Open vSwitch实验

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

  Open vSwitch实验_第1张图片

 

   3、执行程序

Open vSwitch实验_第2张图片

 

  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。

 

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