WO1996039759A1 - Controlling the flow of atm cells in an atm network - Google Patents
Controlling the flow of atm cells in an atm network Download PDFInfo
- Publication number
- WO1996039759A1 WO1996039759A1 PCT/US1996/008906 US9608906W WO9639759A1 WO 1996039759 A1 WO1996039759 A1 WO 1996039759A1 US 9608906 W US9608906 W US 9608906W WO 9639759 A1 WO9639759 A1 WO 9639759A1
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- cells
- value
- buffer
- switch
- abr
- Prior art date
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
- H04L49/506—Backpressure
-
- 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
- H04L49/3081—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
- 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
- H04L2012/5614—User Network Interface
- H04L2012/5616—Terminal equipment, e.g. codecs, synch.
-
- 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
- H04L2012/5629—Admission control
- H04L2012/5631—Resource management and allocation
- H04L2012/5636—Monitoring or policing, e.g. compliance with allocated rate, corrective actions
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L12/00—Data switching networks
- H04L12/54—Store-and-forward switching systems
- H04L12/56—Packet switching systems
- H04L12/5601—Transfer mode dependent, e.g. ATM
- H04L2012/5638—Services, e.g. multimedia, GOS, QOS
- H04L2012/5646—Cell characteristics, e.g. loss, delay, jitter, sequence integrity
- H04L2012/5652—Cell construction, e.g. including header, packetisation, depacketisation, assembly, reassembly
-
- 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
- H04L49/00—Packet switching elements
- H04L49/20—Support for services
- H04L49/205—Quality of Service based
-
- 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
Definitions
- This invention relates to a method of controlling the flow of ATM cells in an ATM network, and to an ATM network switch in which the method is carried out.
- the ABR (Available Bit Rate) service in Asynchronous Trans ⁇ fer Mode (ATM) networks is intended to make the best use of remaining capacity after higher priority services such as CBR (Constant Bit Rate) and VBR (Variable Bit Rate) have been pro ⁇ vided for.
- CBR Constant Bit Rate
- VBR Very Bit Rate
- Rm cells special ATM cells known as Resource Management or Rm cells are sent from the source, through the destination and back to the source to provide information on the congestion level in the switches in the path. This is used by the source to modify its transmission rate, the objective being to utilize link capacity fully while not losing any cells as a result of congestion.
- An Explicit Rate (ER) parameter is set in the Rm cells passing through the switch in the forwards and backwards directions, the ER being reduced as congestion occurs down to the Minimum Cell Rate (MCR) value to reduce the rate at which the source sends.
- MCR Minimum Cell Rate
- the Message Type field in the Rm cell includes Congestion Indication (CI) and No Increase (NI) bits which may be set respectively to signal to the source that a predetermined decrease in the transmission rate should be effected and that the source should not automatically increase the send rate - it is normally arranged to keep pushing the send rate up again after the ER has signalled a reduction, in order to ensure that the rate is not permanently depressed.
- the switch may generate a backwards Rm cell (known as BECN) to the source to indicate congestion, the rate of these being limited to 10 per second per connection.
- BECN backwards Rm cell
- the Explicit Rate or ER parameter thus dictates the maximum rate at which the source is allowed to send in cells per second.
- MCR dictates the minimum rate at which a source may always send. ER must therefore not be set less than MCR.
- the present invention provides a method of controlling the flow of ATM cells in an ATM network, comprising signalling to the source of cells on a connection to reduce the transmission rate when congestion occurs in a switch in the network, the signalling being carried out by way of insertion into Resource Management Rm cells of a new Explicit Rate (ER) value for the connection, wherein the ER value is obtained at a given point in the network for each cell arriving at said point, said point including a buffer for the cells, by: counting the number of ABR cells output from the buffer within a predetermined time interval to give an ABR Output Band ⁇ width value (AOB) ;and calculating an ER value as a function of AOB.
- AOB ABR Output Band ⁇ width value
- the method comprises: determining the Number Nact of ABR VCs with more than a predetermined number of cells stored in the buffer; determining the number of cells VcCnt on the connection stored in the buffer; determining the total number of cells TSC currently stored in the buffer and the remaining capacity BS of the buffer; and calculating the ER value as a function of AOB, Nact, VcCnt, TSC and BS.
- the ER value is calculated from the fol ⁇ lowing formula:
- MAX is a predetermined function reflecting the delay from the source of ABR cells in the network to the said point
- Ker is a predetermined offset value which determines the occupancy of the buffer for the VC on which the cell is being transmitted.
