Classifications

• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
  • H04L47/00—Traffic control in data switching networks
  • H04L47/10—Flow control; Congestion control
  • H04L47/28—Flow control; Congestion control in relation to timing considerations
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
  • H04L47/00—Traffic control in data switching networks
  • H04L47/10—Flow control; Congestion control
• • H—ELECTRICITY
  • H04—ELECTRIC COMMUNICATION TECHNIQUE
  • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
  • H04L47/00—Traffic control in data switching networks
  • H04L47/10—Flow control; Congestion control
  • H04L47/24—Traffic characterised by specific attributes, e.g. priority or QoS
  • H04L47/2408—Traffic characterised by specific attributes, e.g. priority or QoS for supporting different services, e.g. a differentiated services [DiffServ] type of service

Definitions

• This invention relates to Class Based Weighted Fair Queuing (CBWFQ) and more particularly to adaptively changing the CBWFQ coefficients for preservation of throughput on high priority classes of traffic through a network.
• CBWFQ Class Based Weighted Fair Queuing
• Class based network services are an emerging trend in communications " network systems. Class based services allow efficient handling of a mix of traffic types, including voice, video, and data traffic. Classes can be differentiated based on whether or not they are delay, jitter, or loss tolerant, and whether they are bursty, in addition to their peak data requirements.
• Class Based Weighted Fair Queuing involves establishing a system for weighting of different classes of service to establish which of the classes of services is given priority in the transmission or servicing of data packets relating to that class.
• Each packet of data that is queued for transmission from a given queue service center has a header which maps to the class of service to which that packet belongs (i.e. Diff Serve).
• Some classes of service may be, for example voice, video, data, and e-mail.
• voice packets may be highest in priority since the receiver needs to receive voice packets in close proximity in order to be able to reproduce intelligible speech with minimally perceptible delay.
• Video may also be a high priority packet type in order for the receiver to receive relatively smooth video images rather than jittery or hesitant images. If voice accompanies the video, the associate voice packets may enjoy a similar priority in order to provide synchronization between the video and voice.
• e-mail may have a relatively low priority since it rarely is critical that e-mail be received on a real-time basis.
• a data queue service center and method of operation therefor is provided for routing data packets of different Classes of Service over a transmission path.
• a queue is established for each different Class of Service to be serviced or transmitted and a desired queue residence time for each Class of Service is preallocated by applying a Class Based Weighted Fair Queueing weighting factor to the queue for each Class of Service.
• the actual residence time of packets for each Class of Service is determined and compared with the preallocated residence time for each Class of Service. If the measured residence time of a particular Class of Service exceeds the preallocated residence time, the CBWFQ weight for that Class of Service is dynamically increased.
• FIG. 1 is a block diagram of a typical data router incorporating features according to the invention.
• FIG. 2 is a flow diagram showing the operation of the instant invention in accordance with the apparatus of FIG. 1.
• FIG. 1 shows is a block diagram of a typical data queue service center (QSC), which may be a router, a packet processing function, or other device for processing packets of data, incorporating features according to the invention.
• the router is shown generally at 10.
• Within the router 10 are a series of queues or buffers, 12, 14, 16, 18, and 20.
• Each of the buffers 12-20 may be assigned as a buffer to queue and process a series of data packets for a given Class of Service.
• buffer 12 may be assigned all voice packets, buffer 14 all video packets, buffer 16 other data packets, and buffer 18 all e-mail packets.
• Each separate packet is usually identifiable by means of characters in the header of the packet which may also contain, for example, sender information, destination address, source address, port number, sequence number, number of characters contained therein and other classification or processing information.
• Each queue or buffer 12-20 is coupled to a Central Processing Unit (CPU) 22 which receives in a predetermined sequence, the packets from each of the buffers or queues.
• the processor determines the proper routing for a packet as it is presented, and sends a serial string of packets on to subsequent processing or packet servicing functions or to a transmission medium 24 which may be coaxial cable, copper wire, of fiber optic cable.
• a transmission medium 24 which may be coaxial cable, copper wire, of fiber optic cable.
