What is an Internet Appliance?

Network equipment and components are physical entities connected to the network. There are many types of network equipment, and they are increasing every day. Basic network devices are: computers (whether they are personal computers or servers), hubs, switches, bridges, routers, gateways, network interface cards (NICs), wireless access points (WAP), printers and modems, fiber optic transceivers , Optical cable, etc.

Chinese name: Network equipment
Foreign name: network devices
Types of: Physical entity

Function: Connect to the network
Species: Hubs, switches, bridges
On behalf of: Repeater

Introduction to network equipment

Whether it is a local area network, a metropolitan area network, or a wide area network, it is usually physically composed of network connection devices and transmission media such as network cards, hubs, switches, routers, network cables, and RJ45 connectors. Network equipment includes repeaters, bridges, routers, gateways, firewalls, switches and other equipment.

Network device server

The server is the most important device on a computer network. A server refers to a device that runs corresponding application software in a network environment and provides users in the network with shared information resources and services. The composition of the server is basically similar to that of a microcomputer. There are processors, hard disks, memory, and system buses. However, the server is specially formulated for specific network applications. Therefore, the server and the microcomputer have a processing power, stability, reliability, There are great differences in scalability and manageability. Generally, servers have more processing power, more memory, and hard disk space than clients. The network operating system on the server can manage not only data on the network, but also users, user groups, security, and applications. ^[1]

The server is the backbone of the network and the core of information technology. It has the characteristics of high performance, high reliability, high availability, strong I / O throughput, large storage capacity, and strong networking and network management capabilities.

The server can adapt to a variety of different functions and different environments, and the classification standards have become diversified: divided by application level (entry level, work group level, department level, enterprise level), divided by processor architecture (X86 \ IA64 \ RISC), according to the instruction system used by the processor of the server (CISC \ RISC \ VLIW), by the use (general, dedicated), by the server chassis architecture (desktop server, rack server, Rack server, blade server) and so on.

Server selection:

1. The performance must be stable. In order to ensure the normal operation of the network, the selected server must first ensure stability. On the other hand, a stable server means saving maintenance costs for the company.

2. Ask enough guidelines.

3. Expansibility should be considered. In order to reduce the extra overhead brought by the update server and the impact on work, the server should have high scalability. The configuration can be adjusted in time to suit development.

4. Easy to operate and manage.

5. Meet special requirements.

6. The hardware matching is reasonable. In order to make the server run more efficiently, the performance of the internal accessories of the purchased server must be properly matched. ^[1]

Network equipment repeater

(Repeater)

Network equipment A repeater is the simplest device for LAN interconnection. It works at the physical layer of the OSI architecture. It receives and recognizes network signals, then regenerates the signals and sends them to other branches of the network. To ensure that the repeater can work correctly, the data packets and logical link protocols in each branch must first be the same. For example, between an 802.3 Ethernet LAN and an 802.5 Token Ring LAN, repeaters cannot make them communicate.

However, repeaters can be used to connect different physical media and transmit data packets across various physical media. Some multiport repeaters are much like multiport hubs in that they can connect different types of media.

Repeaters are the cheapest way to expand your network. When the purpose of expanding the network is to overcome the limits of distance and nodes, and the connected network branches will not generate too much data traffic, and the cost cannot be too high, you can consider choosing a repeater. The number of repeaters used to connect network branches is limited by the specific network architecture.

The repeater does not have isolation and filtering functions. It cannot block abnormal packets from one branch to another. This means that failure of one branch may affect every other network branch.

A hub is a repeater with multiple ports. Referred to as HUB

Network equipment bridge

(Bridge)

The bridge works at the data link layer of the OSI system. Therefore, the information of the layers above the data link layer of the OSI model has no effect on the bridge. So the understanding of the protocol depends on the respective computer.

The bridge contains the functions and features of the repeater, which can not only connect a variety of media, but also connect different physical branches, such as Ethernet and token network, which can transmit data packets in a larger range. The typical application of a bridge is to segment the local area network into subnets, thereby reducing the bottleneck of data transmission. Such a bridge is called a "local" bridge. The bridges used on the WAN are called "remote" bridges. Both types of bridges perform the same function, except that the network interfaces used are different.

The switch in life is the bridge.

