A set of network devices (computer, printer and ...) which use a method of communication (cable, radio waves, satellite) and to share physical resources (printers) and share logical resources (files) to each are connected. Networks can be linked together and also included are the following networks.
Category Tfsym networks
. Computer networks based on different components should be divided. Continues to divide some of the most common reference is available.
Divided according to type of task
Computer in their respective duties according to two main groups: service providers (Servers) and clients (Clients) should be divided. Computers to other computers on the network services and offer services, are called servers. Computers and services offered by service providers they use, are called the client. Network Client-Server, a computer network can also server as well as the client, duty to playing.
Networks Peer-To-Peer, a computer can also server as well as playing duties to the client.
A LAN network in the simplest case consists of the following components:
Two personal computers. A network can contain several hundred computer. At least one computer as the server must be specified. (If the network is the type of Client-Server). Server, the computer core operating system will be installed on it.
A number of network card (NIC) for each device. Network card which is cards like modems and sound for the computer is used. Responsible for the network card to receive, transfer, organize and store temporary data during network. In order to perform these tasks with processor network cards, memory, and are crossing their own.
Divided based on topology
Geometric model used for connecting computers, called topology. Topology selected for implementation of networks, an important factor in order to detect and resolve network will make the error. Select a particular topology can not be transferred without contact with the environment and methods of use of the line is raised. Type of topology choice for connecting computers to each other directly, "the type of transmission medium and methods of use affects the line. According to the direct effect of choice in the type of cabling topology and its associated costs, and must accurately reflect the choosing a network topology efforts appointment. different factors to select an optimal topology is discussed. The most important of these factors is as follows:
- Cost. Any transmission medium that is selected for the LAN network, the network installation process must end in a building should be implemented. These operations a long process to install the appropriate channels to cable and cable crossing is in the building. Ideally, cabling and must establish appropriate channels prior to capturing and using the building is done. However, the cost of installing the network must be optimized.
- Flexibility. One advantage of network LAN, data processing ability and the extent and distribution of nodes is a medium. Thus, computing power and system resources available to all users will be. Offices will change everything. (Office supplies, room and ...). Topology chosen must allow easy configuration changes in the network provide. For example, "circuit from point to point or other transfer to create a new station in the network do.
Three types of LAN topology commonly used are:
BUS
STAR
RING
BUS Topology
One of the most common topology for implementation of LAN is. In the above model of a cable as the main backbone network and all computers used in the network (server, client) are connected to it.
BUS Topology benefits
Low cable length. Because of a transmission line to connect all computers in the topology of these little cable is used. The above post makes low cost installation and facilities needed to support network will be.
Simple structure. BUS topology has a simple structure. In the above model, only "a cable used for data transfer.
Easy to develop. A new computer can easily spot the network added. If the addition of more stations in a segment, such amplifiers can be used to name Repeater.
BUS topology disadvantages
Difficulty troubleshooting. Although simple in Tvyvlvzhy BUS possible pitfalls and reduce, but in case of error will not be easy to discover. Topology of the networks that utilize the above, each node in the network control has not centralism must in case of error points to a lot of error detection and investigation should be viewed.
Error is difficult to isolate. If a computer is in trouble in the above topology, the local computer must be connected to the network that has made troubleshooting. In special cases, a node can be separated from the network. Haltykh difficulty in transport medium, all of a segment must be from outside the network.
Nature is Iterators. In the uplink for the development of networks Iterators are used, may also be changes to the network structure. Involves applying the above subject and add more cable connections for the network.
STAR Topology
In this type of topology as it is clear from the name of a model similar to "star" is used. In this model, all the computers on the network, usually "a special device called a" hub "will be attached.
STAR Topology benefits
Simple network service. STAR topology includes a number of connection points is a central point. Attribute these changes in structure and service network makes it easy.
Ykdstgah any connection. Connection points in the network inherently "are prone to problems. The STAR topology forms a connection, causing the line of departure and debugging network and service lines is mentioned. These operations affect the performance of other computers on the network will not.