• a commutation pattern generator 26 is also coupled to the CPU 22 for determining in which sequence the CPU 22 will accept packets from each of the buffers 12-20. This commutation pattern is typically established in advance based on overall system capacity for each Class of Service, the types of data being routed, and the priority needs of the individual Classes of Service.
• Class Based Weighted Fair Queuing involves establishing a system for weighting of different classes of service to establish which of the classes of services is given attention in the servicing or transmission of data packets relating to that class.
• a Class Based Weighted Fair Queuing system may establish weights for various Classes of Service as follows:
• CoS n represent different Classes of Service or data types and the numerical prefixes establish the relative weighting or percentage of total available service cycles given to each Class of Service.
• CoS. with its relatively high weighting of 0.5, may represent voice data that must be processed and transmitted at near real time speeds in order to provide intelligible speech at the receiver.
• CoS 3 with a relatively low weighting (0.1) may represent e-mail packets where time constraints usually are not severe. While these are exemplary of a possible weighting scheme, system characteristics would also be taken into account. For example if, because of the particular nature of the network the expected amount of voice traffic is low, or, if for some reason a certain other kind of data were to have higher priority than voice, the voice CoS may have assigned a relatively lower priority.
• An algorithm of this type may be used to determine the commutation pattern of the commutation pattern generator 26. In typical systems this algorithm is fixed and may be changed only through operator intervention.
• an overload may occur in one or more of the Classes of Service.
• this overload usually results in high priority traffic being delayed or disrupted until a system supervisor can adjust the priorities to smooth and properly prioritize the data flow.
• flow control is used to reduce the influx to the queue service center of certain Classes of Service so that the higher priority Classes of Service can be efficiently transmitted.
• a processor 28 receives from the QSC 10 over lines 30 certain information related to queue length and residency time as will be fully described following, and uses that information to dynamically adjust the weighting values of the CBWFQ algorithm.
• the adjusted weighting values are provided to the commutation pattern generator over lines 32, and the commutation pattern generator utilizes the new weighting regimen to adjust the commutation pattern of CPU 22.
• the total system load factor is calculated and provision may be made for flow control to be invoked if the total system load factor exceeds a predetermined value.
• FIG. 2 is a flow diagram showing the operation of the instant invention in accordance with the apparatus of FIG. 1.
• the algorithm of FIG. 2 is initialized at 40, where the following initial conditions are established: Let W. represent the integer number of visitations that a queue service center applies to CoS queue i.
• the commutation pattern is then: [W. W 2 ... WJ with a total of ⁇ W. services per commutation cycle.
• the queue depth at each queuing station is determined at 42 for all Classes of Service. This can be accomplished by determining how full the buffers for each CoS are. This provides information to be used at 44 to determine residence time for each Class of Service. In block 44, given the queuing service time for a particular queue, the associated expected packet residence time is calculated as R CoS (n) for each Class of Service and for all Classes of Service combined.
• the system load factor is determined by dividing the total residence time for all Classes of Service combined by the established system design total residency time for all CoSs as follows:
• Load_f actor ⁇ R CoS (n) / ⁇ k(n)
• k residence time limit for a given Class of Service.
• the session manager is notified at 50 that the system is overloaded and flow control should be implemented in order not to disrupt data flow of high priority Classes of Service.
• the session manager is responsible for throttling network ingress flow rate or providing admission control to the network.
• the information derived is used to program the commutation pattern generator 26 to provide a new commutation pattern to the CPU 22 in order to properly prioritize the various Classes of Service for subsequent service or efficient transmission to the transmission medium.

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• Engineering & Computer Science (AREA)
• Computer Networks & Wireless Communication (AREA)
• Signal Processing (AREA)
• Data Exchanges In Wide-Area Networks (AREA)
• Communication Control (AREA)

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• 2001
  • 2001-11-01 AU AU2002227151A patent/AU2002227151A1/en not_active Abandoned
  • 2001-11-01 WO PCT/US2001/045761 patent/WO2002039680A2/en not_active Application Discontinuation
  • 2001-11-01 EP EP01994006A patent/EP1336281A2/de not_active Withdrawn
  • 2001-11-01 JP JP2002541876A patent/JP2004514324A/ja active Pending

Non-Patent Citations (1)

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