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 protocol. Unlike TCP, these

traffic do not respond to congestion signal; i.e., a packet loss. As a , A5 r/ b$ C+ C1 _! Z; T1 M3 dresult, audio/video

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applications may take an unfair share of the network bandwidth and , Q1 u5 u- K* K' valso cause persistent

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congestion. To avoid congestion collapse, the IETF has proposed that ( j# Z2 h5 c2 G7 ?audio/video applications

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

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page).

In this assignment, you will simulate n 0 [ \2 G# a, p" n) q' s8 Ksources that uses equation based congestion control to

set their transmission rate. From your simulation, you will determine whether equation based

congestion control 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.

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

to be generated.

Body

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FOR t=1 to SIM_TIME DO

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

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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 packet. Otherwise,

discard the packet.

3. Determine whether any packet loss rate messages are generated by receivers. If yes,

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 until the next packet

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arrives.

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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

factors: (i) increasing source and receiver pairs, (ii) varying N $ ^4 j2 _1 V! y' ? ?values, (iii) different packet loss

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

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instead of one packet per‐tic, try k packets, and (vii) z ; u/ t4 h# P4 |2 _9 q, P# ^number of new flows . i% e( m" m8 h0 E M/ X/ d w' @! Yarriving at time t .

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Do with sources - {% o/ e7 p9 {1 ^ C2 M' xusing a token/leaky bucket to control their transmission rate.

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:

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In the diagram above, an application generates a packet when it is in 8 u% v: t% V othe ON state. With

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probability k, it will transition to the OFF state where it will remain idle. In ( r' a: {+ E. Jthis state, it has

probability z of moving back to the ON state.

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The pseudo‐code is as follows:

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

2. At every simulation tic, do

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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.

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

d. If state equals ON, generate a packet.

Design an algorithm to control the token/leaky‐bucket rate of each ( @! u$ u4 X: ysource (or all sources

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

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different k 7 ]3 p V; n& t9 U' B& Y- G( Yand z values and determine ) G) T3 S9 d+ C' n/ Gtheir impact on congestion.

Reference

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

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Applications, ACM SIGCOMM, May, 2000.

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