Hey guys, this is Cxuan, welcome to read my latest article. As you know, I’ve been serializing computer networks for a while. Whenever I get to know a new technology or framework, I always want to understand the concept of the name first. The concepts in computer networks are also very complex and difficult to understand, so HERE I have compiled 89 common concepts in computer networks to help you.

  1. The hostAny device on a computer network that can connect to the network is called a host or hostEnd systemSuch as mobile phones, tablets, TVS, game consoles, cars, etc. With the arrival of 5G, there will be more and more terminal devices connected to the network.
  2. Communications link: A communication link is a physical path consisting of physical links (coaxial cables, twisted-pair cables, and optical fibers) connected together.
  3. Transmission rate: The unit is bit/s or BPS, which measures the data transmission rate of different links from one end system to another.
  4. groupingWhen one end system sends data to another, it usually fragments the data and adds the first byte to each segment to form the computer networking term grouping. These packets are sent over the network to the end system, where the data is then processed.
  5. The router: it andLink layer switchBoth switches are used to forward data.

  1. Path: THE path through which a packet travels through a series of communication links and packet switches called the path through the network.

  2. Internet service provider: also called ISP, not LSP. This is easy to understand, is the network operators, mobile, telecom, Unicom.

  3. Network protocol: Network protocols are rules, standards, or conventions established for data exchange in computer networks.

  4. IP: The Internet protocol that specifies the format of packets sent and received between the router and the end system.

  5. TCP/IP protocol cluster: not only TCP and IP, but a series of protocols based on TCP and IP, such as ICMP, ARP, UDP, DNS laundry, and SMTP.

  6. Distributed applications: An end system that exchanges data between multiple end systems is called a distributed application.

  7. Socket interface: Refers to the socket interface, which defines the way data is exchanged between end systems over the Internet.

  8. Protocol: A protocol defines the standards for the format and sequence of packets exchanged between two or more communication entities.

  9. Client: Acts as a requester in a client-server architecture, usually a PC, smart phone, etc.

  10. Server: Plays the role of server in a client-server architecture, usually with a large cluster of servers playing the role of server.

  11. Forwarding table: Internal route records the mapping of packet paths.

  12. Delay: Delay refers to the time required for a packet or group to be transmitted from one end of the network to the other end. Delay is classified into sending delay, propagation delay, processing delay, and queuing delay. Total delay = sending delay + propagation delay + processing delay + queuing delay.

  13. Packet loss: In computer networks, the loss of packets.

  14. Throughput: Throughput in computer networks is the number of successful data transfers per unit of time.

  15. Packet: Usually refers to packets at the application layer.

  16. Packet segment: Packets at the transport layer are usually referred to as packet segments.

  17. Datagrams: Packets at the network layer are commonly referred to as datagrams.

  18. Frames: Link layer groups are generally called frames.

  19. Customer-service architecture: It is an architecture for web applications. The different systems in the system are divided into client and server. The client sends a service request to the server, and the server completes the requested service, and sends the processing result back to the client. In client-server architecture, there is a host that is always open called a Server, which provides services from clients. Our most common server is a Web server, which serves requests from browsers.

  1. CIDR: Network and host identifiers that use arbitrary lengths to separate IP addresses

  2. P2P system: peer-to-peer architecture, equivalent to no server, everyone is a client, each client can send requests, but also can respond to requests.

  1. IP address: An IP address is an Internet protocol address that uniquely identifies a host on the Internet. Each device connected to the network has an IP address, which is divided into internal IP address and public IP address.

  2. Port number: A port number identifies different application processes on the same host.

  3. A Uniform Resource Identifier (URI) is a Uniform Resource Identifier (URI) that uniquely identifies resources on the Internet.

  4. URL: The full name of URL is Uniform Resource Locator. It is actually a subset of URI.

  1. HTML: HTML, known as hypertext Markup Language (HTML), is an identifier language. It includes a series of tags. These tags unify the format of documents on the network and connect scattered Internet resources into a logical whole. HTML text is descriptive text composed of HTML commands that describe text, graphics, animations, sounds, tables, links, etc.

  2. Web pages: A Web Page, also known as a Web Page, is composed of objects. An object is simply a file. This file can be an HTML file, an image, a Java application, etc., all of which can be found through a URI. A Web page contains many objects. A Web page can be said to be a collection of objects.

  3. Web Server: The official name of the Web Server is called the Web Server. The Web Server can provide documents to Web clients such as browsers, and can also place website files for the world to browse. You can place data files for the world to download. The three most popular Web servers are Apache, Nginx and IIS.

