alternative embodiment of the invention each buffer stare may embody a plurality of data thresholds, request signals being transmitted determined in 211~~Or~
accordance with the threshold reached. Thus the bandwidth a-equest can be tailored according to the quantity of data to be transmitted.
According to a further embodiment of the present invention, an ATM communication system includes a queuing arrangement for bandwidth requests received during periods when there is no available bandwidth capacity, the arrangement being such that requests are released in a pi°edetermined order when capacity becomes available.
The order of release may be, simply first to arrive, first to be processed.
Various embodiments of the invention will now be described by way of example only with reference to the accompanying drawings, in which;
FIGURE 1 is a somewhat schematic block diagram of a switch having associated with it input port servers and output port servers, FIGURE 2 is a block diagram indicating a bandwidth allocation mechanism, FIGURE 3 is a block schematic diagram of buffer stores embodying a plurality of thresholds, and FIGURE 4 is a schematic block diagram of part of an ATM
communication system in accordance with a further embodiment of the present invention.
Referring now to Figure 1, an ATM communication system comprises a switch 1 which is fed from servers 2, 3 and 4 via 21.~~2~~
input lines 5, 6 and 7 respectively. The input port servers 2, 3 and 4 are arranged to feed a plurality of output port servers one only of which, bearing the reference numeral 8 is shown. It will appreciated that in practice a large number of input port servers may be provided and by the same token a very large numbex of output port servers will be provided which are placed in communication with the input port servers via the switch 1. In the present arrangement each input port server is provided with a plurality of buffer stores A, B........Z, one for each of the output port servers such as the output port server 8. Thus it will be apparent that signals in the input port buffers A of the input port servers 2, 3 and 4 will be routed via the switch 1 to the output port server 8.
Similarly signals in the buffers B of the input port servers 2, 3 and 4 will be routed to the line 9 for a corresponding output port server not shown. Thus with this arrangement it will be appreciated that if the servers 2, 3 and 4 each demand access to the output port server A, an overload condition can occur which may mean that data is lost.
In order to avoid this situation it is arranged that before data is transmitted a request is transmitted which must be appropriately acknowledged. Thus in one specific case if data is to be transmitted from buffer store A in the input server 2 to the output port servea~ 8, a request transmission is made from the input port server 2 to the output port server 8 and if there is available data capacity then an acknowledgement signal is 2~.19~O;a ..7_ transmitted from the output port server 8 to input port server 2 indicating that data can be transferred therebetween.
As shown schematically in Figure l, a total output port bandwidth may be available as indicated by the arrow 10 comprising an isochronous portion of storage 11 for essential data which must be transmitted without undue delay, a control data storage portion 12 for conta-ol data and a further storage portion 13 for bursty data. Thus, provided space is available in the output port server 8 in an appropriate one of the storage portions 11, 12 or 13, a positive acknowledgement will be sent across the switch 1 which will result in subsequent data transfer.
The mechanism for handling a bandwidth request is shown in Figure 2 and consequent upon receipt of a bandwidth request on a line 14, a comparison is made in a comparator 15 with the available bandwidth as stored in a bandwidth allocation table 16.
If sufficient bandwidth is available, a signal is sent via a line 17 to provide a positive acknowledgement on a line 18 from a bandwidth allocator 19 which also provides a feedback signal via a line 20 to update the bandwidth allocation table 16. If sufficient bandwidth is available to meet the request on the line 14, a signal is sent via a line 21 which rejects the request and a negative acknowledgement signal is provided via the line 18.
The amount of bandwidth requested may be determined in dependence upon the anticipated mean frame size. Each frame normally comprises a number of cells, each cell having a predetermined quantity of data contained therein. In one ~~.l~~Oa _$_ arrangement the last cell of each frame includes an end of frame marker and consequent upon transmission of the next consecutive cell following an end of frame marker a bandwidth request is made corresponding to the mean frame bandwidth.
In an alternative embodiment of the invention, as shown in Figure 3, each buffer such as buffers 22 and 23 of an input port server which is arranged to communicate with an input port 24 has three thresholds Tl, T2 and T3. In operation of the system a bandwidth request is arranged to be transmitted as each threshold is reached, but as will be appreciated, the bandwidth requested will be determined by the quantity of data to be transmitted and thus bandwidth will not be reserved unnecessarily.
In arrangements as just before described a dynamic bandwidth allocation protocol will operate between an input port server and another server on a desired switch output port. The server on the output port maintains, in effect, a table containing data relating to the current bandwidth reserved for that output.
