Welcome to my “Wide area networks.”
A wide area network is a network of computer devices that are distributed over a wider area network (such as a city, a country, or even the whole world), often operated and managed by postal utilities, beyond the departments and the local area, to the general public Provides the use of a remote public information communication network, also sometimes referred to as a remote network.
WAN communication subnet can make use of the public packet-switched network, satellite communication network and wireless packet-switched network, it will be distributed in different regions of the LAN or computer systems interconnection, to achieve the purpose of resource sharing.
WAN structure
The structure of the WAN is divided into communication subnets and resource subnets, as shown in Figure 1 (WAN structure diagram).
WAN communication subnet can make use of the public packet-switched network, satellite communication network and wireless packet-switched network, it will be distributed in different regions of the LAN or computer systems interconnection, to achieve the purpose of resource sharing.
WAN structure
The structure of the WAN is divided into communication subnets and resource subnets, as shown in Figure 1 (WAN structure diagram).
WAN has divided into communication subnet and resource subnet two parts, mainly by a number of node switches and links connecting these switches. The node switch performs the function of storing and forwarding the packet. WAN link is generally divided into transmission trunk and end-user lines, according to the different types of end-user lines and wide area networks, there are a variety of access to the WAN technology and provide a variety of interface standards.
WAN characteristics
1, the main provider of communication-oriented services to support users to use computers for the long-distance exchange of information.
2, covering a wide range of communication distance, the factors that need to be considered more, such as media costs, line redundancy, the use of media bandwidth and error handling.
3. The telecommunications department or company shall be responsible for the formation, management, and maintenance of the network and shall provide the whole society with paid services, traffic statistics and accounting issues for communication.
Compared with the coverage of the smaller LAN, WAN is characterized by:
1, covering a wide range, up to thousands of kilometers or even the world.
2, there is no fixed WAN topology.
3, WAN usually use high-speed optical fiber as the transmission medium.
4, the LAN can be used as WAN end users and WAN connections.
5, wide area network backbone bandwidth, but to provide a single end-user bandwidth is small.
6, data transmission distance, often go through multiple WAN equipment forwarding, longer delay.
7, WAN management, maintenance difficulties.
The type of WAN
WAN can be divided into public transport networks, private transport networks, and wireless transport networks.
1, public transport network: generally established by the government telecommunications sector, management and control, transmission and switching devices within the network can provide (or rent) to any department and unit.
Public transport networks can generally be divided into two categories:
1) circuit switched network. Including the public switched telephone network (PSTN) and Integrated Services Digital Network (ISDN);
2) packet switched network. Mainly include X.25 packet switched network, frame relay and switched multi-megabit data service (SMDS).
2, Dedicated transmission network: It is a private communication network established, used, controlled and maintained by an organization or a group. A private network must have its own communication and switching equipment, at least, it can set up its own line service, can also be leased to the public network or other private networks.
The dedicated transmission network is mainly digital data network (DDN). The DDN establishes a permanent, dedicated digital channel between the two endpoints. It is characterized by the leased private line, the user exclusive the bandwidth of the line.
3, wireless transmission network: mainly mobile wireless network, typically GSM and GPRS technology.
In our country, for example, the wide area network includes the following types of communication networks:
1, the public telephone network. Telephone network transmission of data, the user terminal from the connection to cut off, to take up a line, so-called circuit-switched mode, the charges in accordance with the user occupy the line time to decide. Before the popularity of data networks, the circuit switching mode is the most important means of data transmission.
2, the public packet switched data network. Packet-switched data network will be divided into "group" of information, according to the provisions of the path by the sender will be grouped information transmitted to the receiver, the data packet can work in the sending terminal can also be carried out in the switch. Each set of information contains an "address" for the purpose of the message. Packet-switched networks can take different paths to different parts of the message for the most efficient use of the communication network. At the receiving point, various data sets must be classified, monitored, and reassembled.
