What are the differences between HUB, switch, router, and MODEM ???

What are the differences between hub, switch, router, and modem ???

What types of networks are available (local area, wide area, and enterprise )?
How should the above components be connected for each network type?

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Hub ------- a hub is also called a hub. It works on the physical layer (bottom layer) and does not have a matching software system. It is a pure hardware device. A hub is used to connect a computer and other network terminals.

The Hub is a shared bandwidth. When any device connected to the Hub sends data, all other devices must wait. The device has full bandwidth, communication is complete, and other devices can use the bandwidth. As a result, the hub connects to a network with a conflict domain. All devices use each other in turn, just as if everyone had a zhuqiao together.

The Hub cannot determine the destination and type of data packets. Therefore, if broadcast data packets are still forwarded, and all devices send data to each interface in broadcast mode, in this way, the hub is connected to a broadcast domain network.

Switch ------- switch, which works on the data link layer (Layer 2). A slightly higher-end switch is supported by an operating system. Like a hub, it is mainly used to connect network terminal devices such as computers.

A vswitch is more advanced than a hub. It allows devices connected to a vswitch to communicate in parallel. For example, if a vehicle on a highway runs in parallel, communication between devices will not conflict, therefore, the switch breaks the conflict domain. Each interface of the switch is a conflict domain and does not conflict with other interfaces.

In addition, a system switch can record the MAC address table, and the sent data is not sent to each interface in broadcast mode, but directly to the Target Interface, saving the interface bandwidth. However, the vswitch and the hub cannot determine the broadcast data packet and send the broadcast to all interfaces. Therefore, the vswitch and the hub are connected to a broadcast domain network.

A high-end switch can not only record MAC address tables, but also divide VLAN (Virtual LAN) to isolate broadcast, but also cannot communicate between VLANs. To enable communication between VLANs, a layer-3 device must be involved.

Router ------- router, working at the network layer (Layer 3). All routers have their own operating systems for maintenance and need personnel debugging. Otherwise, they cannot work. Vrouters do not have so many interfaces and are mainly used to connect networks to networks.

Simply put, a router sends data from one network to another. This process is called routing. A vro not only isolates conflicting domains like a vswitch, but also detects broadcast packets and discards broadcast packets to isolate broadcast domains, effectively Expanding the network scale.

The route table is recorded in the router, and the router forwards data to achieve inter-network communication. Vro intervention enables communication between VLANs divided by vswitches.

Summary:

Hub: hardware-only, used to connect to network terminals, cannot break the conflict domain and broadcast domain.

Vswitch: it has a software system and is used to connect to a network terminal. It can break the conflict domain, but cannot split the broadcast domain.

Vro: it has a software system, is used to connect to the network, can break the conflict domain, can also be divided into broadcast domain, is connected to large network ratio Slave Device

In fact, modem is combined by the abbreviations of modulatordemodulator. It is translated into Chinese as "modem ". The main function of modem is to convert data between a digital signal and a analog signal for transmission over a telephone line. The current modem basically has fax and voice functions, so it is usually called Fax/Voice/MODEM.
In the telephone lines used in daily life, all information is represented and transmitted by a continuous analog signal, that is, an audio signal. For a computer, only the numbers 0 and 1 are known, all information is expressed and transmitted using discontinuous digital signals. This modem is useful! The computer first handed over the data to the modem. The Modem converted the digital signal into an audio analog signal and sent it to the telephone line. This process is called "modulation". When the receiving modem receives the audio analog signal, it is called "demodulation ". The role of modem is like the bridgehead at both ends of the bridge.

How do we communicate between the computer and modem? Hayes, a famous communication equipment manufacturer, has developed a set of commands for controlling Modem operations through computers (mainly through the communication software), which is what we often call "AT commands ". Each instruction except "A/" is expressed at the beginning of "at" ("Attention"). It seems to be a reminder to modem.

There are several eye-catching panel lights on the modem. When the modem works normally, it will appear extremely busy and flashing, according to the actual transmission rate of the line.
Data. Of course, we should know the meaning of each lamp so that we can know the current status of the modem in time. Of course, there are also some products on the market now. There is a simple prompt icon next to each lamp, which is very considerate to users.

First, the hub, that is, the hub. Its function can be simply understood as connecting some machines to form a LAN. The switch (also known as the switch-type hub) works basically the same as the hub. However, there is a difference between the two in terms of performance: the hub uses the shared bandwidth method, while the switch is the exclusive bandwidth. In this way, when there are many machines or a large amount of data, the two will be obvious. A vro differs significantly from the preceding two. Its function is to connect different CIDR blocks and find the most suitable path for data transmission in the network. In general, individual users have little need. A vro is generated after a vswitch, just as a vswitch is generated after a hub. Therefore, the vro and vswitch are also associated, and they are not completely independent of each other. Vro mainly overcomes the problem that vswitches cannot route and forward data packets.

