1.1 BACKGROUND TO THE STUDY
A local area network ( LAN ) is a computer network that interconnects computers within a limited area such as a residence, school, laboratory, university campus or office building.
By contrast, a wide area network (WAN) not only covers a larger geographic distance, but also generally involves leased telecommunication circuits .
Ethernet and Wi-Fi are the two most common technologies in use for local area networks. Historical technologies include ARCNET , Token ring, and AppleTalk.
History
The increasing demand and use of computers in universities and research labs in the late 1960s generated the need to provide high-speed interconnections between computer systems. A 1970 report from the Lawrence Radiation Laboratory detailing the growth of their "Octopus" network gave a good indication of the situation
A number of experimental and early commercial LAN technologies were developed in the 1970s. Cambridge Ring was developed at Cambridge University starting in 1974. [4] Ethernet was developed at Xerox PARC between 1973 and 1974.[5][6] ARCNET was developed by Datapoint Corporation in 1976 and announced in 1977. [7] It had the first commercial installation in December 1977 at Chase Manhattan Bank in New York.[8]
The development and proliferation of
personal computers using the CP/M operating system in the late 1970s, and later DOS -based systems starting in 1981, meant that many sites grew to dozens or even hundreds of computers. The initial driving force for networking was generally to share storage and
printers, which were both expensive at the time. There was much enthusiasm for the concept and for several years, from about 1983 onward, computer industry pundits would regularly declare the coming year to be, “The year of the LAN”
In practice, the concept was marred by proliferation of incompatible physical layer and network protocol implementations, and a plethora of methods of sharing resources. Typically, each vendor would have its own type of network card, cabling, protocol, and
network operating system . A solution appeared with the advent of Novell NetWare which provided even-handed support for dozens of competing card/cable types, and a much more sophisticated operating system than most of its competitors. Netware dominated the personal computer LAN business from early after its introduction in 1983 until the mid-1990s when Microsoft introduced Windows NT Advanced Server and Windows for Workgroups .
Of the competitors to NetWare, only
Banyan Vines had comparable technical strengths, but Banyan never gained a secure base. Microsoft and 3Com worked together to create a simple network operating system which formed the base of 3Com's 3+Share , Microsoft's LAN Manager and IBM's
LAN Server - but none of these was particularly successful.
In 1983, TCP/IP was first shown capable of supporting actual defense department applications on a Defense Communication Agency LAN test bed located at Reston, Virginia. [13] [14] The TCP/IP-based LAN successfully supported Telnet, FTP, and a Defense Department Teleconferencing application. This demonstrated the feasibility of employing TCP/IP LANs to interconnect Worldwide Military Command and Control System ("WWMCCS") computers at command centers throughout the United States. However, WWMCCS was superseded by the Global Command and Control System (GCCS) before that could happen.
During the same period, Unix workstations were using TCP/IP networking. Although this market segment is now much reduced, the technologies developed in this area continue to be influential on the Internet and in both Linux and Apple Mac OS X networking—and the TCP/IP protocol has replaced IPX, AppleTalk , NBF, and other protocols used by the early PC LANs.
Cabling
Early LAN cabling had generally been based on various grades of coaxial cable. Shielded twisted pair was used in IBM's Token Ring LAN implementation, but in 1984, StarLAN showed the potential of simple unshielded twisted pair by using Cat3 cable—the same simple cable used for telephone systems. This led to the development of 10BASE-T (and its successors ) and structured cabling which is still the basis of most commercial LANs today. While fiber-optic cabling is common for links between switches , use of fiber to the desktop is rare.
Wireless media
Many LANs use wireless technologies that are built into Smartphones, tablet computers and laptops. In a wireless local area network , users may move unrestricted in the coverage area. Wireless networks have become popular in residences and small businesses, because of their ease of installation. Guests are often offered Internet access via a hotspot service.
Technical aspects
Network topology describes the layout of interconnections between devices and network segments. At the data link layer and physical layer, a wide variety of LAN topologies have been used, including ring , bus , mesh and star . At the higher layers, NetBEUI, IPX/SPX , AppleTalk and others were once common, but the Internet Protocol Suite (TCP/IP) has prevailed as a standard of choice.