Network equipment router

(Router)

The router works at the network layer in the OSI architecture, which means that it can exchange and route data packets on multiple networks. Routers achieve this by exchanging information for specific protocols in a relatively independent network. Compared with bridges, routers can not only

Filter and separate network traffic, connect network branches, and access more information in packets. And used to improve the transmission efficiency of data packets.

The routing table contains network addresses, connection information, path information, and sending costs.

Routers are slower than bridges and are mainly used for WAN or WAN-LAN interconnection.

Bridge Router (Brouter)

Brouter is a merger of bridges and routers.

Network equipment gateway

(Gateway) The purpose of the gateway to repackage information is to meet the requirements of the target environment.

Gateways can interconnect heterogeneous networks,

The gateway reads the data from an environment, strips the old protocol of the data, and then repackages it with the protocol of the target network.

A more common use of a gateway is to translate between a local computer and a minicomputer or mainframe.

A typical application for a gateway is a dedicated network server.

Network device firewall

(Firewall)

In network equipment, it refers to a hardware firewall.

Hardware firewall refers to putting the firewall program into the chip and executing these functions by the hardware, which can reduce the burden on the CPU and make routing more stable.

A hardware firewall is an important barrier to securing your internal network. Its security and stability are directly related to the security of the entire internal network. Therefore, the daily routine inspection is very important to ensure the security of the hardware firewall.

Many hidden dangers and faults in the system will appear before or after the outbreak. The task of routine inspection is to find these hidden dangers, and to locate the problem as far as possible to facilitate the solution of the problem.

Network equipment switch

Switching is a technology collectively referred to the requirements of transmitting information at both ends of the communication, using manual methods or equipment to automatically complete the information to be transmitted to the corresponding routes that meet the requirements.

A switch in the broad sense is a device that performs information exchange functions in a communication system. In the computer network system, the exchange concept is proposed to improve the shared working mode. The HUB hub we introduced before is a shared device. HUB itself cannot identify the destination address. When A host in the same local area network transmits data to B host, the data packets are transmitted in a broadcast manner on the network based on HUB. Each terminal determines whether to receive it by verifying the address information of the packet header. That is to say, in this working mode, only a group of data frames can be transmitted on the network at the same time. If a collision occurs, you must retry. This way is to share network bandwidth.

The switch has a high-bandwidth back bus and an internal switching matrix. All the ports of the switch are connected to this back bus. After the control circuit receives the data packet, the processing port will look up the address comparison table in the memory to determine the NIC (network card) of the destination MAC (the hardware address of the network card). On which port, the data packet is quickly transmitted to the destination port through the internal switching matrix. If the destination MAC does not exist, it is broadcast to all ports. After receiving the response from the port, the switch learns the new address and adds it to the internal MAC. Address table. Using a switch can also "segment" the network. By comparing the MAC address table, the switch allows only necessary network traffic to pass through the switch. The filtering and forwarding of the switch can effectively isolate broadcast storms, reduce the occurrence of error packets and error packets, and avoid sharing conflicts.

The switch can perform data transmission between multiple port pairs at the same time. Each port can be regarded as an independent network segment, and the network equipment connected to it can enjoy the full bandwidth alone, without the need to compete with other equipment. When node A sends data to node D, node B can send data to node C at the same time, and both transmissions enjoy the full bandwidth of the network and have their own virtual connection. If a 10Mbps Ethernet switch is used here, the total traffic of the switch at this time is equal to 2 × 10Mbps = 20Mbps, and when a 10Mbps shared HUB is used, the total traffic of a HUB will not exceed 10Mbps.

In short, a switch is a network device based on MAC address identification that can complete the function of encapsulating and forwarding packets. The switch can "learn" the MAC address and store it in the internal address table. By establishing a temporary exchange path between the initiator and the target receiver of the data frame, the data frame can reach the destination address directly from the source address.

Network equipment other

Personal computer: A typical personal computer is a desktop computer, workstation, or laptop owned by an individual user. The most common type of microcomputer is the personal computer, which is used in most organizations.

Server: A computer or other network device on the network that stores all necessary information and is dedicated to providing specific services. For example, a database server stores all data and software related to certain databases, allows other network devices to access them, and handles access to the database. A document server is a combination of a computer and a storage device that is dedicated to storing files on the server by any user on the network. A print server is a device that manages one or more printers, and a network server is a computer that manages network transmissions.

