Lecture 4 Mininet¶

Introduction¶

How to maintain connection between two hosts without high cost?
Easily Utilized on Laptop
linux命令行 + 进入root用户 (su)

Create Network Namespaces¶

Bash
ip netns add h1   # 前三个是reserved，h1是自定义的namespace => linux自建立轻量“虚拟机”
ip netns add h2  

ip netns show     # 显示当前所有的名字空间 => h1 / h2 / root (不会显示)

Hence, there are 3 network namespaces in system now

h1
h2
root

Create Virtual Ethernet Pair¶

Bash
ip link add h1-eth0 type veth peer name s1-eth1  # h1 -> h1-eth0  --->-- s1-eth1
ip link add h2-eth0 type veth peer name s1-eth2 # h2 -> h2-eth0 --->-- s1-eth2

ip link show # 显示在root名字空间内的链路

Hence, we created 2 links now in the root namespace

h1-eth0 => s1-eth1
h2-eth0 => s1-eth2

Move Ports into Host Namespaces¶

Bash
ip link set h1-eth0 netns h1   # h1-eth0 从 root 名字空间移动到 h1 名字空间下
ip link set h2-eth0 netns h2  # h2-eth0 从 root 名字空间移动到 h2 名字空间下

ip netns exec h1 ip link show # 在h1名字空间下执行ip link show => 可见h1-eth0
ip netns exec h2 ip link show # 在h2名字空间下执行ip link show => 可见h2-eth0

Now, we put NIC h1-eth0 and h2-eth0 into namespace h1 and h2 independently

Hence, if we try to input "ip link show" in the CLI now:

We will not see the link h1-eth0->s1-eth1 and h2-eth0->s1-eth2

Configure Host Interfaces¶

Bash
ip netns exec h1 ifconfig h1-eth0 10.1 # offer IP to the NIC
ip netns exec h2 ifconfig h2-eth0 10.2
ip netns exec h1 ifconfig lo up # 在该网络命名空间中将 `lo` 接口（本地回环接口）启用
ip netns exec h1 ifconfig lo up

In fact, ip netns exec h1 ifconfig lo up and ip netns exec h2 ifconfig lo up can be ignored practically

Create Virtual Switch¶

Bash
ovs-vsctl show
ovs-vsctl add-br s1 # 添加bridge(switch)，这个软件交换机called: S1
ovs-vsctl show

ovs-vsctl 是 Open vSwitch 的管理工具之一，用于配置和管理 OVS。
show 参数指示该命令显示当前 OVS 的配置信息，包括网桥、端口、控制器、流表等。

运行 ovs-vsctl show 命令将列出当前 OVS 实例中的各种配置信息

Create Switch Ports to OVS¶

Bash
ovs-vsctl add-port s1 s1-eth1 # port->link in root namespace
ovs-vsctl add-port s1 s1-eth2
ovs-vsctl show

The ports of S1 Switch are connected with links

Test the Network¶

Bash
ip netns exec h1 ping -c10 10.2 # 在h1名字空间中; -c10表示ping的次数 => 此时NIC仍处于关闭态
ifconfig s1-eth1 up                      # s1-eth1的NIC开启
ifconfig s1-eth2 up                     # s1-eth2的NIC开启
ip netns exec h1 ping -c10 10.2 # 此时可以ping通了

Test Client and Server¶

Bash
ip netns exec h1 wget -O - 10.2
ip netns exec h2 python -m SimpleHTTPServer 80 &

Mininet¶

Mininet creates a realistic virtual network, running real kernel, switch and application code, on a single machine (VM/cloud/native), in seconds, with a single command

Traits: - A simple API that did this for us automatically - Easily create topologies of varying size - You must make orders in su

A summary for the listed orders above:

They can be easily transmitted as below:

Bash
net = Mininet()
# Create hosts
h1 = net.addHost('h1')
h2 = net.addHost('h2')
# Create switch
s1 = net.addSwitch('s1')
# Create links
net.addLink(h1,s1)
net.addLink(h2,s1)

Show Nodes and Links¶

Bash
mininet> nodes
- Display nodes

Bash
mininet> net
- Display links

Bash
mininet> dump
- Dump ß(倾泻/详细显示) information about all nodes

Show Interface Configurations¶

Bash
mininet> h1 ifconfig -a
    - h1-eth0
    - lo

== 在主机 h1 上查看所有接口的配置信息

Bash
mininet> si ifconfig -a
    - eth0
    - lo

== 在交换机s1上查看所有接口的配置信息

Show the Process¶

Bash
mininet> h1 ps -a
    - show the process seen by h1...
mininet> h2 ps -a
    - show the process seen by h2...

Conclusion

Only the network is virtualized
Each host process sees the same set of processes and directories

Test Connectivity¶

Bash
mininet> h1 ping -c5 h2
    - Test connectivity between h1 and h2
    - The first ping takes a much longer time usually
mininet> pingall
    - Test all-pair connectivity

Simple Web Server and Client¶

Bash
mininet> xterm h1 h2
h1> python -m SimpleHTTPServer 80 &
h2> wget -O 10.0.0.1

Customize Topologies¶

详见Lab1 Tutorial