3, digital data network. It is the use of optical fiber (or digital microwave and satellite) digital circuits and digital cross-connect equipment consisting of the digital data service network, mainly to provide users with permanent, semi-permanent rental business. Digital data network can be timed or regularly scheduled according to the needs of a dedicated line can both call and send the fax, you can also send data, and the transmission of high quality.
WAN characteristics
1, the main provider of communication-oriented services to support users to use computers for the long-distance exchange of information.
2, covering a wide range of communication distance, the factors that need to be considered more, such as media costs, line redundancy, the use of media bandwidth and error handling.
3. The telecommunications department or company shall be responsible for the formation, management, and maintenance of the network and shall provide the whole society with paid services, traffic statistics and accounting issues for communication.
Compared with the coverage of the smaller LAN, WAN is characterized by:
1, covering a wide range, up to thousands of kilometers or even the world.
2, there is no fixed WAN topology.
3, WAN usually use high-speed optical fiber as the transmission medium.
4, the LAN can be used as WAN end users and WAN connections.
5, wide area network backbone bandwidth, but to provide a single end-user bandwidth is small.
6, data transmission distance, often go through multiple WAN equipment forwarding, longer delay.
7, WAN management, maintenance difficulties.
The type of WAN
WAN can be divided into public transport networks, private transport networks, and wireless transport networks.
1, public transport network: generally established by the government telecommunications sector, management and control, transmission and switching devices within the network can provide (or rent) to any department and unit.
Public transport networks can generally be divided into two categories:
1) circuit switched network. Including the public switched telephone network (PSTN) and Integrated Services Digital Network (ISDN);
2) packet switched network. Mainly include X.25 packet switched network, frame relay and switched multi-megabit data service (SMDS).
2, Dedicated transmission network: It is a private communication network established, used, controlled and maintained by an organization or a group. A private network must have its own communication and switching equipment, at least, it can set up its own line service, can also be leased to the public network or other private networks.
The dedicated transmission network is mainly digital data network (DDN). The DDN establishes a permanent, dedicated digital channel between the two endpoints. It is characterized by the leased private line, the user exclusive the bandwidth of the line.
3, wireless transmission network: mainly mobile wireless network, typically GSM and GPRS technology.
In our country, for example, the wide area network includes the following types of communication networks:
1, the public telephone network. Telephone network transmission of data, the user terminal from the connection to cut off, to take up a line, so-called circuit-switched mode, the charges in accordance with the user occupy the line time to decide. Before the popularity of data networks, the circuit switching mode is the most important means of data transmission.
2, the public packet switched data network. Packet-switched data network will be divided into "group" of information, according to the provisions of the path by the sender will be grouped information transmitted to the receiver, the data packet can work in the sending terminal can also be carried out in the switch. Each set of information contains an "address" for the purpose of the message. Packet-switched networks can take different paths to different parts of the message for the most efficient use of the communication network. At the receiving point, various data sets must be classified, monitored, and reassembled.
3, digital data network. It is the use of optical fiber (or digital microwave and satellite) digital circuits and digital cross-connect equipment consisting of the digital data service network, mainly to provide users with permanent, semi-permanent rental business. Digital data network can be timed or regularly scheduled according to the needs of a dedicated line can both call and send the fax, you can also send data, and the transmission of high quality.
Communication subnet is the part responsible for data communication in the computer network. The communication subnet is composed of communication control processor, communication line, and other devices. The communication transmission medium can be twisted pair, coaxial cable, radio communication, microwave, optical fiber, etc.
Communication subnet overview
(A) the demand factor
Depends on the distance between the resource node and the user node that uses the resource and the medium of transmission.
(1) In the case of direct communication, the data communication is directly completed by the low-level interface circuits on the two nodes, and there is no need to construct a communication subnet. In this case, the computer network has only a resource subnet.
(2) When the distance is far, the maximum distance of the transmission medium without relay transmission is the distance that the communication subnet needs to exist.
(3) Communication subnet is an integral part of the modern computer network.
(B) research content
(1) How to construct nodes and paths of communication subnet
(2) the source of the resource subnet information accurately and quickly transmitted to the destination.