When an input port server requires to send a burst, it thus first sends a reservation across the switch network to the output port server. The reservation cell contains the requested bandwidth. If the output port server can accept the requested bandwidth, a positive acknowledgement cell is sent back to the requested input port server. At this point the data burst can be sent from the input port to the output port. The bandwidth is de-allocated on completion of the burst transmission by means of an explicit clear ~1~.~~t~~i down signal. The system as just before described, in effect, comprises a dynamic reservation protocol wherein only one multiplexing point is involved. Thus coupled with the data service tolerance to delays of 10's of milliseconds and the fact that requests could be queued if blocking occurs rather than re-sent, a very large burst blocking probability (~l'P) of say 0.9 of higher could be used, and this would also increase performance for a highly bursty high peak bit rate data service.
Referring now to Figure 4, the part of the ATM system under consideration comprises an ATM switching network 25 which is arranged in communication with an input port 26 and an output port 27. it will of course be appreciated that although only one input port and one output port are shown, there will be a plurality of input ports and a plurality of output ports. Data is fed to the input port 26 from a number of different sources which are arranged to feed stores 28, 29 and 30> one store for each source.
Although only three stores 28, 29 and 30 are shown in the drawing it will be appreciated that many more sources may be arranged to communicate with the port 26 each via a separate store. Data fed to the stores 28, 29 and 30 is obviously transmitted in the form of ATM cells which may include control signals as well as data. It will appreciated that since there is a maximum available bandwidth in the communication link between the input port 26 and the output port 27 across the switching network 25, a situation can arise where if a large number of stores such as the stores 28> 29 and 30 require access, 2~.~.~~~~
-lo-the available bandwidth may be exceeded. Accordingly, an input port resource allocation unit 31 is provided which checks the current use of the available bandwidth by the sources appertaining to the stores 28, 29 and 30, and assesses bandwidth requests received from the store as is illustrated schematically by an arrow 32. The requests received may be modified in accordance with bandwidth available and thus a request from the store 28 for a predetermined bandwidth may be modified in the input resource allocation unit 31 and the modified request will be passed via a line 33 to the input port 26 for onward transmission via the switching network 25 on a line 34 which is a schematic illustration of the route. The route through the switch will be occupied by bandwidth requests and data. Bandwidth requests are fed via the line 34 to a queuing store arrangement 35 whereas data will by-pass the queuing arrangerrzent and pass through the system and out of the output port 27 on a line 36. Bandwidth available at the output port 27 is assessed by an output port resource allocation unit 27 which monitors the bandwidth currently used by the output port via a line 38 and provides acknowledgement signals via a line 39 which are returned through the switching network 25 and a line 40 to the source making a request. Thus in the present example, if the store 28 makes a request over the line 32 the input port resource allocation unit may modify this request which is passed through the switching network via the line 34 and queued in the store 35.
The request eventually receives attention by the output port 21~.~20 resource allocation unit 37 which serves to provide an appropriate acknowledgement signal via the lines 39 and ~0 which serve to release the data from the stare 4 at a rate determined in accordance with the bandwidth available.
It will be appreciated that by arranging for bandwidth requests to be queued as hereinbefore described, a more efficient system is provided with less passibility of delays.
Various modifications may be made to the arrangements before described without departing from the scape of the invention and, for example, any suitable buffer thresholding method and apparatus may be used. Furthermore, any number of input sources with appropriate stores will be provided in a practical example.
TRANSFER MODE COMMUNICATION SYSTEMS
This invention relates to asynchronous transfer mode (ATM) communication systems.
More especially the invention relates to apparatus operative to facilitate ATM switch operation during periods of peak data traffic, and to the problem of efficiently allocating bandwidth resources in a situation where a multiplexed stream of ATM cells are to be individually switched to different ports.
The above problem has already been addressed and discussed in Great Britain published patent application GB 2288372, to which attention is hereby directed and is further discussed hereafter.
ATM data traffic is predominantly bursty data traffic. By its nature, bursty traffic requires high bandwidths for a part of the time and little or no bandwidth for the rest of the time. In order to efficiently use available bandwidth it is necessary to allocate the bandwidth using the mean bandwidth requirement of each data source and not the peak bandwidth. Thus it will be appreciated that if mean bandwidth allocation is used, the total peak bandwidth may thus be greater than the bandwidth available. Thus in operation of an ATM switch, a problem occurs when a number of data sources burst at the same time causing a peak overload condition to occur inside an ATM
switch/multiplexer. If not controlled or limited this condition will ~11~~~j cause data overflow in one or many of the switch/multiplexer internal data buffers, and this will result in data being lost.
Data destined for a particular output port will enter a switch from many different input ports. The total instantaneous data rate across a switch may be greater than an output port can sustain, and therefore buffering is required. However, even with the provision of buffering, eventual loss of data due to buffer overflow may occur. To reduce this probability to an operationally acceptable level by simply increasing peak capability, results in a low utilisation of the switch for much of the time, which is clearly unacceptable. A dynamic bandwidth allocation protocol, as described hereafter, provides a method of allocating bandwidth by sending requests for bandwidth to a designated output port and sending data thereafter only when bandwidth has been allocated as indicated by a return acknowledgement message.
