How Many type Network And devices Using in Scenario

Network devices are components used to connect computers or other electronic devices together so that they can share files or resources like printers or fax machines. Devices used to setup a Local Area Network (LAN) are the most common types of network devices used by the public. A LAN requires a hub, router, cabling or radio technology, network cards, and if online access is desired, a high-speed modem. This is much less complicated than it might sound to someone new to networking.

 

Routers

A router is a communications device that connects multiple computers or other routers togehter and transmits data to its correct destination on the network. A router can be used on any size of network. On the largest scale, routers along the Internet backbone forward data packets to their destination using the fastest available path. For smaller business and home networks, a router allows multiple computers to share a single high-speed Internet connection such as through a cable modem or DSL modem. These routers connect from 2 to 250 computers.

To prevent unauthorized users from accessing files and computers, many routers are protected by a built-in antivirus protection. Routers also support wireless communications, eliminating the need for a separate wireless access point in a wireless network. If network has a separate wireless access point, it connects to the router via a cable. Some routers also include additional functionaliity such as including a built-in print server. Today’s routers or combination wireless access point/routers are easy to configure and secure against unauthorized access.

 

A modem links your home entwork to the Internet through your Internet Service Provider (ISP). The high speed types o data outside o your home arn’t suitable or your direct use, so modems convert the data into digital Ethernet, which all the network equipment in your home can use.
The internet services that are outside your home (or business) whcih are supplied by your ISP are either DSL, cable, dial-up, or satelite. Modems are often combind with a router into a single unit, whcih then also gives you a firewall protecting your network rom attack. If your modem is not also a router, then you will probably want a router in addition to your modem.

    

Dial-up Modems

A computer’s digital signals must be converted to analog signals before they are transmitted over standard telephone lines. The communications devices that perorm this conversion in a modem, sometimes called a dial-up modem. The word, modem, is derived rom the combination of the words, modulate, to change into an analog signal, and demodulation, to convert an analog signal into a digital signal.
Both the sending and receiving ends o a standard telephone line (communications channel) must have a dial-up modem or data transmission to occur. For example, a dial-up modem connected to a sending computer converts the computer’s digital signals into analog signals. The analog signals then can travel over a standard telephone line. At the receiving end, i necessary, another dial-up modem converts the analog signals back into digital signals that a receiving computer can process.
 

A dial-up modem usually is in the form o an adapter card that you insert in an expansion slot on a computer’s motherboard. One end o a standard telephone cord attaches to a port on the modem card and the other end plugs into a telephone outlet. Devices other than computers also use modems. A stand-alone fax machine, for example, has a modem that converts a scanned digitized image into an analog signal that is sent to a recipient’s fax machine.

ISDN and DSL Modems

If you access the Internet using ISDN or DSL, you need a communications device to send and receive the digital ISDN or DSL signals. A digital modem is a modem that sends and receives data and inormation to and rom a digital telephone line such as ISDN or DSL. An ISDN modem sends digital data and information to and from a computer to an ISDN line and receives digital data and information rom an ISDN line. A DSL modem sends digital data and information rom a computer to a DSL line and receives digital and information rom a DSL line. ISDN and DSL modems usually are external devices, in which one end connects to the telephone line and the other end connects to a port on the system unit. Most include built-in Wi-Fi connectivity.

Cable Modems

A cable modem, sometimes called a broadband modem, is a digital modem that sends and receives digital data over the cable television (CATV) network. With more than 110 million homes wired or cable television, cable modems provide a faster Internet access alternative to dial-up or the home user and have speeds similar to DSL. Cable modems currently can transmit data at speeds that are much faster than either a dial-up modem or ISDN. Cable modems typically include built-in Wi-Fi connectivity. CATV service enters your home through a single line. To access the Internet using the CATV service, the CATV company installs a splitter inside your house. From the splitter, one part of the cable runs to your televisions and the other part connects to the cable modem.

Wireless Modem

Some mobile users have a wireless modem that users the mobile phone network to connect to the Internet wirelessly from a notebook computer, a smart phone, or other mobile device. Wireless modems, which have an external or built-in antenna, are available as PC Cards, Express Card modules, and flash cards.

Switch

A switch or network switch is a small hardware device that joins multiple computers togethern within one Local Area Network (LAN). Technically, network switches operate at layer two (Data Link Layer) o the OSI Model.

Network switches appear nearly identical to network hubs, but a switch generally contains more intelligence (and a slightly higher price tag) than a hub. Unlike hubs, network switches are capable of inspecting data packets as they are received, determining the source and destination device of each packet, and forwarding them appropriately. By delivering messages only to the connected device intended, a network switch conserves network bandwidth and offers generally better performance than a hub. As with hubs, Ethernet implementations of network switches are the most common. Mainstream Ethernet switches support either 10/100 Mbps Fast Ethernet or Gigabit Ethernet (10/100/1000) standards.
Difference models o network switches support differing numbers of connected devices. Most consumer-grade network switches provide either four or eight connections or Ethernet devices. Switches can be connected to each other, a so-called daisy chaining method to add progressively larger number of devices to a LAN.