Network card: A network interface card (NIC) is an adapter that is attached to a computer or other network device and is used to connect the computer to the network. Each type of network interface card is designed for a specific type of network, such as Ethernet, token network, FDDI, or wireless local area network. The network interface card (NIC) operates using the protocol standards of the physical layer (layer 1) and the data link layer (layer 2). The network interface card (NIC) mainly defines the physical method for connecting with the network line and the framing method for transmitting binary data streams on the network. It also defines a control signal that provides a method of timing for data to be transmitted over the network.

Hub: A hub is the simplest network device. The computer is connected to the hub via a twisted pair. In the hub, data is forwarded to all ports, regardless of whether the system connected to the port is scheduled to receive the data. In addition to the port connected to the computer, even in a very cheap hub, there is a port designated as the upstream port, which is used to connect the hub to other hubs to form a larger network.

Modem: A modem is an access device that translates a computer's digital signals into analog signals that can be transmitted on a regular telephone line. The modem modulates the signal at the transmitting end and demodulates the signal at the receiving end. Many access methods cannot be separated from modems, such as 56k modems, ISDN, DSL, and so on. They can be internal devices plugged into system expansion slots; or external devices plugged into serial or USB ports; or PCMCIA boards for laptops; or devices designed for use in systems such as laptops. In addition, many laptops are equipped with integrated modems. Rack modems are also available for a wide range of modems, such as ISPs.

Network equipment supplier

As the saying goes: "Prevent the situation before it happens", network devices are like organs in various parts of our body, and each organ is healthy and normal. The same is true for the network. Only when network connection devices and transmission media such as network cards, hubs, switches, routers, network cables, and RJ45 connectors operate normally, the network will be unobstructed. We know how to maintain our physical fitness through exercise, hygiene, attention to safety, and regular physical examinations. So how should network equipment be maintained? The author believes that it is resistant to power outages, lightning strikes, static electricity, dust, electromagnetic interference, and moisture. Measures such as heat dissipation are indispensable. With the continuous expansion of the network scale, the number of devices that make up the network is expanding rapidly, and the types of devices are constantly being renovated. If these devices are not maintained daily and they are not regularly maintained, it will cause a lot of inexplicability over time. Failures, and these failures are highly hidden, which is not easy to find and makes you headache. If you encounter an unexpected situation, such as a thunder and lightning, if you don't usually take adequate protective measures, you may be reimbursed immediately. The so-called: "Do not burn incense usually, temporarily hold your feet", wait until the network performance is degraded and the network service is terminated, you have to hurriedly test each network device one by one, which will consume a lot of manpower and material resources, and it is difficult to short-term Accurately locate equipment failures that affect performance and services, at least delaying the normal work of the equipment, and severely causing equipment damage and major losses, so daily network equipment maintenance is an important point that cannot be ignored.

Network equipment anti-power-off

In the current situation of often insufficient power supply, it is a common phenomenon for the city power to implement power cuts on enterprises. Moreover, due to insufficient voltage during the power supply process, there may be intermittent and intermittent power supply. The power supply is suddenly high or low (the voltage is too low, such as (Below 150V; or too high, such as higher than 260V), and the often unstable power supply will cause routers, switches, servers and other equipment in the LAN to continue to work normally, which will affect the quality of Internet access. In the long run, this will greatly shorten the life of the equipment. Therefore, to ensure the "health" of network equipment, it is necessary to equip them with an excellent and stable UPS power system. The UPS power supply can solve problems such as power outages, lightning spikes, surges, frequency oscillations, voltage changes, voltage fluctuations, frequency drifts, voltage sags, pulse interference, and so on, and precision network equipment does not allow electricity to have Intermittent, so it is self-evident that a network center with servers, large switches, and routers as the core must be equipped with a UPS.

The protection god of network equipment UPS is simple to use but it is more coquettish. Scientific maintenance and maintenance will extend the life of UPS. Maintenance methods include: Try not to connect the inductive load. It should not be full load or excessive light load. The long-term full load condition will directly affect the life of the UPS. Generally, the load of online UPS should be controlled at 70% to 80%, and the load of backup UPS should be controlled at 60% to 70. %. In addition, it is necessary to protect the battery. Although it does not require maintenance on the surface, it is not well taken care of, and it will also cause problems. The battery is required to work in the environment of 0-30 ° C, and the efficiency is the highest at 25 ° C. Therefore, we must pay attention to the working environment of the UPS in winter and summer. If the temperature is high, the battery life will be shortened. If the temperature is low, the nominal delay will not be achieved. In addition, regular maintenance is required. If there is no blackout in the local area for a long time, the power must be interrupted artificially for three months on a regular basis to discharge the UPS with a load. Finally, the UPS should be placed in a well-ventilated place.