- N is a value which is incremented when a cell is written into the buffer on a VC having a VcCnt of less than
- the method includes multiplying the number of ABR cells output during the predetermined period by a predeter ⁇ mined constant to give the AOB value.
- the invention further provides an ATM network switch com ⁇ prising a buffer means for buffering the flow of ATM cells and means for calculating the Explicit Rate (ER) value for a connec ⁇ tion thereon, the calculating means comprising: means for counting the number of ABR cells output from the buffer within a predetermined time interval to give an ABR Output Bandwidth value (AOB) ; and means for calculating an ER value as a function of AOB.
- AOB ABR Output Bandwidth value
- the switch comprises: means for determining the Number Nact of ABR VCs with more than a predetermined number of cells stored in the buffer; means for determining the number of cells VcCnt stored in the buffer for the cell's VC; means for determining the total number of cells TSC cur ⁇ rently stored in the buffer and the remaining capacity BS of the buffer; and wherein the calculating means is arranged to calculate the ER value as a function of AOB, Nact, VcCnt, TSC and BS.
- the switch comprises means for storing for each VC established through the switch an offset value Ker which determines the maximum occupancy of the buffer for the connection and a value MAX which is a predetermined function reflecting the delay from the source of ABR cells in the network to the switch, and the calculating means is arranged to calculate the ER value according to the following formula:
- Another aspect of the invention provides an ATM network switch comprising transmitting means and receiving means associ ⁇ ated with an external data link to the switch, and memory means connected to the transmitting means and to the receiving means, and wherein the transmitting means is arranged to write to the memory means congestion data contained in Resource Management (Rm) cells being transmitted by the transmitting means and the receiving means is arranged to read the said data from the memory means and to modify in accordance with the said data congestion data contained in reverse Rm cells arriving at the receiving means from the external data link.
- Rm Resource Management
- the congestion data preferably comprises the ER, NI and CI fields in the Rm cell, and may be modified in the reverse Rm cells so as to OR the NI and CI fields with the values from the memory means and to set the reverse Rm ER value as the MCR or the lowest of the new and old ER values if this is greater than the MCR value.
- Figure 1 is a diagrammatic representation of the ER calcu ⁇ lating means in an ATM network switch
- Figure 2 is a diagrammatic representation of further com ⁇ parison means.
- FIG. 3 is a diagrammatic representation of the ATM switch. Detailed Description of the Illustrated Embodiment
- ABRATE is a factor which converts AOB, the number of cells in a predetermined arbitrary period, into a uniform rate of cells per unit time, this is because divisions are difficult to im ⁇ plement in hardware, and this form requires only one division operation, with the numerator and denominator being calculated separately before the division is performed.
- a factor of 4 is used because ⁇ act is divided by four in the implementation described to reduce the size of the numbers to be accommodated in an 18x18 multiplier.
- Multiplexers 11 and 12 pass the successive inputs to the adder/subtracter 13. First the Buffer Space BS and the offset Ker are added together and the result stored in a first register 14. The Total of Stored Cells TSC is then supplied to the adder/subtracter 13 via multiplexer 12 and the BS+K result is read out of register 14 and returned to the adder/subtracter 13 via multiplexer 11, a subtraction operation yielding BS+K-TSC, which is stored in register 15. Finally, the value MAX is sup ⁇ plied to the adder/subtracter 13 via multiplexer 11 and the VcCnt value is supplied via multiplexer 12, and another subtraction operation is performed to yield MAX-VcCnt, which is stored in register 16. If the result of either subtraction is negative, a flag is stored in register 17, the flag signalling that ER is to be set to zero.
- the multiplication operations are carried out in the second part of the mechanism, illustrated in Figure lb.
- the results of the addition and subtractions are supplied to the multiplier 18 via multiplexers 19 and 20 via holding registers 21 and 22. Since the products of the various numerator and denominator parameters lead potentially to 68 bit values, the calculation is simplified by treating the numbers as powers of two, with an 18 bit mantissa and 7 bit exponent.
- the splitter 25 receives the 36-bit numbers from the multiplier and converts the numbers to 18/7 format by left-justifying all results, using the full 18 bits for the number, even if a negative exponent results, to ensure a constant resolution.
- the resulting mantissa is passed back to the relevant one of the multiplexers 19 and 20 until the full calculation is complete, when the result is stored in registers 23a and 23b for the mantissas.
- the exponents are accumulated in accumulators 24a and 24b, these being reset to zero at the beginning of each calculation cycle.
- the mantissas are then passed to divider 27 while the exponents pass to subtracter 26.