  4. CDN: The full name of CDN is Content Delivery Network. It applies caching and proxy technologies in HTTP protocol to respond to client requests instead of source sites. CDN is a network built on the basis of the existing network. It relies on the edge servers deployed in various places, through the central platform of load balancing, content distribution, scheduling and other functional modules, users can obtain the required content nearby, reduce network congestion, and improve user access response speed and hit ratio.

  5. WAF: WAF is an application protection system that implements HTTP/HTTPS security policies to protect Web applications. It is an application-layer firewall that detects HTTP traffic and protects Web applications.

  6. WebService: WebService is a Web application. WebService is a remote call technology across programming languages and operating system platforms.

  7. HTTP: ONE of the TCP/IP protocols. It is a protocol and specification for the transfer of hypertext data, such as text, pictures, audio, and video, between two points in the computer world.

  8. Session: A Session is essentially a cache of client sessions, designed to compensate for the stateless nature of HTTP. The server can use the Session to store records of the client’s operations during the same Session. When a client requests a server, the server allocates a memory space for the request. This object is the Session object, and the storage structure is ConcurrentHashMap.

  9. Cookie: HTTP Cookie includes Web Cookie and browser Cookie. It is a small piece of data sent by the server to the Web browser. Cookies sent by the server to the browser are stored by the browser and sent to the server with the next request. Typically, it is used to determine whether two requests are coming from the same browser, for example when the user remains logged in.

  10. SMTP: The protocol that provides the email service is called SMTP. SMTP also uses TCP at the transport layer. SMTP protocol is mainly used for mail information transfer between systems, and provide notification about letters.

  11. DNS protocol: Because THE IP address is the address that the computer can recognize, and we humans are not convenient to remember this address, so for the convenience of human memory, DNS protocol is used to map the network address that we can easily remember as the IP address that the host can recognize.

  1. TELNET protocolA remote login protocol that allows a user (Telnet client) to communicate with a remote device through a negotiation process. It provides the user with the ability to perform remote host work on the local computer.

  1. SSH: SSH is a secure encryption protocol based on the application layer. Because TELNET has a very obvious shortcomings, that is on the host and the remote host to send data packets is clear in the process of transmission, without any security encryption, the consequences of this is likely to be Internet criminals to the packet sniffer to do bad things, for the safety of data, we usually use SSH for remote login.

  2. FTP: a file transfer protocol. It is an application-layer protocol. The FTP protocol consists of two parts: an FTP server and an FTP client. The FTP server is used to store files. Users can use the FTP client to access resources on the FTP server through FTP. FTP is used to transfer large files with high transmission efficiency.

  1. MIME type, which represents the type of resource on the Internet, Common types include hypertext Markup language text. HTML text/ HTML, XML document.xml text/ XML, plain text. TXT text/plain, PNG image.png image/ PNG, and GIF graph.gif Image/JPEG,.jpg image/ JPEG, AVI file.avi video/ X-MSVideo etc.

  2. Multiplexing: At the receiving end, the transport layer checks fields such as the source port number and destination port number, and then identifies the received socket. The process of delivering the data of the transport layer packet segment to the correct socket is called multiplexing.

  3. Multiplexing: At the sender, the process of collecting data blocks from different sockets and encapsulating header information into the blocks to generate message segments, which are then passed to the network layer is called multiplexing.

  4. Known port numbers: In host applications, port numbers from 0 to 1023 are restricted and are called known as known port numbers. These port numbers are generally not available.

  5. Unidirectional data transfer: Data flows only in one direction, that is, from the sender -> the receiver.

  6. Bidirectional data transmission: The data flow is bidirectional, also called full-duplex communication. The sender and receiver can send data to each other.

  7. Connection-oriented: Connection-oriented means that application processes need to shake hands before sending data to another application process. That is, they must first send each other a preparatory packet segment that establishes parameters to ensure data transmission.

  8. Three-way handshake: To establish a TCP connection, three packet segments are sent. This process is called three-way handshake.

  1. Maximum packet segment length: MSS, which refers to the maximum value taken from the cache and put into the packet segment.

  2. Maximum transmission unit (MTU), which refers to the size of the payload that the communication parties can receive. MSS is usually set according to the MTU.

  3. Redundant ACK: Indicates the ACK of a packet segment. The loss of a packet segment results in redundant ACKS.

  4. Fast retransmission: Retransmits the lost packet segment before the packet segment timer expires.

  5. Select confirmation: In the case of a packet segment loss, TCP can select a packet segment that is out of order. This mechanism is usually used in conjunction with retransmission.

