@ Switches and Routers for stories – Read Illustrated Network Hardware
create by db on 2020-10-30 11:35:16
Recently revised in 2020-10-31 17:33:24Idle time to have a tight mind, busy time to have leisure fun
directory
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preface
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Reference documentation
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Switches and routers
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Read Illustrated Network Hardware
preface
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Recently I was reading “Illustrated Network Hardware”, in which I didn’t know much about the concept of network protocol. It happened that ZHIhu saw a very good answer, which vividly explained the characteristics and development history of network hardware such as switch, router and firewall, so I would like to share it with you.
Reference documentation
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With small white explain the difference between a router and switch | how to zhihu – schrodinger was not at home
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With small white explain the difference between a router and switch | how to zhihu – FS network
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Basic knowledge of computer network summary | cxuan nuggets – programmer
Gateway routing and all that stuff
A game-driven hardware revolution
Note, part of the story to answer zhihu, original link, deleted.
I’m sure we’ve all played a particularly popular game: Age of Empires. When I was a child, IF I wanted to play age of Empire, I needed to go to the software city to buy pirated CD installation (about 3 yuan a piece of appearance, at that time I thought it was very cheap, who thought it was free after the network). The download can only be performed in standalone mode.
Small A is an imperial age god, he beat all the levels of the game, can be A single person against 8 crazy computers. Gradually he felt bored, want to find a small partner PK together.
But how do you connect the two devices? Small A is very clever, he invented A kind of USB port can transmit data, he named itso. User A connects his computer to the network port of user B through A network cable, and the two computers are connected.
Two small friends are very happy, online play, then was passing by the small C saw, small C also want to join in. But we know, each computer has only one network port, can not realize three computers connected to each other, how to do that?
At this time, small B came up with an idea: let’s find a computer and design several network ports for him. Each of us can connect to the network ports of this computer, so we can realize the interconnection between several elder brothers.
Hub
So they designed a mini computer, which has multiple network ports and is designed to connect multiple computersA hub. As the name suggests,A hubIt plays a role of assembling network cables to achieve the most elementary network interconnection. A hub transmits data directly through a network cable, and we say it works inThe physical layer.
With the hub, more and more small partners to join the game, small D, small E and other people are attracted to come. One problem with the hub, however, is that because it is connected to each device, it cannot tell to whom specific messages are being sent, only to broadcast them widely. For example, Little A wanted to ask little C: Have you eaten? As A result, all users connected to the hub, such as little B, little D and little E, have received this message, and because they are in the same network, others cannot speak when little A speaks, otherwise there will be collisions between messages, causing errors, which is called the same deviceCollision domainInside.
NetWork Switch
The user experience of this device is terrible, so the friends discuss improvement measures together. Then smart little D said: we add a command to this device, so that it can automatically address data transmission according to the name of the network port. Let’s say I named little A’s network portmacA, and name little C asmacCIn this case, if little A wants to send data to little C, the device will use the network port namemacA 和 macCAutomatically transfer data from A’s computer to C’s computer without letting little B, little D and little E receive it. In other words, this device solves the problem of conflict, enables any two computers to connect, greatly increases the speed of transmission between networks, we call itswitches. Since a switch transmits information according to the address of the network port, one step more than the direct transmission of the network cable, we also say that the switch works inData link layer.
This time the little friends are happy, they play happily. Gradually, they gained local fame and attracted more and more friends to join their team. Until one day, a village boy suddenly come to the door, hope to be able to interconnect with them, the realization of cross-village network war. Small A said can ah, so they found A super long network cable will be connected to the two villages of the exchange together. A strange thing was discovered: the two villages could not communicate with each other. Well, it turns out that the computer over there doesn’t use the same operating system as they do, which leads to a mismatch in the way information is transmitted. During this period, people from other villages also came to xiao A, but Xiao A found that the operating system used by each village was different.
Router (Router)
In this way, through such A series of modifications, Little A finally led the villagers to realize the communication of the whole town. As more and more people from the city join in the agreement of Little A, little A leads the villagers to gradually realize the communication of the whole city, the whole country and even the whole world. This set of protocols isTCP/IP protocol suiteAnd so the Internet was formed.
Later, the next village two dogs with small A lost the game, but he was unconvinced. So; He contacted A batch of evil friend dog friend, collude with them good, every day fixed A time everybody sends message to small A their village together, content what have, for example “thunder, rain receives clothes!” “, “People are born of his mother, the devil is born of his mother”, “What is your mother’s name” and so on. Make little “A” they play game card death, finally the network crashed. This is called a denial of service (DoS) attack.
