A network is group of computers interconnected with each other to exchange information or resource.
A computer network is collection of interconnected autonomous computers interconnected in a single technology.
Two computers are said to interconnected with each other if they share some information between them.
What are the advantages of having computer network?
1.Increased communication capabilities.
2.File sharing: Network offer quick and easy way to share files directly at a rapid speed thus saving time and integrity of files.
3.Resouce sharing : All computers in a network can share resources like printer, scanner, modem, fax machines, hard disk.
4. Security: Specific directories can be password protected to limit access to authorized users. Also, files and programs on a network can be designated as "copy inhibit" so you don’t have to worry about the illegal copying of programs.
5. It is also possible to share data files across the network by creating a share on the hard drive and allowing other people access to that information.
6.Increases the productivity.
7. You can connect all the computers which are connected through a network to the internet by using a single line. So it means that you can save the connection cost for each computer but you internet connection must be fast.
8. Internet connection sharing - Using a home network, multiple family members can access the Internet simultaneously without having to pay an ISP for multiple accounts. You will notice the Internet connection slows down when several people share it, but broadband Internet can handle the extra load with little trouble. Sharing dial-up Internet connections works, too.
Connect your entire office to the Internet through one line.
What are the disadvantages of computer network?
1.Network faults can cause loss of data.
2.Network faults could lead to loss of resources.
3.Systems open to hackers.
4.Could become inefficient.
5.Could degrade to performance.
6.Resources could be located too far from users.
7.As a work group user cannot Login from other work group machine within LAN network.
8.User also cannot login from any remote machine from WAN environment.
What are the different types of computer networks?
PAN( personal area network) : Network that is meant for one person
Eg: A wireless network connecting a computer with it’s mouse, keyboard, printer is PAN. Covers 1m distance only.
LAN (local area network) : LAN’s are privately owned network which covers a room, building or a campus ( 10m, 100m, 1km) of distance.
LAN’s are widely used in offices, companies, industries.
* Lan’s are restricted in size
*Lan’s uses transmission media as cable , to which all the machine are attached.
*Lan’s basically uses Bus and Ring Topologies( network structure) to broadcast.
Traditional Lan’s runs at the speed of 100Mbps and newer Lan’s runs at the speed of 10Gbps.
MAN (metropoliterian area network): MAN covers city ( about 10Km) in distance.
The best example of Man is the CABLE TV NETWORK available .
Cable TV is not the only MAN ,development in high speed wireless internet access resulted in MAN.
MAN’s are also un-switched ( i.e don’t have routers)
WAN (wide area network): A wide area network covers a large geographical areas like country or a continent ( about 100Km, 1000Km, 10,000Km)in distance.
In WAN, subnet consist of two components Transmission lines like copper cable, optical fiber ( move bits between machines) and Switching elements or routers (specialized computers or devices that connects 3 or more transmission lines, when date arrives to incoming line, router choose an outgoing line on which to forward them.
Hosts ( user’s computers) are connected to subnet.
Subnet is owned and operated by telephone company or isp.
The subnet is collection of communication lines and routers ( but not hosts).
The job of subnet is to carry message from host to host .
In most WAN’s , the network contains numerous transmission lines , each one connecting pair of router. If two routers do not share a transmission line , wish to communicate they must do this indirectly via other router .
When a packet is sent from one router to another via one or more intermediate routers, the packet is received at each intermediate router in its entirety , stored until the required output is free, and then forwarded.
This principle is known as “store and forward or packet switched subnet”.
Signals are usually transmitted over some transmission media that are broadly classified in to two categories.
These are those that provide a conduit from one device to another that include twisted-pair, coaxial cable and fiber-optic cable. A signal traveling along any of these media is directed and is contained by the physical limits of the medium. Twisted-pair and coaxial cable use metallic that accept and transport signals in the form of electrical current. Optical fiber is a glass or plastic cable that accepts and transports signals in the form of light.
This is the wireless media that transport electromagnetic waves without using a physical conductor. Signals are broadcast either through air. This is done through radio communication, satellite communication and cellular telephony.
What are the different types of network hardware?
The gateway computer reads the destination address and forwards the packet to an adjacent gateway that in turn read the destination address and so forth across the internet until one gateway recognizes the packet as belonging to computer within its immediate neighborhood or domain.
The gateway then forwards the packet directly to the computer whose address is specified.
Because message is divided into number of packets, each packet can, if necessary , be sent by a different route across the internet.
Packets can arrive in the different order they were sent in.
The internet protocol just delivers them. It is up to other protocol, the TCP/IP to put back in the right order.
IANA has assigned class A with single octet (8-bits) for network portion and three octet (24-bits) for host portion. DSM (default subnet mask) : 255.0.0.0 IANA has assigned class B with two octet (16-bits) for network portion and two octets (16-bits) for host portion. DSM (default subnet mask) : 255.255.0.0 IANA has assigned class C with three octet (24-bits) for network portion and single octet (8-bits) for host portion. DSM (default subnet mask) : 255.255.255.0 A subnet mask defines network portion of ip address and host portion of ip address.By knowing the subnet mask information, we can easily identify a particular machine ip belongs to which class. IP Address is dividedinto two types: 1. Private IP Address. 2. Public IP Address. Private ip address are basically used within the LAN environment.All private ip address are free to use you don't have to pay to any one for using these address.It is also known as Free IP Address. Private IP Address range: Class A = 10.0.0.0 - 10.255.255.255 Class B = 172.16.0.0 - 172.31.255.255 Class C = 192.168.0.0 - 192.168.255.255 Public IP Address: Public ip address are used in WAN environment.Used for connection to internet.Public ip address are not free , you need to pay for ip address (to isp or iana). A part from above private ip address range from each and every class all the ip's are public ip's.
A HUB is a device which connects various machines in a network. It’s major function is to replicate data it receives from one device attached to it. Hub is "Signal Splitter" Operates in "Physical Layer" “Collisions” will occur in hub and it listen for collision domains.
In bus topology all the systems are connected to a single cable/channel or back bone .Computers are connected with this cable using BNC connector or T connector. At the both ends of cable Terminators are connected.
Advantage: Cheap and Easy to implement.
Disadvantage: If terminators are not connected or open then data will bounce back.
In ring topology each computer is connected to each other .ie every system is connected to their next system in form of ring .
Advantage: Easy to install and easy to troubleshoot.
Disadvantage: If one of the computer goes down or if one of the cable break between two machines then whole the network is down.Data packets can’t go further.
Token Ring Topology:
In token ring toplogy, all the systems are connected to a central device ”MSAU” multiple station access unit Hub.