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What is a Networking ?

Networking is the concept of sharing resources and services. A network of computers is a group of inter connected system sharing resources and interacting using a shared communication link.A network is a set  of inter connected systems. The shared resources can be data, a printer, a fax modern, or a service such as a database or an email system.

The individual system must be connected through a pathway. This pathway is called the Transmission medium. It is used to transmit the resources or service between the computers. All the system on the pathway must follow a set of common communication rules. These rules are called Protocols.

A network can be a wired network or a wireless network. Some of the network are combination of both. Wired network will use Ethernet cable for transmission whereas wireless network will use routers and modems.

Some basic concepts :

1. Bandwidth :


Bandwidth is the measure of the capacity of a medium to transmit data. Data transmission rates is number of bits transmitted per second. Bandwidth of a cable depends on cable length. A short cable can have greater bandwidth than a long cable so far all cable designs. Maximum length for cable runs are specified. 

2. Band usage :


The bandwidth is shared so that maximum usage is obtained. There are two transmission modes, base band and broad band transmission. Base band devotes the entire capacity of the medium to one communication channel. Broad band enables two or more communication channels to share the bandwidth of communication medium. Base band is most common mode of operation. Most local area network (LAN) function in base band mode. In base band, signaling can be analog or digital. 

3. Attenuation : 


Attenuation is a measure of how much a signal weakens as it travels through a medium. As signals pass through the medium part of the signal is absorbed and makes the signal weak. Attenuation decides the cable length when signal strength falls below certain limits, then at receiving station noise may appear. Repeaters are used to regenerate signal.

4. MAC Address :


Mac address means media access control access. It is a permanent address of a device which can be connected to Internet. Mac  address is not like IP address that changes frequently as you can your ISP. Mac address is generated from the manufacturer and is permanent throughout life time. It is a permanent identity of your device.
It looks something like this : 00-14-2c-01-2e-45
You can easily find your mac address just by typing getmac in your command prompt.

Types of Networks

There are several types of network depending upon the area and the work to be done. Some of the most common Networks are :

1. Local Area Network (LAN) :


A LAN is a group of computers interconnected within a small area such as room, building or a campus. Data Transfer speed is higher. Coaxial cables are generally used to connect the computers and other devices. Due to short distance , technical and noise errors are minimum. 

For eg : A computer lab in college.

2.. Metropolitan Area Network (MAN) :


A MAN is larger than LAN. It basically covers a particular city or town and rarely expand more than 100 KM and is made of different transmission media. Sometimes MAN is a single network such as TV cable networks or LAN to LAN connection to share resources. Security is  the main component here as data is shared between two dissimilar networks. Fibre optic cables are used for better transmission of data over long distances.

3. Wide Area Network (WAN) :


A WAN is the interconnection of LAN or MAN can be located entirely within a state, country or around the world. Data transfer rate is comparatively slower such as in Kbits/sec. In WAN links may be established by using telephone cable or microwave tower or satellite. In this network, short circuits errors, noise errors, atmospheric error are higher than any other network.

For eg : Pager

Networking Topologies : 

A topology is a map of the network. It is a plan for how the cabling will interconnect the nodes, or device and how the nodes will function in relation to one another.

There are two categories of Network topology :

1. Physical topology :-


It describes actual layout of the network  transmission media. It defines the way the network looks.

2. Logical Topology :-


It describes the logical pathway a signal follows as it passes among the network nodes. It defines the data passes among the nodes.

Both physical and logical topology can take several forms :

some common are -

1. BUS Topology :


In a BUS physical topology, all devices are connected to a common shared cable. This shared cable is called backbone of network. The BUS is available for each node to send its data to each and every computer node. Most of the buses transmits signal in both direction on backbone cable and hence all workstation are able to receive signals. But some buses are unidirectional and data is transmitted only in one direction of backbone cable.Hence only down stream devices can receive signals. The backbone cable carries transmission message along the cable. As message arrives at a workstation, it checks whether the destination address matches to its own or not. If not, it does no more and the message goes to next workstation. The BUS cable is terminated at each end by placing terminators to prevent signals from reflecting back. The commonly used implementation for BUS topology is Ethernet at 10 MBPS.

