Real-time estimation and dynamic renegotiation of UPC values for arbitrary traffic sources in ATM networks
First Claim
1. A method of characterizing an arbitrary asynchronous transfer mode (ATM) traffic stream in real-time comprising the steps of:
- characterizing the traffic stream statistically over an observation interval T;
mapping the statistically characterized traffic stream to usage parameter control (UPC) values of a dual leaky bucket which minimize a cost function subject to predetermined constraints of a user, said dual leaky bucket including a peak rate leaky bucket and a sustainable rate leaky bucket, and said UPC values including a peak rate λ
p, a sustainable rate λ
s, and a sustainable bucket size Bs;
detecting a predetermined change in the traffic stream; and
renegotiating the UPC values with a network when said predetermined change is detected.
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Abstract
A scheme for determining the usage parameter control (UPC) values for an arbitrary traffic source from observations of its emitted cell stream is disclosed. The UPC values are used in a traffic shaping mechanism based on a dual leaky bucket, which shapes the cell stream by either discarding or delaying cells. The choice of UPC values is a function of the statistical characteristics of the observed cell stream; the user'"'"'s tolerance for delay prior to the network access point; and the cost incurred on the network side. The chosen UPC values are then negotiated with the network. The source traffic characteristics may change dramatically over time, making the initially negotiated UPC descriptor inappropriate for the entire traffic stream. Hence, a method is disclosed for dynamically renegotiating UPC parameters whenever a predetermined change in traffic characteristics is detected. This method for real-time estimation and dynamic renegotiation of UPC parameters is the basis for a self-contained module which allows the source to make efficient use of the network resources.
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Citations
20 Claims
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1. A method of characterizing an arbitrary asynchronous transfer mode (ATM) traffic stream in real-time comprising the steps of:
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characterizing the traffic stream statistically over an observation interval T;
mapping the statistically characterized traffic stream to usage parameter control (UPC) values of a dual leaky bucket which minimize a cost function subject to predetermined constraints of a user, said dual leaky bucket including a peak rate leaky bucket and a sustainable rate leaky bucket, and said UPC values including a peak rate λ
p, a sustainable rate λ
s, and a sustainable bucket size Bs;
detecting a predetermined change in the traffic stream; and
renegotiating the UPC values with a network when said predetermined change is detected. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
offering the traffic stream to a bank of N constant service rate queues with spaced rates that are spaced between an estimated mean rate {circumflex over (λ
)}m and an estimated peak rate {circumflex over (λ
)}p, said spaced rates being candidates for sustainable rates; and
approximating a tail waiting time distribution for each of said queues by an exponential equation having a form of
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3. The method of claim 2, wherein the offering step comprises the step of choosing rates for the bank of N queues, said choosing step comprising the steps of:
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dividing the N queues into a set of Nc coarse queues each having a coarse rate, Nf fine queues each having a fine rate, and a queue having a rate equal to a current sustainable rate;
assigning the coarse rates to be spaced between a current estimated mean rate {circumflex over (λ
)}m(n) and a current estimated peak rate {circumflex over (λ
)}p(n) according to a coarse rate resolution given byassigning the fine rates to be spaced symmetrically about a current sustainable rate according to the fine rate resolution given by
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4. The method of claim 2 further comprising the step of estimating the parameters a(μ
- ) and b(μ
) in the tail waiting time distribution for each queue of constant service rate μ
, said estimating step comprising the steps of;estimating an average remaining service time, Tr(μ
), for a customer in service as seen by an arriving customer conditional on there being a customer in service;
estimating a probability that an arbitrary arriving customer sees a customer in service, and setting a(μ
) equal to said probability;
estimating q(μ
), which is an expected number of customers in a queue seen by the arbitrary arriving customer; and
computing b(μ
) according to
- ) and b(μ
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5. The method of claim 2 further comprising computing a smallest sustainable bucket size Bs(μ
- ) for a predetermined sustainable rate μ
, such that a sustainable rate leaky bucket with parameters (μ
,Bs(μ
)) satisfies a constraint on one of a violation probability and a mean shaping delay according towhen the violation probability is constrained to be no larger than a predetermined violation probability ε
, and according towhen the mean shaping delay is constrained to be no more than a predetermined mean shaping delay {overscore (D)}.
- ) for a predetermined sustainable rate μ
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6. The method of claim 1 further comprising computing an approximate required resource as a cost function, c(λ
-
p, λ
s, Bs) of a predetermined UPC set (λ
p, λ
s, Bs) according towhere K is a parameter used to match approximately a connection admission control function of the network.
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p, λ
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7. The method of claim 2, wherein the mapping step comprises the steps of:
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computing, for each of the candidate sustainable rates μ
used in the characterizing step, a corresponding value Bs(μ
) for a smallest sustainable bucket size such that a sustainable rate leaky bucket with parameters (μ
,Bs(μ
)) satisfies a constraint which bounds one of a cell violation probability and a mean shaping delay;
computing, for each of the candidate sustainable rates μ
used in the characterizing step, a corresponding value c(λ
p, μ
, Bs(μ
)) of the cost function that determines cost to the network;
selecting, among the candidate sustainable rates, an optimal sustainable rate μ
=λ
*s that minimizes the cost function c(λ
p, μ
, Bs(μ
)); and
choosing new UPC values that include the peak rate λ
p, the optimal sustainable rate λ
s*, and the sustainable bucket size Bs(λ
s*).
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8. The method of claim 1, wherein the detecting step comprises the steps of:
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estimating a mean cell delay, {circumflex over (d)}, for a leaky bucket parameterized by the sustainable rate λ
s and the sustainable bucket size Bs;
estimating the peak rate μ
p to obtain an estimated peak rate {circumflex over (λ
)}p;
signaling a change when the mean cell delay {circumflex over (d)} falls outside a range of values in a neighborhood of a user-specified tolerable mean delay {overscore (D)}, or when the estimated peak rate {circumflex over (λ
)}p falls outside a range of values in a neighborhood of the peak rate λ
p.
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9. The method of claim 8, wherein said leaky bucket is a sustainable rate leaky bucket of a dual leaky bucket that includes a peak rate leaky bucket connected in series to said sustainable rate leaky bucket.
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10. A device for managing an arbitrary asynchronous transfer mode (ATM) cell stream from a source comprising:
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a usage parameter control selector which characterizes the cell stream statistically over an observation interval T and maps the statistical characterization to dual leaky bucket usage parameter control (UPC) values once every observation interval T, in response to observations of the cell stream and source shaping constraints received from the source;
a usage parameter control shaper that shapes, in accordance with said UPC values, the cell stream received from the source and outputs shaped stream data; and
a change detector which receives the cell stream, source shaping constraints, and the UPC values, and outputs a change signal indicative of whether an update of the UPC values stored in a memory is required. - View Dependent Claims (11, 12, 13, 14, 16, 17)
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15. A device for managing an arbitrary asynchronous transfer mode (ATM) cell stream from a source comprising:
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a usage parameter control selector which characterizes the cell stream statistically over an observation interval T and maps the statistical characterization to dual leaky bucket usage parameter control (UPC) values once every observation interval T, in response to observations of the cell stream and source shaping constraints received from the source;
a usage parameter control shaper that shapes, in accordance with said UPC values, the cell stream received from the source and outputs shaped stream data; and
a signaling module which receives said UPC values from said usage parameter control selector and outputs a UPC renegotiation request to the network, said usage parameter control shaper providing a shaper overload signal to said source when an accept/reject signal from the network provided in response to the UPC renegotiation request indicates a rejection of said renegotiation request. - View Dependent Claims (18, 19, 20)
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Specification