参考：Open vSwitch使用案例扩展实验
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。
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。
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是三层数据包的服务类型标记，也是3个bit，范围0-7，同样可当作优先级标记，另外5个实际指示Delay，Throughput，Reliability等特性的bit位一般没有使用；现在为了更好的控制数据流分类，使用DSCP（Differential Services Code Point），扩展了Tos的后三个bit，因此，范围从0-63。
实验步骤
环境：Ubuntu 14.04，Mininet。
任务1：
通过vi ovsSingleBr.py创建脚本并添加内容。本实验通过python脚本自定义拓扑
vim ovsSingleBr.py
脚本内容：
#!/usr/bin/python
from mininet.net import Mininet
from mininet.node import Node
from mininet.link import Link
from mininet.log import setLogLevel, info
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' )
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()
此脚本并未连接控制器，只通过脚本中手动给交换机下发流表实现主机间的通信。
给权限：
chmod u+x ovsSingleBr.py
执行脚本：
./ovsSingleBr.py
任务2：
vim ovsMultiBr.py
脚本内容：
#!/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()
此脚本并未连接控制器，只通过脚本中手动给交换机下发流表实现主机间的通信。在此任务二中，给多个交换机下发流表，通过ping操作测试验证主机间的连通性，并通过-Q参数设置不通的tos值查看主机间的连通性。
给权限：
chmod u+x ovsMultiBr.py
实验结论
此实验并未连接控制器，只通过脚本在单个/多个交换机中下发静态流表实现主机间的通信。在给多个交换机下发流表时，通过ping操作测试验证主机间的连通性，并通过-Q参数设置不同的tos值验证主机间的连通性及到达目的地址的时间，通过验证发现，tos值设置越大，时间使用越少。
2016/11/25