what is ip

The full English name of ip is "Internet Protocol", which means Internet Protocol. It is the network layer protocol in the "TCP/IP" system; IP is the core and component of the entire "TCP/IP" protocol family. The foundation of the Internet; IP mainly includes three aspects, namely "IP addressing scheme", "packet encapsulation format" and "packet forwarding rules".

IP is the abbreviation of Internet Protocol and is the network layer protocol in the TCP/IP system. The purpose of designing IP is to improve the scalability of the network: first, to solve Internet problems and realize the interconnection of large-scale and heterogeneous networks; second, to separate the coupling relationship between top-level network applications and underlying network technologies to facilitate the two. Develop independently. According to the end-to-end design principle, IP only provides a connectionless, unreliable, best-effort packet transmission service to the host.

IP is the core of the entire TCP/IP protocol suite and the foundation of the Internet. IP is located in the network layer of the TCP/IP model (equivalent to the network layer of the OSI model). The upper layer can carry information of various protocols in the transport layer, such as TCP, UDP, etc.; the lower layer can put IP information packets into the link layer. , transmitted through various technologies such as Ethernet and Token Ring networks.
In order to adapt to heterogeneous networks, IP emphasizes adaptability, simplicity and operability, and makes certain sacrifices in reliability. IP does not guarantee the delivery time and reliability of packets. The transmitted packets may be lost, duplicated, delayed or out of order.

Main content

IP mainly includes three aspects: IP addressing scheme, packet encapsulation format and packet forwarding rules.

Related introduction:

Internet Protocol Address (English: Internet Protocol Address, also translated as Internet Protocol Address), abbreviated as IP Address (English: IP Address), is assigned to The digital label of the Internet Protocol (IP) device used by the user to access the Internet. Common IP addresses are divided into two categories: IPv4 and IPv6, but there are also other less commonly used smaller categories.

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##Network interconnection

NNT traffic

How is the Internet Association implemented? Network interconnection equipment, such as Ethernet, packet switching network, etc., cannot interoperate with each other. The main reason why they cannot interoperate is because the formats of the basic units of data they transmit (technically called "frames") are different. The IP protocol is actually a set of protocol software composed of software and programs. It uniformly converts various "frames" into the "Network Association data packet" format. This conversion is one of the most important features of the Internet, making all All kinds of computers can communicate with each other on the Internet, that is, they have the characteristics of "openness".

Data packet

So, what is "data packet"? What are its characteristics? Data packets are also a form of packet switching, which means that the transmitted data is segmented into "packets" and then sent out. However, unlike traditional "connection-type" packet switching, it is "connectionless". Each "packet" (group) is sent out as an "independent message", so it is called "data". Bag". In this way, there is no need to connect a circuit before starting communication, and each data packet is not necessarily transmitted through the same path, so it is called "connectionless". This feature is very important as it greatly improves the robustness and security of the network.

TCP/IP data packet format

Each data packet has two parts: header and message. The header contains necessary content such as the destination address, so that each data packet does not go through the same path can accurately reach the destination. Reassemble and restore the originally sent data at the destination. This requires IP to have the functions of packet packaging and collection assembly.

During the transmission process, the length of the data packet is 30,000 bytes (Byte) (1 byte = 8 binary bits).

In addition, special attention should be paid to the fact that the ip data packet refers to a complete ip information, that is, the value range or regulations of each item in the ip data packet format. For example, the version number can be 4 or 6, and the ip packet header length It can be 20 bytes to 60 bytes, and the total length does not exceed 65535 bytes. The encapsulated upper layer protocol can be tcp, udp, etc.

IP address

There is also a very important content in the IP protocol, that is, an address is specified for every computer and other device on the Internet. It's called an "IP address." Because of this kind of address, it is ensured that users can efficiently and conveniently select the objects they need from thousands of computers when operating on connected computers. Nowadays, the telecommunications network is integrating with the IP network. New technologies based on IP are popular technologies. For example, the technology of using IP network to transmit voice (VoIP) is very popular. Others such as IP overATM, IPoverSDH, IP over WDM, etc. , are the research focus of IP technology.

IP Protocol

Internet Architecture

A TCP/IP Internet provides three sets of services. The lowest layer provides connectionless transport services and provides the basis for services at other layers. A reliable transport service in the second layer provides a high-level platform for the application layer. The highest level is the application layer service.
2. IP protocol: This unreliable, connectionless transmission mechanism is called Internet protocol.

Three definitions of IP protocol:
(1) IP defines the basic unit and data format of data transmission on the TCP/IP Internet.
　(2) The IP software completes the routing function and selects the path for data transmission.
　(3) IP contains a set of rules for unreliable packet transmission, specifying the rules for packet processing, error message generation, and grouping.
4. IP data packet: The basic transmission unit of networking is the IP data packet, including the data packet header and data area.
5. IP packet encapsulation: The physical network encapsulates the entire packet including the packet header as data in a frame.
6. MTU network maximum transmission unit: Different types of physical networks have different upper bounds on the amount of data that can be transmitted in a physical frame.
7. Reorganization of IP data packets: first, reorganization through a network; second, reorganization after reaching the destination host. The latter is better because it allows each packet segment to be routed independently and does not require the router to store or reassemble the segments.
8. Lifetime: There is a survival time field in the IP data packet format, which is used to set the time that the data packet is allowed to exist in the network, in seconds. If its value is 0, it is removed from the Internet and an error message is sent back to the originating site.
9. IP packet options:
The IP packet option field is mainly used for network testing or debugging. Including: record routing options, source routing options, timestamp options, etc.
Routing and timestamp options provide a way to monitor or control how packets are routed by Internet routers.

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