The centerpiece product of many home computer networks is a wireless router. These routers support all home computers configured with wireless network adapters see below. They also contain a network switch to allow some computers to be connected with Ethernet cables. Wireless routers allow cable modem and DSL Internet connections to be shared. Additionally, many wireless router products include a builtin firewall that protects the home network from intruders.
Illustrated above is the Linksys compare prices. This is a popular wireless router product based on the WiFi network standard. Wireless routers are small boxlike devices generally less than in length, with LED lights on the front and with connection ports on the sides or back. Some wireless routers like the feature external antennas that protrude from the top of the device; others contain builtin antennas.Wireless router products differ in the network protocols they support, or a combination, in the number of wired device connections they support, in the security options they support, and in many other smaller ways. Generally only one wireless router is required to network an entire household. A wireless access point sometimes called an AP or WAP serves to join or "bridge" wireless clients to a wired Ethernet network. Access points centralize all WiFi clients on a local network in socalled infrastructure mode. An access point in turn may connect to another access point, or to a wired Ethernet router.
Wireless access points are commonly used in large office buildings to create one wireless local area network WLAN that spans a large area. Each access point typically supports up client computers. By connecting access points to each other, local networks having thousands of access points can be created. Client computers may move or roam between each of these access points as needed. In home networking, wireless access points can be used to extend an existing home network based on a wired broadband router. The access point connects to the broadband router, allowing wireless clients to join the home network without needing to rewire or re-configure the Ethernet connections.
As illustrated by the Linksys compare prices shown above, wireless access points appear physically similar to wireless routers. Wireless routers actually contain a wireless access point as part of their overall package. Like wireless routers, access points are available with support for or combinations.
Tuesday, May 5, 2009
Window firewell
Windows Firewall is a free network firewall software application for Windows XP, introduced in Windows XP Service Pack. Older version of Windows XP contained a different software firewall called Internet Connection Firewall ICF. Windows Firewall replaces Internet Connection Firewall and offers significant improvements over its predecessor. Windows Firewall comprises both a firewall application, a Windows service called ipnathlp, and a Security Center service called wscsvc. The Windows Firewall is switched on by default when XP SP is installed. The older ICF application, on the other hand, required users to manually set the service to start. The new Security Center also makes Windows Firewall easy for the average non-technical person to understand and use.
Windows Firewall provides one way network protection only. It blocks incoming traffic as configured, but it will not block any outgoing traffic. This behavior is by design, as Microsoft and various security experts recommend controlling outgoing traffic through a separate network device such as the broadband router. On the other hand, alternative software firewall products on the market today usually support traffic blocking in either direction. Modern trojans and spyware applications can easily disable these outbound firewall traffic blocks, however. Overall, the lack of outbound traffic blocking in Windows Firewall detracts very little from its power.
The design of Windows Firewall has also been criticized in another respect. Some feel that it is too easy for Windows Firewall to be switched off by malicious applications and users. It appears more likely, however, that Windows Firewall is no more or less secure in this respect than any other popular software firewall for Windows. The introduction of XP requires makers of other commercial firewall software for Windows to ensure their applications are compatible with Windows Firewall.
Users of ZoneAlarm and other commercial firewalls will upgrade their software to new versions that are built to coexist with Windows. Running Windows Firewall together with another company's firewall on the same computer could cause networking problems. Bottom line Windows Firewall for Windows XP is a significant step forward in improving the security of Windows computers. With, home computer users will get a significant additional level of network security support without needing to fuss with detailed technical configurations. Those who already run thirdparty firewall software should consult the vendor's Web site to ensure they have the needed related updates.
Windows Firewall provides one way network protection only. It blocks incoming traffic as configured, but it will not block any outgoing traffic. This behavior is by design, as Microsoft and various security experts recommend controlling outgoing traffic through a separate network device such as the broadband router. On the other hand, alternative software firewall products on the market today usually support traffic blocking in either direction. Modern trojans and spyware applications can easily disable these outbound firewall traffic blocks, however. Overall, the lack of outbound traffic blocking in Windows Firewall detracts very little from its power.
