1 实验目的
熟悉Mininet自定义拓扑脚本的编写与损耗率的设定；
2 实验原理
在SDN环境中，控制器可以通过对交换机下发流表操作来控制交换机的转发行为，此外，还可以利用控制器测量路径的损耗率。在本实验中，基于Mininet脚本，设置特定的交换机间的路径损耗速率，然后编写POX脚本，实现对路径的损耗率的测量
3 实验内容
这是本实验的拓扑图，在该环境下，h0向h1发送数据包，由于在mininet脚本中设置了连接损耗率，在传输过程中会丢失一些包，本次实验的目的是展示如何通过控制器计算路径损耗速率（h0-s0-s1-h1）。这里假设控制器预先知道网络拓扑，所以没有显示发现网络的代码以及其他相关代码。控制器将向s0和s1发送flow_stats_request，当控制器接收到来自s0的response时，将特定流的数据包数保存在input_pkts中，当控制器接收到来自s1的response时，将接收到特定流的数据包数保存在output_pkts中，差值就是丢失的数据包数量。
搭建环境：本实验需要安装POX和支持OpenFlow1.3协议的Mininet。POX的安装教程如下：
Https://blog.csdn.net/shallynever/article/details/48522941
关于python中的logging以及相关函数的使用说明：
https://www.jb51.net/article/126681.htm
1.1 在装有mininet的虚拟机上创建脚本mymininet.py
cd mininet
gedit mymininet.py
1.2 编辑脚本（稍微解释了一下）
1 2 #!/usr/bin/python 3 4 #coding:utf-8 5 6 7 8 # 调用关于mininet和time的一些模块 9 10 from mininet.net import Mininet 11 12 from mininet.node import Node 13 14 from mininet.link import TCLink 15 16 from mininet.log import setLogLevel, info 17 18 from threading import Timer 19 20 from mininet.util import quietRun 21 22 from time import sleep 23 24 25 26 #定义mynet函数 27 28 def myNet(cname='controller', cargs='-v ptcp:'): 29 30 #通过使用OVS抓取来创建网络 31 32 33 34 #诊断信息然后开始创建节点,其中有控制器C0和交换机s0,s1,还有主机h0,h1 35 36 info( "*** Creating nodes\n" ) 37 38 controller = Node( 'c0', inNamespace=False ) 39 40 switch = Node( 's0', inNamespace=False ) 41 42 switch1 = Node( 's1', inNamespace=False ) 43 44 h0 = Node( 'h0' ) 45 46 h1 = Node( 'h1' ) 47 48 49 50 #诊断以后开始创建链路（这一块不是很懂） 51 52 info( "*** Creating links\n" ) 53 54 55 56 #这是链路选项设置，丢包以及延迟还有带宽等等 57 58 linkopts0=dict(bw=100, delay='1ms', loss=0) 59 60 linkopts1=dict(bw=100, delay='1ms', loss=10) 61 62 63 64 #链路0,1,2分别表示h0和s0，s0和s1，h1和s1的链路并调用以上两行的参数 65 66 link0=TCLink( h0, switch, **linkopts0) 67 68 link1 = TCLink( switch, switch1, **linkopts1) 69 70 link2 = TCLink( h1, switch1, **linkopts0) 71 72 73 74 #MAC地址设置：按照拓扑图来设置的，这一块有些不理解，个人理解为，链路0，2只需要设置一个能连上 75 76 #s0/s1的端口就行，而1需要左边的s0端口和右边的s1端口 77 78 link0.intf2.setMAC("0:0:0:0:0:1") 79 80 link1.intf1.setMAC("0:0:0:0:0:2") 81 82 link1.intf2.setMAC("0:1:0:0:0:1") 83 84 link2.intf2.setMAC("0:1:0:0:0:2") 85 86 87 88 #诊断后设置主机ip 89 90 info( "*** Configuring hosts\n" ) 91 92 h0.setIP( '192.168.123.1/24' ) 93 94 h1.setIP( '192.168.123.2/24' ) 95 96 97 98 #通过使用OVS开始网络连接，然后单引号里的意思是搭建和删除桥梁 99 100 info( "*** Starting network using Open vSwitch\n" ) 101 102 switch.cmd( 'ovs-vsctl del-br dp0' ) 103 104 switch.cmd( 'ovs-vsctl add-br dp0' ) 105 106 switch1.cmd( 'ovs-vsctl del-br dp1' ) 107 108 switch1.cmd( 'ovs-vsctl add-br dp1' ) 109 110 111 112 #控制器的设置不是很懂 113 114 controller.cmd( cname + ' ' + cargs + '&' ) 115 116 117 118 #打印出每个交换机的链路信息 119 120 for intf in switch.intfs.values(): 121 122 print intf 123 124 print switch.cmd( 'ovs-vsctl add-port dp0 %s' % intf ) 125 126 for intf in switch1.intfs.values(): 127 128 print intf 129 130 print switch1.cmd( 'ovs-vsctl add-port dp1 %s' % intf ) 131 132 133 134 # 控制器和交换机同属根命名空间所以我们可以通过环回接口连接，对了，10.0.0.13是别的up主的主机 135 136 # ip，需要用自己的，因为控制器是你自己的 137 138 switch.cmd( 'ovs-vsctl set-controller dp0 tcp:10.0.0.13:6633' ) 139 140 switch1.cmd( 'ovs-vsctl set-controller dp1 tcp:10.0.0.13:6633' ) 141 142 143 144 #诊断并等待交换机连接上控制器，在连接完成前会一秒一个点 145 146 info( '*** Waiting for switch to connect to controller' ) 147 148 while 'is_connected' not in quietRun( 'ovs-vsctl show' ): 149 150 sleep( 1 ) 151 152 info( '.' ) 153 154 info( '\n' ) 155 156 157 158 #运行测试20次h0和h1的传输情况 159 160 #info( "*** Running test\n" ) 161 162 h0.cmdPrint( 'ping -Q 0x64 -c 20 ' + h1.IP() ) 163 164 165 166 #休息一秒后关闭网络：删除“桥梁” 167 168 sleep( 1 ) 169 170 info( "*** Stopping network\n" ) 171 172 controller.cmd( 'kill %' + cname ) 173 174 switch.cmd( 'ovs-vsctl del-br dp0' ) 175 176 switch.deleteIntfs() 177 178 switch1.cmd( 'ovs-vsctl del-br dp1' ) 179 180 switch1.deleteIntfs() 181 182 info( '\n' ) 183 184 185 186 #主函数，看不懂，意思应当是如果是个主函数就设定info的等级然后开始获取网络demo然后运行 187 188 #mynet（）函数 189 190 if __name__ == '__main__': 191 192 setLogLevel( 'info' ) 193 194 info( '*** Scratch network demo (kernel datapath)\n' ) 195 196 Mininet.init() 197 198 myNet()
2.1 我们在pox文件里面创建脚本
cd pox
gedit flow_stats.py
2.2 编辑脚本 （中文部分是对程序的解释，未翻译部分是对具体代码的代码解释）
1 2 #!/usr/bin/python 3 4 # Copyright 2012 William Yu 5 6 # wyu@ateneo.edu 7 8 # 9 10 # This file is part of POX. 11 12 # 13 14 # POX is free software: you can redistribute it and/or modify 15 16 # it under the terms of the GNU General Public License as published by 17 18 # the Free Software Foundation, either version 3 of the License, or 19 20 # (at your option) any later version. 21 22 # 23 24 # POX is distributed in the hope that it will be useful, 25 26 # but WITHOUT ANY WARRANTY; without even the implied warranty of 27 28 # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 29 30 # GNU General Public License for more details. 31 32 # 33 34 # You should have received a copy of the GNU General Public License 35 36 # along with POX. If not, see <http://www.gnu.org/licenses/>. 37 38 # 39 40 41 42 """ 43 44 This is a demonstration file created to show how to obtain flow 45 46 and port statistics from OpenFlow 1.0-enabled switches. The flow 47 48 statistics handler contains a summary of web-only traffic. 49 50 """ 51 52 53 54 # standard includes 55 56 from pox.core import core 57 58 from pox.lib.util import dpidToStr 59 60 import pox.openflow.libopenflow_01 as of 61 62 from pox.lib.addresses import IPAddr, EthAddr 63 64 65 66 # include as part of the betta branch 67 68 from pox.openflow.of_json import * 69 70 from pox.lib.recoco import Timer 71 72 import time 73 74 75 76 log = core.getLogger() 77 78 #初始化网络的参数0 79 80 src_dpid = 0 81 82 dst_dpid = 0 83 84 input_pkts = 0 85 86 output_pkts = 0 87 88 89 90 def getTheTime(): 91 92 #设定当地时间的函数 93 94 flock = time.localtime() 95 96 then = "[%s-%s-%s" %(str(flock.tm_year),str(flock.tm_mon),str(flock.tm_mday)) 97 98 99 100 if int(flock.tm_hour)<10: 101 102 hrs = "0%s" % (str(flock.tm_hour)) 103 104 else: 105 106 hrs = str(flock.tm_hour) 107 108 if int(flock.tm_min)<10: 109 110 mins = "0%s" % (str(flock.tm_min)) 111 112 else: 113 114 mins = str(flock.tm_min) 115 116 if int(flock.tm_sec)<10: 117 118 secs = "0%s" % (str(flock.tm_sec)) 119 120 else: 121 122 secs = str(flock.tm_sec) 123 124 then +="]%s.%s.%s" % (hrs,mins,secs) 125 126 return then 127 128 129 130 # 用于将请求发送到连接到控制器的所有交换机的定时器功能的处理程序 131 132 def _timer_func (): 133 134 for connection in core.openflow._connections.values(): 135 136 connection.send(of.ofp_stats_request(body=of.ofp_flow_stats_request())) 137 138 connection.send(of.ofp_stats_request(body=of.ofp_port_stats_request())) 139 140 log.debug("Sent %i flow/port stats request(s)", len(core.openflow._connections)) 141 142 143 144 # 显示在事件的JSON格式结构中接收到的流统计信息的处理程序由ofp_flow_stats()定义 145 146 def _handle_flowstats_received (event): 147 148 #stats = flow_stats_to_list(event.stats) 149 150 #log.debug("FlowStatsReceived from %s: %s", dpidToStr(event.connection.dpid), stats) 151 152 global src_dpid, dst_dpid, input_pkts, output_pkts 