Hub

A hub is used in a wired network to connect Ethernet cables from a number of devices together. The hub allows each device to talk to the others. Hubs aren’t used in networks with only wireless connections, since network devices such as routers and adapters communicate directly with one another.
Hubs are such simple devices – they require no configuration, and have no manuals – that their function is now included in other devices such as routers and modems.

Difference between a Network Switch and a Hub

A switch is effectively a higher-perormance alternative to a hub. People tend to beneit rom a switch over a hub i their home network has four or more computers, or if they want to use their home network applications that generate significant amounts of network traffic, like multiplayer games or heavy music file sharing. In most cases, home networkers will not notice an appreciable diference between a hub and a switch (hubs do cost slightly less).
Technically speaking, hubs operate using a broadcast model and switches operate using virtual cicuit model. When four computers are connected to a hub, for example, and two of those computer communicate with each other, hubs simply pass through all network traffic to each of the four computers. Switches, on the other hand, are cabable o determining the destination of each individual traffic element (such as an Ethernet frame) and selectively forwarding data to the one comptuer that actually needs it. By generating less network traic in delivering messages, a switch perfroms better than a hub on busy networks

Firewall

A firewall is hardware and/or software that protects a network’s resources from intrusion by users on another network such as the Internet. All networked and online computer users should implement a firewall solution.
Companies use firewalls to protect network resources rom outsiders and to restrict employees’ access to sensitive data such as payroll or personnel records. Businesses can implement a firewall solution themselves or outsource their needs to a company specializing in providing firewall protection. Large companies oten route all their communications trhough a proxy server, which typically is a component o the firewall. A proxy server is a server outside the company’s network that controls which communications pass into the company’s network. That is, a proxy server carefully screens all incoming and outgoing messages. Proxy servers use a variety o screening techniques. Some check the domain name or IP address o the message or legitimacy. Others require that the message have digital signatures.

Home and small office/home office users often protect their computers with personal firewall. A personal firewall is a utility that detects and protects a personal computer and its data from unauthorized intrusions. Personal firewalls constantly monitor all transmissions to and from the computer and inorm you of any attempted intrusion. Some operating systems, such as Windows Vista, include personal firewalls. For enhanced firewall protection , many users purchase stand-alone personal firewall, and other similar software.
Some small office/home office users purchase a hardware firewall, such as a router or other device that has a built-in firewall, in addition to or instead of personal firewall sotware. Hardware firewalls stop intrusions beore they break in your computer.
  Wireless Access PointA wireless access point is a central communications device that allows computers and devices to transfer data wirelessly among themselves or to transfer data wirelessly to a wired network. Wireless access points have high-quality antennas for optimal signals. For the best signal, some manufacturers suggest positioning the wireless access point at the highest possible location.
Wireless access points around school’s allow students to access the school network wirelessly from their classrooms, the notebook computer, or mobile device must have built-in wireless capability or a wireless network card.


 

Repeaters

A repeater connects two segments of your network cable. It retimes and regenerates the signals to proper amplitudes and sends them to other segments. When talking about, ethernet topology, you are probably talking about using a hub as a repeater. Repeaters require a small amount o time to regenerate the signal. This can cause a propagation delay which can affect network communication when there are several repeaters in a row.
Many network architectures limit the number of repeaters that can be used in a row. Repeaters work only at the physical layer of the OSI network model.

 

 

 

Bridge 

A bridge reads the outermost section of data on the data packet, to tell where the message is going. It reduces the traffic on other network segments, since it does not send all packets. Bridges can be programmed to reject packets from particular networks. Bridging occurs at the data link layer of the OSI model, whcih means the bridge cannot read IP address, but only the outermost hardware address of the packet. In our case the bridge can read the ethernet data whcih gives the hardware address of the destination address, not the IP address. Bridges forward all broadcast messages. Only a special bridge called a translation bridge will allow two networks of different architectures to be connected. Bridges do not normally allow connection of networks with different architectures. The hardware address is also called the MAC (media access control) address. To determine the network segment a MAC address belongs to, bridges use one of the followin Transparent Bridging – They build a table of addresses (bridging table) as they receive packets. If the address is not in the bridging table, the packet is forwarded to all segments other than the one it came from. This type of bridge is used on ethernet networks. Source Route Bridging – The source computer provides path information inside the packet. This is used on Token Ring networks. 
Gateways

A gateway can translate information between different network data formats or network architectures. It can translate TCP/IP to AppleTalk so computers supporting TCP/IP can communicate with Apple brand computers. Most gateways operate at the application layer, but can operate at the network or session layer o the OSI model. Gateways will start at the lower level and strip information until it gets to the required level and repackage the information and work its way back toward the hardware layer of the OSI model. To confuse issues, when talking about a router that is used to interface to another network, the word gateway is often used. This does not mean the routing machine is a gateway as defined here, although it could be.