The design of Windows Firewall has also been criticized in another respect. Some feel that it is too easy for Windows Firewall to be switched off by malicious applications and users. It appears more likely, however, that Windows Firewall is no more or less secure in this respect than any other popular software firewall for Windows. The introduction of XP requires makers of other commercial firewall software for Windows to ensure their applications are compatible with Windows Firewall.
Users of ZoneAlarm and other commercial firewalls will upgrade their software to new versions that are built to coexist with Windows. Running Windows Firewall together with another company's firewall on the same computer could cause networking problems. Bottom line Windows Firewall for Windows XP is a significant step forward in improving the security of Windows computers. With, home computer users will get a significant additional level of network security support without needing to fuss with detailed technical configurations. Those who already run thirdparty firewall software should consult the vendor's Web site to ensure they have the needed related updates.
Proxy servers
Proxy servers work at the Application layer, layer of the OSI model. They aren't as popular as ordinary firewalls that work at lower layers and support application-independent filtering. Proxy servers are also more difficult to install and maintain than firewalls, as proxy functionality for each application protocol like HTTP, SMTP, or SOCKS must be configured individually. However, a properly configured proxy server improves network security and performance. Proxies have capability that ordinary firewalls simply cannot provide.
Some network administrators deploy both firewalls and proxy servers to work in tandem. To do this, they install both firewall and proxy server software on a server gateway. Because they function at the OSI Application layer, the filtering capability of proxy servers is relatively intelligent compared to that of ordinary routers. For example, proxy Web servers can check the URL of outgoing requests for Web pages by inspecting HTTP GET and POST messages. Using this feature, network administrators can bar access to illegal domains but allow access to other sites. Ordinary firewalls, in contrast, cannot see Web domain names inside those messages. Likewise for incoming data traffic, ordinary routers can filter by port number or network address, but proxy servers can also filter based on application content inside the messages.
Various software products for connection sharing on small home networks have appeared in recent years. In medium and largesized networks, however, actual proxy servers offer a more scalable and cost-effective alternative for shared Internet access. Rather than give each client computer a direct Internet connection, all internal connections can be funneled through one or more proxies that in turn connect to the outside.
The caching of Web pages by proxy servers can improve a network's "quality of service" in three ways. First, caching may conserve bandwidth on the network, increasing scalability. Next, caching can improve response time experienced by clients. With an HTTP proxy cache, for example, Web pages can load more quickly into the browser. Finally, proxy server caches increase availability. Web pages or other files in the cache remain accessible even if the original source or an intermediate network link goes offline.
Some network administrators deploy both firewalls and proxy servers to work in tandem. To do this, they install both firewall and proxy server software on a server gateway. Because they function at the OSI Application layer, the filtering capability of proxy servers is relatively intelligent compared to that of ordinary routers. For example, proxy Web servers can check the URL of outgoing requests for Web pages by inspecting HTTP GET and POST messages. Using this feature, network administrators can bar access to illegal domains but allow access to other sites. Ordinary firewalls, in contrast, cannot see Web domain names inside those messages. Likewise for incoming data traffic, ordinary routers can filter by port number or network address, but proxy servers can also filter based on application content inside the messages.
Various software products for connection sharing on small home networks have appeared in recent years. In medium and largesized networks, however, actual proxy servers offer a more scalable and cost-effective alternative for shared Internet access. Rather than give each client computer a direct Internet connection, all internal connections can be funneled through one or more proxies that in turn connect to the outside.
The caching of Web pages by proxy servers can improve a network's "quality of service" in three ways. First, caching may conserve bandwidth on the network, increasing scalability. Next, caching can improve response time experienced by clients. With an HTTP proxy cache, for example, Web pages can load more quickly into the browser. Finally, proxy server caches increase availability. Web pages or other files in the cache remain accessible even if the original source or an intermediate network link goes offline.
Packet framing
A packet consists of two kinds of data control information and user data also known as payload. The control information provides data the network needs to deliver the user data, for example: source and destination addresses, error detection codes like checksums, and sequencing information. Typically, control information is found in packet headers and trailers, with user data in between.
Different communications protocols use different conventions for distinguishing between the elements and for formatting the data. In Binary Synchronous Transmission, the packet is formatted in bit bytes, and special characters are used to delimit the different elements. Other protocols, like Ethernet, establish the start of the header and data elements by their location relative to the start of the packet. Some protocols format the information at a bit level instead of a byte level.