(C) the role
(1) The data on the source host will be delivered to the destination host through transit transmission.
(2) The object of the communication subnet service is the host in the end system.
Communication subnet tasks
The guarantee is that the data sent from the network interface of the host of the source node is sent to the network interface of the host of the sink node, that is to say, the direct object of each service of the communication subnet is the network interface of the two host systems on the resource subnet.
Communication Subnet To complete the work:
(A) connectivity nodes
(1) The nodes that are in communication with each other for storing and using resources include the mechanical communication of communication media, the electrical connectivity of electrical communication signals, and the distribution of data link connectivity over transmission data channels.
(2) The connectivity of nodes is achieved through the two-in-one connection between the communication subnet nodes.
(B) point by point data transmission
(1) Realize the reliable transmission of data of adjacent nodes on the basis of connectivity.
(2) The data transmission of several adjacent nodes constitutes the transmission of the entire path from the source to the destination. This path refers to the channel used to transmit information data.
(3) The communication subnet is to allocate and use transmission media resources on the channel basis.
(C) to determine the transmission path
(1) When there are multiple paths between the source and the destination, find a current best transmission path.
(2) The best path can be the fastest path, the cheapest path, and the shortest path between source and sink. It can also be the path that allows the network to be in the best running state, the fairest use of network resources, and the most efficient use of network resources.
(Iv) Monitor the communication process
(1) In order to ensure the reliable transmission of information data in the communication subnet, the problems that may occur in the data transmission process must be monitored and dealt with in time to ensure the smooth communication subnet.
(2) Problems that may arise in the network include line interruption, node congestion, transmission distance too far, transmission time-consuming and so on.
Communication subnet overview
(A) the demand factor
Depends on the distance between the resource node and the user node that uses the resource and the medium of transmission.
(1) In the case of direct communication, the data communication is directly completed by the low-level interface circuits on the two nodes, and there is no need to construct a communication subnet. In this case, the computer network has only a resource subnet.
(2) When the distance is far, the maximum distance of the transmission medium without relay transmission is the distance that the communication subnet needs to exist.
(3) Communication subnet is an integral part of the modern computer network.
(B) research content
(1) How to construct nodes and paths of communication subnet
(2) the source of the resource subnet information accurately and quickly transmitted to the destination.
(C) the role
(1) The data on the source host will be delivered to the destination host through transit transmission.
(2) The object of the communication subnet service is the host in the end system.
Communication subnet tasks
The guarantee is that the data sent from the network interface of the host of the source node is sent to the network interface of the host of the sink node, that is to say, the direct object of each service of the communication subnet is the network interface of the two host systems on the resource subnet.
Communication Subnet To complete the work:
(A) connectivity nodes
(1) The nodes that are in communication with each other for storing and using resources include the mechanical communication of communication media, the electrical connectivity of electrical communication signals, and the distribution of data link connectivity over transmission data channels.
(2) The connectivity of nodes is achieved through the two-in-one connection between the communication subnet nodes.
(B) point by point data transmission
(1) Realize the reliable transmission of data of adjacent nodes on the basis of connectivity.
(2) The data transmission of several adjacent nodes constitutes the transmission of the entire path from the source to the destination. This path refers to the channel used to transmit information data.
(3) The communication subnet is to allocate and use transmission media resources on the channel basis.
(C) to determine the transmission path
(1) When there are multiple paths between the source and the destination, find a current best transmission path.
(2) The best path can be the fastest path, the cheapest path, and the shortest path between source and sink. It can also be the path that allows the network to be in the best running state, the fairest use of network resources, and the most efficient use of network resources.
(Iv) Monitor the communication process
(1) In order to ensure the reliable transmission of information data in the communication subnet, the problems that may occur in the data transmission process must be monitored and dealt with in time to ensure the smooth communication subnet.
(2) Problems that may arise in the network include line interruption, node congestion, transmission distance too far, transmission time-consuming and so on.
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