Simple LANs generally consist of cabling and one or more switches . A switch can be connected to a router , cable modem , or ADSL modem for Internet access. A LAN can include a wide variety of other network devices such as firewalls, load balancers , and network intrusion detection. situation. LANs are characterized by their use of redundant links with switches using the spanning tree protocol to prevent loops, their ability to manage differing traffic types via quality of service (QoS), and to segregate traffic with VLANs . LANs can maintain connections with other LANs via leased lines, leased services, or across the Internet using virtual private network technologies. Depending on how the connections are established and secured, and the distance involved, such linked LANs may also be classified as a metropolitan area network (MAN) or a wide area network (WAN).
1.2 STATEMENT OF THE PROBLEM
As the LAN (Local Area Network) environment gets increasingly complex, IDEAL Networks has issued guidance to help technicians identify the source of errors more simply and get the most from their network troubleshooting tester.
“Network transmission media can be copper, fiber or wireless so network technicians need to be armed with troubleshooting tools that can tackle any problem they encounter,” explains Tim Widdershoven, Global Marketing Manager at IDEAL Networks. “This makes it more challenging for technicians - if errors occur, these could be located in a wide range of different media and layers of the network.”
There are six ways that technicians can use a tester to effectively troubleshoot errors:
1. Physical Faults in Network Cabling
Most common network errors are at a physical level, such as problems with copper or fiber optic cabling, so this should always be the first place a technician starts. For copper cabling, a network troubleshooting tester should be able to locate faults anywhere along a cable link using TDR (time domain reflectometer) technology to pinpoint distance to common faults. A tester that checks individual conductors in the cable versus checking only paired conductors reduces the time required to identify and repair the fault. Typically cable testers display wiremap faults as a pair even when only one conductor is at fault. When checking optical fiber, a tester that accepts common optical SFP (small form pluggable) modules allows the user to quickly determine whether the cabling or the network equipment is at fault.
2. Endpoint Network Testing
In this configuration the tester acts like any other device on the network yet it has the capability to monitor and detect problems that may not be visible when using software troubleshooting tools. An essential part of identifying the source of errors is understanding the Ethernet network. This mode can verify that the network port to which the tester is connected has complete access to all network resources and can test for PoE (Power over Ethernet) when necessary.
3. In-line
Dual port testers can be inserted between any two points in the network allowing it to monitor all data passing through that point. The device can show the type of Ethernet connection at the two ports and identify speed mismatches as well as detect and identify the source of network errors. It can also be connected between the internet router and the network to measure data transfer rate to the internet. In-line mode features such as Top 10 lists can also help detect devices that are using a particularly large amount of bandwidth.
4. Network map
A network map feature provides an overview of all devices on a LAN. For troubleshooting, saving this map and returning to it later can show where changes to a network have occurred. For example, if a user can no longer access a particular server, the network map can show if the server is still accessible on the network. If the troubleshooting tester has an integrated trace-route function, faulty routers can be identified in large LANs and even across WAN (wide area network) environments.
5. VoIP
Diagnostic options for VoIP (Voice over IP) connections can also be helpful for troubleshooting. The tester can be connected between a VoIP telephone and the network, measuring call quality of service (QoS) metrics to confirm reported call quality issues and identify the problem.
6. Wi-Fi
Wi-Fi networks are particularly susceptible to problems and an access point (AP) can be the source of errors, although it appears to be working correctly. A nearby AP may be utilizing the same channel, creating interference and reducing the range of the Wi-Fi network. Using the in-line capability the tester can be connected between the AP and the network to monitor the combined traffic of all wireless devices. This may result in adding APs to increase bandwidth when demand exceeds the capacity of a single AP. In addition, the copper wire connecting the AP to the network could be faulty.
The IDEAL Networks LanXPLORER Pro network troubleshooter provides technicians with a tester that simplifies troubleshooting, supports the versatility of modern networks and helps avoid downtime.
1. 3 OBJECTIVE OF THE STUDY
A LAN, or Local Area Network, is a small network of computers, usually in the same building. They consist of several nodes (the PCs, or to be technical, the Network Interface Cards), all connected together using a topology and the cables that connect the nodes.