2. RING Topology :


RING topology are wired in circle. Each node is connected to its neighbours on either side and the data transmits along the ring in one direction only. Each device incorporates a receiver and a transmitter and serve as a repeater that passes the signal on to the next device in the RING. RING topology are suited for networks that uses token passing access methods. The token passes around the RING , and the only node that holds the token can transmit data. The topology is always implemented as a logical topology.
Eg: In token ring network, The topology is physically a STAR topology. But logical topology is a RING topology.
The commonly used implementation for RING topology is token ring at 4 - 16 MBPS.

3.STAR Topology :


In a STAR topology all the workstation are connected to central hub. The HUB receives signals from a workstation and the routes it to the proper destination. STAR physical topology is often implemented to implement BUS and RING logical topology.

4.MESH topology :


A MESH topology is a hybrid model. It incorporates all topologies. In MESH devices are connected to every other devices. This increases fault tolerance but involves extra work. If media break data transfer can take alternative routes. Cabling is complicated here.

Ethernet 


Ethernet is a very popular local area network architecture. This uses contention (CSMA / CD) access method. Ethernet is also called IEEE 802.3 standard. There are different varieties of Ethernet network.
Typically Ethernet network can use BUS physical topology. Some Ethernet network uses STAR physical topology and BUS logical topology. The Ethernet topologies are :

10 BASE 2
10 BASE 5
10 BASE -T
10 BASE -FL
100 VG - Any LAN
100 BASE -X

The name of Ethernet topology begins with number 10 or 100. That specifies the transmission speed for the network.
10 BASE 5 is designed to operate at 10 MBPS.
100 BASE -X operates at 100 MBPS.
"BASE" specifies that base band transmission are being used.
T is for unshielded twisted -pair wiring.
"FL" is for Fibre optic cabling,
"VG - any LAN" implies voice grade.
"X" implies multiple media types.
Ethernet networks transmit data in small unit called frames.

The size of Ethernet frame is 64 to 1518 bytes. Eighteen bytes of total frame size are taken up by frame over head, such as the source and destination address. Protocol information and error - checking information, Ethernet frames are Ethernet II , 802.2 and 802.3 .

Protocols


Protocols are rules by which computers communicate. Computers can use any number of systems for passing messages. But for this they must be using same rules. i.e computers should agree on common protocols before they can communicate.

Network data is encapsulate in packets at source. It is send via the network to a destination. At destination it is reconstructed in to the appropriate file, Instruction or request. The exact composition of a network packet depends on the protocols you are using. In general , Network packet contain the followings : 

1. HEADER : This signifies start of the packet. It contains source and destination address and time / synchronization information.

2. DATA : This portion contains the original data being transmitted 

3. TRAILER : It marks the end of the  packet. It contains error checking (CRC) information. When packet reaches the transmission medium, the network adapter card examines the packet. It checks packet's destination address. If destination address matches the PC's address, the network adapter interrupts the processor, and protocol layer of destination PC process the incoming packet.

Internet Protocol 


Internet protocols were developed by the defense department of united states. Internet protocols are also TCP/IP protocols (Transmission control protocol / Internet protocol). TCP/IP is required for communication over the Internet. A large number of protocols are associated with TCP/IP . This can be grouped into following categories :

1. General TCP/IP transport protocol : In transport protocol there are two main forms of address : A node address and a logical network address. A node address is the address of the entity of device on the network. logical network address is a segment on the network to which node is attached. TCP/IP uses numbering scheme .

An IP address is a set of four numbers , they can range in a value between 0 to 255. each number is separated by period. 

