拓撲模型和業(yè)務源模型

1、第六章 拓撲模型和業(yè)務源模型,NS2 oriented tools,One helpful web site:http://www.matlab.nitech.ac.jp/~khpoo/research/ns2.html,本次課內容,網(wǎng)絡拓撲及統(tǒng)計模型GT-ITM拓撲生成工具BRITE拓撲生成工具業(yè)務源及生成器,1.1 隨機圖(ER)模型,圖表示：G(V, E)度(Degree):2|E|/|V|結點間以一定概率隨機連接

2、ER給出生成模型/微觀模型,1. Topograph,ER圖的統(tǒng)計性質,任意一對結點間存在直連邊的概率：p任意結點,結點度為k的概率：P(k)=C(k,N-1)pk(1-p)N-1-kN趨向無限時，P(k)=Poisson(k,pN) = pNvar(k) = sqrt(pN),1. Topograph,生成過程,1. Topograph,for {set i 0} {$i<$nn} {incr i} { for {

3、set j 0} {$j<$nn} {incr j} { if {$i==$j} continue set rv [expr rand()] if {$rv<[expr $p/2.0]} { $ns duplex-link $n($i) $n($j) \ $bw $delay DropTail } }},1.2 Waxman模型,一對結點u,v間，直連概

4、率P(u,v) = ?exp(-d/?L)0< ?, ?<1; ?決定邊總數(shù)， ?影響長邊比例d為空間距離L為最大結點間空間距離,1. Topograph,B M Waxman. Routing of multipoint connections. IEEE Sel.Areas in Comm. 6(9):1617~1622,1988.,2.1 Transit-Stub模型,2. GT-ITM,~/ns-alli

5、none-xxx/gt-tim/docs/models.ps,生成算法,生成連通的隨機圖，對應于Transit區(qū)每個Transit區(qū)內生成連通的隨機圖每個Transit內結點，生成對應隨機圖，對應于Stub，并與該結點相連不同Stub間，增加結點連接邊平均邊數(shù)目，由三個參數(shù)決定Wtt, Wts, Wss,2. GT-ITM,2.2 GT-ITM用法,命令格式itm ...定義格式ts []

6、 {top-level params} {transit params} {stub params}結果格式Standford Graph Based (SGB)sgb2ns 轉換為tcl腳本,2. GT-ITM,2.3 An example,2. GT-ITM,3.1 Scale Free Network,3. BRITE,Router Level (b) Movie Act

7、or(c) Co-authorship of high energy physicists(d) That of neuroscientists,3.2 標度/尺度無關,3. BRITE,100%,200%,6400%,BA生長模型,3. BRITE,,安裝與使用,3. BRITE,http://www.cs.bu.edu/brite/,內嵌的業(yè)務源,Application/FTP：持繼性的協(xié)議業(yè)務源Application/Tra

8、ffic：統(tǒng)計性業(yè)務源Application/Traffic/CBRApplication/Traffic/ExponentialApplication/Traffic/ParetoApplication/Traffic/Trace：實測源,4. Traffics,set tfile [new Tracefile]$tfile filename example-traceset t1 [new Application/Tra

9、ffic/Trace]$t1 attach-tracefile $tfile,實測源文件格式,4. Traffics,2個32位長字段：時間間隔+分組大小,~\ns-2.32\tcl\ex\example-trace,00 00 16 6C 00 00 03 E8 00 00 1E 38 00 00 01 F4......,,,,,5740 (ms),1000 (byte),500 (byte),7736 (ms),Poisson

10、源,相繼到達分組的時間間隔為負指數(shù)分布,4. Traffics,A Tcl program,4. Traffics,set rnd [new RandomVariable/Exponential]$rnd set avg_ 0.01proc pg {udp pksize} { global ns rnd $udp send $pksize 1 set t [$rnd value] set t [expr $

11、t+[$ns now]] $ns at $t "pq $udp $pksize"},MMPP源,若干Poisson源輪流生成分組各源之間的遷移過程滿足Morkov條件,4. Traffics,S = S0 : p(?) = ?0exp(-?0?)S = S2 : p(?) = ?1exp(-?1?),MMPP by C++,4. Traffics,4個配置參數(shù)：lambda0_lambda1_o