Ethernet
Ethernet is a family of frame-based computer networking technologies for local area networks (LANs). The name comes from the physical concept of the ether. It defines a number of wiring and signaling standards for the Physical Layer of the OSI networking model, through means of network access at the Media Access Control (MAC) /Data Link Layer, and a common addressing format.
Ethernet is standardized as IEEE 802.3. The combination of the twisted pair versions of Ethernet for connecting end systems to the network, along with the fiber optic versions for site backbones, is the most widespread wired LAN technology. It has been in use from around 1980[1] to the present, largely replacing competing LAN standards such as token ring, FDDI, and ARCNET.
Ethernet was originally based on the idea of computers communicating over a shared coaxial cable acting as a broadcast transmission medium. The methods used show some similarities to radio systems, although there are fundamental differences, such as the fact that it is much easier to detect collisions in a cable broadcast system than a radio broadcast. The common cable providing the communication channel was likened to the ether and it was from this reference that the name "Ethernet" was derived.
From this early and comparatively simple concept, Ethernet evolved into the complex networking technology that today underlies most LANs. The coaxial cable was replaced with point-to-point links connected by Ethernet hubs and/or switches to reduce installation costs, increase reliability, and enable point-to-point management and troubleshooting. StarLAN was the first step in the evolution of Ethernet from a coaxial cable bus to a hub-managed, twisted-pair network. The advent of twisted-pair wiring dramatically lowered installation costs relative to competing technologies, including the older Ethernet technologies.
Above the physical layer, Ethernet stations communicate by sending each other data packets, blocks of data that are individually sent and delivered. As with other IEEE 802 LANs, each Ethernet station is given a single 48-bit MAC address, which is used to specify both the destination and the source of each data packet. Network interface cards (NICs) or chips normally do not accept packets addressed to other Ethernet stations. Adapters generally come programmed with a globally unique address, but this can be overridden, either to avoid an address change when an adapter is replaced, or to use locally administered addresses.
Despite the significant changes in Ethernet from a thick coaxial cable bus running at 10 Mbit/s to point-to-point links running at 1 Gbit/s and beyond, all generations of Ethernet (excluding early experimental versions) share the same frame formats (and hence the same interface for higher layers), and can be readily interconnected.
Due to the ubiquity of Ethernet, the ever-decreasing cost of the hardware needed to support it, and the reduced panel space needed by twisted pair Ethernet, most manufacturers now build the functionality of an Ethernet card directly into PC motherboards, eliminating the need for installation of a separate network card.
1.4 SCOPE OF THE STUDY
The scope of a network refers to its geographical size. A network can range in size from just a few computers in one office to thousands of computers linked together over great distances.
Network scope is determined by the size of the organization or the distance between users on the network. The scope determines how the network is designed and what physical components are used in its construction.
There are two general types of network scope;
Local Area Networks
Wide Area Networks
A local area network (LAN) connects computers that are located near eachother.
For example, two computers connected together in an office or two buildings connected together by a high-speed wire can be considered a LAN. A corporate network that includes several adjacent buildings can also be considered a LAN.
A wide area network (WAN) connects a number of computers located at a greater distance from one another.
For example, two or more computers connecting opposite sides of the world is considered a WAN. A WAN can be made up of a number of interconnected LANs. For example, the Internet is really a WAN.
Network Adapters
Network Cables
Wireless Communication Devices
The basic connectivity components of a network include the cables, network adapters, and wireless devices that connect the computers in the network.
These components enable data to be sent to each computer on the network, thereby permitting the computers to communicate with each other.
Common connectivity components of a network are:
Network adapters.
Network cables.
Wireless communication devices.
Network adapters constitute the physical interface between the computer and the network cable. Network adapters, also known as network interface cards, are installed into an expansion slot in each computer and server on the network. After the network adapter is installed, the network cable is attached to the adapter's port to physically connect the computer to the network.
As the data passes through the cable to the network adapter, it is formatted into packets. A packet is a logical grouping of information that includes a header, which contains location information and user data. The header contains address fields that include information about the data's origin and destination. The network adapter reads the destination address to determine if the packet is to be delivered to this computer. If it is, the network adapter then passes the packet on to the operating system for processing. If not, the network adapter discards the packet
Each network adapter has a unique address that is incorporated into chips on the card. This address is called the physical, or media access control (MAC), address.