For eg : 34.120.66.79 or 107.219.2.34

there are three classes of address -

i. Class A :


In class A the number between 1 and 127 appears before first dot (.) the first number represent the network address. The last three numbers the node or Host number . In 34.120.66.79 , the Host number is 120.66.79 on the network 34. 

ii. Class B :


In class B, the first number can range in value from 128 to 191. The first two numbers forms network address and last two forms Host ID.

iii. Class C :


In class C, the first number can range from 192 to 223. The first three numbers make up the network address and last number forms Host ID.

2.TCP/IP service : IP is connection-less protocol. It is packet - switching protocol that performs addressing and route selection. IP routes packets through Internet works . It also performs disassembly and reassembly . IP also performs error checking.

3. TCP/IP routing  : TCP is an Internet work connection - oriented protocol . TCP provides full duplex, end to end connection . TCP maintains a logical connection between sending and receiving computer systems. The integrity of transmission is maintained . TCP detects any problem in the transmission quickly and takes action to correct them. TCP also provides message fragmentation and reassembly. TCP fragments message into segments. These segments can be handled by IP . TCP can combine multiple message into same segment. Apart from IP and TCP there are UDP (User data gram protocol), ARP (Address resolution protocol) and Internet controlling message protocol (ICMP).

Connectivity Devices 

1. Modem :


Computers store digital data while telephone  line can transmit only analog data. Modem can transmit digital computer signals over telephone lines by converting them to analog forms. Converting one signals form to another is called modulation and recovering original signal is called demodulation. Modem is Modulator / Demodulator. Modem is used to connect computer to Internet . Email, Data transfer activities can be performed by using modem. Modems offers limited bandwidth. The speed of modem is number of bits transferred per second. Modems are classified into two categories according to transmission method

a. Asynchronous modems : In asynchronous modem clock is not used for synchronization . Instead it uses, bits synchronization . Here each frame begins with a start bit that enables the receiving device to adjust to the time of transmitted signal. Messages are kept short.It is used to transmit character data. Asynchronous transmission is simple, inexpensive technology. It is used for to Pc to PC communication.

b. Synchronous modems : Synchronous transmission uses clock on transmitting and receiving devices. It uses sync signal, which is a bit pattern and can be easily recognized by the receiver. A wide variety  of data types can be transmitted . A long series of bits can also be transmitted. A cyclic redundancy check CRC technique is used for error checking. 

2. HUBS :


Hubs are wiring concentrators, they provide central attachment point for network cabling. There are three types of HUBS :

i. Passive Hubs : It is used to combine the  signal from several network cable segments. This do not contains any electronic component and do not process the data signal in any way.All devices are attached to passive hub receive all packets that pass through hub. 

ii. Active Hubs : It can amplify and clean up the electronic signals. The process of cleaning up is called signal regeneration. Active hub consist of electronic components.

iii. Switching Hubs : The latest is switching hub . It quickly routes the signal between ports of hub. These can be used in place of routers.

3. Repeater :


The repeaters are used to extend the range of network cabling. A repeater is a network device that repeats a signal from one port to another port. It does not filter or interpret, it simply regenerates a signal. This device is inexpensive and simple. By adding repeater we can increase the length of the network .

4. Routers :


 Routers are Internet work connectivity devices . An Internet work may consist of two or more physical connected independent networks. These networks can be of different types. 

For eg : they can be Ethernet and Token - Ring network.

Each address to assist efficient delivery of message. Delivering packets according to logical network address is called routing. Routers perform routing. Routers are Intelligent. They can use algorithms to determine the most efficient path for sending a packet to any given network.

Routers can also be used to divide large, Busy LAN's into smaller segments. The protocols like IP , IPX and DDP are used to support routing function. Routers are also employed to connect LAN to WAN. Routers are of two types : 

i. Static routers : These routers do not determine paths, but you need to specify them.

ii. Dynamic Routers : These routers have capacity to determine routes. 

What is a Networking ? What is a Networking ? Reviewed by Shirley Bloggastron on 10:04 AM Rating: 5

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