CN103888385A - VOQ switch packet scheduling algorithm based on packet accumulation effect - Google Patents

Abstract

The invention discloses a VOQ switch packet scheduling algorithm based on a packet accumulation effect. The VOQ switch packet scheduling algorithm based on the packet accumulation effect is an algorithm based on frames. According to the VOQ switch packet scheduling algorithm based on the packet accumulation effect, N completely-matched matrixes are selected for a switch with N*N ports on the basis of a round robin matching mode; the matched matrixes are multiplied by the lengths of virtual output queues of input ports of the switch at the beginning of a frame boundary so that occupation of the matched matrixes can be obtained; the matched matrix with the maximum occupation value is selected as a matching scheme for the ports of the frame switch. Stability of the VOQ switch packet scheduling algorithm is theoretically certified; according to comparison of simulation results, the VOQ switch packet scheduling algorithm is better than a typical scheduling algorithm in the aspect of packet average delay; meanwhile, iteration complexity of the VOQ switch packet scheduling algorithm is only O(1), and the VOQ switch packet scheduling algorithm can be applied to large-scale high-speed networks, and have good extensibility.

Description

Based on the VOQ switch packet scheduling algorithm of grouping cumulative effect

Technical field

The invention belongs to high-performance packet switch control technology field.

Background technology

(the Virtual Output Queued of high performance virtual output work queue, VOQ) packet switch of structure because of the former of non-competing ruling thereby the grouping long period that causes being stored in input port buffer memory can not leave input port, by the accumulation that causes being grouped in input port.The reason that produces this phenomenon may be diversified.For example based on microelectromechanical systems (Micro-Electro-Mechanical System, MEMS) thus the photoelectricity hybrid optical switching machine of composition has caused being grouped in the accumulation during reshuffling because time of reshuffling of light path is long.For another example in wireless network, cannot effectively transmit grouping because the interference of wireless delivery channel causes channel, thereby cause being grouped in the accumulation in input port during channel disturbance.For the channel of time delay bandwidth product greatly, for example high-speed synchronous track (Geostationary Earth Orbit, GEO) space-borne switchboard really, this situation is more outstanding.

For the VOQ switch that has grouping cumulative effect, the main packet scheduling algorithm adopting comprises LQF (Longest Queue First)+Hold and i-LQF (iterative the LQF)+Hold based on frame at present.These class methods are couplings that the state that starts switch based on a frame decides an image duration, owing to constantly there being new grouping to arrive in a frame, and matching relationship is changeless in a frame, be not likely optimum in the determined coupling in the border of frame like this.The simulation experiment result demonstration, the performance performance under non-homogeneous business of i-LQF algorithm is poor, and switch is unstable, can not reach 100% percent of pass.Someone has discussed respectively the weight limit based on the time slot of m before frame boundaries, and maximum port match MSM algorithm is improved and weighting three step iterative method scheduling algorithms.The method that adopts dynamic recognition to realize variable frame length scheduling has also been discussed simultaneously.This method cannot pre-determine frame period, therefore in practical application, cannot effectively determine speed-up ratio.Somebody has proposed to guarantee the DOUBLE algorithm of time delay, and this algorithm adopts multi-frame structure, once determines the coupling matrix of multiple different length frames.But time delay circle that this algorithm provides is too large, is not suitable for large switch.

The invention provides a kind of new maximum based on poll coupling and take Priority-driven Scheduling Algorithm RR-LMO (RR Largest Matched Occupancy).For the VOQ switch of N × N port, build N and mate matrix completely, in the time that starting, calculates every frame corresponding the taking of each coupling matrix, select to have the coupling matrix that maximum takies.

Summary of the invention

The object of this invention is to provide for the VOQ switch that has grouping Accumulation Phenomenon is the packet scheduling algorithm of O (1) based on the good average packet delay performance of having of frame and iteration complexity.For achieving the above object, the technology path that the present invention adopts is:

The first step builds mates matrix completely.

For the switch of N × N port, according to RR matching way, select N to mate matrix P completely ^kas follows, wherein k=1 ..., N.

Wherein i=1 ..., N and=1 ..., N,

represent that in k coupling matrix, input port i mates with output port j.

The coupling that second step calculates corresponding coupling matrix takies (matched occupancy).

Make Q _ijrepresent VOQ _ijthe team leader in the time of frame boundaries, F is frame length,

The coupling of calculating corresponding coupling matrix take into

$O_{\mathrm{ij}}^k=\underset{i,j}{\mathrm{\Σ}}{\stackrel{\‾}{O}}_{ij}{\mathrm{\π}}_{i,j}$

The 3rd step selects to have the coupling matrix that maximum coupling takies

as the coupling matrix of next frame, if the matrix that has multiple maximum couplings to take is selected one at random.

Beneficial effect of the present invention: the present invention is directed to and have the corresponding VOQ fabric switch machine of grouping accumulation, it is only O (1) dispatching algorithm that a kind of complexity is provided, and simulation result is presented at packeting average delay performance aspect and has outstanding advantage.Theory analysis proves that algorithm of the present invention meets S in speed-up ratio _p>=(C+T)/T(wherein C is that grouping can not be left time of input port, and T equals frame length F and deducts C) time can obtain 100% percent of pass, wherein Fig. 2 has provided F, the relation between T and C.In the time not there is not Accumulation Phenomenon, all can obtain 100% percent of pass for arbitrarily accessible smooth traffic or Diagonal business in addition.Therefore algorithm provided by the invention has good practical value and autgmentability in extensive high-performance VOQ switch.

