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This article mainly introduces "HTTP link layer, network layer, transport layer and application layer concept is what", in daily operation, I believe many people in HTTP link layer, network layer, transport layer and application layer concept is what problem there is doubt, Xiaobian consulted all kinds of information, sorted out simple and easy to use operation method, hope to answer "HTTP link layer, network layer, transport layer and application layer concept is what" doubt helpful! Next, please follow the small series to learn together!

1. A seven-layer protocol can be simplified to a four-layer protocol

Link Layer Network Layer Transport Layer Application Layer

2. Two networks connected by routers

IP provides a hop-by-hop protocol, providing an unreliable service that may be lost in the middle.

Transport layer tcp provides a reliable transport layer on top of ip

Comparison: tcp is Taobao seller, ip is package, if the package is lost in the middle, the seller will re-send a package, there will be a confirmation process

3. udp is unreliable, it will not confirm, lost, such as voice use this, syslog also use this

4. icmp is a subsidiary protocol, ping is used for this.

5. Encapsulation, each layer will leave its own mark, starting from the application layer plus a header, tcp plus a header, ip plus a header, Ethernet plus a header, encapsulated into frames; frame data length between 46 and 1500 bytes

6. Split, the receiver is split, from the above package, extract the header inside

7. Port number, the source port number is generally randomly assigned, the destination port number is generally a well-known port or a designated port, be sure to pay attention to whether to go or back, because tcp is full duplex

8. Link layer, ethernet and ieee 802 encapsulation

Distinguish Ethernet and 802.3 encapsulation, only need to see Ethernet encapsulation is 2 bit type, 802.3 encapsulation is 2 bit length, we generally see Ethernet frames, rarely see 802.3 frames

Ethernet header on three, source, destination, protocol type, 0800 represents ip protocol

Other additions:

1. Subnet mask is to tell us which is the network part, which is the host part, such as subnet mask is 255.0.0.0, ip is 13.0.0.0 is to tell us 13 is the network part, the rest is the host part

2. Gateway is to other network segments, who should be given, for example, my gateway is 192.168.1.1, the role of routers is to forward data in different network segments

3.MAC address is fixed in the chip when the factory, also known as physical address, 48 bits binary, computer display is 12 bits hexadecimal, such as mine is 50- 7B-9D-25-B0-EF ipconfig /all

4. Computer network card has mac address, computer has ip address

5. Packet: data-source address-destination address-source mac address-destination mac address (router) modifies mac address step by step to the server when passing the next hop

At this point, the study of "what is the concept of HTTP link layer, network layer, transport layer and application layer" is over, hoping to solve everyone's doubts. Theory and practice can better match to help everyone learn, go and try it! If you want to continue learning more relevant knowledge, please continue to pay attention to the website, Xiaobian will continue to strive to bring more practical articles for everyone!

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