高酬matlab编程救助（能做的高手请与我联系QQ 346719984）

cherrielee18

在network 中 如何用token bucket to control packet transmission rate.
编程序后做图表分析
能做的高手请与我联系QQ 346719984

内容如下

The risk of congestion collapse on the Internet is becoming a reality given the increasing number

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of audio/video applications that use UDP as their main transport $ x- \. j, D2 d6 }1 I+ ^: _protocol. Unlike TCP, these

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traffic do not respond to congestion signal; i.e., a packet loss. As a - z; N# r1 F. L+ l! D1 X/ H6 Q4 M7 Aresult, audio/video

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applications may take an unfair share of the network bandwidth and also cause persistent

congestion. To avoid congestion collapse, the IETF has proposed that ; G$ w; ?5 ^. l: K0 T/ w" E4 iaudio/video applications

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use equation based congestion control (see Lecture‐7 and the reference given on the next

page).

In this assignment, you will simulate n 6 X1 r5 C$ j( Nsources that uses 1 C7 X n- u3 _/ _' X1 i8 Cequation based congestion control to

set their transmission rate. From your simulation, you will determine , W* U" O' c# P+ zwhether equation based

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congestion % G/ S0 m' V7 F6 @/ ~8 |- P) z- G+ Jcontrol is effective in reducing packet loss, and hence congestion.

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The above network can then be simulated as follows:

Initialization

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Set the router’s queue size to N, meaning it can hold up to N packets.

For each sender, set an initial transmission rate, and determine the time when the first packet is

to be generated.

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Body

FOR t=1 to SIM_TIME DO

{

1. IF the router’s queue is not empty then dequeue a packet, and enqueue that packet in

the corresponding receiver’s queue.

2. IF a sender has a packet to send THEN

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‐ Check if the router’s queue is full. If not, enqueue the sender’s 4 h" {$ T) T# f& p1 {, ?0 |packet. Otherwise,

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discard the packet.

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3. Determine whether any packet loss rate messages are generated by ; H" p# H2 L1 A9 O: _receivers. If yes,

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then re‐compute the sender’s transmission rate. Determine the new time when the

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next packet will be generated. I.e, t+k, where k is the time interval + _! v1 B6 \4 \1 g" P, N8 [; xuntil the next packet

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arrives.

4. Collect all required statistics.

}

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In your simulation, collect the (a) queue length over time, (b) average queue length, (c) average

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end‐to‐end packet delay, and (d) Jain’s fairness index. Determine the effect of the following

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factors: (i) increasing source and receiver pairs, (ii) varying N f+ ]4 h% S1 _! Ovalues, (iii) different packet loss

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reporting periods, (iv) loss calculation methods, (v) load p, (vi) router’s transmission rate;

instead of one packet per‐tic, try k packets, and (vii) z / W% v2 Z" n% }4 Rnumber of new flows J& Y, @# l3 `arriving at time t .

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% m5 i0 \6 J9 ~- X% C/ Y Do with sources using a token/leaky bucket to control their transmission rate.

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Another difference is that each source has an application that generates bursty traffic, where

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multiple packets arrive in consecutive time intervals.

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To generate bursty traffic, use the following method:

In the diagram above, an application generates a packet when it is in the ON state. With

probability k, it will transition to the OFF state where it will remain idle. In & x* v8 x8 ]7 D% K0 z5 ]this state, it has

probability z of moving back to the ON state.

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The pseudo‐code is as follows:

1. Start at a random state: ON/OFF.

2. At every simulation tic, do

a. Select a random number R in 0<= R <=1.

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b. If in state=ON AND R>=k, set state=OFF.

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c. If in state=OFF AND R>z, set state=ON.

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d. If state equals ON, generate a packet.

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Design an algorithm to control the token/leaky‐bucket rate of each , k: @; h E" P+ Zsource (or all sources

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simultaneously) such that congestion does not happen. Note, you must experiment with

different k ( z. ~! j; U6 Z. w7 i1 v" ]( iand z ) Z7 u' J. r* q8 m$ g- L3 Zvalues and determine 5 p) B3 x# W; ^/ [ N7 K* q% m; }3 A. Ftheir impact on congestion.

Reference

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S. Floyd, M. Handley, J. Padhye, and J. Widmer (2000) Equation-based Congestion Control for Unicast

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Applications, ACM SIGCOMM, May, & C' X8 c0 j p" [3 K% W1 i- t' m2000.

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