Lightning protection for network equipment

Minefields are not uncommon in China. Taking Guangzhou as an example, the average annual thunderstorm weather can reach 80.3 times, so there are many enterprises and owners of Internet cafes that are damaged due to lightning strikes. According to a survey by Qinuo engineers, 30% of network equipment failures are related to lightning strikes. Various data transmission lines (such as power lines, power lines, signal lines, cable lines, telephone lines, etc.) that enter and exit the building are exposed outside the protection area of the lightning protection device for a long time and are extremely vulnerable to the invasion of lightning. Without adequate lightning protection measures, the loss of network equipment affected by lightning will often be severe, which may directly cause the server, switch, HUB, network card and other equipment to be burned and the network to be paralyzed for a long time. Sometimes the induced voltage caused by a lightning strike is not enough to damage the network equipment at one time. Even if there was no network failure at that time, the long-term over-voltage impact on the network equipment can easily cause the aging of network equipment parts and make the life of the network equipment sharp Down, and old equipment is more vulnerable to damage, which seriously affects the stable performance of the network.

The lightning protection method of network equipment is to do a good job of grounding the equipment and install an effective lightning protection system. The first thing to do is to securely ground the network equipment, but also use wireless APs as signal bridges to reduce exposure. In addition, the network lightning protection system is roughly divided into a power lightning protection device and a network lightning protection device, which respectively protect the network power supply and the network signal system. For the protection of high-precision network equipment, it is necessary to set a power lightning arrester in front of their power input terminals. In this way, lightning overvoltage inrush waves coming along the power supply line can be protected. The switch's lightning protection can enhance the lightning protection design on the RJ45 signal port of the switch. The upgraded switch's RJ45 signal port has 6kV common mode surge protection and 2kV common mode common surge protection (surge protection is lightning protection). The upgraded version of the "Youken" switch has three times the lightning protection function compared to ordinary ones, and the network lightning protection device is roughly divided into air gap interval type and semiconductor type.

Most of the network lightning arresters on the market use different components to form a three-stage method. The first stage is primary protected by a large-flow gas discharge tube to reduce the residual voltage and discharge most of the lightning current into the ground. The second stage uses Decoupling resistor or PTC for blocking delay and voltage division to meet the characteristics requirements of the first and third stage components; the third stage uses TVS for fine protection to further reduce the residual voltage and make it reach the equipment's safe voltage requirements . For example: JaRa 3207 terminal equipment lightning arrester, Pingyu SJ05FF4H layered lightning arrester, ASP RJ45-XE series backbone network lightning arrester are all good choices.

Network equipment anti-static

Everyone knows that ElectroStatic Discharge (ESD) can easily cause damage to the hardware of computers and peripherals. Therefore, it is also difficult for network equipment to escape static doom. Static electricity is ubiquitous. The lightning in nature mentioned above is a typical ESD phenomenon in a strong convective climate, but ESD phenomena in daily life also occur frequently. With the advancement of network equipment chip technology, the speed and function of the chip have been improved, but the chip has become more fragile. A not too high ESD voltage can break down the transistor, and a not too high ESD current can blow the connection. Since static electricity is the invisible killer of network equipment, then we usually need to effectively maintain and maintain network equipment and take corrective measures.

(1) All parts of network equipment should maintain good contact and have reliable grounding. Shield and isolate the key equipment susceptible to ESD.

(2) Humidifiers should be used in autumn and winter in the northern region to maintain a certain humidity in the indoor air to prevent a large amount of static electricity from accumulating on equipment, furniture and the body.

(3) When the equipment needs to be opened for maintenance, it is standard practice to wear anti-static gloves, but for the general user, the power can be cut off first.

Put your hand on the wall or water pipe for a while to discharge your static electricity. The author himself encountered such a case that the router setting parameters were lost due to static electricity. My company's local area network uses ADSL pppoe to access and share Internet access with routers, and all computers are connected to the router through switches. It has been used for nearly two years and has always behaved normally, but after the winter, router settings parameters are always lost and the Checking the Internet for faults left and right, but no results were found. Later, it was found that all network equipment was placed in one place and interlaced with the computer's connection lines. So I immediately noticed that it might be caused by static electricity, and immediately put the router and switch to the On one side, clean it up after power failure, re-fix and install it, and solve the problem.