A good analogy is to consider a packet to be like a letter: the header is like the envelope, and the data area is whatever the person puts inside the envelope. A difference, however, is that some networks can break a larger packet into smaller packets when necessarynote that these smaller data elements are still formatted as packets.A network design can achieve two major results by using packets: error detection and multiple host addressing.It is more efficient and reliable to calculate a checksum or cyclic redundancy check over the contents of a packet than to check errors using character-by-character parity bit checking.The packet trailer often contains error checking data to detect errors that occur during transmission.
Modern networks usually connect three or more host computers together; in such cases the packet header generally contains addressing information so that the packet is received by the correct host computer. In complex networks constructed of multiple routing and switching nodes, like the ARPANETand the modern Internet, a series of packets sent from one host computer to another may follow different routes to reach the same destination. This technology is called packet switching.
In general, the term packet applies to any message formatted as a packet, while the term datagram is generally reserved for packets of an "unreliable" service. A reliable service is one that notifies the user if delivery fails, while an "unreliable" one does not notify the user if delivery fails. For example, IP provides an unreliable service. Together, TCP and IP provide a reliable service, whereas UDP and IP provide an unreliable one. All these protocols use packets, but UDP packets are generally called datagrams. When the ARPANET pioneered packet switching, it provided a reliable packet delivery procedure to its connected hosts via its. A host computer simply arranged the data in the correct packet format, inserted the address of the destination host computer, and sent the message across the interface to its connected IMP. Once the message was delivered to the destination host, an acknowledgement was delivered to the sending host. If the network could not deliver the message, it would send an error message back to the sending host.
Different communications protocols use different conventions for distinguishing between the elements and for formatting the data. In Binary Synchronous Transmission, the packet is formatted in bit bytes, and special characters are used to delimit the different elements. Other protocols, like Ethernet, establish the start of the header and data elements by their location relative to the start of the packet. Some protocols format the information at a bit level instead of a byte level.
A good analogy is to consider a packet to be like a letter: the header is like the envelope, and the data area is whatever the person puts inside the envelope. A difference, however, is that some networks can break a larger packet into smaller packets when necessarynote that these smaller data elements are still formatted as packets.A network design can achieve two major results by using packets: error detection and multiple host addressing.It is more efficient and reliable to calculate a checksum or cyclic redundancy check over the contents of a packet than to check errors using character-by-character parity bit checking.The packet trailer often contains error checking data to detect errors that occur during transmission.
Modern networks usually connect three or more host computers together; in such cases the packet header generally contains addressing information so that the packet is received by the correct host computer. In complex networks constructed of multiple routing and switching nodes, like the ARPANETand the modern Internet, a series of packets sent from one host computer to another may follow different routes to reach the same destination. This technology is called packet switching.
In general, the term packet applies to any message formatted as a packet, while the term datagram is generally reserved for packets of an "unreliable" service. A reliable service is one that notifies the user if delivery fails, while an "unreliable" one does not notify the user if delivery fails. For example, IP provides an unreliable service. Together, TCP and IP provide a reliable service, whereas UDP and IP provide an unreliable one. All these protocols use packets, but UDP packets are generally called datagrams. When the ARPANET pioneered packet switching, it provided a reliable packet delivery procedure to its connected hosts via its. A host computer simply arranged the data in the correct packet format, inserted the address of the destination host computer, and sent the message across the interface to its connected IMP. Once the message was delivered to the destination host, an acknowledgement was delivered to the sending host. If the network could not deliver the message, it would send an error message back to the sending host.
Internetworking
involves connecting two or more distinct computer networks or network segments via a common routing technology. The result is called an internetwork often shortened to internet. Two or more networks or network segments connected using devices that operate at layer the 'network' layer of the OSI Basic Reference Model, such as a router. Any interconnection among or between public, private, commercial, industrial, or governmental networks may also be defined as an internetwork.
In modern practice, the interconnected networks use the Internet Protocol. There are at least three variants of internetwork, depending on who administers and who participates in them,Intranet, Extranet, Internet. Intranets and extranets may or may not have connections to the Internet. If connected to the Internet, the intranet or extranet is normally protected from being accessed from the Internet without proper authorization. The Internet is not considered to be a part of the intranet or extranet, although it may serve as a portal for access to portions of an extranet.
