foreword
This article is mainly a summary of the network protocol, which is convenient for subsequent reference and review. Of course, if there is new cognition or new understanding, it will continue to be updated
What is a network protocol?
Definition of network protocol: A collection of rules, standards, or conventions established for the exchange of data in a computer network
A model of a network protocol
There are currently three accepted models:OSI seven-layer model, TCP five-layer model, TCP/IP four-layer model
Briefly explain the three models
OSI seven-layer model (from bottom to top): physical layer, data link layer, network layer, transport layer, session layer, presentation layer, application layer TCP
five-layer model (from bottom to top): Physical layer, data link layer, network layer, transport layer, application layer
TCP/IP four-layer model (from bottom to top): network access layer, network layer, transport layer, application layer
Correspondence between the three：
The role of each layer：
Network protocols corresponding to each layer：
TCP/IP common protocols:
HTTP
HTTP protocol: hypertext transfer protocol, used for www web pages, default port 80
HTTPS
HTTPS protocol: secure hypertext transfer protocol, default port 443
HTTPS protocol is to add SSL shell on the basis of HTTP to keep data confidential and ensure security
FTP
FTP protocol: remote file transfer protocol; local file upload server, or server file download to local,
fast transmission speed, high reliability and stability
DNS
DNS protocol: domain name resolution protocol, the default port is 53, and communicates through UDP protocol by default, but if the message is too large, it will switch to TCP protocol. Its role is to convert
domain names (such as www.baidu.com) into machine-readable IP Address (such as 10.51.7.18)
SMTP
SMTP protocol: mail transfer protocol
TCP
TCP protocol: Transmission Control Protocol
Main features:
1. Connection-oriented, you need to establish a connection first, and then disconnect after the end. The common three-way handshake and four-way wave are used for this protocol. 2. The
transmission speed is slow
3. The data requirements are pressed Sequential transmission, the datagram does not need to carry the destination address during the transmission process, ensuring the correctness of the data
4. Based on the stream mode transmission, large data can be transmitted
5. Many system resource requirements
UDP
UDP protocol: User Datagram Protocol
Main features:
1. Non-connection-oriented
2. Fast transmission speed
3. No requirement for transmission sequence, accuracy cannot be guaranteed, and packet loss may occur
4. Based on datagram mode, transmit data by packet The amount is small, and the size of data transmitted at one time is limited, the maximum is 64k
5. Less resource requirements
Video and audio in daily life are transmitted using UDP, so there will be packet loss and lag
IP
IP protocol: Network protocol; responsible for IP addressing, routing, and segmentation and assembly of IP packets. Usually what we call an IP address can be understood as an address that conforms to the IP protocol.
Main features:
1. No connection
2. Low security and possible packet loss.
3. Point-to-point network layer protocol
IP protocol is the carrier of TCP/IP, all TCP and UDP are transmitted in IP datagram format
ICMP
ICMP protocol: The Internet Control Message Protocol
is used to transmit control messages between IP and routers, describing network status such as whether the network is unobstructed, whether the host is reachable, whether the router is available, etc. ICMP itself does not transmit data, but for data transfer between users transmission plays an important role
ARP
ARP protocol: address resolution protocol; resolve IP address to MAC address
RARP
RARP protocol: reverse address translation protocol; resolve MAC address to IP address