Central control and troubleshooting. According to the central point of this issue directly "to each station on the network is connected, bugs and discrepancies in the network will be easily diagnosed and were inhibited.
Simple access methods. Each connection consists of a central point in the network and has a side knot. In this case trying to achieve transmission medium to send and receive information with a simple algorithm will be.
STAR topology disadvantages
Cable being too long. Because direct connection to each node center point, plenty of cable is used. Given that the cost to all network cables, is low density in cable channel for drawing and installation issues Pshtybny they considerably increase the costs.
The problem of development. Adding a new node requires a network connection point is central to the new node. Although at the time of cabling provision for development will be considered, but in some cases, such as when a large length of cable was needed, or connect a set of nodes unpredictable primary problem with network development will face.
Dependence on the central point. If the central point (hub) is in the network fails, the whole network will be useless.
RING topology
In this type of a ring topology as all computers are linked together. All computers on the network (server, client) as a cable that has a closed circle, are connected. Each node in the above model in two and only two adjacent neighbors is connected. Information received from adjacent nodes and are sent to the next node. Thus the data only in one direction and transfer the station to other stations are found.
RING topology benefits
Low cable length. The cable length used in this model is comparable to the BUS topology not take long in a little. These features reduce the number of connections (connectors) and the coefficient of trust in the network to the network will increase.
Require special space for the cabling will be ramifications. Because of the use of a cable to connect each node to its neighbor nodes, assign to specific places will be necessary cabling.
Suitable for optical fiber. Using fiber optic rate increase data speed network. Because in the above topology data traffic in one direction, the optical fiber can be used to transport medium. If you want to set any part of a type Azshbkh cable as transmission medium used. For example, "the administrative environment of the model factory of copper and fiber optic medium used.
RING topology disadvantages
A bug causes problems in all network nodes are. In case of error in a node, all network problems will be encountered. And as long outside the network node is not defective, no data traffic on the network can not be found.
Debugging is difficult. Update Error in one node can affect all the other nodes are. Troubleshooting should be to review several nodes to the desired node is found.
Changes in network structure is difficult. During development or modification geographical areas covered by the network, due to cyclic nature of the network will create problems.
Topology on the type of access affects. Each node in the network has a responsibility to pass that data has been received from adjacent nodes. Before a node can send its data to, must be to ensure that the environment can be accessed for transmission.
Divided based on geography field covered.
Computer network according to the geographical areas covered are divided into three groups:
Local network (small) LAN
Average network MAN
WAN wide network
Network LAN. Geographical areas by the type of networks are covered, such a small environment is an office building. This type of network features are:
Ability to send high-speed data
Distance constraints
Ability to use cheap communications medium such as telephone lines to send data
Lower error rates in the sending data according to the limited space
Network MAN. Geographical areas by this type of networks are covered, the extent of a town or city. Characteristics of this type of networks is as follows:
More complexity than the local network
Ability to send images and sound
Capability of linking several networks
Network WAN. Geographical areas by this type of networks are covered, the extent and size of the country and continent. Attribute this type of networks is as follows:
Ability to send information between countries and continents
Linking capabilities of LAN
Low speed to post information of LAN
High error rate considering the extensive area covered
Cable Network
Local cable networks as a medium of transmission and to send information is used. Azchndyn type LAN cable is used. In some cases may be merely a network of "a type of cable used and given the current situation of several types of cable be used. The type of cable chosen for a network of different factors, including: network topologies, protocols and network size will depend on found. aware of the unique characteristics and different characteristics of each cable and each of their impact on other network properties, in order to design and implement a highly successful networking is required.
Cable Unshielded Twisted pair) UTP)
The most common type of cable that is used in data transmission, cable are twisted together. These cables have two wires together was complicated than the earth has both a Ampdansh are equal. Thus the possibility of taking effect of this type of cable adjacent cables or other external sources will be reduced. Wires twisted together with two different models: Shielded (coated) and Unshielded (without covering) are. STP Cable UTP cable to the far more common and most local networks are used. Quality varied UTP cables and wires used for regular phones to high-speed cable is included. Cable has four pairs of wire and placed within a crown fall. Each paired with a certain number of screws Tabandh (in inch units) to the effectiveness of couples and other electrical devices Yasayr reduced.