An intranet is a set of networks, using the Internet Protocol and IP-based tools such as web browsers and file transfer applications, that is under the control of a single administrative entity. That administrative entity closes the intranet to all but specific, authorized users. Most commonly, an intranet is the internal network of an organization. A large intranet will typically have at least one web server to provide users with organizational information.An extranet is a network or internetwork that is limited in scope to a single organization or entity but which also has limited connections to the networks of one or more other usually, but not necessarily, trusted organizations or entities ., a company's customers may be given access to some part of its intranet creating in this way an extranet, while at the same time the customers may not be considered 'trusted' from a security standpoint. Technically, an extranet may also be categorized as a CAN, MAN, WAN, or other type of network, although, by definition, an extranet cannot consist of a single LAN; it must have at least one connection with an external network.
The Internet is a specific internetwork. It consists of a worldwide interconnection of governmental, academic, public, and private networks based upon the networking technologies of the Internet Protocol Suite It is the successor of the Advanced Research Projects Agency Network ARPANET developed by DARPA of the U.S. Department of Defense. The Internet is also the communications backbone underlying the World Wide Web WWW. The 'Internet' is most commonly spelled with a capital 'I' as a proper noun, for historical reasons and to distinguish it from other generic internetworks.
Participants in the Internet use a diverse array of methods of several hundred documented, and often standardized, protocols compatible with the Internet Protocol Suite and an addressing systemIP Addresses administered by the Internet Assigned Numbers Authority and address registries. Service providers and large enterprises exchange information about the reachability of their address spaces through the Border Gateway Protocol BGP, forming a redundant worldwide mesh of transmission paths. involves connecting two or more distinct computer networks or network segments via a common routing technology. The result is called an internetwork often shortened to internet. Two or more networks or network segments connected using devices that operate at layer the 'network' layer of the OSI Basic Reference Model, such as a router. Any interconnection among or between public, private, commercial, industrial, or governmental networks may also be defined as an internetwork.
In modern practice, the interconnected networks use the Internet Protocol. There are at least three variants of internetwork, depending on who administers and who participates in them,Intranet, Extranet, Internet. Intranets and extranets may or may not have connections to the Internet. If connected to the Internet, the intranet or extranet is normally protected from being accessed from the Internet without proper authorization. The Internet is not considered to be a part of the intranet or extranet, although it may serve as a portal for access to portions of an extranet.
An intranet is a set of networks, using the Internet Protocol and IP-based tools such as web browsers and file transfer applications, that is under the control of a single administrative entity. That administrative entity closes the intranet to all but specific, authorized users. Most commonly, an intranet is the internal network of an organization. A large intranet will typically have at least one web server to provide users with organizational information.An extranet is a network or internetwork that is limited in scope to a single organization or entity but which also has limited connections to the networks of one or more other usually, but not necessarily, trusted organizations or entities ., a company's customers may be given access to some part of its intranet creating in this way an extranet, while at the same time the customers may not be considered 'trusted' from a security standpoint. Technically, an extranet may also be categorized as a CAN, MAN, WAN, or other type of network, although, by definition, an extranet cannot consist of a single LAN; it must have at least one connection with an external network.
The Internet is a specific internetwork. It consists of a worldwide interconnection of governmental, academic, public, and private networks based upon the networking technologies of the Internet Protocol Suite It is the successor of the Advanced Research Projects Agency Network ARPANET developed by DARPA of the U.S. Department of Defense. The Internet is also the communications backbone underlying the World Wide Web WWW. The 'Internet' is most commonly spelled with a capital 'I' as a proper noun, for historical reasons and to distinguish it from other generic internetworks.
Participants in the Internet use a diverse array of methods of several hundred documented, and often standardized, protocols compatible with the Internet Protocol Suite and an addressing systemIP Addresses administered by the Internet Assigned Numbers Authority and address registries. Service providers and large enterprises exchange information about the reachability of their address spaces through the Border Gateway Protocol BGP, forming a redundant worldwide mesh of transmission paths.
