EFFICIENT METHOD AND SYSTEM FOR WEIGHTED FAIR POLICING
Technical Field
The present invention relates generally to communication networks, and more particularly to techniques for queuing data traffic in communication networks.
Access to and use of wireless net-works is becoming increasingly importan, and popular for business, social, and recreational purposes. Users of wireless networks now rely on them for both voice and data communications. Furthermore, an ever increasing number of users demand both an increasing array of services and capabilities as well as greater bandwidth for activities such as Internet surfing. To address and meet the demands for new services and greater bandwidth, the wireless communications industry constantly strives lo improve the number of services and the throughput of their wireless networks. Expanding and improving the infrastructure necessary to provide additional services and higher bandwidth is an expensive and manpower-intensive undertaking. Moreover, high-bandwidth data streams will eventually be demanded by consumers to support features such as real-time audio-visual downloads and live audio-visual communication between two or more people. In the future, it will therefore become necessary and/or more cost-effective to introduce next generation wireless system(s) instead of attempting to upgrade existing system(s).
To that end, the wireless communications industry intends to continue to improve the capabilities of the technology upon which it relies and that it makes available to its customers by deploying next generation system(s). Protocols for a next-generation standard that is designed to meet the developing needs of wireless customers is being standardizad by the3.seped Generation Partnership Projed (3GPP). The set of protocols is known collectively us the Universal Mobile Telecommunications System (UMTS).
In the current state of the Internet, the issues of guaranteed bandwidth fairness and support for multiple levels of latency are becoming increasingly important.
Guaranteed bandwidth fairness is typically provided using so called "Fair Queuing" algorithms. These algorithms guarantee that bandwidth of a certain link (or virtual link) is fairly apportioned among its various flows. Fair Queuing algorithms are incorporated into network systems using fair queuing (or bandwidth) schedulers. These schedulers seek to control congestion even in the presence of ill-behaved sources, so ihut a single source tht sends packets to a gateway at a sufficiently high. speed cannot capture an arbitrarily high portion of the bandwidth of the outgoing line. While providing bandwidth guarantees is important, it is also important that latency-critical traffic flows (such as Voice Over IP and Video) experience as low latency as possible. Prioritizing traffic flows so that latency-critical flov/s experience low latency is currently provided by priority (or latency) schedulers.
Conventional network solutions have attempted to resolve both fair queuing and priority scheduling, and, despite the inherent tension between the two concerns, have been somewhat successful in incorporating both features in network systems.
Background of the Invention
Weighted fair queuing (WFQ) is a well known flow-based queuing technique as for example disclosed in US 6810426 or US 6850540. The WFQ simultaneously schedules interactive traffic to the front of the queue to reduce response time and it fairly shares the remaining bandwidth between high bandwidth flows. FIG. 1 shows in prior art a conventional WFQ system 100 that includes N queues 110-1 through 110-N. Each queue 110 serves a single source (or connection) and is assigned with a respective weight. Each packet leaving its respective queue 1 10 is forwarded directly to on output channel 120. The scheduling method implemented in WFQ system 100 ensures that the waiting time of packets in queues 1 10 is always in proportion to queue's weights.
For example, a WFQ system having three queues Ql, Q2, and Q3 and respectively assigned with the weights W,= 5, W2 = 2, and W3 = 3. The maximum allowable rate of the output channel is 10 MB/Sec. In this exemplary system, if all queues have packets waiting, then Q2 and Q3 receive a guaranteed bandwidth of 2 and 3 MB/Sec respectively, and Ql receives a guaranteed bandwidth of 5 MB/sec. If Ql does not have any packets waiting, then the excess
bandwidth is equal to 5 MBS/second. In a WFQ system, this excess bandwidth is redistributed in proportion to the associated weights of the queues that have packets waiting. That is, when queue Q1 does not have packets waiting, the excess bandwidth is distributed proportionally to queues Q2 and Q3 so that they now receive bandwidth of 4 and 6 MB/Sec respectively.
One advantage of the WrQ technique is ihe end-to-end delay guarantees, i.e., each packet is guaranteed a certain rate for each packet flow in the stream. Another advantage is the underutilization of capacity when flow is particularly bursty idle time. In such case the WFQ technique facilitates the redistribution of the unused bandwidth so as to preserve work-conservation property.