UTP cables have been numerous standards in groups (Categories) are divided into different:
Type
Application
Cat 1 only audio (telephone cable)
Cat 2 data rate 4 Mbps
Cat 3 data rate 10 Mbps
Cat 4 Data rate 20 Mbps
Cat 5 data rate 100 Mbps
Benefits cables twisted together:
Simplicity and easy installation
Appropriate flexibility
With low weight and are easily convoluted.
Disadvantages cables twisted together:
Frequency attenuation
Without the use of Iterators, the carry signals over long distances are not.
Low bandwidth
Admission because of heavy electrical interference in the environment are not taken Bkhdmt.
Standard connectors for cable UTP, RJ-45 type is. These connectors similar to telephone connectors (RJ-11) is. Each of these connector pins must be configured properly. (RJ: Registered Jack)
Coaxial cable
One of the most important transmission medium in telecommunications and coaxial cable is coaxial. This type of cable in 1936 to deliver news and information have been used Dnyar. In this type of cable, two wire formed a couple of symmetric mode and out of each pair of wires in a brain and a copper layer woven around it are formed. In other types of coaxial cable, the copper layer woven Hay, of a cylindrical copper tube is used. Plastic material from the two conductors are separated. Plastic material may be plastic or glass disks as a frequently used and prevents contact of two conductors with each other or may be two-conductor cable through the entire plastic materials are separated.
Benefits of coaxial cable:
High reliability
Transfer capacity, maximum bandwidth of 300 MHz
Good durability and sustainability
Maintenance costs being Paytn
Used in analog and digital systems
Development at low cost
Relatively bandwidth "used by the vast majority of telecommunications services including voice and video conference is a trap.
Disadvantages of coaxial cable:
High installation costs
More difficult to install cables twisted together
Distance constraints
Require the use of certain elements for splits
Connectors of BNC) Bayone-Neill - Concelman) with coaxial cable is used. Most network cards have connectors are required in this regard.
Optical fiber
One of the newest medium in transmission over computer networks, optical fiber. Optical fiber from a cylindrical rod is called the nucleus and is made from silicate is formed. Cylinder radius is between two to three microns. The nucleus, another cylinder (the core of the same sex) is called the sheath, you will be established. Refractive index of the core refractive index with M1 and M2 shown with the sheath and always M1> M2 is. This type of fiber, the light reflections of the overall interface core and sheath, will find release. Light sources in these cables, laser diode or diodes are emitting light. Resources above, electrical signals to light convert.
Benefits of optical fiber:
Size and weight
High bandwidth
Low signal loss and therefore the gap is large amplifiers.
Frequency of their ingredient
Being immune to the effects of electro Alqahay Mnatysy other circuits
They are not flammable because they lack the electrical pulse
Being protected against humidity and atmospheric factors
The ease of cabling and installation
Used in analog and digital telecommunication networks
Immunity against parasites
Disadvantages of optical fiber:
Easily broken and must be with a proper cover. The above issue with the advent of all plastic fiber and plastic / glass has decreased.
Connecting two sections of the fiber or fiber connection to a light source, is a difficult process. In this case thicker fibers can be used but it causes high mortality and low bandwidth are.
T in the form of fiber optic connections can not be used to get Anshhab. In this case cut fiber must be added and a Detector. Fvfq device must be able to receive the signal to be repeated.
Enhance optical signals in one of the major problems is optical fiber. To strengthen the signal must mesh signals into electrical signals, and re-strengthen "the symptoms become light.
Cables used in Ethernet networks
Specification Cable Type Maximum length
10BaseT Unshielded Twisted Pair 100 meters
10Base2 Thin Coaxial 185 meters
10Base5 Thick Coaxial 500 meters
10BaseF Fiber Optic 2000 meters
100BaseT Unshielded Twisted Pair 100 meters
100BaseTX Unshielded Twisted Pair 220 meters