  6. Congestion control, congestion control to say is, when a certain period of time in the network packet is overmuch, too late to make the receiving end, causing some or the entire network performance degradation phenomenon of a kind of inhibiting the sender to send data, such as after a period of time or network improvements continue to send a message and then a method.

  7. Quadruple wave: TCP disconnects through four packet segments. This disconnection process is quadruple wave.

  1. Routing algorithm: An algorithm at the network layer that determines the routing of packets.

  2. Forwarding: This refers to the action of moving packets from an input link to an appropriate output link.

  3. Packet scheduling: Packet scheduling deals with how packets are transmitted through the output link. There are three main scheduling methods: first-in, first-out, priority queuing, and “circular and weighted fair queuing”.

  4. IPv4: The fourth and most widely used version of the Internet protocol. IPv4 is a connectionless protocol that does not ensure reliable data delivery. Use 32-bit addresses.

  5. IPv6: the sixth version of the Internet protocol. The address length of IPv6 is 128 bits. The biggest problem of IPv4 is the lack of network address resources, which seriously restricts the application and development of the Internet. The use of IPv6 can not only solve the problem of the number of network address resources, but also solve the obstacles of a variety of access devices connected to the Internet.

  6. Interface: Boundary between a host and a physical link.

  7. ARP: ARP is a protocol to solve the address problem. Based on the IP bit clue, it can locate the MAC address of the next network device that receives data. If the destination host and the host are on different links, you can use ARP to search for the IP address of the next hop route. However, ARP is only applicable to IPv4, not IPv6.

  8. RARP: RARP is a protocol that reverses ARP and locates IP addresses using MAC addresses.

  1. Proxy ARP is used to resolve the problem that ARP packets are isolated by routers. Proxy ARP is used to forward ARP requests to neighboring network segments.

  2. ICMP: An Internet packet control protocol. If an IP packet fails to reach the destination host for some reason during IP communication, ICMP messages are sent. ICMP is actually a part of IP.

  1. DHCP protocol: DHCP is a dynamic host configuration protocol. DHCP can automatically set IP addresses, assign IP addresses in a unified manner, and plug and play.

  2. NAT: A network address translation protocol, which translates all hosts with local addresses into global IP addresses on the NAT router before they can communicate with other hosts.

  3. IP tunneling: IP tunneling refers to the process by which a router encapsulates a network-layer protocol into another protocol for transmission across the network to another router.

  4. Unicast: The biggest feature of unicast is 1-to-1. The early fixed-line telephone is an example of unicast

  1. radio: We used to broadcast gymnastics when we were kids. This is an example of a broadcast. The host is connected to all the end systems connected to it.

  1. multicastMulticast is similar to broadcast in that messages are sent to multiple receiving hosts, except that multicast is limited to a single group of hosts.

  1. As a broadcastAnycast is a communication method in which a receiver is selected from a specified number of hosts. Although similar to multicast, but different from multicast in behavior, anycast selects a host that best meets network conditions as the target host to send messages. The selected particular host will then return a unicast signal before communicating with the target host.

  1. IGP: Internal gateway protocol, which is used in autonomous routing systems (aS) built by enterprises.
  2. EGP: External gateway protocol, EGP is used to exchange routing information between network hosts.
  3. RIP: a distance vector routing protocol widely used in LAN networks.
  4. OSPF: IS a link-state protocol based on THE OSI IS-IS protocol. This protocol can also effectively solve the problem of network loop.
  5. MPLS: It is a tag switching technology. Tag switching sets a tag for each IP packet and forwards it according to this tag.
  6. node: Refers to devices in the link layer protocol.
  7. link: Generally, the communication channel connecting adjacent nodes along the communication path is called a link.
  8. MAC protocols: media access control protocol, which specifies the rules for frames to be transmitted over a link.
  9. Parity bit: a method of error detection, mostly used in computer hardware error detection, parity check is usually used in data communication to ensure the validity of data.
  10. Forward error correction: The receiver’s ability to detect and correct errors is called forward error correction.
  11. EthernetEthernet is one of the most common local area network technologies today, which specifies the physical layer of wiring, electronic signals, and MAC protocol content.
  12. VLANVirtual local area network (VLAN) is a group of logical devices and users. These devices and users are not limited by physical location, but can be organized according to functions, departments, and applications. They communicate with each other as if they are in the same network segment.
  13. The base station: Wireless network infrastructure.

Afterword.

Hope this article can help you better understand the computer network, but also hope you can like, see, share, forward!

In addition, I have uploaded six PDFS by myself, with over 10W + spread across the Internet. After searching the public account of “Programmer Cxuan” on wechat, I reply to CXuan in the background and get all PDFS. These PDFS are as follows

Six PDF links