此实验为sdnlab上Open vSwitch系列实验。
实验一 Open vSwitch使用案例扩展实验
一、实验目的
- 通过python脚本调用OpenvSwitch命令；
- 学习Mininet基于python脚本创建拓扑的实现；
- 进一步深度使用“ovs-vsctl”命令直接控制Open vSwitch;
二、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。在本实验中，使用Mininet基于python的脚本，调用“ovs-vsctl”命令直接控制Open vSwitch。使用默认的交换机泛洪规则，设置更高的优先级规则进行预先定义IP报文的转发。在多个交换机中通过设置不同TOS值的数据包将通过不同的方式到达目的地址，验证主机间的连通性及到达目的的时间。
三、实验步骤
本实验api：http://mininet.org/api/annotated.html
1、创建ovsSwitch.py，代码如下
#!/usr/bin/python from mininet.net import Mininet from mininet.node import Node from mininet.link import TCLink from mininet.log import setLogLevel, info def myNet(): "Create network from scratch using Open vSwitch." info( "*** Creating nodes\n" ) #创造节点 switch0 = Node( 's0', inNamespace=False ) #是否使用本机原有的网络命名空间 switch1 = Node( 's1', inNamespace=False ) switch2 = Node( 's2', inNamespace=False ) switch3 = Node( 's3', inNamespace=False ) switch4 = Node( 's4', inNamespace=False ) h0 = Node( 'h0' ) h1 = Node( 'h1' ) info( "*** Creating links\n" ) linkopts0=dict(bw=100, delay='1ms', loss=0)//带宽，延时，?? linkopts1=dict(bw=1, delay='100ms', loss=0) linkopts2=dict(bw=10, delay='50ms', loss=0) linkopts3=dict(bw=100, delay='1ms', loss=0) TCLink( h0, switch0, **linkopts0) TCLink( switch0, switch1, **linkopts0) TCLink( switch0, switch2, **linkopts0) TCLink( switch0, switch3, **linkopts0) TCLink( switch1, switch4,**linkopts1) TCLink( switch2, switch4,**linkopts2) TCLink( switch3, switch4,**linkopts3) TCLink( h1, switch4, **linkopts0) info( "*** Configuring hosts\n" ) h0.setIP( '192.168.123.1/24' ) h1.setIP( '192.168.123.2/24' ) info( str( h0 ) + '\n' ) info( str( h1 ) + '\n' ) #创建逻辑交换机dp0~dp4 info( "*** Starting network using Open vSwitch\n" ) switch0.cmd( 'ovs-vsctl del-br dp0' ) switch0.cmd( 'ovs-vsctl add-br dp0' ) switch1.cmd( 'ovs-vsctl del-br dp1' ) switch1.cmd( 'ovs-vsctl add-br dp1' ) switch2.cmd( 'ovs-vsctl del-br dp2' ) switch2.cmd( 'ovs-vsctl add-br dp2' ) switch3.cmd( 'ovs-vsctl del-br dp3' ) switch3.cmd( 'ovs-vsctl add-br dp3' ) switch4.cmd( 'ovs-vsctl del-br dp4' ) switch4.cmd( 'ovs-vsctl add-br dp4' ) #将每台真实交换机的端口加入刚刚创建的逻辑交换机 for intf in switch0.intfs.values(): print intf print switch0.cmd( 'ovs-vsctl add-port dp0 %s' % intf ) for intf in switch1.intfs.values(): print intf print switch1.cmd( 'ovs-vsctl add-port dp1 %s' % intf ) for intf in switch2.intfs.values(): print intf print switch2.cmd( 'ovs-vsctl add-port dp2 %s' % intf ) for intf in switch3.intfs.values(): print intf print switch3.cmd( 'ovs-vsctl add-port dp3 %s' % intf ) for intf in switch4.intfs.values(): print intf print switch4.cmd( 'ovs-vsctl add-port dp4 %s' % intf ) #手工构造d1~d4流表 print switch1.cmd(r'ovs-ofctl add-flow dp1 idle_timeout=0,priority=1,in_port=1,actions=flood' ) print switch1.cmd(r'ovs-ofctl add-flow dp1 idle_timeout=0,priority=1,in_port=1,actions=output:2' ) print switch1.cmd(r'ovs-ofctl add-flow dp1 idle_timeout=0,priority=1,in_port=2,actions=output:1' ) print switch2.cmd(r'ovs-ofctl add-flow dp2 idle_timeout=0,priority=1,in_port=1,actions=output:2' ) print switch2.cmd(r'ovs-ofctl add-flow dp2 