In modern practice, the interconnected networks use the Internet Protocol. There are at least three variants of internetwork, depending on who administers and who participates in them,Intranet, Extranet, Internet. Intranets and extranets may or may not have connections to the Internet. If connected to the Internet, the intranet or extranet is normally protected from being accessed from the Internet without proper authorization. The Internet is not considered to be a part of the intranet or extranet, although it may serve as a portal for access to portions of an extranet.
An intranet is a set of networks, using the Internet Protocol and IP-based tools such as web browsers and file transfer applications, that is under the control of a single administrative entity. That administrative entity closes the intranet to all but specific, authorized users. Most commonly, an intranet is the internal network of an organization. A large intranet will typically have at least one web server to provide users with organizational information.An extranet is a network or internetwork that is limited in scope to a single organization or entity but which also has limited connections to the networks of one or more other usually, but not necessarily, trusted organizations or entities ., a company's customers may be given access to some part of its intranet creating in this way an extranet, while at the same time the customers may not be considered 'trusted' from a security standpoint. Technically, an extranet may also be categorized as a CAN, MAN, WAN, or other type of network, although, by definition, an extranet cannot consist of a single LAN; it must have at least one connection with an external network.
The Internet is a specific internetwork. It consists of a worldwide interconnection of governmental, academic, public, and private networks based upon the networking technologies of the Internet Protocol Suite It is the successor of the Advanced Research Projects Agency Network ARPANET developed by DARPA of the U.S. Department of Defense. The Internet is also the communications backbone underlying the World Wide Web WWW. The 'Internet' is most commonly spelled with a capital 'I' as a proper noun, for historical reasons and to distinguish it from other generic internetworks.
Participants in the Internet use a diverse array of methods of several hundred documented, and often standardized, protocols compatible with the Internet Protocol Suite and an addressing systemIP Addresses administered by the Internet Assigned Numbers Authority and address registries. Service providers and large enterprises exchange information about the reachability of their address spaces through the Border Gateway Protocol BGP, forming a redundant worldwide mesh of transmission paths. involves connecting two or more distinct computer networks or network segments via a common routing technology. The result is called an internetwork often shortened to internet. Two or more networks or network segments connected using devices that operate at layer the 'network' layer of the OSI Basic Reference Model, such as a router. Any interconnection among or between public, private, commercial, industrial, or governmental networks may also be defined as an internetwork.
In modern practice, the interconnected networks use the Internet Protocol. There are at least three variants of internetwork, depending on who administers and who participates in them,Intranet, Extranet, Internet. Intranets and extranets may or may not have connections to the Internet. If connected to the Internet, the intranet or extranet is normally protected from being accessed from the Internet without proper authorization. The Internet is not considered to be a part of the intranet or extranet, although it may serve as a portal for access to portions of an extranet.
An intranet is a set of networks, using the Internet Protocol and IP-based tools such as web browsers and file transfer applications, that is under the control of a single administrative entity. That administrative entity closes the intranet to all but specific, authorized users. Most commonly, an intranet is the internal network of an organization. A large intranet will typically have at least one web server to provide users with organizational information.An extranet is a network or internetwork that is limited in scope to a single organization or entity but which also has limited connections to the networks of one or more other usually, but not necessarily, trusted organizations or entities ., a company's customers may be given access to some part of its intranet creating in this way an extranet, while at the same time the customers may not be considered 'trusted' from a security standpoint. Technically, an extranet may also be categorized as a CAN, MAN, WAN, or other type of network, although, by definition, an extranet cannot consist of a single LAN; it must have at least one connection with an external network.
The Internet is a specific internetwork. It consists of a worldwide interconnection of governmental, academic, public, and private networks based upon the networking technologies of the Internet Protocol Suite It is the successor of the Advanced Research Projects Agency Network ARPANET developed by DARPA of the U.S. Department of Defense. The Internet is also the communications backbone underlying the World Wide Web WWW. The 'Internet' is most commonly spelled with a capital 'I' as a proper noun, for historical reasons and to distinguish it from other generic internetworks.
Participants in the Internet use a diverse array of methods of several hundred documented, and often standardized, protocols compatible with the Internet Protocol Suite and an addressing systemIP Addresses administered by the Internet Assigned Numbers Authority and address registries. Service providers and large enterprises exchange information about the reachability of their address spaces through the Border Gateway Protocol BGP, forming a redundant worldwide mesh of transmission paths.
