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Speed and rating of a variety of Ethernet

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	speed	cable class
Ethernet ( Ethernet)	-
Fast Ethernet (Fast Ethernet)	100mbps	g bit Ethernet (Gigabit Ethernet)	1000mbps	CAT 5e/cat 6

Two intersecting lines and straight lines

• Crossover line: One side is 568A, one side is 568B connector when called intersection, used in direct connection to two host network card.

• Straight line: Both sides of the joint with 568A or 568B is called a direct connection, used to connect the host network card and hub between the cable.

Cross or straight connection (auto Mdi/mdix) of three automatic resolution network cables

Do we need to be aware that the connected cable is a crossover or straight line? No need. Because switch contains auto Mdi/mdix function, it will automatically distinguish the connector of the network cable to adjust the connection, so you do not need to pipe the cable is the intersection line or direct connection.

Types of four IPs

1 IPv4 only two IP categories

• Public IP: This IP is used to connect to the Internet through a unified IP that is planned by the Inter NIC.

• Private IP: IP or reserved IP, not directly connected to the Internet IP, mainly for the host connection planning within the LAN.

2 Private IPs are retained in a, B, and C three categories, respectively:

Class a:10.0.0.0~10.255.255.255

Class b:172.16.0.0~172.31.255.255

Class c:192.168.0.0~192.168.255.255

Five-IP acquisition method download

1 Direct manual configuration (static)

You can directly ask your network administrator for available IP-related parameters and then directly edit the configuration file (or use some software) to set up your web. Common in the Campus network environment, as well as to the ISP to apply for a fixed IP connection environment.

2 made by dialing

Apply for registration with your ISP, get your account password, dial directly to your ISP, and your ISP will get the correct network parameters for your operating system via their own settings. You do not need to manually edit the configuration-related network parameters at this time.

3 automatic access to network parameters (DHCP)

There will be a host in the LAN is responsible for the management of all the computer network parameters, your network will be active to the server when the IP parameters, if you get network-related parameters, your host will be able to set your own server to your network parameters. Most often used in the enterprise internal, IP router back end, campus network and dormitory environment.

Six common port-to-Network service tables

Port	Service Name and content
20	Ftp-data, the active data port used by the file Transfer Protocol
21st	FTP, File Transfer Protocol command port
22	SSH, a more secure remote connection service
23	Telnet, early remote connection service software
25	SMTP, Simple Mail delivery protocol, used in ports as mail server
53	DNS, used in domain name servers that are resolved as names
80	WWW, is the Global Information network server
110	POP3, Mail receiving Protocol, office use of the receiving software are all through it
443	HTTPS, WWW server with encryption mechanism

Seven-TCP three-time handshake

TCP is known as a reliable data transfer protocol, the most important of which is the three-time handshake function, three-time Handshake data Packet connection mode such as. Download

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A: Packet Sending

When a client wants to connect to a server, it must send a packet that requires a connection, at which point the client must randomly take a port greater than 1024 to communicate with the program. Then in the TCP header, you must have an active connection (syn=1) with SYN, and note the sequence number (SEQ=10001) that sends the connection packet to the server side.

B: Packet reception and acknowledgement packet delivery

When the server receives this packet, and confirms that the packet is received, it will start making a packet with Syn=1,ack=1, where the ACK number is to be confirmed to the client, so the number is one more than the SEQ in step A. At the same time our server must also confirm that the client can actually receive our packets, so it sends out seq=20001 to the client and begins to wait for the client to respond to our service.

C: Loopback Acknowledgement Packet

When the client receives an ACK from the server, it can confirm that the previously sent packet was received, and if the client also agrees to establish a connection with the service, it sends a confirmation packet ack=1 to the server, ack=20002.

D: Obtain final Confirmation

If all goes well, after receiving ack=1 and ack=20002 serial number packets on the server, we can establish the connection.

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