idle_timeout=0,priority=1,in_port=2,actions=output:1' ) print switch3.cmd(r'ovs-ofctl add-flow dp3 idle_timeout=0,priority=1,in_port=1,actions=output:2' ) print switch3.cmd(r'ovs-ofctl add-flow dp3 idle_timeout=0,priority=1,in_port=2,actions=output:1' ) print switch4.cmd(r'ovs-ofctl add-flow dp4 idle_timeout=0,priority=1,in_port=1,actions=output:4' ) print switch4.cmd(r'ovs-ofctl add-flow dp4 idle_timeout=0,priority=1,in_port=2,actions=output:4' ) print switch4.cmd(r'ovs-ofctl add-flow dp4 idle_timeout=0,priority=1,in_port=3,actions=output:4' ) print switch4.cmd(r'ovs-ofctl add-flow dp4 idle_timeout=0,priority=1,in_port=4,actions=output:3' ) #根据目的IP不同，tos值不同构造dp0流表 #print switch0.cmd(r'ovs-ofctl add-flow dp0 idle_timeout=0,priority=10,ip,nw_dst=192.168.123.2,actions=output:4') print switch0.cmd(r'ovs-ofctl add-flow dp0 idle_timeout=0,priority=10,ip,nw_dst=192.168.123.2,nw_tos=0x10,actions=output:2') print switch0.cmd(r'ovs-ofctl add-flow dp0 idle_timeout=0,priority=10,ip,nw_dst=192.168.123.2,nw_tos=0x20,actions=output:3') print switch0.cmd(r'ovs-ofctl add-flow dp0 idle_timeout=0,priority=10,ip,nw_dst=192.168.123.2,nw_tos=0x30,actions=output:4') #print switch0.cmd(r'ovs-ofctl add-flow dp0 idle_timeout=0,priority=10,ip,nw_dst=192.168.123.1,actions=output:1') #switch0.cmd('tcpdump -i s0-eth0 -U -w aaa &') #h0.cmd('tcpdump -i h0-eth0 -U -w aaa &') info( "*** Running test\n" ) h0.cmdPrint( 'ping -Q 0x10 -c 3 ' + h1.IP() )#指定不同的QOS值 h0.cmdPrint( 'ping -Q 0x20 -c 3 ' + h1.IP() ) h0.cmdPrint( 'ping -Q 0x30 -c 3 ' + h1.IP() ) #h1.cmdPrint('iperf -s -p 12345 -u &') #h0.cmdPrint('iperf -c ' + h1.IP() +' -u -b 10m -p 12345 -t 10 -i 1') #print switch0.cmd( 'ovs-ofctl show dp0' ) #print switch1.cmd( 'ovs-ofctl show dp1' ) #print switch2.cmd( 'ovs-ofctl show dp2' ) #print switch3.cmd( 'ovs-ofctl show dp3' ) #print switch4.cmd( 'ovs-ofctl show dp4' ) #print switch0.cmd( 'ovs-ofctl dump-tables dp0' ) #print switch0.cmd( 'ovs-ofctl dump-ports dp0' ) #print switch0.cmd( 'ovs-ofctl dump-flows dp0' ) #print switch0.cmd( 'ovs-ofctl dump-aggregate dp0' ) #print switch0.cmd( 'ovs-ofctl queue-stats dp0' ) #print "Testing video transmission between h1 and h2" #h1.cmd('./myrtg_svc -u > myrd &') #h0.cmd('./mystg_svc -trace st 192.168.123.2') info( "*** Stopping network\n" ) switch0.cmd( 'ovs-vsctl del-br dp0' ) switch0.deleteIntfs() switch1.cmd( 'ovs-vsctl del-br dp1' ) switch1.deleteIntfs() switch2.cmd( 'ovs-vsctl del-br dp2' ) switch2.deleteIntfs() switch3.cmd( 'ovs-vsctl del-br dp3' ) switch3.deleteIntfs() switch4.cmd( 'ovs-vsctl del-br dp4' ) switch4.deleteIntfs() info( '\n' ) if __name__ == '__main__': setLogLevel( 'info' ) info( '*** Scratch network demo (kernel datapath)\n' ) Mininet.init() myNet()
2、构造实验拓扑
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3、执行程序
由结果得出，TOS值越大，延时越小。来看以下关于TOS值的介绍：
在ICMP数据报中设置与服务相关的比特的质量。TOS可以是十进制数，也可以是十六进制数。传统上(RFC 1349)，它们被解释为：0表示保留(当前被重新定义为拥塞控制)，1-4表示服务类型，5-7表示优先级。服务类型的可能设置是：最低成本：0x02，可靠性：0x04，吞吐量：0x08，低延迟：0x10。不能同时设置多个TOS位。特殊优先级的可能设置范围从优先级(0x20)到净控制(0xe0)。
所以这里的0x10,0x20,0x30是设置特殊优先级，值越大优先级越高，所以传输延时越小。