In general, the main difference between a vro and a vswitch lies in the following aspects:

(1) different levels of work

The original switch was working on the data link layer of the OSI/RM open architecture, that is, the second layer. At the beginning, the router was designed to work on the network layer of the OSI model. Because the switch operates on the second layer (data link layer) of OSI, its working principle is relatively simple, while the router works on the third layer (Network Layer) of OSI ), more protocol information can be obtained, and routers can make more intelligent forwarding decisions.

(2) Data Forwarding depends on different objects

A vswitch uses a physical address or a MAC address to determine the destination address for data forwarding. A vro uses the idnumber (IP address) of different networks to determine the data forwarding address. IP addresses are implemented in software and describe the network where the device is located. Sometimes these layer-3 addresses are also called protocol addresses or network addresses. The MAC address is usually provided by the hardware and allocated by the NIC manufacturer, and has been fixed to the NIC. Generally, it cannot be changed. The IP address is usually automatically assigned by the network administrator or the system.

(3) Traditional vswitches can only be divided into conflicting domains, but not broadcast domains. vrouters can be divided into broadcast domains.

The CIDR Block connected by the vswitch still belongs to the same broadcast domain. broadcast packets are transmitted across all CIDR blocks connected to the vswitch. In some cases, communication congestion and security vulnerabilities may occur. The CIDR blocks connected to the vro are allocated to different broadcast domains, and the broadcast data does not pass through the vro. Although vswitches above Layer 3 Have VLAN functions and can also be divided into broadcast domains, communication between subbroadcast domains is not allowed, and communication between them still requires routers.

(4) The router provides firewall services.

A vro only forwards data packets of a specific address. It does not support packet transmission through the routing protocol or unknown destination network, thus preventing broadcast storms.

The switch is generally used for the LAN-WAN connection, the switch belongs to the bridge, is the data link layer equipment, some switches can also realize the third layer of the exchange. A vro is used for Wan-WAN connections. It can resolve forwarding groups between different networks and act on the network layer. They only accept the input group from one line and then forward it to another line. These two lines may belong to different networks and adopt different protocols. In comparison, vro features more powerful than vswitches, but the speed is relatively slow and expensive. layer-3 vswitches have both the ability to forward packets at the wire speed of vswitches and the good control function of vrouters, therefore, it is widely used.

At present, I am personally using ADSL for many broadband access methods. Therefore, I will give a brief description of the access to ADSL. Most of the purchased ADSL cats have the routing function (in many cases, the routing function is blocked when the manufacturer leaves the factory, because the routing function is not enabled during Telecom installation and DHCP is enabled. Enable the ADSL routing function). If an individual accesses the Internet or a few computers pass through ADSL, you only need to purchase one or more hubs or switches if the computer is large. Please purchase a vswitch because the price difference between the hub and the vswitch is very small. There is no need to pursue high prices, because product homogeneity is very serious today, and there is no problem with my cheapest switch. We recommend that you purchase an eight-port service to meet the expansion requirements. The general price is about 100 yuan. Connect all the computers to the vswitch. The only thing to do is to insert the network cable of each machine into the interface of the switch and insert the cat network cable into the uplink interface. Then you can set the routing function and DHCP to share the internet.

After reading the above explanation, you should have some knowledge about vswitches, hubs, and vrouters. The current usage is mainly based on the combination of vswitches and vrouters, the specific combination method can be determined based on the specific network conditions and requirements.

Differences between vswitches and vrouters

"Exchange" is the most frequently used word on the network today. It can be applied on any occasions from the bridge to the ATM to the telephone system. It is hard to figure out what is the real exchange. In fact, the word exchange first appeared in the telephone system, specifically to achieve the exchange of voice signals between two different telephones, the device to complete this work is the telephone switch. Therefore, in terms of intention, exchange is only a technical concept, that is, to complete the forwarding of signals from the device entry to the exit. Therefore, any device that complies with this definition can be called an exchange device. It can be seen that "Exchange" is a widely used term. When it is used to describe the second layer of the data network, it actually refers to a bridge device; when it is used to describe the third-layer device of the data network, it also refers to a routing device. We often mention that an Ethernet switch is actually a multi-port L2 network device based on the bridge technology, it provides low-latency and Low-overhead channels for data frame forwarding from one port to another.
It can be seen that the core of the switch should have an exchange matrix to provide a channel for communication between any two ports, or a fast exchange bus, to send data frames received by any port from other ports. In actual devices, the function of the switching matrix is usually completed by a dedicated chip (ASIC. In addition, there is an important assumption in the design philosophy of the Ethernet switch, that is, the speed of the switching core is very fast, so that the normal large-volume data will not cause congestion. In other words, the exchange capability is infinite relative to the amount of information transmitted (on the contrary, the design idea of the ATM switch is that the exchange capability is limited to the amount of information transmitted ). Although the second layer Ethernet switch is developed based on a multi-port bridge, after all, the switch has more features, making it the best way to get more bandwidth, it also makes the network easier to manage.
A router is a group exchange device (or network layer Relay Device) in the network layer of the OSI protocol model. The basic function of a router is to transmit data (IP packets) to the correct network, including:
1. IP datagram forwarding, including path finding and transmission of the datagram;
2. subnet isolation to prevent broadcast storms;
3. Maintain the route table and exchange route information with other routers. This is the basis for IP packet forwarding.
4. IP datagram error handling and simple congestion control;
5. Filtering and accounting of IP datagram.
Vrouters of different regions have different roles.
On the backbone network, the main role of a router is routing selection. The router on the backbone network must know the path to all the lower-Layer Networks. This requires maintaining a large route table and responding to connection status changes as quickly as possible. A Router failure may cause serious information transmission problems.
In the regional network, the main role of the router is network connection and route selection, that is, to connect to the lower-layer grass-roots network units-the campus network, while responsible for data forwarding between the lower-Layer Networks.
Inside the campus network, the main role of a router is to separate subnets. In the early days, the basic unit of the Internet connection was LAN, where all hosts were in the same logical network. With the continuous expansion of the network scale, the LAN has evolved into a campus network composed of multiple subnets connected to the high-speed trunk and router. The subnet is logically independent, and the router is the only device that can separate them. It is responsible for packet forwarding and broadcast isolation between subnets, the vro on the border is responsible for connecting to the upper-layer network.