Firewall
So what to do? Clever little E invented a new device. The device monitors traffic in and out of their village network and can dictate what data can and cannot go in and out, thereby blocking data that poses a threat to the village. They set the data of Erdogi village off limits, so that Erdogi and his friends could not attack the network of Xiao A’s village. People think that they are like a fire, and this thing can prevent them, so the device is called firewall (hardware). Later, small E feel that every computer has a firewall, but every family to buy a firewall is too expensive, so he taught himself programming, made up an anti-virus software installed on the computer, used to filter the information that does not need, this is software firewall.
With A firewall, small A their village (local area network) do not have to worry about outside the village (Internet) random access to their data, also do not have to worry about their village children to see ** small movies.
Even though the whole network has spread all over the world now, when little A and his village friends are fighting against the empire, they still use the switch. Only use routers and firewalls to communicate with the larger world. Conclusion: Switches are suitable for intra-LAN interconnection, routers for the whole network segment interconnection, and firewalls for filtering unnecessary data during interaction.
The link between them looks like this: router – firewall – switch, and then switch connects to other network devices.
Cat (Modem)
Here’s a separate explanation for modems: Cat named modems, its role is to the sender (computer want to send information) through modulation converts digital signals to analog signals, and at the receiving end (optical signals in the electrical or optical fiber cables) through demodulation and then converts analog signals to digital signals, so that the information transmission in the network.
Since the computer only knows 1000011 binary data, all its signals are transmitted by current pulses, so the cat is necessary. At present, household routers are generally routing cats, that is, routers take into account the functions of both cats and simple switches. Therefore, when choosing a cost-effective routing cat, it is ok to choose one.
Transmission medium
The transmission of network needs medium. A bit packet travels from one end system through a series of links and routers to another end system. This bit will be forwarded many times, so the media that this bit crosses in the process of transmission is called physical medium. There are many kinds of physical media, such as twisted-pair copper wire, coaxial cable, multi-mode fiber optic olive, land radio spectrum and satellite radio spectrum. In fact, there are roughly two types: guiding media and non-guiding media.
Twisted-pair copper wire
The cheapest and most commonly used guided transmission medium is twisted-pair copper wire, which has been used on telephone networks for many years. More than 99% of the connection from the telephone to the local telephone exchange is made up of twisted-pair copper wire, as shown below
Twisted-pair copper wire consists of two insulated copper wires, each about 1cm thick, arranged in a regular spiral shape. Usually, many twisted-pair cables are tied together to form a cable, and a protective layer is covered on the outside of the twisted-pair filling. A pair of cables form a communication link. Unshielded twisted pair cables are commonly used in local area networks (Lans).
Coaxial cable
Like twisted-pair, coaxial cable is made up of two copper conductors, as shown below
With the help of this structure and special insulation and protection layer, coaxial cable can achieve higher transmission rate, coaxial cable is widely used in cable TV system. Coaxial cables are often user-guided shared media.
Optical fiber
An optical fiber is a thin, flexible medium capable of guiding pulses of light, each pulse representing a bit. A single optical fiber can support extremely high bit rates, up to tens or even hundreds of Gbps. They are not subject to electromagnetic interference. Optical fiber is a guided physical medium. The following is a physical picture of optical fiber
Fiber optics are used extensively in the backbone of the Internet.
Terrestrial radio channel
Radio channels carry signals in the electromagnetic spectrum. It requires no physical wiring and has the ability to penetrate walls, provide connectivity to mobile users and carry signals over long distances.
Satellite radio channel
A satellite channel connects two or more Microblog transmitters/receivers on Earth, called ground stations. Two types of satellites are often used in communications: synchronous satellites and near-Earth satellites.
Read Illustrated Network Hardware
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Read Illustrated Network Hardware
Today, I have finished reading “Graphic Network hardware” and said how I feel about it.
This is a professional book (for xiaobai). This book details the hardware knowledge of constructing network, including switch, router, firewall, wireless network, etc. The detailed explanation is positioned between popular science books and technical books, suitable for Baymax, who is between xiaobai and Great God.
However, the equipment listed in the book is Cisco, there is no domestic hardware knowledge. It has a lot of pictures (this is crap, illustrated… Series are a lot of pictures), but did not touch the network hardware also do not understand. For non communication engineering, belong to read do not understand, understand also do not have what use series.
In general, if you are not interested in network hardware, it is not recommended to read; Speed reading is recommended if you want to learn about it.
The road ahead is long, and I see no end.
Postscript: Hello friends, if you think this article is good, remember to give a thumbs-up or star, your thumbs-up and star is my motivation to write more and richer articles!Making the address
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