The network adapter performs the following functions:
Receives data from the computer's operating system and converts it into electrical signals that are transmitted onto the cable
Receives electrical signals from the cable and translates them into data that the computer's operating system can understand
Determines whether data received from the cable is intended for the computer
Controls the flow of data between the computer and the cabling system
To ensure compatibility between the computer and the network, the network adapter must meet the following criteria:
Fit in the computer's expansion slot
Use the correct type of cable connector for the cabling
Be supported by the computer's operating system
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. Cables differ in their capabilities and are categorized according to their ability to transmit data at varying speeds, with different error rates. The three major categories of cables that connect most networks are:
Twisted-pair
Coaxial
Fiber-optic
Twisted-pair cable (lObaseT) consists of two insulated strands of copper wire twisted around each other. There are two types of twisted-pair cable: unshielded twisted pair (UTP) and shielded twisted pair (STP). These are the most common cables used in networks and can carry signals for 100 meters (about 328 feet).
UTP cable is the most popular type of twisted-pair cable and is the most popular LAN cable.
STP cable uses a woven copper-braid Jacket that is more protective and of a higher quality than the jacket used by UTP. STP also uses a foil wraparound each of the wire pairs. This gives STP excellent shielding that protects the transmitted data from outside interference, which in turn allows STP to support higher transmission rates over longer distances than UTP.
Twisted-pair cabling uses Registered Jack 45 (RJ-45) connectors to connect to a computer. These are similar to Registered Jack 11 (RJ-11) connectors.
Coaxial cable consists of a copper wire core surrounded by insulation, a braided metal shielding, and an outer cover. The core of a coaxial cable carries the electronic signals that make up the data. This wire core can be either solid or stranded. There are two types of coaxial cable: ThinNet coaxial cable (10Base2) and ThickNet coaxial cable (10Base5). Coaxial cabling is a good choice when transmitting data over long distances and for reliably supporting higher data rates when using less sophisticated equipment.
Coaxial cable must be terminated at each end.
ThinNet coaxial cable can carry a signal for approximately 185 meters
(about 607 feet).
ThickNet coaxial cable can carry a signal for 500 meters (about 1,640 feet).
Both ThinNet and ThickNet cable use a connection component, known as a BNC connector, to make the connections between the cable and the computers.
Fiber-optic cable uses optical fibers to carry digital data signals in the form of modulated pulses of light. Because fiber-optic cable carries no electrical impulses, the signal cannot be tapped and its data cannot be stolen. Fiber-optic cable is good for very high-speed, high-capacity data transmission because the signal is transmitted very quickly and with very little interference.
A disadvantage of fiber-optic cable is that it breaks easily if you are not careful duSTUDY
installation. It is more difficult to cut than other cables and requires special equipment to cut it.
1.5 LIMITATION OF THE STUDY
High Setup Cost
Although the LAN will save cost over time due to shared computer resources but the initial setup costs of installing Local Area Networks is high. This is because any organization that will setup a network, will have to purchase necessary hardware equipment for networking. It may require a sophisticated server computer - a Mini Computer, Network LAN cards, Network Routers, HUBS / Switches, Networking Cables (for wired networks only) and connectors etc. Additionally a Network technician will be required for setting up a new network in an organization. If an organization has a large network, it must hire a network administrator for smooth running of network and solving any problems.
Privacy Violations
The LAN administrator has the rights to check personal data files of each and every LAN user. Moreover he can check the internet history and computer use history of the LAN users.
Data Security
Linkhorized users can access important data of an organization if centralized data repository is not secured properly by the LAN administrator. LAN Administer is responsible for the security of the whole data resource in an organization.
LAN Maintenance Job
Local Area Network requires a LAN Administrator. Because, there are problems of software installations or hardware failures or cable disturbances in Local Area Network. A LAN Administrator is needed at this full time job.A LAN Administrator may be with a M.C.S. or B.S.C.S. degree holder person additionally with a diploma in network field.
Covers Limited Area
Local Area Network covers a small area like one office, one building or a group of nearby buildings.