153 154 #print "src_dpid=", dpidToStr(src_dpid), "dst_dpid=", dpidToStr(dst_dpid) 155 156 for f in event.stats: 157 158 if f.match.dl_type==0x0800 and f.match.nw_dst==IPAddr("192.168.123.2") and f.match.nw_tos==0x64 and event.connection.dpid==src_dpid: 159 160 #print "input: ", f.byte_count, f.packet_count 161 162 input_pkts = f.packet_count 163 164 if f.match.dl_type==0x0800 and f.match.nw_dst==IPAddr("192.168.123.2") and f.match.nw_tos==0x64 and event.connection.dpid==dst_dpid: 165 166 #print "output: ", f.byte_count, f.packet_count 167 168 output_pkts = f.packet_count 169 170 if input_pkts !=0: 171 172 print getTheTime(), "Path Loss Rate =", (input_pkts-output_pkts)*1.0/input_pkts*100, "%" 173 174 175 176 # 处理程序以显示JSON格式接收的端口统计信息 177 178 def _handle_portstats_received (event): 179 180 #print "\n<<<STATS-REPLY: Return PORT stats for Switch", event.connection.dpid,"at ",getTheTime() 181 182 #for f in event.stats: 183 184 #if int(f.port_no)<65534: 185 186 #print " PortNo:", f.port_no, " Fwd's Pkts:", f.tx_packets, " Fwd's Bytes:", f.tx_bytes, " Rc'd Pkts:", f.rx_packets, " Rc's Bytes:", f.rx_bytes 187 188 #print " PortNo:", f.port_no, " TxDrop:", f.tx_dropped, " RxDrop:", f.rx_dropped, " TxErr:", f.tx_errors, " RxErr:", f.rx_errors, " CRC:", f.rx_crc_err, " Coll:", f.collisions 189 190 stats = flow_stats_to_list(event.stats) 191 192 log.debug("PortStatsReceived from %s: %s", dpidToStr(event.connection.dpid), stats) 193 194 195 196 def _handle_ConnectionUp (event): 197 198 global src_dpid, dst_dpid 199 200 print "ConnectionUp: ", dpidToStr(event.connection.dpid) 201 202 for m in event.connection.features.ports: 203 204 if m.name == "s0-eth0": 205 206 src_dpid = event.connection.dpid 207 208 elif m.name == "s1-eth0": 209 210 dst_dpid = event.connection.dpid 211 212 #设置网络的参数（优先级，时间，端口号） 213 214 msg = of.ofp_flow_mod() 215 216 msg.priority =1 217 218 msg.idle_timeout = 0 219 220 msg.match.in_port =1 221 222 msg.actions.append(of.ofp_action_output(port = of.OFPP_ALL)) 223 224 event.connection.send(msg) 225 226 227 228 msg = of.ofp_flow_mod() 229 230 msg.priority =1 231 232 msg.idle_timeout = 0 233 234 msg.match.in_port =2 235 236 msg.actions.append(of.ofp_action_output(port = of.OFPP_ALL)) 237 238 event.connection.send(msg) 239 240 241 242 msg = of.ofp_flow_mod() 243 244 msg.priority =10 245 246 msg.idle_timeout = 0 247 248 msg.hard_timeout = 0 249 250 msg.match.dl_type = 0x0800 251 252 msg.match.nw_tos = 0x64 253 254 msg.match.in_port=1 255 256 msg.match.nw_dst = "192.168.123.2" 257 258 msg.actions.append(of.ofp_action_output(port = 2)) 259 260 event.connection.send(msg) 261 262 263 264 msg = of.ofp_flow_mod() 265 266 msg.priority =10 267 268 msg.idle_timeout = 0 269 270 msg.hard_timeout = 0 271 272 msg.match.dl_type = 0x0800 273 274 msg.match.nw_tos = 0x64 275 276 msg.match.nw_dst = "192.168.123.1" 277 278 msg.actions.append(of.ofp_action_output(port = 1)) 279 280 event.connection.send(msg) 281 282 283 284 # 启动模块的主函数 285 286 def launch (): 287 288 # attach handsers to listners 289 290 core.openflow.addListenerByName("FlowStatsReceived", 291 292 _handle_flowstats_received) 293 294 core.openflow.addListenerByName("PortStatsReceived", 295 296 _handle_portstats_received) 297 298 core.openflow.addListenerByName("ConnectionUp", _handle_ConnectionUp) 299 300 301 302 # 定时器每5秒执行一次 303 304 Timer(1, _timer_func, recurring=True)
3 执行两个脚本
此处为mymininet的脚本
此处为flow_stats脚本
总结：
1.能看懂2/3的脚本内容，以及脚本的程序意义
2.明白了pox的安装
3.对网络的了解还是不够深刻