Open vSwitch系列实验（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、实验任务

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，不同TOS值的数据包将通过不同的方式到达目的地址。

TOS包括共8位，包括3 bit的优先权字段（取值可以从000-111所有值），4 bit的TOS子字段和1 bit未用位但必须置0。

3bit的8个优先级的定义如下：

111--Network Control（网络控制）；

110--Internetwork Control（网间控制）；

101--Critic（关键）；

100--Flash Override（疾速）；

011--Flash（闪速）；

010--Immediate（快速）；

001--Priority（优先）；

000--Routine（普通）。

优先级6和7一般保留给网络控制数据使用，如路由。

优先级5推荐给语音数据使用。

优先级4由视频会议和视频流使用。

优先级3给语音控制数据使用。

优先级1和2给数据业务使用。

优先级0为默认标记值。

1.ovsSingleBr

 #!/usr/bin/python
 #调用mininet模块
 from mininet.net import Mininet
 from mininet.node import Node
 from mininet.link import Link
 from mininet.log import  setLogLevel, info
 #mynet函数
 def myNet():
     "Create network from scratch using Open vSwitch."

     info( "*** Creating nodes\n" )
     switch0 = Node( 's0', inNamespace=False )

     h0 = Node( 'h0' )
     h1 = Node( 'h1' )
     h2 = Node( 'h2' )

     info( "*** Creating links\n" )
     Link( h0, switch0)
     Link( h1, switch0)
     Link( h2, switch0)

     info( "*** Configuring hosts\n" )
     h0.setIP( '192.168.123.1/24' )
     h1.setIP( '192.168.123.2/24' )
     h2.setIP( '192.168.123.3/24' )

     info( "*** Starting network using Open vSwitch\n" )
     switch0.cmd( 'ovs-vsctl del-br dp0' )
     switch0.cmd( 'ovs-vsctl add-br dp0' )
     #print all the intf of the values
     for intf in switch0.intfs.values():
         print intf
         print switch0.cmd( 'ovs-vsctl add-port dp0 %s' % intf )

     # Note: controller and switch are in root namespace, and we
     # can connect via loopback interface
     #switch0.cmd( 'ovs-vsctl set-controller dp0 tcp:127.0.0.1:6633' )

     print switch0.cmd(r'ovs-vsctl show')

     print switch0.cmd(r'ovs-ofctl add-flow dp0 idle_timeout=0,priority=1,in_port=1,actions=flood' )
     print switch0.cmd(r'ovs-ofctl add-flow dp0 idle_timeout=0,priority=1,in_port=2,actions=flood' )
     print switch0.cmd(r'ovs-ofctl add-flow dp0 idle_timeout=0,priority=1,in_port=3,actions=flood' )

     print switch0.cmd(r'ovs-ofctl add-flow dp0 idle_timeout=0,priority=10,ip,nw_dst=192.168.123.1,actions=output:1' )
     print switch0.cmd(r'ovs-ofctl add-flow dp0 idle_timeout=0,priority=10,ip,nw_dst=192.168.123.2,actions=output:2' )
     print switch0.cmd(r'ovs-ofctl add-flow dp0 idle_timeout=0,priority=10,ip,nw_dst=192.168.123.3,actions=output:3')

     #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 -c 3 ' + h1.IP() )
     h0.cmdPrint( 'ping -c 3 ' + h2.IP() )

     #print switch0.cmd( 'ovs-ofctl show dp0' )
     #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' )

     info( "*** Stopping network\n" )
     switch0.cmd( 'ovs-vsctl del-br dp0' )
     switch0.deleteIntfs()
     info( '\n' )

 if __name__ == '__main__':
     setLogLevel( 'info' )
     info( '*** Scratch network demo (kernel datapath)\n' )
     Mininet.init()
     myNet()

2.ovsMultiBr

这里通过设置不通的tos值和和不通的优先级来改变数据包的转发方式，其中在代码中可以看出priority的值，然后tos的值用的是16进制来表示，TOS表示服务类型，一共8bits，比如0x30：00110000，然后有相应的对照，http://www.mamicode.com/info-detail-542445.html

 #!/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" )
     switch0 = Node( 's0', inNamespace=False )
     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)
     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' )

     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' )

     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 )

     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' )

     #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() )
     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()

总结：

1.泛洪规则是根据优先级以及tos值而定

2.tos值设置越大，时间使用越少