A local area network ( LAN ) is a computer network that interconnects computers within a limited area such as a residence, school, laboratory, university campus or office building.
By contrast, a wide area network (WAN) not only covers a larger geographic distance, but also generally involves leased telecommunication circuits .
Ethernet and Wi-Fi are the two most common technologies in use for local area networks. Historical technologies include ARCNET , Token ring, and AppleTalk.
History
The increasing demand and use of computers in universities and research labs in the late 1960s generated the need to provide high-speed interconnections between computer systems. A 1970 report from the Lawrence Radiation Laboratory detailing the growth of their "Octopus" network gave a good indication of the situation
A number of experimental and early commercial LAN technologies were developed in the 1970s. Cambridge Ring was developed at Cambridge University starting in 1974. [4] Ethernet was developed at Xerox PARC between 1973 and 1974.[5][6] ARCNET was developed by Datapoint Corporation in 1976 and announced in 1977. [7] It had the first commercial installation in December 1977 at Chase Manhattan Bank in New York.[8]
The development and proliferation of
personal computers using the CP/M operating system in the late 1970s, and later DOS -based systems starting in 1981, meant that many sites grew to dozens or even hundreds of computers. The initial driving force for networking was generally to share storage and
printers, which were both expensive at the time. There was much enthusiasm for the concept and for several years, from about 1983 onward, computer industry pundits would regularly declare the coming year to be, “The year of the LAN”
In practice, the concept was marred by proliferation of incompatible physical layer and network protocol implementations, and a plethora of methods of sharing resources. Typically, each vendor would have its own type of network card, cabling, protocol, and
network operating system . A solution appeared with the advent of Novell NetWare which provided even-handed support for dozens of competing card/cable types, and a much more sophisticated operating system than most of its competitors. Netware dominated the personal computer LAN business from early after its introduction in 1983 until the mid-1990s when Microsoft introduced Windows NT Advanced Server and Windows for Workgroups .
Of the competitors to NetWare, only
Banyan Vines had comparable technical strengths, but Banyan never gained a secure base. Microsoft and 3Com worked together to create a simple network operating system which formed the base of 3Com's 3+Share , Microsoft's LAN Manager and IBM's
LAN Server - but none of these was particularly successful.
In 1983, TCP/IP was first shown capable of supporting actual defense department applications on a Defense Communication Agency LAN test bed located at Reston, Virginia. [13] [14] The TCP/IP-based LAN successfully supported Telnet, FTP, and a Defense Department Teleconferencing application. This demonstrated the feasibility of employing TCP/IP LANs to interconnect Worldwide Military Command and Control System ("WWMCCS") computers at command centers throughout the United States. However, WWMCCS was superseded by the Global Command and Control System (GCCS) before that could happen.
During the same period, Unix workstations were using TCP/IP networking. Although this market segment is now much reduced, the technologies developed in this area continue to be influential on the Internet and in both Linux and Apple Mac OS X networking—and the TCP/IP protocol has replaced IPX, AppleTalk , NBF, and other protocols used by the early PC LANs.
Cabling
Early LAN cabling had generally been based on various grades of coaxial cable. Shielded twisted pair was used in IBM's Token Ring LAN implementation, but in 1984, StarLAN showed the potential of simple unshielded twisted pair by using Cat3 cable—the same simple cable used for telephone systems. This led to the development of 10BASE-T (and its successors ) and structured cabling which is still the basis of most commercial LANs today. While fiber-optic cabling is common for links between switches , use of fiber to the desktop is rare.
Wireless media
Many LANs use wireless technologies that are built into Smartphones, tablet computers and laptops. In a wireless local area network , users may move unrestricted in the coverage area. Wireless networks have become popular in residences and small businesses, because of their ease of installation. Guests are often offered Internet access via a hotspot service.
Technical aspects
Network topology describes the layout of interconnections between devices and network segments. At the data link layer and physical layer, a wide variety of LAN topologies have been used, including ring , bus , mesh and star . At the higher layers, NetBEUI, IPX/SPX , AppleTalk and others were once common, but the Internet Protocol Suite (TCP/IP) has prevailed as a standard of choice.