In ATM systems, request messages for increases in bandwidth are sent by an input port server to an output port bandwidth allocation mechanism for initial processing. When a switch is heavily loaded, bandwidth is only available from an output port when a bandwidth cleardown message arrives which serves to release some bandwidth. Therefore, bandwidth request messages will always be y-ejected until after a cleardown. Under these circumstances the first request to be received after a cleardown will be allocated the recently cleared down bandwidth.
This is clearly unfair to request messages which may have been ~~.J.~20:1 _~_ rejected just before the bandwidth cleardown message arrived.
Requests rejected by an output port are re-sent after a suitable backoff delay. 'This may lead to unacceptable delays and perhaps to periods during backoff delays when there is bandwidth.
It is an object of the present invention to provide for A'TM
switch operation during periods of peak data traffic so that data is not lost.
It is a further object of the present invention to provide a system wherein this problem is substantially eliminated.
According to the present invention an ATM communication - system comprises an ATM switch having a plurality of input ports and a plurality of output ports, each of the input ports being fed from an input port server and each of the output ports being arranged to feed an output port server, the input port servers each having a plurality of buffer stores, one for each of the output ports, to which said output ports data is transmitted through the switch, each buffer store in the input port servers being arranged to interrogate the output port server with which it communicates before the transmission of data, thereby to determine whether output port server data handling capacity is available, whereby ATM switch operation during periods of peak data traffic is facilitated.
'The interrogation may take the form of a bandwidth request signal fiom an input port server in respect of an associated buffer stoa-e, the request signal being directed to an output port server 4vith which that buffer store communicates via the switch, and an ~~l~~Oa _~_ acknowledgement signal from this output port server in the presence of available capacity, in response to which acknowledgement signal data is thereafter transmitted from the buffer store to the output port via the switch.
It will be appreciated that by the expedient of providing in each input port server a buffer store for each output port server and by ensuring that no transmission takes place across the switch if output port server capacity is not available to accept it, data loss through output port server overload is obviated and ATM
operation during peaks of data traffic without loss of data is facilitated.
ATM data traffic is transmitted in frames, wherein each fa-ame camprises a plurality of cells, an end of frame marking being transmitted in the final cell of each frame.
In one contemplated embodiment of the invention the request signal is sent in the first cell of each frame, ie. a cell following a cell which includes an end of frame marker.
In this case the request cell may be arranged to request a bandwidth allotment which is based on mean frame size, ie. the mean data capacity of a frame.
According to an alternative embodiment of the invention the request signal may be sent in dependence upon the data stored from time to time in a buffer store.
In accordance with this alternative embodiment of the invention each buffer stare may embody a plurality of data thresholds, request signals being transmitted determined in 211~~Or~
accordance with the threshold reached. Thus the bandwidth a-equest can be tailored according to the quantity of data to be transmitted.
According to a further embodiment of the present invention, an ATM communication system includes a queuing arrangement for bandwidth requests received during periods when there is no available bandwidth capacity, the arrangement being such that requests are released in a pi°edetermined order when capacity becomes available.
The order of release may be, simply first to arrive, first to be processed.
Various embodiments of the invention will now be described by way of example only with reference to the accompanying drawings, in which;
FIGURE 1 is a somewhat schematic block diagram of a switch having associated with it input port servers and output port servers, FIGURE 2 is a block diagram indicating a bandwidth allocation mechanism, FIGURE 3 is a block schematic diagram of buffer stores embodying a plurality of thresholds, and FIGURE 4 is a schematic block diagram of part of an ATM
communication system in accordance with a further embodiment of the present invention.
Referring now to Figure 1, an ATM communication system comprises a switch 1 which is fed from servers 2, 3 and 4 via 21.~~2~~
input lines 5, 6 and 7 respectively. The input port servers 2, 3 and 4 are arranged to feed a plurality of output port servers one only of which, bearing the reference numeral 8 is shown. It will appreciated that in practice a large number of input port servers may be provided and by the same token a very large numbex of output port servers will be provided which are placed in communication with the input port servers via the switch 1. In the present arrangement each input port server is provided with a plurality of buffer stores A, B........Z, one for each of the output port servers such as the output port server 8. Thus it will be apparent that signals in the input port buffers A of the input port servers 2, 3 and 4 will be routed via the switch 1 to the output port server 8.
Similarly signals in the buffers B of the input port servers 2, 3 and 4 will be routed to the line 9 for a corresponding output port server not shown. Thus with this arrangement it will be appreciated that if the servers 2, 3 and 4 each demand access to the output port server A, an overload condition can occur which may mean that data is lost.
