网络基础知识
1、简述osi七层模型和TCP/IP五层模型
1).osi七层模型
OSI模型把网络通信的工作分为7层，分别是物理层、数据链路层、网络层、传输层、会话层、表示层和应用层。每一层对于上一层来讲是透明的，上层只需要使用下层提供的接口，并不关心下层是如何实现的。
2).TCP/IP五层模型
TCP/IP模型把网络通信的工作分为5（或4）层，分别是物理层、数据链路层（如果是四层模型数据链路层和物理层在一层）、网络层、传输层、应用层。每一层都呼叫它的下一层提供的网络来完成自己的需求。
2、总结描述TCP三次握手四次挥手
以S表示server端，以C表示client端
1）.建立TCP连接：三次握手协议
C：S你在吗？有个小问题请教你，OVER；
S：我在呢，能听清吗？知无不言，OVER;
C：能听清，OVER
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2）.关闭TCP连接：四次握手协议
C：我说完了，谢谢你的解答，OVER；
S：收到，有一些事情还需要向你交代
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balabalabalabalabalabalabalabala········
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S：我说完了，OVER；
C：收到，我会等一会（两个最大报文生命周期），如果你没有收到我的会话，请在告诉我，OVER
（S收到确认，会话结束）
3、描述TCP和UDP区别
| UDP | TCP | |
|---|---|---|
| 是否连接 | 无连接 | 面向连接 |
| 是否可靠 | 不可靠传输，不使用流量控制和拥塞控制 | 可靠传输，使用流量控制和拥塞控制 |
| 连接对象个数 | 支持一对一，一对多，多对一和多对多交互通信 | 只能是一对一通信 |
| 传输方式 | 面向报文 | 面向字节流 |
| 首部开销 | 首部开销小，仅8字节 | 首部最小20字节，最大60字节 |
| 适用场景 | 适用于实时应用（IP电话、视频会议、直播等） | 适用于要求可靠传输的应用，例如文件传输 |
4、网卡绑定bond0的实现
实验环境为Ubuntu18.04
查看网卡
gw@node2:~$ ip a
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
inet 127.0.0.1/8 scope host lo
valid_lft forever preferred_lft forever
inet6 ::1/128 scope host
valid_lft forever preferred_lft forever
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP group default qlen 1000
link/ether 00:0c:29:dc:64:01 brd ff:ff:ff:ff:ff:ff
3: eth1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP group default qlen 1000
link/ether 00:0c:29:dc:64:0b brd ff:ff:ff:ff:ff:ff
4: eth2: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP group default qlen 1000
link/ether 00:0c:29:dc:64:15 brd ff:ff:ff:ff:ff:ff
inet 192.0.2.129/24 brd 192.0.2.255 scope global dynamic noprefixroute eth2
valid_lft 1766sec preferred_lft 1766sec
inet 192.0.2.99/24 brd 192.0.2.255 scope global secondary noprefixroute eth2
valid_lft forever preferred_lft forever
inet6 fe80::1c67:1e7a:bf5:dc15/64 scope link noprefixroute
valid_lft forever preferred_lft forever
选择eth0和eth1两块网卡做bond0
gw@node2:~$ sudo nmcli connection add type bond con-name bond0 ifname bond0 autoconnect yes mode balance-rr
Connection 'bond0' (25626852-cdea-4826-9558-8ad1074647e1) successfully added.
gw@node2:~$ sudo nmcli connection add type bond-slave ifname eth0 master bond0
Connection 'bond-slave-eth0' (fae60b5a-4492-4f4d-8dfc-ad45d85680e1) successfully added.
gw@node2:~$ sudo nmcli connection add type bond-slave ifname eth1 master bond0
Connection 'bond-slave-eth1' (69307142-0c78-4f1c-8e85-9c61e7c6e78f) successfully added.
gw@node2:~$ nmcli connection show
NAME UUID TYPE DEVICE
bond-slave-eth0 fae60b5a-4492-4f4d-8dfc-ad45d85680e1 ethernet eth0
bond-slave-eth1 69307142-0c78-4f1c-8e85-9c61e7c6e78f ethernet eth1
bond0 25626852-cdea-4826-9558-8ad1074647e1 bond bond0
eth2 6e598b7b-888e-44e2-b441-8c4ac5ce5c89 ethernet eth2
gw@node2:~$ sudo nmcli connection modify bond0 ipv4.addresses 192.0.2.100/24 ipv4.gateway 192.0.2.1 ipv4.method manual
gw@node2:~$ sudo nmcli connection reload
gw@node2:~$ sudo nmcli connection up bond0
Connection successfully activated (master waiting for slaves) (D-Bus active path: /org/freedesktop/NetworkManager/ActiveConnection/18)
gw@node2:~$ ip a
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
inet 127.0.0.1/8 scope host lo
valid_lft forever preferred_lft forever
inet6 ::1/128 scope host
valid_lft forever preferred_lft forever
2: eth0: <BROADCAST,MULTICAST,SLAVE,UP,LOWER_UP> mtu 1500 qdisc fq_codel master bond0 state UP group default qlen 1000
link/ether 00:0c:29:dc:64:01 brd ff:ff:ff:ff:ff:ff
3: eth1: <BROADCAST,MULTICAST,SLAVE,UP,LOWER_UP> mtu 1500 qdisc fq_codel master bond0 state UP group default qlen 1000
link/ether 00:0c:29:dc:64:01 brd ff:ff:ff:ff:ff:ff
4: eth2: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP group default qlen 1000
link/ether 00:0c:29:dc:64:15 brd ff:ff:ff:ff:ff:ff
inet 192.0.2.129/24 brd 192.0.2.255 scope global dynamic noprefixroute eth2
valid_lft 1562sec preferred_lft 1562sec
inet 192.0.2.99/24 brd 192.0.2.255 scope global secondary noprefixroute eth2
valid_lft forever preferred_lft forever
inet6 fe80::1c67:1e7a:bf5:dc15/64 scope link noprefixroute
valid_lft forever preferred_lft forever
6: bond0: <BROADCAST,MULTICAST,MASTER,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP group default qlen 1000
link/ether 00:0c:29:dc:64:01 brd ff:ff:ff:ff:ff:ff
inet 192.0.2.100/24 brd 192.0.2.255 scope global noprefixroute bond0
valid_lft forever preferred_lft forever
inet6 fe80::ff15:9380:3289:f4e1/64 scope link noprefixroute
valid_lft forever preferred_lft forever