Simple LANs generally consist of cabling and one or more switches . A switch can be connected to a router , cable modem , or ADSL modem for Internet access. A LAN can include a wide variety of other network devices such as firewalls, load balancers , and network intrusion detection. situation. LANs are characterized by their use of redundant links with switches using the spanning tree protocol to prevent loops, their ability to manage differing traffic types via quality of service (QoS), and to segregate traffic with VLANs . LANs can maintain connections with other LANs via leased lines, leased services, or across the Internet using virtual private network technologies. Depending on how the connections are established and secured, and the distance involved, such linked LANs may also be classified as a metropolitan area network (MAN) or a wide area network (WAN).
1.2 STATEMENT OF THE PROBLEM
As the LAN (Local Area Network) environment gets increasingly complex, IDEAL Networks has issued guidance to help technicians identify the source of errors more simply and get the most from their network troubleshooting tester.
“Network transmission media can be copper, fiber or wireless so network technicians need to be armed with troubleshooting tools that can tackle any problem they encounter,” explains Tim Widdershoven, Global Marketing Manager at IDEAL Networks. “This makes it more challenging for technicians - if errors occur, these could be located in a wide range of different media and layers of the network.”
There are six ways that technicians can use a tester to effectively troubleshoot errors:
1. Physical Faults in Network Cabling
Most common network errors are at a physical level, such as problems with copper or fiber optic cabling, so this should always be the first place a technician starts. For copper cabling, a network troubleshooting tester should be able to locate faults anywhere along a cable link using TDR (time domain reflectometer) technology to pinpoint distance to common faults. A tester that checks individual conductors in the cable versus checking only paired conductors reduces the time required to identify and repair the fault. Typically cable testers display wiremap faults as a pair even when only one conductor is at fault. When checking optical fiber, a tester that accepts common optical SFP (small form pluggable) modules allows the user to quickly determine whether the cabling or the network equipment is at fault.
2. Endpoint Network Testing
In this configuration the tester acts like any other device on the network yet it has the capability to monitor and detect problems that may not be visible when using software troubleshooting tools. An essential part of identifying the source of errors is understanding the Ethernet network. This mode can verify that the network port to which the tester is connected has complete access to all network resources and can test for PoE (Power over Ethernet) when necessary.
3. In-line
Dual port testers can be inserted between any two points in the network allowing it to monitor all data passing through that point. The device can show the type of Ethernet connection at the two ports and identify speed mismatches as well as detect and identify the source of network errors. It can also be connected between the internet router and the network to measure data transfer rate to the internet. In-line mode features such as Top 10 lists can also help detect devices that are using a particularly large amount of bandwidth.
4. Network map
A network map feature provides an overview of all devices on a LAN. For troubleshooting, saving this map and returning to it later can show where changes to a network have occurred. For example, if a user can no longer access a particular server, the network map can show if the server is still accessible on the network. If the troubleshooting tester has an integrated trace-route function, faulty routers can be identified in large LANs and even across WAN (wide area network) environments.
5. VoIP
Diagnostic options for VoIP (Voice over IP) connections can also be helpful for troubleshooting. The tester can be connected between a VoIP telephone and the network, measuring call quality of service (QoS) metrics to confirm reported call quality issues and identify the problem.
6. Wi-Fi
Wi-Fi networks are particularly susceptible to problems and an access point (AP) can be the source of errors, although it appears to be working correctly. A nearby AP may be utilizing the same channel, creating interference and reducing the range of the Wi-Fi network. Using the in-line capability the tester can be connected between the AP and the network to monitor the combined traffic of all wireless devices. This may result in adding APs to increase bandwidth when demand exceeds the capacity of a single AP. In addition, the copper wire connecting the AP to the network could be faulty.
The IDEAL Networks LanXPLORER Pro network troubleshooter provides technicians with a tester that simplifies troubleshooting, supports the versatility of modern networks and helps avoid downtime.
1. 3 OBJECTIVE OF THE STUDY
A LAN, or Local Area Network, is a small network of computers, usually in the same building. They consist of several nodes (the PCs, or to be technical, the Network Interface Cards), all connected together using a topology and the cables that connect the nodes.