US 6192032 Bl describes a video frame transmitter with a traffic smoother for adjusting the video frame packet transmission rates, a traffic policing device for controlling video frame packet entry into the network and a transmission rate attenuator, which provides a mechanism for the policing device to work in conjunction with the traffic smoother. Typically, a policing device and a traffic smoother operate independently causing packet priority downgrades. According to the teaching of US 6192032 Bl, by reducing the transmission rate of a video frame, a policing device is allowed to create more tokens so that all packets within the video frame are transmitted without any priority downgrades.
Summary of the Invention
The drawback of the WFQ technique inherits in its implementation. The conventional WFQ systems are based on multiple queues, this configuration is costly and complicated. Furthermore, queue based system requires to maintain the state of each packet. This requirement is not compliant with most of the communication networks. It would be therefore advantageous to provide an efficient weighted fairness bandwidth distribution system.
These and other objects that appear below are achieved by a fair policing method according to claim 1 and by n weighted fair policing (WFP) system according to claim 5. Advantageous improvements are described in the dependent claims.
Brief Description of the Drawings
Figure 1 - is a conventional WFQ system (prior art)
Figure 2 - is a non-limiting an exemplary block diagram of an efficient weighted
fairness system that discloses one embodiment of the present invention
Figure 3 - is a non-limiting and exemplary graph of an attenuation function
Figure 4 - is an example for the operation the disclosed weighted fairness system
Figure 5 - is a non-limiting flowchart describing method for performing a
weighted fair policing that discloses on embodiment of the present invention
Figure 6 - is a non-limiting an exemplary diagram of an efficient weighted fair policing system having prioritized queues that discloses one embodiment of the present invention
Detailed Description of the Invention
The present invention discloses an efficient weighted fair policing (WFP) system capable of weighted fairness bandwidth distribution. The system is based on a plurality of policers and a single queue. To achieve fairness, the rate of policed packets is adoptively controlled.
Fig. 2 shows a non-limiting and an exemplary block diagram of a WFP system 200 that discloses one embodiment of the present invention. WFP system 200 includes M policers 210-1 through 210-M connected to a single queue 220, a bandwidth adjustment module 230, and an output channel 240. Each policer 210 is parameterized by an input rate (InRate) and a maximum excess information rate (EIRmax). A policer is a rate limiting device that rejects data packets that arrive to the policer at a instantaneous rate that is above some predefined threshold rate. Specifically, each policer 210 is capable of handling a single data flow and computing a new EIR to be enforced. Namely, packets of a respective data flow are transferred from a policer 210 to queue 220 if their instantaneous rate does not exceed the rate equal to the newly computed EIR. The new EIR is computed according to the following equation:
(Equation Removed)

where the "Attn" parameter is determined by an attenuation function, as described in more detail below. The EIRmox is the maximum bandwidth that a policer can transfer. In fact, the EIRmax are preconfigured values that determine the weighs of the WFP algorithm. Data packets flowing through the policer cannot exceed InRate. An example for a policer 210 may be found in PCT application No. PCT/112004/00781 by Zeitak, entitled "A Policer and Method for Resource Bundling'', assigned to a common assignee and hereby incorporated by reference for all that it contains.

The output rate of output channel 240 is determined by a maximum allowable rate (hereinafter the "RATEmax") parameter. Congestion occurs whenever the total rate that the policers 210 allow is in excess of the RATEmax. The bandwidth adjustment module 230 monitors the queue occupancy and queue ingress rate (hereinafter the "Qocc") and computes an Attn value using the attenuation function. Fig. 3 shows a non-limiting and exemplary graph of an attenuation function 310. As seen, the Attn value ranges between 0 and 1, where a 1 value is when queue 220 is empty and a 0 value is when the queue 220 is full. The Attn value is sent to each of policers 210, which in turn calculates the EIRnew to be enforced. An exemplary embodiment of the attenuation function (AT) would be:
(Equation Removed)
where, Th2 is a normalization factor that determines the maximum occupancy (in bytes) of the queue and Thl is a threshold equals to