一、實驗目的

通過python腳本調用OpenvSwitch命令；
學習Mininet基於python腳本創建拓撲的實現；
進一步深度使用“ovs-vsctl”命令直接控制Open vSwitch。

二、實驗原理

在SDN環境中，控制器可以通過對交換機下發流表操作來控制交換機的轉發行爲。在本實驗中，使用Mininet基於python的腳本，調用“ovs-vsctl”命令直接控制Open vSwitch。使用默認的交換機泛洪規則，設置更高的優先級規則進行預先定義IP報文的轉發。在多個交換機中通過設置不同TOS值的數據包將通過不同的方式到達目的地址，驗證主機間的連通性及到達目的的時間。

三、實驗任務

使用默認的交換機泛洪規則，設置更高的優先級規則進行預先定義IP報文的轉發，不同TOS值的數據包將通過不同的方式到達目的地址。

TOS包括共8位，包括3 bit的優先權字段（取值可以從000-111所有值），4 bit的TOS子字段和1 bit未用位但必須置0。

3bit的8個優先級的定義如下：

111--Network Control（網絡控制）；

110--Internetwork Control（網間控制）；

101--Critic（關鍵）；

100--Flash Override（疾速）；

011--Flash（閃速）；

010--Immediate（快速）；

001--Priority（優先）；

000--Routine（普通）。

優先級6和7一般保留給網絡控制數據使用，如路由。

優先級5推薦給語音數據使用。

優先級4由視頻會議和視頻流使用。

優先級3給語音控制數據使用。

優先級1和2給數據業務使用。

優先級0爲默認標記值。

1.ovsSingleBr

#!/usr/bin/python
#調用mininet模塊 
from mininet.net import Mininet
from mininet.node import Node
from mininet.link import Link
from mininet.log import  setLogLevel, info
#mynet函數 
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

這裏通過設置不通的tos值和和不通的優先級來改變數據包的轉發方式，其中在代碼中可以看出priority的值，然後tos的值用的是16進制來表示，TOS表示服務類型，一共8bits，比如0x30：00110000，然後有相應的對照，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()

總結：

1.泛洪規則是根據優先級以及tos值而定

2.tos值設置越大，時間使用越少

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