In order to avoid this situation it is arranged that before data is transmitted a request is transmitted which must be appropriately acknowledged. Thus in one specific case if data is to be transmitted from buffer store A in the input server 2 to the output port servea~ 8, a request transmission is made from the input port server 2 to the output port server 8 and if there is available data capacity then an acknowledgement signal is 2~.19~O;a ..7_ transmitted from the output port server 8 to input port server 2 indicating that data can be transferred therebetween.
As shown schematically in Figure l, a total output port bandwidth may be available as indicated by the arrow 10 comprising an isochronous portion of storage 11 for essential data which must be transmitted without undue delay, a control data storage portion 12 for conta-ol data and a further storage portion 13 for bursty data. Thus, provided space is available in the output port server 8 in an appropriate one of the storage portions 11, 12 or 13, a positive acknowledgement will be sent across the switch 1 which will result in subsequent data transfer.
The mechanism for handling a bandwidth request is shown in Figure 2 and consequent upon receipt of a bandwidth request on a line 14, a comparison is made in a comparator 15 with the available bandwidth as stored in a bandwidth allocation table 16.
If sufficient bandwidth is available, a signal is sent via a line 17 to provide a positive acknowledgement on a line 18 from a bandwidth allocator 19 which also provides a feedback signal via a line 20 to update the bandwidth allocation table 16. If sufficient bandwidth is available to meet the request on the line 14, a signal is sent via a line 21 which rejects the request and a negative acknowledgement signal is provided via the line 18.
The amount of bandwidth requested may be determined in dependence upon the anticipated mean frame size. Each frame normally comprises a number of cells, each cell having a predetermined quantity of data contained therein. In one ~~.l~~Oa _$_ arrangement the last cell of each frame includes an end of frame marker and consequent upon transmission of the next consecutive cell following an end of frame marker a bandwidth request is made corresponding to the mean frame bandwidth.
In an alternative embodiment of the invention, as shown in Figure 3, each buffer such as buffers 22 and 23 of an input port server which is arranged to communicate with an input port 24 has three thresholds Tl, T2 and T3. In operation of the system a bandwidth request is arranged to be transmitted as each threshold is reached, but as will be appreciated, the bandwidth requested will be determined by the quantity of data to be transmitted and thus bandwidth will not be reserved unnecessarily.
In arrangements as just before described a dynamic bandwidth allocation protocol will operate between an input port server and another server on a desired switch output port. The server on the output port maintains, in effect, a table containing data relating to the current bandwidth reserved for that output.
When an input port server requires to send a burst, it thus first sends a reservation across the switch network to the output port server. The reservation cell contains the requested bandwidth. If the output port server can accept the requested bandwidth, a positive acknowledgement cell is sent back to the requested input port server. At this point the data burst can be sent from the input port to the output port. The bandwidth is de-allocated on completion of the burst transmission by means of an explicit clear ~1~.~~t~~i down signal. The system as just before described, in effect, comprises a dynamic reservation protocol wherein only one multiplexing point is involved. Thus coupled with the data service tolerance to delays of 10's of milliseconds and the fact that requests could be queued if blocking occurs rather than re-sent, a very large burst blocking probability (~l'P) of say 0.9 of higher could be used, and this would also increase performance for a highly bursty high peak bit rate data service.
Referring now to Figure 4, the part of the ATM system under consideration comprises an ATM switching network 25 which is arranged in communication with an input port 26 and an output port 27. it will of course be appreciated that although only one input port and one output port are shown, there will be a plurality of input ports and a plurality of output ports. Data is fed to the input port 26 from a number of different sources which are arranged to feed stores 28, 29 and 30> one store for each source.
Although only three stores 28, 29 and 30 are shown in the drawing it will be appreciated that many more sources may be arranged to communicate with the port 26 each via a separate store. Data fed to the stores 28, 29 and 30 is obviously transmitted in the form of ATM cells which may include control signals as well as data. It will appreciated that since there is a maximum available bandwidth in the communication link between the input port 26 and the output port 27 across the switching network 25, a situation can arise where if a large number of stores such as the stores 28> 29 and 30 require access, 2~.~.~~~~
-lo-the available bandwidth may be exceeded. Accordingly, an input port resource allocation unit 31 is provided which checks the current use of the available bandwidth by the sources appertaining to the stores 28, 29 and 30, and assesses bandwidth requests received from the store as is illustrated schematically by an arrow 32. The requests received may be modified in accordance with bandwidth available and thus a request from the store 28 for a predetermined bandwidth may be modified in the input resource allocation unit 31 and the modified request will be passed via a line 33 to the input port 26 for onward transmission via the switching network 25 on a line 34 which is a schematic illustration of the route. The route through the switch will be occupied by bandwidth requests and data. Bandwidth requests are fed via the line 34 to a queuing store arrangement 35 whereas data will by-pass the queuing arrangerrzent and pass through the system and out of the output port 27 on a line 36. Bandwidth available at the output port 27 is assessed by an output port resource allocation unit 27 which monitors the bandwidth currently used by the output port via a line 38 and provides acknowledgement signals via a line 39 which are returned through the switching network 25 and a line 40 to the source making a request. Thus in the present example, if the store 28 makes a request over the line 32 the input port resource allocation unit may modify this request which is passed through the switching network via the line 34 and queued in the store 35.