Network equipment protected against dust

The harmfulness of dust cannot be underestimated. Therefore, the dust removal of routers, switches, and other network equipment is also very important. If there is too much dust, and the dust is not cleaned in time, your network will have some weird failures, and even the chips inside the equipment will be burnt. If you think the harm that the author said to routers and switches is "extremely alarmist", then you believe the network card. When the computer is working, it will generate a certain electrostatic field and magnetic field, and the suction generated by the power supply and the CPU fan will suck the dust particles suspended in the air into the chassis and stay on the host, graphics card and network card. If it is not cleaned regularly, more dust will accumulate. In severe cases, it will even reduce the insulation performance of the circuit board, causing short circuits, poor contact, mildew, and hardware failure. Therefore, you should regularly open the case, and use a clean soft cloth, a small hair brush that is not easy to shed hair, and a blower to remove the components inside the case, including the network card.

If the network card has not been cleaned for a long time, the accumulated dust is too much, and the air is humid, it will cause a short circuit between the pins of the chip on the network card, and it will not be able to exchange data with the motherboard, and many strange things will appear. Network problems, serious network cards will be reimbursed. In addition, other network equipment is also the same. It is necessary to always remove dust, such as crystal heads, routers, switch interfaces, etc., where maintenance is easy. If you want to remove the dust from the router and switch panel, you can wipe it with a soft damp cloth and a neutral high-concentration washing solution. After cleaning, you do not need to wash with water. The washing solution left on it will help isolate the dust. Just wipe with a moist towel.

Network equipment anti-electromagnetic interference

Data transmission in the network cable will be affected in many ways. Electromagnetic interference is one of the main aspects, so when we conduct wiring, the network cable should avoid the electromagnetic interference area. After the cable is laid, it is necessary to perform maintenance. In addition to avoiding frequent bending and pulling of the network cable and using heavy objects, such as motors, speakers, and radio transceivers, keep them away from the network cable and network equipment to ensure that network signals are not protected. Influence of external radiation. In addition, the interference of the network card in the computer will often occur, because the network card and the graphics card are too close to produce interference. When the interference is not serious, the network card can barely work, and the user often cannot feel it when the data traffic is not large, but when communicating with a large amount of data, a "Insufficient network resource" prompt will appear under Windows98, causing the machine to crash.

I have a friend. After installing ADSL at home, the Internet speed is much faster, but it is very unstable, and often disconnects. The operating system has been reinstalled, and devices such as network cards have been replaced, and possible software problems have been ruled out, but the situation has not improved. Later one day at noon, a friend noticed that the speed of the Internet had suddenly increased sharply, and there was no disconnection. However, at night, he returned to his old style. Later, I checked the line carefully, and found that there was a transformer next to the line that didn't work at noon. It seems that the problem is caused by the interference caused by the transformer. Therefore, the external circuit was extended in a roundabout way, bypassing the transformer, and using a super-type five shielded twisted pair with super shielding function. As a result, the problem was solved and the Internet speed was very stable.

Network equipment moisture-proof

Because network devices such as routers, switches, and hubs are made up of many compact electronic components, it is important to keep them in a dry place to prevent short circuits caused by humidity. In particular, network cables and telephone lines are prone to mildew and oxidation at the crystal joints in an excessively humid environment, resulting in poor contact, which will reduce the Internet access speed. In addition, since the chip of the device emits a lot of heat during the operation of the network device, if it is not released in time, it may cause the chip to overheat and work abnormally. Therefore, it is best to place the router, switch, hub, etc. in a cool and ventilated place. s position. I have a MM friend who covers the router with a decorative cloth all year round and asks why he did it. There is also a buddy. Contrary to that MM, it is extremely dirty and messy. On the desktop, a lot of books, sundries, etc. surround the router densely and densely.

Summary of network equipment

In fact, the maintenance of network equipment is the same as many IT products. The six defenses mentioned above must be paid attention to. Of course, there are other details that are not mentioned above, such as anti-rat, waterproof, anti-fall and so on. However, in general, as long as everyone stays a little more attentive, works harder, and takes good care of these network equipment, they can guarantee the normal operation of the network system of your home, your company, and your Internet cafe. ^[2]