- Converter 28 outputs the results of these calcu ⁇ lations as a 9 bit mantissa with a 5 bit exponent, which matches the format of the cell rates in the Rm cell.
- Figure 2 represents the situation at the receive side of the switch.
- the comparison is carried out additionally with the ER value calcu ⁇ lated at the receive side.
- the ER value is transmitted from the receiver to the transmitter across the switch fabric by writing it to the MCR field in the cell.
- the ER value is read out again, and replaced by the MCR value which is stored in the routing table in the switch when the VC is set up.
- Figure 3 illustrates in simplified form an ATM switch having a receiver 30 receiving cells on a connection from its source, a switch fabric 31, and a transmitter 32 passing the cells on to the next stage of the connection.
- a second receiver 33 receives Rm cells being returned to the source from the destination, a second transmitter 34 passing the cells on to the next stage back towards the source.
- a dual-ported RAM 35 is connected to the transmitter 32 and to the second receiver 33. It will be appre ⁇ ciated that connections may be configured with a source at each end so that forward and backward Rm cells will flow through each link to the switch.
- the EFCI bit is set in all user data cells, and when a Rm cell arrives, the CI or NI bits are used according to programmable options (per connection) ;
- the transmitter 32 performs the same behavior as the re ⁇ DCver 30, but also with the option of writing ER, CI and NI data to the dual-ported RAM 35.
- the switch can function with two alternative modes: simple, in which the new ER value is written to the cell for forward transmission, the changed ER then being signalled back to the source from the destination; or more complex, in which the cell is passed onwards or forwards with the old ER value unchanged, the test establishing the lowest value of ER to be written to the DPRAM 35.
- the ER value stored is written in to the next cell only if it is lower than the existing value in the cell. If there is no congestion, the maximum possible value of ER is put into the DPRAM so that the backward ER in the back ⁇ ward cells is not changed.
Abstract
Description
Claims
Priority Applications (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
EP96917182A EP0878068A4 (en) | 1995-06-05 | 1996-06-05 | Controlling the flow of atm cells in an atm network |
US08/973,442 US6115358A (en) | 1995-06-05 | 1996-06-05 | Controlling the flow of ATM cells in an ATM network |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
GBGB9511319.7A GB9511319D0 (en) | 1995-06-05 | 1995-06-05 | Controlling the flow of ATM cells in an ATM network |
GB9511319.7 | 1995-06-05 |
Publications (1)
Publication Number | Publication Date |
---|---|
WO1996039759A1 true WO1996039759A1 (en) | 1996-12-12 |
Family
ID=10775513
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
PCT/US1996/008906 WO1996039759A1 (en) | 1995-06-05 | 1996-06-05 | Controlling the flow of atm cells in an atm network |
Country Status (4)
Country | Link |
---|---|
EP (1) | EP0878068A4 (en) |
CA (1) | CA2222413A1 (en) |
GB (2) | GB9511319D0 (en) |
WO (1) | WO1996039759A1 (en) |
Cited By (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US6115359A (en) * | 1997-12-30 | 2000-09-05 | Nortel Networks Corporation | Elastic bandwidth explicit rate (ER) ABR flow control for ATM switches |
US6118764A (en) * | 1997-12-30 | 2000-09-12 | Nortel Networks Corporation | Congestion indication/no increase (CI/NI) ABR flow control for ATM switches |
US6359884B1 (en) | 1998-06-26 | 2002-03-19 | Nortel Networks Limited | Modular scalable packet scheduler with rate based shaping and virtual port scheduler |
US6404767B1 (en) | 1998-06-17 | 2002-06-11 | Nortel Networks Corporation | Architecture for ABR processing within an ATM switch |
US6438132B1 (en) | 1998-10-14 | 2002-08-20 | Nortel Networks Limited | Virtual port scheduler |
Families Citing this family (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
CA2160172A1 (en) * | 1995-10-10 | 1997-04-11 | Jozef Z. Babiarz | End-to-end clock recovery for atm networks |
CA2229652C (en) * | 1997-02-14 | 2002-05-21 | Naoki Mori | Atm network with a filtering table for securing communication |
US6088359A (en) * | 1997-07-11 | 2000-07-11 | Telefonaktiebolaget Lm Ericsson | ABR server |