The request eventually receives attention by the output port 21~.~20 resource allocation unit 37 which serves to provide an appropriate acknowledgement signal via the lines 39 and ~0 which serve to release the data from the stare 4 at a rate determined in accordance with the bandwidth available.
It will be appreciated that by arranging for bandwidth requests to be queued as hereinbefore described, a more efficient system is provided with less passibility of delays.
Various modifications may be made to the arrangements before described without departing from the scape of the invention and, for example, any suitable buffer thresholding method and apparatus may be used. Furthermore, any number of input sources with appropriate stores will be provided in a practical example.
Claims (9)
1. An ATM communication system comprising an ATM switch having a plurality of input ports and a plurality of output ports, each of the input ports being fed from an input port server and each of the output ports being arranged to feed an output port server, the input port servers each having a plurality of buffer stores, one for each of the output ports, to which said output ports data is transmitted through the switch, each buffer store in the input port servers being arranged to interrogate the output port server with which it communicates before the transmission of data, thereby to determine whether output port server data handling capacity is available, whereby ATM switch operating during periods of peak data traffic is facilitated.
2. A system as claimed in Claim 1, wherein the interrogation takes the form of a bandwidth request signal from an input port server in respect of an associated buffer store, the request signal being directed to an output port server with which that buffer store communicates via the switch, and an acknowledgement signal from this output port server in the presence of available capacity, in response to which acknowledgement signal data is thereafter transmitted from the buffer store to the output port via the switch.
3. A system as claimed in Claim 1 or Claim 2, wherein ATM data traffic is transmitted in frames, wherein each frame comprises a plurality of cells, an end of frame marker being transmitted in a final cell of each frame, the request signal being sent in a first cell of each frame, said first cell following a cell which includes an end of frame marker.
4. A system as claimed in Claim 3, wherein the request cell is arranged to request a bandwidth allotment which is based on mean frame size, ie. the mean data capacity of a frame.
5. A system as claimed in Claim 1 or Claim 2, wherein the request signal is sent in dependence upon the data stored from time to time in a buffer store.
6. A system as claimed in Claim 5, wherein each buffer store embodies a plurality of data thresholds, request signals being transmitted in accordance with a threshold reached.
7. An ATM communication system as claimed in any one of claims 1 to 6 characterised by a queuing arrangement for bandwidth requests received during periods when there is no available bandwidth capacity, the arrangement being such that requests are released in a predetermined order when capacity becomes available.
8. A system as claimed in Claim 7, wherein the order of release is first to arrive, first to be processed.
9. A system as claimed in Claim 7, wherein a priority releasing system is provided for queued requests determined in dependence upon a character of data appertaining to each queued request.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB9309468.8 | 1993-05-07 | ||
| GB939309468A GB9309468D0 (en) | 1993-05-07 | 1993-05-07 | Improvements in or relating to asynchronous transfer mode communication systems |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA2119205A1 CA2119205A1 (en) | 1994-11-08 |
| CA2119205C true CA2119205C (en) | 2004-02-17 |
Family
ID=10735122
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002119205A Expired - Fee Related CA2119205C (en) | 1993-05-07 | 1994-03-16 | Improvements in or relating to asynchronous transfer mode communication systems |
Country Status (7)
| Country | Link |
|---|---|
| US (1) | US5448559A (en) |
| EP (1) | EP0624015B1 (en) |
| JP (1) | JP3497556B2 (en) |
| AT (1) | ATE240620T1 (en) |
| CA (1) | CA2119205C (en) |
| DE (1) | DE69432655T2 (en) |
| GB (1) | GB9309468D0 (en) |
Families Citing this family (66)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP3044983B2 (en) * | 1993-08-25 | 2000-05-22 | 株式会社日立製作所 | Cell switching method for ATM switching system |
