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
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The risk of congestion collapse on the Internet is becoming a reality ! n. O" t. c% N5 L. u4 Y; O' U- Ugiven the increasing number

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of audio/video applications that use UDP as their main transport protocol. Unlike TCP, these

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traffic do not respond to congestion signal; i.e., a packet loss. As a , q, ^1 u$ r9 s+ k9 Sresult, audio/video

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

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congestion. To avoid congestion collapse, the IETF has proposed that audio/video applications

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

page).

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In this assignment, you will simulate n 2 d/ G6 D( u; X" S3 e Z2 gsources that uses equation based congestion control to

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set their transmission rate. From your simulation, you will determine ! b' V" P/ O# A4 Q- |whether equation based

congestion 3 @1 R) n. J* a2 d7 }; q' Scontrol is effective in reducing packet loss, and hence congestion.

The above network can then be simulated as follows:

Initialization

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

{

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

‐ Check if the router’s queue is full. If not, enqueue the sender’s packet. Otherwise,

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discard the packet.

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

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then re‐compute the sender’s transmission rate. Determine the new time . v0 U! y0 u6 b# d# V& r2 O4 D+ }8 _when the

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next packet will be generated. I.e, t+k, where k is the time interval , G; w* |* w' Q7 Q8 i& a" w. C; Luntil the next packet

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arrives.

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4. Collect all required statistics.

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}

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In your simulation, collect the (a) queue length over time, (b) & ?) Z( E: B) ^; l6 N: ]/ i5 j# ?average queue length, (c) average

end‐to‐end packet delay, and (d) Jain’s fairness index. Determine the 6 d& Z- T+ P, b9 z+ deffect of the following

factors: (i) increasing source and receiver pairs, (ii) varying N # {/ g* E8 H! ?; _5 C- Fvalues, (iii) different packet loss

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reporting periods, (iv) loss calculation methods, (v) load p, (vi) 3 a" C+ I. f0 t X4 i' y" I* drouter’s transmission rate;

instead of one packet per‐tic, try k packets, and (vii) z number of new flows arriving at time t .

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0 B1 w$ ~- p1 W9 R2 m* D Do with sources ) d8 q% H( S7 t$ ?using a token/leaky bucket to control their transmission rate.

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Another difference is that each source has an application that . A* [; r# d* hgenerates bursty traffic, where

multiple packets arrive in consecutive time intervals.

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 the ON state. With

probability k, it will transition to the OFF state where it will remain idle. In - Q% ]+ }6 ^; u [this state, it has

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probability z of moving back to the ON state.

The pseudo‐code is as follows:

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.

b. If in state=ON ; c, s0 c' J: n- O, k/ BAND R>=k, set state=OFF.

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

d. If state equals ON, generate a packet.

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Design an algorithm to control the token/leaky‐bucket rate of each 5 i+ b' V4 M8 nsource (or all sources

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simultaneously) such that congestion does not happen. Note, you must 5 E3 r8 ~* o3 A6 T' F; ~6 ~) Dexperiment with

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different k and z + h- ^6 i" i& T8 c" xvalues and determine 3 D1 A! t2 h# }. Ltheir impact on congestion.

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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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