According to the OSI architecture, the hub belongs to the first layer of the OSI physical layer device, while the switch belongs to the second layer of the OSI data link layer device. This means that the hub only plays a role in synchronization, amplification, and shaping of data transmission. It cannot effectively process short frames and fragments in data transmission, and cannot guarantee the integrity and correctness of data transmission; the switch not only synchronizes, scales up, and shaping data transmission, but also filters short frames and fragments.

Difference between a HUB and a vswitch

In terms of working method, the hub is a broadcast mode, that is to say, when a port of the hub is working, all other ports are well-known to listen to the information, which is prone to broadcast storms. When the network is large, the network performance will be greatly affected. So how can this problem be avoided? The switch can play this role. When the switch works, only the request port and the destination port respond to each other without affecting other ports, then, the vswitch can isolate conflicting domains and effectively suppress the generation of broadcast storms.

From the bandwidth perspective, no matter how many ports the hub has, all ports share a bandwidth. At the same time, only two ports can transmit data, and other ports can only wait; at the same time, the hub can only work in half duplex mode. For a vswitch, each port has an exclusive bandwidth. When the two ports work, other ports are not affected, at the same time, the switch can not only work in half duplex mode, but also in full duplex mode.

ADSL
(Asyuncrical Digital Subscriber Line) is an asymmetric Digital user Line. It is a member of the xDSL family and is hailed as "express on the modern information highway" by Western countries ". In short, ADSL separates the low-frequency signal transmitted by ordinary telephone lines from the high-frequency signal. Less than Hz is used by telephone; higher than Hz is used by the Internet, that is, data and voice signals are transmitted separately on the same copper line, and data signals are not transmitted through telephone switches. In this way, high-speed transmission can be provided: uplink (from the user to the network) Low-speed transmission can reach 640 Kbps, and downlink (from the network to the user) high-speed transmission can reach 7 Mbps; in addition, accessing the Internet without affecting the normal use of the phone, which also means that when using ADSL to access the Internet, there is no need to pay another phone fee.
The protocols used by ADSL include PPPoE, PPPOVER, RFC1483 BRIDGE, and RFC1483 ROUTED. Currently, Guangzhou Telecom supports PPPoE.

I recommend vro

50-

To put it simply:
The Hub and the router are not the same thing. The Hub and vswitch have less functions. However, the four LAN ports of commonly used routers act as vswitches.
Hubs and switches are used for networking, and routers are used to connect networks of different levels. We often use vrouters to share the internet. Our commonly used vrouters cost-yuan.
If you want to set up a small peer network with four machines and want to share the broadband network, I will buy a router
(VroItself has the hub function, that is, the formation of LAN function, but because the built-in port is relatively small, so can only make up a small network), I used TP-link410, 460, very good settings, now there is another cheaper 402,
If you want to group A small peer network with more than four machines and want to share the internet, you 'd better buy a vro and add a vswitch, and the switch price is not expensive.
I have been talking about this for a long time. It may not be very scientific, but it is definitely experience.

 

 

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Hub is the hub
The router is used on the Internet.
Others are applied to lan.

 

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Let's see what you are doing. If your room only has one broadband access and you want more than two machines to access the Internet at the same time, you must buy a router, if only a few machines are connected to the game and you do not need to access the Internet, you can buy a switch.
The performance of a hub is worse than that of A vswitch, and the price is not much lower. We do not recommend that you purchase a hub.

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The earliest form of the hub network device is also known as the hub with 10 or MB. It is shared bandwidth shared by all port users.

The switch is upgraded by the hub. Generally, the bandwidth of each port is mb. The total internal bandwidth of the switch is the sum of the data volume of each port.

A router is an intermediate device between an internal switch or a hub and an external modem, which is equivalent to a translation role.

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Hub is a simple way to combine all the lines and then concentrate the signals on an online device. It seems like a power outlet is similar. Besides the hub function, a router, there are also IP routing,Automatic dialing, Software firewalls, and many other functions can also be considered as an upgraded version of the hub.

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As shown in the following figure: