What is a network?
Network is an interconnection of computers and other devices, which is used to share resources and for communication.
Advantage of network?
- Allow sharing resources
- Use as a communication medium
- Centralized administration
- High reliability
Scope of network
Local area network (LAN)
A LAN connects computers that are located near each other and in the same geographical location.
For example, two computers connected together in an office, or two buildings connected together by a high-speed wire can be considered as a LAN. A cooperate network that includes several adjacent buildings can also be considered as a LAN.
Wild area network (WAN)
A WAN connects a number of computers located at a greater distance from one another and different geographical locations.
For example, two a more computers connecting opposite side of the world is considered as a WAN. A WAN can be made up of a number of interconnected LANs. The internet really a WAN.
A network topology is the arrangement of computers cables, and other components on a network. It is a map of the physical network.
The type of topology you use affects the capabilities of the network’s hardware, its management and possibility for the future expansion and etc. there are several topologies available.
Pont -to-point topology
In this network two computers are connected with one communication line. This the simplest and most commonly use network. The number of users are limited to two. The distance between two computers is limited to one meter. If a computer or the communication line breaks the entire network fails.
In a bus topology, all of the computers in a network are attached to a continuous cable or segment that connects in a straight line.
Here a data packet is transmitted to all network adapters on that segment. data will be transmitted in either direction.
The end of the cable must be terminated by a hardware device called Terminators, which acts as boundaries and Define the segment. if it is not terminated the signals will travel back and forth across the network and all communication will stop.
Bus topology can have file server attached, which will provide different services. suitable for large number of users as it is easy to expand and inexpensive. but the number of computers attached to a bus also affects network performance.
In a star topology, cable segments from each computer on the network are connected to a central computer, a hub.
A hub is a device that connects several computers together.
in a star topology, signals are transmitted from the computer, through a hub, to all computers on the network. Multiple LANs also can be connected to each other in a star topology. even one computer fails, others can communicate. but if the hub fails, the entire network fails.
in ring topology, computers are connected on a single circle of cable. Unlike the bus topology, there are no terminated ends.
as the signal travel in loop in one Direction each computer acts repeater to boost the signal.
In a large scale, multiple LANs can be connected to each other in a ring topology by using thick net coaxial or fiber optic cable. Increasing the number of nodes causes communication delay.
Types of network
Based on how the computers access information, network is classified into two types.
- Per-to -per networks. (workstations)
- server-based networks. (domains)
peer to peer network (workgroups)
in a peer-to-peer network, there are no dedicated severe and there is no hierarchy among the computers. All computers are of equal status. Each function as both a client and a server. Usually, no administrator and security are provided by the local directory database on each computer. The user at each computer determines What data on that computer is shared on the network.
In a peer-to-peer network the use of each PC is responsible for the Administration and sharing of resources for his PC, which is known as distributed or workgroup administration.
(A per to per network with computers that are both service and clients)
peer-to-peer networks are suitable for environments where
- no specialized services exist.
- Security is not an issue.
- Network will experience only limited growth within the foreseeable future.
server-based network (Domains)
(a client-server network with server and client computers)
To accommodate the increased demand and provide additional functionality, most networks has dedicated services. client-server networks have become standard models for networking with the expansion of network several servers can be e used to distribute the tasks.
protocols are set of common rules or software, which must be installed on network components that need them. computers can communicate with each other if they use the same protocol. A variety of protocols are available for use in specific network environment. mainly there are two types of protocols
- open protocol
- vendor-specific protocol
open protocols are protocols that are written to publicly unknown industry standards. These protocols are compatible with other protocols written to the same standards.These are non-proprietary.
Eg: transmission control protocol/ internet protocol[TCP/IP]
vendor-specific protocols proprietary And have been developed by different vendors for use in specific environments.
eg: inter network packet exchange/sequenced packet exchange[ IPX/SPX] developed by novel for its network environment.
the common network protocols that you can use with Windows 2000 are
- Apple Talk
communication interfaces modem
A modem is a peripheral device that enables computers to communicate with each other over Conventional telephone lines,ISDN cable lines,or even without wires. the words modem comes from combining the words Modulator and the Demodulator.
a multiplexer combines multiple signals for transmission over a single circuit. This allows for the transfer of various data simultaneously, such as video, sound, text, etc.
you connect computers together in a network by using cables to carry signals between computers. a cable that connects two computers or network components is called a segment. there are three major categories of cables that connect most networks.
- Twisted pair
- Coaxial cable
- fiber optic
Twisted pair cable
Twisted pair cable(10 base T) consists of two Insulated strands of copper wire twisted around each other. there are two types
- unshielded twisted pair(UTP)
- shielded twisted pair(STP)
They can carry signals 100 meters. (about 328 feet)
UTP Is the most popular LAN Cable because of its flexibility and low cost. six Categories of STPs are Available according to their data transmission speeds. (rang from 4Mbps to Mbpd)
STP Cable uses a Woven copper braid jacket that is more protective and of a higher quality than the jacket used by UTP. it supports secure, Higher transmission rates over longer distance then UTP.
Twisted pair cabling uses registered Jack 45 (RJ 45) connectors to connect to a computer.
coaxial cable consists of a copper wire core surrounded by insulation, a braided metal shading, and an outer cover. the core of coaxial cables carries the electronic signals that make up the data. There are two types of coaxial cables.
- ThinNet coaxial cable (10Base 2)
- Thick Net coaxial cable(10 Base 5)
Coaxial cable is suitable for reliable, long distances, high-speed data transmission. the cable must be terminated at each end.Thin Net Coaxial cable can carry a signal for approximately 185 meters (about 607 feet) and Thick Net coaxial cable can carry a signal for 500 meters.( about 1640). Coaxial uses a connection component known as a BNC(Bayonne-Neill-concelman)connector how to make the connections between the cables and the computers.
fiber optic cable
fiber optic cable uses Optical Fibre to carry digital data signals in the form of modulator pulses of light. because fiber optic cable carries no electrical impulses, the signal cannot be tapped and its data cannot be stolen. it is suitable for the very highest speed, high capacity data transmission because the signal is transmitted very quickly with very little interference. segment length is 100 miles.
wireless communication devices
you can use wireless components to connect network over distance for which standard Network adapters and cable options are not feasible. A Wireless network adapter with a transceiver( a device that both transmits and receives analog and digital signals)is installed in each computer.
operators by using an infrared light beam to carry the data between devices clear line of sight between the transmitting and receiving devices must be there.
most popular long-distance transmission used Line of Sight Technology usually consists of two radio trans services one send and one receive install on tall Towers.
Uses satellite technology
A global initiative by Ericsson,IDM, Intel, Nokia,and Toshiba to set a Standard for free cable connectivity between mobile phones mobile, PCs, handheld computers, and other peripherals.
wi-fi short for wireless fidelity. Wi-Fi has gained acceptance in many environments as an alternative to a wired LAN. many airports hotels and other services of LIC access to Wi-Fi networks so many people can log on to the internet and receive emails on the move.
Network interconnecting devices
to better to the growing networking needs of an organization you need to expand the size or improve the performance of a network. you cannot make networks large by adding computers and cables. each network topology architecture has limits. Therefore, you have to install components to increase the size of the network within its accepting environment. following some components, you can use for this purpose.
repeaters receive Signals and retransmit at their original strength and definition. Installing a repeater between cable segments enables signals to travel farther. Repeaters do not translate or filter signals. for a repeater to work, both segments connected to the repeater must use the same access method.
eg: repeat cannot translate the Ethernet packet into a token ring packet
we can use Repeater to
- connect two segments of similar of dissimilar cabling
- Generate this signal to increase the distance transmitted
- transmit all traffic in both directions.
