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 4 f: n8 U- ~" V! \& l! X" Ggiven the increasing number

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

- R$ m8 X2 ], V7 d1 ~7 ^

traffic do not respond to congestion signal; i.e., a packet loss. As a result, audio/video

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

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).

3 p" X7 N- z/ i1 b7 S/ j6 y0 O

In this assignment, you will simulate n 6 G7 [% T( s& n4 j& {+ x+ G4 o; Wsources that uses equation based congestion control to

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

" D4 x- } h* `8 U8 U# X

congestion : Y! V3 W' C: a y$ _' T ~control is effective in reducing packet loss, and hence congestion.

( A i5 t9 Y% E/ q: @

The above network can then be simulated as follows:

Initialization

9 q2 ] b- q6 }

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

; s( E) }, T9 h& {. y/ l

to be generated.

6 Z, q/ w# P: r1 L

Body

FOR t=1 to SIM_TIME DO

0 h, [- ^' `8 l

{

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

% T, k6 T6 f; O7 P

the corresponding receiver’s queue.

, f! l% R5 B; G+ Q. k$ g

2. IF a sender has a packet to send THEN

& P8 U& x6 ], l

‐ Check if the router’s queue is full. If not, enqueue the sender’s ) r: t" y! R; A( ]5 o4 Z6 M' W& vpacket. Otherwise,

" F/ i" T$ I* O/ R6 h/ A- }

discard the packet.

( `! [; E+ }- \8 ?; G( `9 m

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

# L9 z5 G6 k6 b4 ^

next packet will be generated. I.e, t+k, where k is the time interval until the next packet

/ Z d$ e7 ]* }' E2 J# d

arrives.

2 _( x! X, a6 W" a3 T9 L, T& Z

4. Collect all required statistics.

}

In your simulation, collect the (a) queue length over time, (b) # U2 l. s' ?8 z4 @average queue length, (c) average

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 0 r% N: v8 L N; P2 P: Dvalues, (iii) different packet loss

% ?4 {* ?; b# |; v! [+ H# x6 \# b

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 number of new flows arriving at time t .

' J& p" b0 j: A6 }# l. i

Do with sources - g5 r0 E/ S; G3 S4 V6 ?using a token/leaky bucket to control their transmission rate.

" I/ k1 P6 y; Q, F

Another difference is that each source has an application that 2 q3 C9 X. o ?0 \0 I( n- l$ W6 I: ogenerates bursty traffic, where

) R4 H* }4 d) p3 v+ S

multiple packets arrive in consecutive time intervals.

To generate bursty traffic, use the following method:

1 n- g% l9 S% p+ c: L& s& u

2 r6 \( x) c9 Y+ h7 D: o

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 this state, it has

1 s4 {' ]5 D* h3 y

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

9 i2 @( @; E, X5 o8 A( s9 _

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

! t' o/ ~5 G8 P; ?

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

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

. V9 z) c/ u7 k3 f! r

d. If state equals ON, generate a packet.

Design an algorithm to control the token/leaky‐bucket rate of each source (or all sources

simultaneously) such that congestion does not happen. Note, you must + c; a; T" @4 T8 Q3 H# {experiment with

different k 1 q5 D, {1 e( Y: Jand z 2 _: A# u3 l8 ?' I: V7 xvalues and determine their impact on congestion.

Reference

% Q- H; M2 b: H

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

# H. @% _, d& E- A! m

Applications, ACM SIGCOMM, May, ; c1 P$ U5 ^+ ?- d8 N& N, W3 p2000.

0 X0 J; K5 I( f# W8 Q' F