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Hello everyone! Today I will share with you the related issues of LAN / MAN / WAN.

1. Basic concept of local area network (LAN)

Definition of local area network: LAN is a communication network that interconnects various communication devices in a small area.

There are three main technologies that determine the characteristics of a local area network:

1), the transmission medium used to transmit data;

2) . Topological structure for connecting various devices;

3) Medium access method for sharing resources.

These three technologies largely determine the type of transmitted data, network response time, throughput and utilization, and various network characteristics such as network applications. The most important of these is the media access control method, which has a very important impact on the characteristics of the network.

Typical characteristics of LAN: high data rate (0.1M ~ 100Mbps), short distance (0.1km ~ 25km), low bit error rate (10-8 ~ 10-11).

The protocol structure of LAN includes physical layer, data link layer and network layer. Since there is no routing problem in the local area network, the network layer is generally not set up separately; because the medium access control of the LAN is more complicated, the data link layer is divided into the logical link control sublayer and the medium access control sublayer.

The local area network includes: Ethernet, tag ring Network, marked bus network, Fast Ethernet, switched LAN, full-duplex Ethernet, Gigabit Ethernet, ATM LAN, wireless LAN.

The common ones are: Ethernet, Fast Ethernet, full-duplex Ethernet, switching local area network. The first two use the CSMA/CD (Carrier Sense Multiple Access/Collision Detection) media access method, the switched LAN uses the switching technology, full-duplex Ethernet runs between switches, and the switching Full-duplex between the switch and the server is a link feature that works with the switch. It is the data stream that flows in both directions in the link at the same time. Not all transceivers support its full-duplex function.

Full-duplex efficiency Depends on the type of local communication. Full duplex can theoretically increase throughput by 100% if the communication between sending and receiving is balanced. If it is unbalanced, the efficiency will be reduced. Theoretically, full-duplex performance can be greater than 100%, because full-duplex links have no collisions, and the efficiency in each direction is higher than that of shared-media links.

2. Basic concept of MAN

Metropolitan Area Network (MAN) is a computer communication network established within a city, referred to as MAN. This was proposed on the basis of the development of LAN in the late 1980s. It has many similarities with LAN in technology, but it is quite different from Wide Area Network (WAN).

The transmission medium of MAN mainly adopts optical cable, and the transmission rate is 100 Mbit /sec or more. All networked devices are connected to the media through a dedicated connection device, but the media access control is different from the LAN in the implementation method.

An important use of MAN is to be used as a backbone network, through which hosts located in different locations in the same city , database, and LAN are connected to each other, which is similar to the role of WAN, but there is a big difference between the two in terms of implementation methods and performance. MAN is not only used for computer communication, but also can be used to transmit voice, image and other information, becoming a communication network for comprehensive utilization, but it belongs to the category of computer communication network, which is different from integrated service communication network (ISDN).

3. Basic concept of wide area network (WAN)

Wide area network (Wide Area Network) is a computer communication network established in a wide geographical range, referred to as WAN, and its scope can go beyond cities and countries to the whole world, so the requirements and complexity of communication are different. Relatively high.

WAN consists of two parts: the communication subnet and the resource subnet: the communication subnet is actually a data network, which can be a private network (switching network or non-switching network) or a public network (switching network) ; The resource subsystem is a variety of computers, terminals, databases, etc. connected to the Internet. This not only refers to hardware, but also includes software and data resources.

In practical applications, LAN can be interconnected with WAN, or connected with WAN in other locations through WAN, and then LAN becomes an end system on WAN.

Wide area network is used for communication The transmission device is generally provided by the company or the telecommunications department. Interconnection mainly adopts public network and private network. If the number of connections is limited, the requirements are not fixed, and the versatility is good, you can choose public data network or value-added network; The network is good.

The realization of WAN is carried out according to the corresponding protocol of a certain network architecture. In order to realize the interconnection and interoperability of different systems, an open system interconnection must be established. The reference model and the corresponding series of international standard protocols play an important guiding role in the realization, establishment and application of WAN.

4. The difference between LAN/MAN and WAN.

Local area network (LoxalAreaNetwork, LAN) refers to a computer network composed of interconnected computers in office buildings or campuses within a range of several hundred meters to more than ten kilometers. Computer local area networks are widely used to connect personal computers or workstations in campuses, factories, and institutions to facilitate sharing of resources (such as printers) and data communication between personal computers or workstations. MetropolitanAreaNetwork (MAN) The technology adopted is basically similar to that of the local area network, but the scale is larger.

A MAN can cover not only several office buildings not far away, but also a city; it can be either a private network or a public network. The land network of the city can not only support data and voice transmission, but also can be connected with cable TV. The metropolitan area network generally only includes one or two cables, and there is no switching equipment, so its design is relatively simple. A wide area network (WidoAreaNetwork, WAN) usually spans a large physical range, such as a country. The wide area network contains many collections of machines used to run user applications. We usually call these machines hosts; connecting these hosts together is the communication subnet (communication subnet). The task of the communication subnet is to transmit messages between hosts. Separating the subnet of the pure communication part of the computer network from the host computer of the application part can greatly simplify the design of the network.

	LAN	MAN	WAN
Acronym	Local Area Network	Metropolitan Area Network	Wide Area Network
Physical Area	LANs span a physically limited area, generally less than two to three kilometers.	MANs span the area of a township.	WANs span entire countries. They operate over the international telephone network, where distances are great.
Data rate	LANs provide high data rate communication (usually several Gbps).	MANs provide high data rate communication.	The data rate is generally less (usually below 1 Mbps).
Media	Communication is over inexpensive media such as coaxial cable or twisted pair.	Communication is over moderately inexpensive media (generally an installed CATV system using coaxial cable).	Communication is over telephone lines, microwave links, or satellites.
Ownership	LANs are usually owned by the user.	MANs are usually owned by cable television companies.	WANs are usually owned by licensed or government agencies.
Reliability	LANs are more reliable.	Reliability is between that of LAN and WAN.	WANs are less reliable.
Resource sharing	LANs permit users to have access to many common hardware and software resources.	MANs permit users to have access to hardware and software resources.	WANs permit users to have access to software resources only.
Subnet	In the case of a LAN, the cable and the hosts form the network. There is no subnet.	In the case of a MAN, the cable and the hosts form the network. There is no subnet.	In the context of WAN, subnet refers to the collection of routers and transmission lines owned by the network operator. The hosts are not part of the subnet.
Type of network	LANs are broadcast networks because all the hosts share a single transmission medium.	MANs are broadcast networks.	WANs are point-to-point networks because all the hosts do not share a single transmission medium.
Medium access	An arbitration mechanism is needed to resolve conflicts when two or more machines want to transmit.	An arbitration mechanism is needed.	An arbitration mechanism is not needed. Instead, the switching function is used for interconnecting computers compared to LANs.

 

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