Ethernet
Ethernet is a family of frame-based computer networking technologies for local area networks (LANs). The name comes from the physical concept of the ether. It defines a number of wiring and signaling standards for the Physical Layer of the OSI networking model, through means of network access at the Media Access Control (MAC) /Data Link Layer, and a common addressing format.
Ethernet is standardized as IEEE 802.3. The combination of the twisted pair versions of Ethernet for connecting end systems to the network, along with the fiber optic versions for site backbones, is the most widespread wired LAN technology. It has been in use from around 1980[1] to the present, largely replacing competing LAN standards such as token ring, FDDI, and ARCNET.
Ethernet was originally based on the idea of computers communicating over a shared coaxial cable acting as a broadcast transmission medium. The methods used show some similarities to radio systems, although there are fundamental differences, such as the fact that it is much easier to detect collisions in a cable broadcast system than a radio broadcast. The common cable providing the communication channel was likened to the ether and it was from this reference that the name "Ethernet" was derived.
From this early and comparatively simple concept, Ethernet evolved into the complex networking technology that today underlies most LANs. The coaxial cable was replaced with point-to-point links connected by Ethernet hubs and/or switches to reduce installation costs, increase reliability, and enable point-to-point management and troubleshooting. StarLAN was the first step in the evolution of Ethernet from a coaxial cable bus to a hub-managed, twisted-pair network. The advent of twisted-pair wiring dramatically lowered installation costs relative to competing technologies, including the older Ethernet technologies.
Above the physical layer, Ethernet stations communicate by sending each other data packets, blocks of data that are individually sent and delivered. As with other IEEE 802 LANs, each Ethernet station is given a single 48-bit MAC address, which is used to specify both the destination and the source of each data packet. Network interface cards (NICs) or chips normally do not accept packets addressed to other Ethernet stations. Adapters generally come programmed with a globally unique address, but this can be overridden, either to avoid an address change when an adapter is replaced, or to use locally administered addresses.
Despite the significant changes in Ethernet from a thick coaxial cable bus running at 10 Mbit/s to point-to-point links running at 1 Gbit/s and beyond, all generations of Ethernet (excluding early experimental versions) share the same frame formats (and hence the same interface for higher layers), and can be readily interconnected.
Due to the ubiquity of Ethernet, the ever-decreasing cost of the hardware needed to support it, and the reduced panel space needed by twisted pair Ethernet, most manufacturers now build the functionality of an Ethernet card directly into PC motherboards, eliminating the need for installation of a separate network card.
1.4 SCOPE OF THE STUDY
The scope of a network refers to its geographical size. A network can range in size from just a few computers in one office to thousands of computers linked together over great distances.
Network scope is determined by the size of the organization or the distance between users on the network. The scope determines how the network is designed and what physical components are used in its construction.
There are two general types of network scope;
Local Area Networks
Wide Area Networks
A local area network (LAN) connects computers that are located near eachother.
For example, two computers connected together in an office or two buildings connected together by a high-speed wire can be considered a LAN. A corporate network that includes several adjacent buildings can also be considered a LAN.
A wide area network (WAN) connects a number of computers located at a greater distance from one another.
For example, two or more computers connecting opposite sides of the world is considered a WAN. A WAN can be made up of a number of interconnected LANs. For example, the Internet is really a WAN.
Network Adapters
Network Cables
Wireless Communication Devices
The basic connectivity components of a network include the cables, network adapters, and wireless devices that connect the computers in the network.
These components enable data to be sent to each computer on the network, thereby permitting the computers to communicate with each other.
Common connectivity components of a network are:
Network adapters.
Network cables.
Wireless communication devices.
Network adapters constitute the physical interface between the computer and the network cable. Network adapters, also known as network interface cards, are installed into an expansion slot in each computer and server on the network. After the network adapter is installed, the network cable is attached to the adapter's port to physically connect the computer to the network.
As the data passes through the cable to the network adapter, it is formatted into packets. A packet is a logical grouping of information that includes a header, which contains location information and user data. The header contains address fields that include information about the data's origin and destination. The network adapter reads the destination address to determine if the packet is to be delivered to this computer. If it is, the network adapter then passes the packet on to the operating system for processing. If not, the network adapter discards the packet
Each network adapter has a unique address that is incorporated into chips on the card. This address is called the physical, or media access control (MAC), address.
