114. Flatten Binary Tree to Linked List
阿新 • • 發佈：2020-09-22
一、實驗目的
- 在實驗 2 的基礎上進一步熟悉 Mininet 自定義拓撲指令碼，以及與損耗率相關的設定；
- 初步瞭解 Mininet 安裝時自帶的 POX 控制器指令碼編寫，測試路徑損耗率。
二、實驗任務
- h0 向 h1 傳送資料包，由於在 Mininet 指令碼中設定了連線損耗率，在傳輸過程中會丟失一些包，本次實驗的目的是展示如何通過控制器計算路徑損耗速率（h0-s0-s1-h1）。這裡假設控制器預先知道網拓撲。控制器將向 s0 和 s1 傳送flow_stats_request，當控制器接收到來自 s0 的 response 時，將特定流的資料包數儲存在 input_pkts 中，當控制器接收到來自 s1 的 response 時，將接收到特定
流的資料包數儲存在 output_pkts 中，差值就是丟失的資料包數量。基於上述拓撲，編寫 Mininet 指令碼，設定特定的交換機間的路徑損耗速率，然後編寫 POX 控制器指令碼，實現對路徑的損耗率的測量。
三、實驗步驟
實驗環境
- 安裝了 Ubuntu 18.04.5 Desktop amd64 的虛擬機器
實驗過程
- SDNLAB 實驗參考資料：https://www.sdnlab.com/15100.html
新建並編輯 pox 指令碼 flowstat.py：
#!/usr/bin/python # Copyright 2012 William Yu # [email protected] # # This file is part of POX. # # POX is free software: you can redistribute it and/or modify # it under the terms of the GNU General Public License as published by # the Free Software Foundation, either version 3 of the License, or # (at your option) any later version. # # POX is distributed in the hope that it will be useful, # but WITHOUT ANY WARRANTY; without even the implied warranty of # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the # GNU General Public License for more details. # # You should have received a copy of the GNU General Public License # along with POX. If not, see <http://www.gnu.org/licenses/>. # """ This is a demonstration file created to show how to obtain flow and port statistics from OpenFlow 1.0-enabled switches. The flow statistics handler contains a summary of web-only traffic. """ # standard includes from pox.core import core from pox.lib.util import dpidToStr import pox.openflow.libopenflow_01 as of from pox.lib.addresses import IPAddr, EthAddr # include as part of the betta branch from pox.openflow.of_json import * from pox.lib.recoco import Timer import time log = core.getLogger() src_dpid = 0 dst_dpid = 0 input_pkts = 0 output_pkts = 0 def getTheTime(): #fuction to create a timestamp flock = time.localtime() then = "[%s-%s-%s" %(str(flock.tm_year),str(flock.tm_mon),str(flock.tm_mday)) if int(flock.tm_hour)<10: hrs = "0%s" % (str(flock.tm_hour)) else: hrs = str(flock.tm_hour) if int(flock.tm_min)<10: mins = "0%s" % (str(flock.tm_min)) else: mins = str(flock.tm_min) if int(flock.tm_sec)<10: secs = "0%s" % (str(flock.tm_sec)) else: secs = str(flock.tm_sec) then +="]%s.%s.%s" % (hrs,mins,secs) return then # handler for timer function that sends the requests to all the # switches connected to the controller. def _timer_func (): for connection in core.openflow._connections.values(): connection.send(of.ofp_stats_request(body=of.ofp_flow_stats_request())) connection.send(of.ofp_stats_request(body=of.ofp_port_stats_request())) log.debug("Sent %i flow/port stats request(s)", len(core.openflow._connections)) # handler to display flow statistics received in JSON format # structure of event.stats is defined by ofp_flow_stats() def _handle_flowstats_received (event): #stats = flow_stats_to_list(event.stats) #log.debug("FlowStatsReceived from %s: %s", dpidToStr(event.connection.dpid), stats) global src_dpid, dst_dpid, input_pkts, output_pkts #print "src_dpid=", dpidToStr(src_dpid), "dst_dpid=", dpidToStr(dst_dpid) for f in event.stats: if f.match.dl_type==0x0800 and f.match.nw_dst==IPAddr("192.168.123.2") and f.match.nw_tos==0x64 and event.connection.dpid==src_dpid: #print "input: ", f.byte_count, f.packet_count input_pkts = f.packet_count if f.match.dl_type==0x0800 and f.match.nw_dst==IPAddr("192.168.123.2") and f.match.nw_tos==0x64 and event.connection.dpid==dst_dpid: #print "output: ", f.byte_count, f.packet_count output_pkts = f.packet_count if input_pkts !=0: print getTheTime(), "Path Loss Rate =", (input_pkts-output_pkts)*1.0/input_pkts*100, "%" # handler to display port statistics received in JSON format def _handle_portstats_received (event): #print "\n<<<STATS-REPLY: Return PORT stats for Switch", event.connection.dpid,"at ",getTheTime() #for f in event.stats: #if int(f.port_no)<65534: #print " PortNo:", f.port_no, " Fwd's Pkts:", f.tx_packets, " Fwd's Bytes:", f.tx_bytes, " Rc'd Pkts:", f.rx_packets, " Rc's Bytes:", f.rx_bytes #print " PortNo:", f.port_no, " TxDrop:", f.tx_dropped, " RxDrop:", f.rx_dropped, " TxErr:", f.tx_errors, " RxErr:", f.rx_errors, " CRC:", f.rx_crc_err, " Coll:", f.collisions stats = flow_stats_to_list(event.stats) log.debug("PortStatsReceived from %s: %s", dpidToStr(event.connection.dpid), stats) def _handle_ConnectionUp (event): global src_dpid, dst_dpid print "ConnectionUp: ", dpidToStr(event.connection.dpid) for m in event.connection.features.ports: if m.name == "s0-eth0": src_dpid = event.connection.dpid elif m.name == "s1-eth0": dst_dpid = event.connection.dpid msg = of.ofp_flow_mod() msg.priority =1 msg.idle_timeout = 0 msg.match.in_port =1 msg.actions.append(of.ofp_action_output(port = of.OFPP_ALL)) event.connection.send(msg) msg = of.ofp_flow_mod() msg.priority =1 msg.idle_timeout = 0 msg.match.in_port =2 msg.actions.append(of.ofp_action_output(port = of.OFPP_ALL)) event.connection.send(msg) msg = of.ofp_flow_mod() msg.priority =10 msg.idle_timeout = 0 msg.hard_timeout = 0 msg.match.dl_type = 0x0800 msg.match.nw_tos = 0x64 msg.match.in_port=1 msg.match.nw_dst = "192.168.123.2" msg.actions.append(of.ofp_action_output(port = 2)) event.connection.send(msg) msg = of.ofp_flow_mod() msg.priority =10 msg.idle_timeout = 0 msg.hard_timeout = 0 msg.match.dl_type = 0x0800 msg.match.nw_tos = 0x64 msg.match.nw_dst = "192.168.123.1" msg.actions.append(of.ofp_action_output(port = 1)) event.connection.send(msg) # main functiont to launch the module def launch (): # attach handsers to listners core.openflow.addListenerByName("FlowStatsReceived", _handle_flowstats_received) core.openflow.addListenerByName("PortStatsReceived", _handle_portstats_received) core.openflow.addListenerByName("ConnectionUp", _handle_ConnectionUp) # timer set to execute every five seconds Timer(1, _timer_func, recurring=True)
執行 pox 指令碼：
- 在 pox 安裝目錄下（Mininet 完整安裝包含了 pox）執行以下命令執行 pox 指令碼
$ ./pox.py flowstat
編寫Mininet指令碼：
編輯檔案mymininet.py，內容如下：
#!/usr/bin/python from mininet.net import Mininet from mininet.node import Node from mininet.link import TCLink from mininet.log import setLogLevel, info from threading import Timer from mininet.util import quietRun from time import sleep def myNet(cname='controller', cargs='-v ptcp:'): "Create network from scratch using Open vSwitch." info( "*** Creating nodes\n" ) controller = Node( 'c0', inNamespace=False ) switch = Node( 's0', inNamespace=False ) switch1 = Node( 's1', inNamespace=False ) h0 = Node( 'h0' ) h1 = Node( 'h1' ) info( "*** Creating links\n" ) linkopts0=dict(bw=100, delay='1ms', loss=0) linkopts1=dict(bw=100, delay='1ms', loss=0) link0=TCLink( h0, switch, **linkopts0) link1 = TCLink( switch, switch1, **linkopts1) link2 = TCLink( h1, switch1, **linkopts0) #print link0.intf1, link0.intf2 link0.intf2.setMAC("0:0:0:0:0:1") link1.intf1.setMAC("0:0:0:0:0:2") link1.intf2.setMAC("0:1:0:0:0:1") link2.intf2.setMAC("0:1:0:0:0:2") info( "*** Configuring hosts\n" ) h0.setIP( '192.168.123.1/24' ) h1.setIP( '192.168.123.2/24' ) info( "*** Starting network using Open vSwitch\n" ) switch.cmd( 'ovs-vsctl del-br dp0' ) switch.cmd( 'ovs-vsctl add-br dp0' ) switch1.cmd( 'ovs-vsctl del-br dp1' ) switch1.cmd( 'ovs-vsctl add-br dp1' ) controller.cmd( cname + ' ' + cargs + '&' ) for intf in switch.intfs.values(): print intf print switch.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 ) # Note: controller and switch are in root namespace, and we # can connect via loopback interface switch.cmd( 'ovs-vsctl set-controller dp0 tcp:127.0.0.1:6633' ) switch1.cmd( 'ovs-vsctl set-controller dp1 tcp:127.0.0.1:6633' ) info( '*** Waiting for switch to connect to controller' ) while 'is_connected' not in quietRun( 'ovs-vsctl show' ): sleep( 1 ) info( '.' ) info( '\n' ) #info( "*** Running test\n" ) h0.cmdPrint( 'ping -Q 0x64 -c 20 ' + h1.IP() ) sleep( 1 ) info( "*** Stopping network\n" ) controller.cmd( 'kill %' + cname ) switch.cmd( 'ovs-vsctl del-br dp0' ) switch.deleteIntfs() switch1.cmd( 'ovs-vsctl del-br dp1' ) switch1.deleteIntfs() info( '\n' ) if __name__ == '__main__': setLogLevel( 'info' ) info( '*** Scratch network demo (kernel datapath)\n' ) Mininet.init() myNet()
執行 mymininet3.py
- sudo python mymininet3.py
平均丟包率為 0，結果符合 Mininet 指令碼中設定的損耗率。
如果修改程式碼中 s0 和 s1 之間鏈路的丟包率為 10。
info( "*** Creating links\n" )
linkopts0=dict(bw=100, delay='1ms', loss=0)
linkopts1=dict(bw=100, delay='1ms', loss=10)
link0=TCLink( h0, switch, **linkopts0)
link1 = TCLink( switch, switch1, **linkopts1)
link2 = TCLink( h1, switch1, **linkopts0)
重新執行 Mininet 指令碼 mymininet3.py
可以看到此時結果丟包率為 10%
四、實驗心得
- 通過這次實驗，我學會了測量路徑的損耗率，熟悉了Mininet 自定義拓撲指令碼，以及與損耗率相關的設定；初步瞭解 Mininet 安裝時自帶的 POX 控制器指令碼編寫。