Types of networks
A local area network LAN is a computer network covering a small physical area, like a home, office, or small group of buildings, such as a school, or an airport. Current wired LANs are most likely to be based on Ethernet technology, although new standards like ITUTG.hn also provide a way to create a wired LAN using existing home wires coaxial cables, phone lines and power lines.
For example, a library may have a wired or wireless LAN for users to interconnect local devices., printers and servers and to connect to the internet. On a wired LAN, PCs in the library are typically connected by category cable, running the IEEE protocol through a system of interconnected devices and eventually connect to the Internet. The cables to the servers are typically on Cat e enhanced cable, which will support IEEE at Gbit. A wireless LAN may exist using a different IEEE protocol, or possibly. n. The staff computers bright green in the figure can get to the color printer, checkout records, and the academic network and the Internet. All user computers can get to the Internet and the card catalog. Each workgroup can get to its local printer. Note that the printers are not accessible from outside their workgroup.
Typical library network, in a branching tree topology and controlled access to resourcesAll interconnected devices must understand the network layer layer because they are handling multiple subnets the different colors. Those inside the library, which have only Ethernet connections to the user device and a Gigabit Ethernet connection to the central router, could be called "layer switches" because they only have Ethernet interfaces and must understand IP. It would be more correct to call them access routers, where the router at the top is a distribution router that connects to the Internet and academic networks' customer access routers.
The defining characteristics of LANs, in contrast to WANs wide area networks, include their higher data transfer rates, smaller geographic range, and lack of a need for leased telecommunication lines. Current Ethernet or other .LAN technologies operate at speeds up to. This is the data transfer rate. IEEE has projects investigating the standardization of, and possibly Gbits.Main article: Campus area network.
A campus area network CAN is a computer network made up of an interconnection of local area networks LANs within a limited geographical area. It can be considered one form of a metropolitan area network, specific to an academic setting.In the case of a university campus-based campus area network, the network is likely to link a variety of campus buildings including; academic departments, the university library and student residence halls. A campus area network is larger than a local area network but smaller than a wide area network WAN in some cases.
The main aim of a campus area network is to facilitate students accessing internet and university resources. This is a network that connects two or more LANs but that is limited to a specific and contiguous geographical area such as a college campus, industrial complex, office building, or a military base. A CAN may be considered a type of MAN metropolitan area network, but is generally limited to a smaller area than a typical MAN. This term is most often used to discuss the implementation of networks for a contiguous area. This should not be confused with a Controller Area Network. A LAN connects network devices over a relatively short distance. A networked office building, school, or home usually contains a single LAN, though sometimes one building will contain a few small LANs perhaps one per room, and occasionally a LAN will span a group of nearby buildings. In TCPIP networking, a LAN is often but not always implemented as a single IP subnet.
For example, a library may have a wired or wireless LAN for users to interconnect local devices., printers and servers and to connect to the internet. On a wired LAN, PCs in the library are typically connected by category cable, running the IEEE protocol through a system of interconnected devices and eventually connect to the Internet. The cables to the servers are typically on Cat e enhanced cable, which will support IEEE at Gbit. A wireless LAN may exist using a different IEEE protocol, or possibly. n. The staff computers bright green in the figure can get to the color printer, checkout records, and the academic network and the Internet. All user computers can get to the Internet and the card catalog. Each workgroup can get to its local printer. Note that the printers are not accessible from outside their workgroup.
Typical library network, in a branching tree topology and controlled access to resourcesAll interconnected devices must understand the network layer layer because they are handling multiple subnets the different colors. Those inside the library, which have only Ethernet connections to the user device and a Gigabit Ethernet connection to the central router, could be called "layer switches" because they only have Ethernet interfaces and must understand IP. It would be more correct to call them access routers, where the router at the top is a distribution router that connects to the Internet and academic networks' customer access routers.
The defining characteristics of LANs, in contrast to WANs wide area networks, include their higher data transfer rates, smaller geographic range, and lack of a need for leased telecommunication lines. Current Ethernet or other .LAN technologies operate at speeds up to. This is the data transfer rate. IEEE has projects investigating the standardization of, and possibly Gbits.Main article: Campus area network.