EP0909106A3 (en) * | 1997-10-10 | 2000-04-12 | Mitsubishi Denki Kabushiki Kaisha | Implementation schemes for a queue length based ABR flow control system |
US6597662B1 (en) | 1998-03-24 | 2003-07-22 | Nortel Networks Limited | Apparatus and method for optimizing max-min fair rate control in ABR sessions |
CA2266307A1 (en) * | 1998-03-24 | 1999-09-24 | Northern Telecom Limited | Apparatus and method for optimizing max-min fair rate control in abr sessions |
Citations (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US5179556A (en) * | 1991-08-02 | 1993-01-12 | Washington University | Bandwidth management and congestion control scheme for multicast ATM networks |
US5313454A (en) * | 1992-04-01 | 1994-05-17 | Stratacom, Inc. | Congestion control for cell networks |
US5457687A (en) * | 1993-09-02 | 1995-10-10 | Network Equipment Technologies, Inc. | Method and apparatus for backward explicit congestion notification (BECN) in an ATM network |
US5515359A (en) * | 1994-08-26 | 1996-05-07 | Mitsubishi Electric Research Laboratories, Inc. | Credit enhanced proportional rate control system |
US5519689A (en) * | 1993-06-12 | 1996-05-21 | Samsung Electronics Co., Ltd. | Traffic control apparatus and method of user-network interface of asynchronous transfer mode |
Family Cites Families (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP0487235B1 (en) * | 1990-11-21 | 1999-02-03 | AT&T Corp. | Bandwidth and congestion management in accessing broadband ISDN networks |
WO1994011971A1 (en) * | 1992-11-16 | 1994-05-26 | Fujitsu Limited | Call reception control in atm network |
GB9312741D0 (en) * | 1993-06-21 | 1993-08-04 | Plessey Telecomm | Nitwork management |
JP2639335B2 (en) * | 1993-12-22 | 1997-08-13 | 日本電気株式会社 | Congestion control method in ATM network |
GB9326276D0 (en) * | 1993-12-23 | 1994-02-23 | Newbridge Network Corp | Frame relay interface |
ZA959722B (en) * | 1994-12-19 | 1996-05-31 | Alcatel Nv | Traffic management and congestion control for packet-based networks |
-
1995
- 1995-06-05 GB GBGB9511319.7A patent/GB9511319D0/en active Pending
-
1996
- 1996-06-05 EP EP96917182A patent/EP0878068A4/en not_active Withdrawn
- 1996-06-05 GB GB9611706A patent/GB2301985B/en not_active Expired - Lifetime
- 1996-06-05 WO PCT/US1996/008906 patent/WO1996039759A1/en not_active Application Discontinuation
- 1996-06-05 CA CA002222413A patent/CA2222413A1/en not_active Abandoned
Patent Citations (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US5179556A (en) * | 1991-08-02 | 1993-01-12 | Washington University | Bandwidth management and congestion control scheme for multicast ATM networks |
US5313454A (en) * | 1992-04-01 | 1994-05-17 | Stratacom, Inc. | Congestion control for cell networks |
US5519689A (en) * | 1993-06-12 | 1996-05-21 | Samsung Electronics Co., Ltd. | Traffic control apparatus and method of user-network interface of asynchronous transfer mode |
US5457687A (en) * | 1993-09-02 | 1995-10-10 | Network Equipment Technologies, Inc. | Method and apparatus for backward explicit congestion notification (BECN) in an ATM network |
US5515359A (en) * | 1994-08-26 | 1996-05-07 | Mitsubishi Electric Research Laboratories, Inc. | Credit enhanced proportional rate control system |
Cited By (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US6115359A (en) * | 1997-12-30 | 2000-09-05 | Nortel Networks Corporation | Elastic bandwidth explicit rate (ER) ABR flow control for ATM switches |
US6118764A (en) * | 1997-12-30 | 2000-09-12 | Nortel Networks Corporation | Congestion indication/no increase (CI/NI) ABR flow control for ATM switches |
US6404767B1 (en) | 1998-06-17 | 2002-06-11 | Nortel Networks Corporation | Architecture for ABR processing within an ATM switch |
US6359884B1 (en) | 1998-06-26 | 2002-03-19 | Nortel Networks Limited | Modular scalable packet scheduler with rate based shaping and virtual port scheduler |
US6438132B1 (en) | 1998-10-14 | 2002-08-20 | Nortel Networks Limited | Virtual port scheduler |
Also Published As
Publication number | Publication date |
---|---|
CA2222413A1 (en) | 1996-12-12 |
GB9611706D0 (en) | 1996-08-07 |
GB9511319D0 (en) | 1995-08-02 |
GB2301985A (en) | 1996-12-18 |
GB2301985B (en) | 2000-02-09 |
EP0878068A1 (en) | 1998-11-18 |
EP0878068A4 (en) | 2001-05-16 |
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