Learn the knowledge points of eight part essay ~ ~ 1

1、 What is? ppp agreement

The internet usually needs to be connected to an Internet service provider to access the Internet
ppp The protocol is the data link layer protocol used by computer and Internet communication

2、 Communication between hosts

1） Simplex communication
2） Half duplex communication
3） Full duplex communication

3、icmp

Realization ip Some functions that the protocol does not realize , It's a network layer protocol
The protocol does not transmit data , Only control information is transmitted to assist network layer concentric
Mainly verify whether the network is smooth and auxiliary ip Protocol to achieve reliable transmission （ping）

4、 The difference between router and switch

The difference between and router is , Switches work with hardware , fast , Can only handle simple routing and forwarding , The router is implemented by software , slower , It can realize complex network routing .

5、 Subnet mask

hold ip The address is divided into network address and host address

6、tcp Three handshakes

client ： The client sends... To the server syn request
Server side ： The server receives syn request , return syn+ack request
client ： The client received syn+ack request , return ack request

7、 tcp Four waves

client ： send out fin Request to the server , And enter fin_wait_1 state
Server side ： received fin After the request , send out ack To the client
client ： received ack Enter after request fin_wait_2 state , Waiting for the server to send it fin request
Server side ： send out ack Request to client , After a while , send out fin To the client
client ： received fin Request entry fin_wait state , Wait for a while , Close the connection