| GB2288096B (en) * | 1994-03-23 | 1999-04-28 | Roke Manor Research | Apparatus and method of processing bandwidth requirements in an ATM switch |
| GB2288947B (en) * | 1994-04-20 | 1999-01-06 | Roke Manor Research | Improvements in or relating to ATM communication systems |
| US6134218A (en) * | 1994-04-28 | 2000-10-17 | Pmc-Sierra (Maryland), Inc. | Many dimensional congestion detection system and method |
| US5657322A (en) * | 1994-06-08 | 1997-08-12 | Alcatel N.V. | Device for the equalization of data flow |
| DE69430627T2 (en) * | 1994-06-28 | 2002-10-17 | Hewlett Packard Co | Method and device for planning cell transmission of virtual channels with guaranteed bandwidth |
| AUPM699394A0 (en) * | 1994-07-25 | 1994-08-18 | Curtin University Of Technology | Link level controlled access to available asynchronous network service |
| US5923657A (en) * | 1994-08-23 | 1999-07-13 | Hitachi, Ltd. | ATM switching system and cell control method |
| EP0700186B1 (en) * | 1994-08-31 | 2005-04-13 | Hewlett-Packard Company, A Delaware Corporation | Method and apparatus for regulating virtual-channel cell transmission |
| US5949781A (en) * | 1994-08-31 | 1999-09-07 | Brooktree Corporation | Controller for ATM segmentation and reassembly |
| DE19507569C2 (en) * | 1995-03-03 | 1997-02-13 | Siemens Ag | Circuit arrangement for receiving and forwarding message cells through an ATM communication device |
| NZ302752A (en) * | 1995-03-08 | 1999-11-29 | British Telecomm | Broadband switching network |
| AU719514B2 (en) | 1995-03-08 | 2000-05-11 | British Telecommunications Public Limited Company | Broadband switching system |
| JPH11501475A (en) | 1995-03-08 | 1999-02-02 | オックスフォード・ブルックス・ユニバーシティー | Broadband switching system |
| 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 |
| GB9514206D0 (en) | 1995-07-12 | 1995-09-13 | British Telecomm | Rate controller |
| WO1997004565A1 (en) * | 1995-07-19 | 1997-02-06 | Fujitsu Limited | Priority arbitration for point-to-point and multipoint transmission |
| US5917805A (en) | 1995-07-19 | 1999-06-29 | Fujitsu Network Communications, Inc. | Network switch utilizing centralized and partitioned memory for connection topology information storage |
| JPH09121217A (en) * | 1995-08-23 | 1997-05-06 | Fujitsu Ltd | Method for burst transfer |
| JPH11512583A (en) | 1995-09-14 | 1999-10-26 | フジツウ ネットワーク コミュニケーションズ，インコーポレイテッド | Transmitter-controlled flow control for buffer allocation in a wide area ATM network |
| FR2740283B1 (en) * | 1995-10-24 | 1997-12-19 | Thomson Csf | DEVICE FOR REGULATING THE ATM CELL FLOW WITHIN AN ATM BREWER |
| EP1457895A3 (en) | 1995-10-26 | 2005-04-20 | Matsushita Electric Industrial Co., Ltd. | File System |
| DE19540160C2 (en) * | 1995-10-27 | 2000-05-31 | Andreas Kirstaedter | Method for coordination via serial lines of input-buffered ATM switching devices to avoid output blockages |
| US5644575A (en) * | 1995-12-06 | 1997-07-01 | Dsc Communications Corporation | Managing memory within a local telecommunications network |
| CA2241957C (en) * | 1996-01-09 | 2004-05-25 | British Telecommunications Public Limited Company | A service multiplexer with bandwith control and signal source feedback |
| JP2000517488A (en) | 1996-01-16 | 2000-12-26 | フジツウ ネットワーク コミュニケーションズ，インコーポレイテッド | Reliable and flexible multicast mechanism for ATM networks |
| US5790545A (en) * | 1996-03-14 | 1998-08-04 | Motorola Inc. | Efficient output-request packet switch and method |
| US6212182B1 (en) * | 1996-06-27 | 2001-04-03 | Cisco Technology, Inc. | Combined unicast and multicast scheduling |
| US6442172B1 (en) | 1996-07-11 | 2002-08-27 | Alcatel Internetworking, Inc. | Input buffering and queue status-based output control for a digital traffic switch |
| US5768257A (en) | 1996-07-11 | 1998-06-16 | Xylan Corporation | Input buffering/output control for a digital traffic switch |
| FR2751160B1 (en) | 1996-07-12 | 1998-10-30 | Thomson Csf | METHOD OF DETECTION OF UPSTREAM CONGESTION WITHIN AN ATM SWITCH WITH DISTRIBUTED ARCHITECTURE AND INPUT STORAGE |
| US5748905A (en) | 1996-08-30 | 1998-05-05 | Fujitsu Network Communications, Inc. | Frame classification using classification keys |
| US6229812B1 (en) * | 1996-10-28 | 2001-05-08 | Paxonet Communications, Inc. | Scheduling techniques for data cells in a data switch |
| CA2281691A1 (en) * | 1996-11-08 | 1998-05-14 | Brian Alleyne | Method and apparatus for detecting disabled physical devices and deleting undeliverable cells |