- connect two segments in the most cost-effective manner
hubs connectivity devices that connect computers in a star topology. Herbs contain multiple Parts for connecting to network components. if you use a hub, a break in network does not affect the entire network. only the segment and the computer attached to that segment fail. A single data packets sent through a hub gets to all connected computers.
we can use hub to
- Easily change and expand writing systems
- Use different ports to accommodate a variety of cable types
- Enable Central monitoring at network activity and traffic.
a bridge is a device that passes data packets between multiple network segments that use the same communication protocol. a bridge one signal at a time. as the data packets passes through the bridge, information about the sending computers MAC address is stored in the bridge’smemory. The bridge uses this information to build a table based on these addresses. as more data is sent, the bridge develops a bridging table that identifies each computer and its location on network segments.
when the bridge receives a packet, the source address is compared to the source address in the table. if the so if not present in the table, it is added to the table. the bridge then compares the destination address with the destination address listed in the table. if the bridge recogzises the location of the destination address, it forwards the packet to this address. if it is not it over the packet to all segments.
we can use bridge to
- expand the length of a segment.
- reduce traffic
- link the similar physical cables
Switchers are similar to bridges but offer a more direct network connection between the source and destination computers. when a switch receives a data packet it creates a separate internal connection with the port of the destination computer, based on the information in heading.
we can use to
- send it directly from the source computer to the destination computer
- provide for a greater rate of data transmission
the router provides more functionality than Bridge or switch in moving data packets between different network segments. Routers exmine a packet header to determined the best part of the packet travel. a router knows the path to all of the segments on the network by accessing information stored in the routing table.
we can use routers to
- send packets directly to a destination computer on another network segment.
- reduce stress on the network.
- only spin packets to known addresses.
gateways enable communication between different network architectures. a Gateway takes the data from one network and repackages it, so that each network can understand the other network’s data.
we can use gateway to link to segment that does not use the same
- set of communication rules and regulations
- data formatting structure
open system interconnection reference model ( OSI model)
International standard organization (ISO) is responsible for standardizing the method by which computers communicate worldwide. To do so, ISO created a model for network communication, called the open system interconnection (OSI) I reference model or the OSI model.
the module provides network communication into seven layers each layer carries out specific functions in transmitting data on the network. the network passes a packet from layer to layer and at each layer in some additional formatting is added to the packet play your having specific protocols which perform some specific.
defines how applications interact with each other file services and printer service will operate. The O/S interact with this player.
adds common formatting for data representation. It will take care of network security
establish and maintains communication channels. it allows a user to access to the network. it will give error messages in case of error or logon failures.
ensures error-free delivery of data it will provide error checking and reliable,
end to end communication
data link layer
define access methods for the physical medium such as the network cable it will arrange data into frames and take care the size of the packet.
addresses messages both within and between networks it will find the shortest way to send the message.
put the data on the physical medium it will describe how the data gets transmitted over a physical medium it will take care of the cable and network traffics.
Transmission control protocol internet protocol (TCP/ IP)
TCP /Ip industry standard for the protocol stack that support routing and enables computers to communicate across network segments routable protocol because of this feature TCP/ IP standard protocol for communication over the internet.
Internet work packet exchange sequence packet exchange IPX/SPX
IPX /SPX is a routable protocol stack developed specifically for NetWare architecture. IPX defines the addressing schemes used on a NetWare network and SPX provides security and reliability to the IPX protocol.
Note- NW link IPX/SPX/NetBIOS compatible transport protocol is Microsoft version of IPX/SPX and is included with windows 2000. Can use NW link to access client and server applications running on NetWare servers. NetWare client can use NW link to access client and server applications running on windows 2000 based server.
NetBIOS Enhanced user interference [NetBEUI]
This is non- routable protocol for PCs. Suitable for small networks which would Not need to be routed to other subnets. it provides high speed of data transfer on the network and it compatible with windows 2000.
the internet protocol IP was created in the 1917s to support early computer networking with the UNIX operating system. Today, IP has become a standard for all modern network operating systems (NOS) to communicate with each other.
- A way to identify machines on a network
- A Unique identifier
- IP addresses can system of 4 section
- each section is 8 bits long