Accompanying drawing explanation

Fig. 1 is virtual output work queue (VOQ) fabric switch machine schematic diagram;

Fig. 2 is the packet scheduling process of the algorithm of the present invention based on the explanation of MEMS structure;

Fig. 3 is packeting average time delay contrast under 16 × 16 port switch Uniform B ernoulli business;

Fig. 4 is packeting average time delay contrast under 16 × 16 port switch diagonal Bernoulli business; ;

Fig. 5 is packeting average time delay contrast under the even ON/OFF business of 16 × 16 port switch;

Fig. 6 is packeting average time delay contrast under 16 × 16 port switch diagonal ON/OFF business.

Embodiment

Fig. 1 has provided the block diagram of VOQ structure packet switch, and Fig. 2 has provided the implementation process take MEMS fabric switch machine as the dispatching algorithm of the present invention of example.The present invention adopts the dispatching algorithm based on frame, and switching fabric is reset can not leave input port corresponding to the grouping in input-buffer, thereby causes grouping accumulation.In wireless network, corresponding many reasons is equivalent to that delivery channel lost efficacy and the grouping accumulation that causes.

The first step builds mates matrix completely.

For the switch of N × N port, according to poll RR(Round Robin) matching way, select N to mate matrix P completely ^kas follows, wherein k=1 ..., N.

Wherein i=1 ..., N and=1 ..., N,

represent that in k coupling matrix, input port i mates with output port j.

The for example switch of 4 × 4 ports, 4 coupling matrixes of selection are respectively:

$\begin{array}{cccc}\left(\begin{array}{cccc}1& 0& 0& 0\\ 0& 1& 0& 0\\ 0& 0& 1& 0\\ 0& 0& 0& 1\end{array}\right)& \left(\begin{array}{cccc}0& 1& 0& 0\\ 0& 0& 1& 0\\ 0& 0& 0& 1\\ 1& 0& 0& 0\end{array}\right)& \left(\begin{array}{cccc}0& 0& 1& 0\\ 0& 0& 0& 1\\ 1& 0& 0& 0\\ 0& 1& 0& 0\end{array}\right)& \left(\begin{array}{cccc}0& 0& 0& 1\\ 1& 0& 0& 0\\ 0& 1& 0& 0\\ 0& 0& 1& 0\end{array}\right)\\ P^1& P^2& P^3& P^4\end{array}$

The coupling that second step calculates corresponding coupling matrix takies (matched occupancy).

Make Q _ijrepresent VOQ _ijthe team leader in the time of frame boundaries, F is frame length,

The coupling of calculating corresponding coupling matrix take into

$O_{\mathrm{ij}}^k=\underset{i,j}{\mathrm{\Σ}}{\stackrel{\‾}{O}}_{ij}{\mathrm{\π}}_{i,j}$

The 3rd step selects to have the coupling matrix that maximum coupling takies

as the coupling matrix of next frame, if the matrix that has multiple maximum couplings to take is selected one at random.

To 4 × 4 port switch above, suppose that frame length F is 50 time slots, and queueing length matrix is

$Q=\left(\begin{array}{cccc}59& 100& 0& 18\\ 70& 50& 30& 60\\ 60& 20& 10& 70\\ 20& 40& 20& 65\end{array}\right)$

Maximum coupling takies vector O ^k=(160150140108).Due to O ¹=160 maximums, selection matrix P ¹for corresponding coupling matrix.

Under Fig. 3 has provided respectively in 16 × 16 port switch all even diagonal whereabouts distribution Bernoulli and ON/OFF business to Fig. 6, the contrast of algorithm of the present invention and main flow algorithm packeting average time delay, wherein LIPF_TM is for the longest input port is preferential and throughput maximum (Longest Input Port First with Throughput Maximization) algorithm, LOPF_TM is for the longest output port is preferential and throughput maximum (Longest Output Port First with Throughput Maximization) algorithm, i-LPF is preferential (the iterative Longest Port First) algorithm of iterative long port, i-OCF is iterative the longest packet priority of stand-by period (Oldest Cell First) algorithm, i-LQF is iterative longest queue first (Longest Queue First) algorithm, RR is poll (Round Robin) algorithm.

In addition, adopt the method for Lyapunov function and Combinational Mathematics can prove the stability of algorithm of the present invention.

Claims (1)

1. a VOQ fabric switch machine packet scheduling algorithm, is characterized in that:

The first step builds mates matrix completely;

For the switch of N × N port, according to RR matching way, select N to mate matrix P completely ^kas follows, wherein k=1 ..., N;

Wherein i=1 ..., N and=1 ..., N,

represent that in k coupling matrix, input port i mates with output port j;

The coupling that second step calculates corresponding coupling matrix takies;

Make Q _ijrepresent VOQ _ijthe team leader in the time of frame boundaries, F is frame length,

The coupling of calculating corresponding coupling matrix take into

$O_{\mathrm{ij}}^k=\underset{i,j}{\mathrm{\Σ}}{\stackrel{\‾}{O}}_{ij}{\mathrm{\π}}_{i,j}$

The 3rd step selects to have the coupling matrix that maximum coupling takies

as the coupling matrix of next frame, if the matrix that has multiple maximum couplings to take is selected one at random.

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