| US6078577A (en) * | 1996-11-21 | 2000-06-20 | Motorola, Inc. | System and method for packet data communication |
| US5953335A (en) * | 1997-02-14 | 1999-09-14 | Advanced Micro Devices, Inc. | Method and apparatus for selectively discarding packets for blocked output queues in the network switch |
| KR100212064B1 (en) | 1997-05-21 | 1999-08-02 | 윤종용 | 2n x n multiplexer switch architecture |
| US6088728A (en) * | 1997-06-11 | 2000-07-11 | Oracle Corporation | System using session data stored in session data storage for associating and disassociating user identifiers for switching client sessions in a server |
| US6243751B1 (en) * | 1997-06-11 | 2001-06-05 | Oracle Corporation | Method and apparatus for coupling clients to servers |
| US6393483B1 (en) * | 1997-06-30 | 2002-05-21 | Adaptec, Inc. | Method and apparatus for network interface card load balancing and port aggregation |
| GB2327317B (en) | 1997-07-11 | 2002-02-13 | Ericsson Telefon Ab L M | Access control and resourse reservation in a communications network |
| KR100233091B1 (en) * | 1997-10-23 | 1999-12-01 | 윤종용 | Atm traffic control apparatus and method |
| US6934253B2 (en) * | 1998-01-14 | 2005-08-23 | Alcatel | ATM switch with rate-limiting congestion control |
| US6594240B1 (en) * | 1998-05-22 | 2003-07-15 | Lucent Technologies Inc. | Methods and apparatus for random backoff based access priority in a communications system |
| IL125271A0 (en) * | 1998-07-08 | 1999-03-12 | Galileo Technology Ltd | Head of line blocking |
| US6496504B1 (en) * | 1998-08-06 | 2002-12-17 | Ricoh Company, Ltd. | Smart allocation of bandwidth for multiple independent calls on a digital network |
| FR2784468B1 (en) * | 1998-10-08 | 2000-12-15 | Cit Alcatel | ATM SWITCHING MATRIX HAVING A PASSIVE OPTICAL CORE |
| US9239763B2 (en) | 2012-09-28 | 2016-01-19 | Oracle International Corporation | Container database |
| GB9828142D0 (en) | 1998-12-22 | 1999-02-17 | Power X Limited | Approximate state control mechanism |
| US6445711B1 (en) | 1999-04-23 | 2002-09-03 | Sony Corporation | Method of and apparatus for implementing and sending an asynchronous control mechanism packet used to control bridge devices within a network of IEEE STD 1394 serial buses |
| US6909715B1 (en) * | 1999-08-31 | 2005-06-21 | Broadcom Corporation | Method and apparatus for the reduction of upstream request processing latency in a cable modem termination system |
| GB2354133A (en) * | 1999-08-31 | 2001-03-14 | Mitel Corp | Multimedia QOS |
| US6625155B1 (en) * | 1999-09-28 | 2003-09-23 | Lucent Technologies Inc. | Model-based admission control adjustment in data networks |
| US7042906B2 (en) * | 2001-03-28 | 2006-05-09 | Brilliant Optical Networks | Method to control a special class of OBS/LOBS and other burst switched network devices |
| US20030046398A1 (en) * | 2001-08-29 | 2003-03-06 | Charles Buckley | Method and system for managing a plurality of console devices in a network |
| EP1561312B1 (en) * | 2002-10-02 | 2017-07-19 | Cisco Technology, Inc. | Method and apparatus for processing superframes using an arbitration system |
| US7415470B2 (en) * | 2004-08-12 | 2008-08-19 | Oracle International Corporation | Capturing and re-creating the state of a queue when migrating a session |
| US7502824B2 (en) * | 2004-08-12 | 2009-03-10 | Oracle International Corporation | Database shutdown with session migration |
| DE102004062116B3 (en) * | 2004-12-23 | 2006-05-11 | Ab Skf | Bearing arrangement for computer tomography has bearing with inner ring, which stores construction unit, and outer ring, which is connected with damping element, fitted as single element and contain hollow cylindrical basic outline |
| US7480304B2 (en) * | 2004-12-29 | 2009-01-20 | Alcatel Lucent | Predictive congestion management in a data communications switch using traffic and system statistics |
| US9176772B2 (en) * | 2005-02-11 | 2015-11-03 | Oracle International Corporation | Suspending and resuming of sessions |
| US8549038B2 (en) | 2009-06-15 | 2013-10-01 | Oracle International Corporation | Pluggable session context |
| US10469404B1 (en) * | 2014-05-12 | 2019-11-05 | Google Llc | Network multi-level rate limiter |
| US10289617B2 (en) | 2015-12-17 | 2019-05-14 | Oracle International Corporation | Accessing on-premise and off-premise datastores that are organized using different application schemas |
| US10387387B2 (en) | 2015-12-17 | 2019-08-20 | Oracle International Corporation | Enabling multi-tenant access to respective isolated data sets organized using different application schemas |
