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Approximated per-flow rate limiting
| Details |
Inventors: Cheriton, David R.;
Assignee: Cisco Technology, Inc. (San Jose, CA)
Primary Examiner: Chin; Wellington
Assistant Examiner: Jain; Raj K.
Attorney, Agent or Firm: Campbell Stephenson Ascolese LLP
A method and apparatus to limit the throughput rate of non-adapting aggressive flows on a packet-by-packet basis. Each packet of an input flow is mapped to an entry in a flow table for each output queue. The mapping is based on a subset of the packet's header data, giving an approximation of per-flow management. Each entry contains a credit value. On packet reception, the credit value is compared to zero; if there are no credits, the packet is dropped. Otherwise, the size of the packet is compared to the credit value. If sufficient credits exist (i.e., size is less than or equal to credits), the credit value is decremented by the size of the packet in cells and the processing proceeds according to conventional methods, including but not limited to those disclosed in the co-pending DBL Application, incorporated herewith by reference in its entirety. If, however, the size of the packet exceeds the available credits, the credit value is set to zero and the packet is dropped. A periodic task adds credits to each flow table entry up to a predetermined maximum. The processing rate of each approximated flow is thus maintained to the rate determined by the number of credits present at each enqueuing decision, up to the allowed maximum. The scheme operates independently of packet flow type, providing packet-specific means for rapidly discriminating well-behaved flows that adapt to congestion situations signaled by packet drop from aggressive, non-adapting flows and managing throughput bandwidth accordingly. Bandwidth is shared fairly among well-behaved flows, large and small, and time-critical (low latency) flows, thereby protecting all from non-adapting aggressive flows. |
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DETAILED DESCRIPTION Overview The present Application discloses a rate limit scheme, using actual flow data rate requirements rather than type/class of service identifiers, that adapts to varying traffic.
This scheme prevents unauthorized use of and denial of service attacks on internetworking systems by malevolent users utilizing flow behavior and data rate to control the bandwidth of all flows in a queue.
The present invention also avoids the high resource and setup overhead costs associated with true per-flow control by using an approximated flow control method.
The present invention ensures good service for fragile voice flows (those sending few packets and those of a time critical nature) such as Voice-over-Internet Protocol (VoIP), thereby protecting them from non-adapting aggressive flows.
In one embodiment of the present invention, a voice flow is assigned to a queue given high priority in order to give voice flows low latency and high immunity from packet drops.
The rate-limiting flow table of the present invention is employed to prevent NAFs and aberrant flows masquerading as voice from overwhelming the high priority voice queue and/or causing starvation of other flows through the switch.
Although the terms switch and/or router will be used generally in this specification, those skilled in the art will realize that other related internetworking devices may be used, in addition to routers or switches, to perform analogous functions.
Accordingly, the invention is not limited to any particular type of internetworking device, router, or switch.
Also, although the primary focus of the current invention is Internet Protocol (IP) packet flows, those skilled in the will art realize that protocols and flows other than IP can be benefit from the present invention and its alternate embodiments.
Accordingly, the invention is not limited to any particular type of protocol or packet format.
Although the circuit of FIG.
1 has been described as prior art, FIG.
1 may also be used to illustrate a router/switch device incorporating the present invention
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File Sharing 