The network adapter performs the following functions:
Receives data from the computer's operating system and converts it into electrical signals that are transmitted onto the cable
Receives electrical signals from the cable and translates them into data that the computer's operating system can understand
Determines whether data received from the cable is intended for the computer
Controls the flow of data between the computer and the cabling system
To ensure compatibility between the computer and the network, the network adapter must meet the following criteria:
Fit in the computer's expansion slot
Use the correct type of cable connector for the cabling
Be supported by the computer's operating system
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. Cables differ in their capabilities and are categorized according to their ability to transmit data at varying speeds, with different error rates. The three major categories of cables that connect most networks are:
Twisted-pair
Coaxial
Fiber-optic
Twisted-pair cable (lObaseT) consists of two insulated strands of copper wire twisted around each other. There are two types of twisted-pair cable: unshielded twisted pair (UTP) and shielded twisted pair (STP). These are the most common cables used in networks and can carry signals for 100 meters (about 328 feet).
UTP cable is the most popular type of twisted-pair cable and is the most popular LAN cable.
STP cable uses a woven copper-braid Jacket that is more protective and of a higher quality than the jacket used by UTP. STP also uses a foil wraparound each of the wire pairs. This gives STP excellent shielding that protects the transmitted data from outside interference, which in turn allows STP to support higher transmission rates over longer distances than UTP.
Twisted-pair cabling uses Registered Jack 45 (RJ-45) connectors to connect to a computer. These are similar to Registered Jack 11 (RJ-11) connectors.
Coaxial cable consists of a copper wire core surrounded by insulation, a braided metal shielding, and an outer cover. The core of a coaxial cable carries the electronic signals that make up the data. This wire core can be either solid or stranded. There are two types of coaxial cable: ThinNet coaxial cable (10Base2) and ThickNet coaxial cable (10Base5). Coaxial cabling is a good choice when transmitting data over long distances and for reliably supporting higher data rates when using less sophisticated equipment.
Coaxial cable must be terminated at each end.
ThinNet coaxial cable can carry a signal for approximately 185 meters
(about 607 feet).
ThickNet coaxial cable can carry a signal for 500 meters (about 1,640 feet).
Both ThinNet and ThickNet cable use a connection component, known as a BNC connector, to make the connections between the cable and the computers.
Fiber-optic cable uses optical fibers to carry digital data signals in the form of modulated pulses of light. Because fiber-optic cable carries no electrical impulses, the signal cannot be tapped and its data cannot be stolen. Fiber-optic cable is good for very high-speed, high-capacity data transmission because the signal is transmitted very quickly and with very little interference.
A disadvantage of fiber-optic cable is that it breaks easily if you are not careful duSTUDY
installation. It is more difficult to cut than other cables and requires special equipment to cut it.
1.5 LIMITATION OF THE STUDY
High Setup Cost
Although the LAN will save cost over time due to shared computer resources but the initial setup costs of installing Local Area Networks is high. This is because any organization that will setup a network, will have to purchase necessary hardware equipment for networking. It may require a sophisticated server computer - a Mini Computer, Network LAN cards, Network Routers, HUBS / Switches, Networking Cables (for wired networks only) and connectors etc. Additionally a Network technician will be required for setting up a new network in an organization. If an organization has a large network, it must hire a network administrator for smooth running of network and solving any problems.
Privacy Violations
The LAN administrator has the rights to check personal data files of each and every LAN user. Moreover he can check the internet history and computer use history of the LAN users.
Data Security
Linkhorized users can access important data of an organization if centralized data repository is not secured properly by the LAN administrator. LAN Administer is responsible for the security of the whole data resource in an organization.
LAN Maintenance Job
Local Area Network requires a LAN Administrator. Because, there are problems of software installations or hardware failures or cable disturbances in Local Area Network. A LAN Administrator is needed at this full time job.A LAN Administrator may be with a M.C.S. or B.S.C.S. degree holder person additionally with a diploma in network field.
Covers Limited Area
Local Area Network covers a small area like one office, one building or a group of nearby buildings.