| US10303894B2 (en) | 2016-08-31 | 2019-05-28 | Oracle International Corporation | Fine-grained access control for data manipulation language (DML) operations on relational data |
Family Cites Families (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5285445A (en) * | 1987-12-17 | 1994-02-08 | U.S. Philips Corporation | Switching network and switching network control for a switching node in a wideband transmission system |
| 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 |
| JPH03182140A (en) * | 1989-12-11 | 1991-08-08 | Mitsubishi Electric Corp | Common buffer type exchange |
| CA2038646C (en) * | 1990-03-20 | 1995-02-07 | Katsumi Oomuro | Atm communication system with optimal traffic control by changing the allocated bandwidth |
| US5303078A (en) * | 1990-12-18 | 1994-04-12 | Bell Communications Research, Inc. | Apparatus and method for large scale ATM switching |
| US5179556A (en) * | 1991-08-02 | 1993-01-12 | Washington University | Bandwidth management and congestion control scheme for multicast ATM networks |
| US5291481A (en) * | 1991-10-04 | 1994-03-01 | At&T Bell Laboratories | Congestion control for high speed packet networks |
-
1993
- 1993-05-07 GB GB939309468A patent/GB9309468D0/en active Pending
-
1994
- 1994-03-08 EP EP94103484A patent/EP0624015B1/en not_active Expired - Lifetime
- 1994-03-08 AT AT94103484T patent/ATE240620T1/en not_active IP Right Cessation
- 1994-03-08 DE DE69432655T patent/DE69432655T2/en not_active Expired - Fee Related
- 1994-03-16 CA CA002119205A patent/CA2119205C/en not_active Expired - Fee Related
- 1994-05-02 JP JP09356994A patent/JP3497556B2/en not_active Expired - Fee Related
- 1994-05-02 US US08/235,926 patent/US5448559A/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| DE69432655D1 (en) | 2003-06-18 |
| ATE240620T1 (en) | 2003-05-15 |
| DE69432655T2 (en) | 2004-03-18 |
| EP0624015A3 (en) | 2001-10-10 |
| GB9309468D0 (en) | 1993-06-23 |
| EP0624015A2 (en) | 1994-11-09 |
| CA2119205A1 (en) | 1994-11-08 |
| EP0624015B1 (en) | 2003-05-14 |
| JPH0715444A (en) | 1995-01-17 |
| US5448559A (en) | 1995-09-05 |
| JP3497556B2 (en) | 2004-02-16 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CA2119205C (en) | Improvements in or relating to asynchronous transfer mode communication systems | |
| EP0678996B1 (en) | Apparatus and method of processing bandwidth requirements in an ATM switch | |
| EP0678997B1 (en) | Improvements in or relating to ATM communication systems | |
| US6205118B1 (en) | Adaptive time slot scheduling apparatus and method for end-points in an ATM network | |
| US5629928A (en) | Dynamic fair queuing to support best effort traffic in an ATM network | |
| EP0587522B1 (en) | Rate-based congestion control in packet communications networks | |
| AU647267B2 (en) | Switching node in label multiplexing type switching network | |
| KR100452952B1 (en) | Method of scheduling data cell transmission in an atm network | |
| US4821264A (en) | Adaptive concentration communication network ISDN access | |
| JPH08307432A (en) | Communication method | |
| US5048013A (en) | Transmission congestion control method and apparatus | |
| EP1154671A1 (en) | Switching matrix for a telecommunications network and method of connection handling in a switching matrix | |
| EP0838970B1 (en) | Method for shared memory management in network nodes | |
| GB2272820A (en) | Improvements in or relating to asynchronous transfer mode communication systems | |
| KR100251778B1 (en) | Adaptive cell scheduling method using queue occupancy information and switching systems | |
| US6134219A (en) | Test of cell conductivity in ATM switching system | |
| US5742601A (en) | ATM communications equipment | |
| EP0593843A2 (en) | Improvements in frame relay data transmission systems | |
| KR100198442B1 (en) | Priority control method for controlling cell service ratio according to cell occupancy status in atm switching system | |
| JPH066381A (en) | Variable setting system for communication line band | |
| KR0175484B1 (en) | Path Control Method using Band Reservation in Fully Distributed Asynchronous Transfer Mode Switching System | |
| US6122297A (en) | Arrangement and method relating to digital communication systems | |
| CN115914145A (en) | Optimization method for switch chip cache management | |
| CA2233555A1 (en) | Asynchronous transfer mode switch |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| EEER | Examination request | ||
| MKLA | Lapsed |