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I saw that there are various protocols written in some message format encyclopedias, but there is no protocol for these dialogues. Is it because they belong to different levels? However, there are also some application layer protocols such as SNMP. Is it the difference between routing protocols? Learning these knowledge points of computer network does not depend on different types of memories, but on understanding. If you understand it, you don’t need to remember it. You remember that HTTPS belongs to the application layer, but you are deceived by books, because this world has no HTTPS protocol at all, and this world only has TLS security protocol and HTTP protocol! TLS is equivalent to security personnel. It is responsible for escorting HTTP materials. When the safety reaches the destination, the security personnel are naturally redundant. Go back to your home, and find your mom. The destination receiver only cares about the transportation material itself, but has no interest i

Of course, the home network, enterprise network, and data center are connected to the operator's access network through optical fiber. The trickle flows from the access network are aggregated into super-large traffic, which is transmitted to the core switching network using higher-speed optical fiber links, where it is distributed to all corners of the world according to the destination of the traffic. The popular science articles that we often see on the Internet, the pictures that see the Internet usually look like this: After reading these pictures, I still can't understand how the Internet is connected. To understand the local connection information, you can refer to this picture: Each Backbone in the picture can represent an operator. You can think of them as "China Telecom", "China Unicom", and "China Mobile". Each operator, like an independent kingdom, uses an AS number to exchange global routing tables with other kingdoms. In t

According to Glassdoor statistics in the United States, the average salary of a network engineer is $72,362, with an annual salary increase of 5% (US Bureau of Labor Statistics data). The minimum degree required is a Bachelor of Information Technology. Network engineers often need to make decisions about the networks they are responsible for, including how much budget they want to allocate for infrastructure and maintenance, and they also need to design and build networks to meet business goals and strategies. Enterprise networks, and the skills that network engineers need to use, vary according to industry and business needs. For example, the manufacturing and retail industries rely more on IoT and need a stable network of large-volume data; medical institutions have higher requirements for network security. Therefore, when applying for the position of network engineer, be sure to keep in mind the needs of the company and adjust your skills to suit specific industries. With the r

For monitoring projects, many causes of failures are related to improper IP address settings, such as IP conflicts, or there are several monitoring images that are not displayed, etc., which are all related to IP, and reasonable allocation of IP addresses is very important. 1. Why should IP be allocated reasonably? For small monitoring projects, the setting of the IP address is relatively simple, and most people will not make mistakes. For monitoring projects with more than 254 points, it is somewhat prone to errors. why? First, if the network segment is not divided by more than 254 points, if the system automatically assigns IP addresses, IP conflicts are likely to occur. Second, if the network segment is divided, the allocation of the ip address and the setting of the subnet mask become a problem. Some friends are not familiar with the allocation of the ip address and are prone to make mistakes. So what should I do? Dividing network segments is a reasonable

MTU (Maximum Transmission Unit) The maximum transmission unit is used to notify the other party of the maximum size of the data service unit that can be accepted, and to indicate the size of the payload that the sender can accept. Both Ethernet and 802.3 have a limit on the length of the data frame, and their maximum values  are 1500 bytes and 1492 bytes, respectively. This characteristic of the link layer is called MTU, which is the maximum transmission unit. Most types of networks have an upper limit on the length of several frames. If there is a datagram to be transmitted in the IP layer, and the length of the data frame is greater than the MTU of the link layer, then the IP layer needs to be fragmented (fragmentation), that is, the datagram is divided into dry slices, so that each slice is smaller than MTU. Different data links have different maximum transmission units (MTU). Since the IP protocol is the upper layer of the data link, it must be able to be used withou

The most important skills of network engineers are solid foundation and very open thinking, solid micro knowledge and outstanding macro capabilities. No matter what certificate you have, you cannot be a good network engineer without these two points. Of course, both of these points require network engineers to accumulate for a long time The foundation is very important. The foundation is the accumulation of knowledge at the micro level of the network. No matter how familiar you are with Cisco's configuration, network engineers need to solve network problems. Once network problems arise, solutions need to be given as soon as possible. At this time, the foundation is very important. A good foundation of network knowledge is obtained through theoretical study and long-term practice. You may be able to get rid of various protocols, but I don’t think this is a good foundation for you. When I was studying at that time, I was constantly capturing packets for various proto

Let me talk about my understanding first, if there is a mistake, please correct it! First, a data packet comes over, the router's network interface will determine a frame through the special marks of the frame header and the frame end and do a CRC check on the frame. If the check is unsuccessful, the frame is discarded. If the check is successful, the frame is stripped. The header and the end of the frame are put into the buffer queue of the network layer. The network layer will decrement the TTL of the IP datagram by one, recalculate the header checksum and other operations, and query the forwarding table to find the network interface to which the packet should go. Then put it into the output buffer of the interface, and the data link layer will add a new destination (next hop) MAC address, source (local router) MAC address, and IP type (such as IPv4) for this IP datagram. Calculate a wave, add an FCS at the end of the frame, and then send the frame through the physical layer.