A campus area network CAN is a computer network made up of an interconnection of local area networks LANs within a limited geographical area. It can be considered one form of a metropolitan area network, specific to an academic setting.In the case of a university campus-based campus area network, the network is likely to link a variety of campus buildings including; academic departments, the university library and student residence halls. A campus area network is larger than a local area network but smaller than a wide area network WAN in some cases.
The main aim of a campus area network is to facilitate students accessing internet and university resources. This is a network that connects two or more LANs but that is limited to a specific and contiguous geographical area such as a college campus, industrial complex, office building, or a military base. A CAN may be considered a type of MAN metropolitan area network, but is generally limited to a smaller area than a typical MAN. This term is most often used to discuss the implementation of networks for a contiguous area. This should not be confused with a Controller Area Network. A LAN connects network devices over a relatively short distance. A networked office building, school, or home usually contains a single LAN, though sometimes one building will contain a few small LANs perhaps one per room, and occasionally a LAN will span a group of nearby buildings. In TCPIP networking, a LAN is often but not always implemented as a single IP subnet.
Networking
The following list presents categories used for classifying networks.Computer networks can also be classified according to the hardware and software technology that is used to interconnect the individual devices in the network, such as Optical fiber,Ethernet,Wireless LAN, HomePNA, Power line communication or G.hn.Ethernet uses physical wiring to connect devices. Frequently deployed devices include hubs, switches, bridges andor routers.Wireless LAN technology is designed to connect devices without wiring. These devices use radio waves or infrared signals as a transmission medium.
ITU-T G.hn technology uses existing home wiring coaxial cable, phone lines and power lines to create a highspeed up to Gigabits local area network.Networks are often classified as Local Area Network LAN, Wide Area Network WAN, Metropolitan Area Network MAN Personal Area Network PAN, Virtual Private Network VPN,Campus Area Network CAN, Storage Area Network SAN, etc. depending on their scale, scope and purpose.
Usage, trust levels and access rights often differ between these types of network - for example, LANs tend to be designed for internal use by an organization's internal systems and employees in individual physical locations such as a building, while WANs may connect physically separate parts of an organization to each other and may include connections to third parties.Computer networks may be classified according to the functional relationships which exist among the elements of the network, e.g., Active Networking, Clientserver and Peertopeer workgrouparchitecture.Main article: Network topology.
Computer networks may be classified according to the network topology upon which the network is based, such as bus network, star network, ring network, mesh network, starbus network, tree or hierarchical topology network. Network topology signifies the way in which devices in the network see their logical relations to one another. The use of the term "logical" here is significant. That is, network topology is independent of the "physical" layout of the network.
Even if networked computers are physically placed in a linear arrangement, if they are connected via a hub, the network has a Star topology, rather than a bus topology. In this regard the visual and operational characteristics of a network are distinct; the logical network topology is not necessarily the same as the physical layout. Networks may be classified based on the method of data used to convey the data, these include digital and analog networks
ITU-T G.hn technology uses existing home wiring coaxial cable, phone lines and power lines to create a highspeed up to Gigabits local area network.Networks are often classified as Local Area Network LAN, Wide Area Network WAN, Metropolitan Area Network MAN Personal Area Network PAN, Virtual Private Network VPN,Campus Area Network CAN, Storage Area Network SAN, etc. depending on their scale, scope and purpose.
Usage, trust levels and access rights often differ between these types of network - for example, LANs tend to be designed for internal use by an organization's internal systems and employees in individual physical locations such as a building, while WANs may connect physically separate parts of an organization to each other and may include connections to third parties.Computer networks may be classified according to the functional relationships which exist among the elements of the network, e.g., Active Networking, Clientserver and Peertopeer workgrouparchitecture.Main article: Network topology.
Computer networks may be classified according to the network topology upon which the network is based, such as bus network, star network, ring network, mesh network, starbus network, tree or hierarchical topology network. Network topology signifies the way in which devices in the network see their logical relations to one another. The use of the term "logical" here is significant. That is, network topology is independent of the "physical" layout of the network.
Even if networked computers are physically placed in a linear arrangement, if they are connected via a hub, the network has a Star topology, rather than a bus topology. In this regard the visual and operational characteristics of a network are distinct; the logical network topology is not necessarily the same as the physical layout. Networks may be classified based on the method of data used to convey the data, these include digital and analog networks
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