Basic Hardware Components
• 3.1 Network Interface Cards
• 3.2 Repeaters
• 3.3 Hubs
• 3.4 Bridges
• 3.5 Switches
• 3.6 Routers
Network Interface Card
A network interface card is used to connect a computer to an Ethernet network. This type of card provides an interface to the media. This may be either using an external transceiver or through an internal integrated transceiver mounted on the network interface card PCB. The card usually also contains the protocol control firmware and Ethernet Controller needed to support the Medium Access Control (MAC) data link protocol used by Ethernet.
About Ethernet-
Local Area Networks (LANS) most often use a core standard IEEE 802.3 (also known informally as "Ethernet"). This is the most widely used LAN technology in the world today. Although IEEE 802.3 differs somewhat from earlier standards such as the predefined “blue book” both types may be used with the same local area networks.
Network Repeater
A repeater connects two segments of your network cable. It retimes and regenerates the signals to proper amplitudes and sends them to the other segments. When talking about, ethernet topology, you are probably talking about using a hub as a repeater. Repeaters require a small amount of 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.
Network Hubs
An Ethernet hub or concentrator is a device for connecting multiple twisted pair or fiber optic Ethernet devices together, making them act as a single segment. Hubs work at the physical layer (layer 1) of the OSI model. The device is thus a form of multiport repeater. Ethernet hubs are also responsible for forwarding a jam signal to all ports if it detects a collision.
Bridges
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, which means the bridge cannot read IP addresses, but only the outermost hardware address of the packet. In our case the bridge can read the ethernet data which 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:
• 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.
Switches
Types of Switches
Switches are data link layer devices that, like bridges, enable multiple physical LAN segments to be interconnected into a single larger network. Similar to bridges, switches forward and flood traffic based on MAC addresses. Any network device will create some latency. Switches can use different forwarding techniques—two of these are store-and-forward switching and cut-through switching.
In store-and-forward switching, an entire frame must be received before it is forwarded. This means that the latency through the switch is relative to the frame size—the larger the frame size, the longer the delay through the switch. Cut-through switching allows the switch to begin forwarding the frame when enough of the frame is received to make a forwarding decision. This reduces the latency through the switch. Store-and-forward switching gives the switch the opportunity to evaluate the frame for errors before forwarding it. This capability to not forward frames containing errors is one of the advantages of switches over hubs. Cut-through switching does not offer this advantage, so the switch might forward frames containing errors. Many types of switches exist, including ATM switches, LAN switches, and various types of WAN switches.
ATM Switch
Asynchronous Transfer Mode (ATM) switches provide high-speed switching and scalable bandwidths in the workgroup, the enterprise network backbone, and the wide area. ATM switches support voice, video, and data applications, and are designed to switch fixed-size information units called cells, which are used in ATM communications. Figure 4-3 illustrates an enterprise network comprised of multiple LANs interconnected across an ATM backbone.
LAN Switch
LAN switches are used to interconnect multiple LAN segments. LAN switching provides dedicated, collision-free communication between network devices, with support for multiple simultaneous conversations. LAN switches are designed to switch data frames at high speeds. Figure 4-4 illustrates a simple network in which a LAN switch interconnects a 10-Mbps and a 100-Mbps Ethernet LAN.
Routers- Types of routers
Network Router
A router is used to route data packets between two networks. It reads the information in each packet to tell where it is going. If it is destined for an immediate network it has access to, it will strip the outer packet, readdress the packet to the proper ethernet address, and transmit it on that network. If it is destined for another network and must be sent to another router, it will re-package the outer packet to be received by the next router and send it to the next router. The section on routing explains the theory behind this and how routing tables are used to help determine packet destinations. Routing occurs at the network layer of the OSI model. They can connect networks with different architectures such as Token Ring and Ethernet. Although they can transform information at the data link level, routers cannot transform information from one data format such as TCP/IP to another such as IPX/SPX. Routers do not send broadcast packets or corrupted packets. If the routing table does not indicate the proper address of a packet, the packet is discarded.
A computer network may fail to function properly for many different reasons. Understanding basic network troubleshooting methods in various situations will help you recover quickly on home networks and elsewhere.
Internet Connection Problems: General Tips For Troubleshooting Your wireless home computer network
If you've finished installing the components, but your home network isn't functioning correctly, troubleshoot methodically:
• Your system does not connect to the internet: Try turning off your firewall to see if you have a firewall configuration problem. Try reconnecting to the web. No luck? Proceed to the next step-
• Wireless Adapters: test wireless adapters one at a time to determine if problems are isolated to a single computer or common to the whole network. Still having problems? Check out the next step: .
• Try ad hoc networking if infrastructure networking isn't functional, and perhaps you'll identify a problem with your access point or router.
Further Networking Suggestions:
To help you work methodically, as you build your network, write down on paper the key settings like network name, WEP passkey, MAC addresses, and channel numbers (then eat the evidence afterward!). Remember that you can go back and correct mistakes in your WLAN (wireless lan) settings any time.
Tips for Troubleshooting Windows File and Printer Sharing
1. Name Each Computer Correctly
On a peer-to-peer Windows network, all computers must possess unique names. Ensure all computer names are unique and each follows the Microsoft naming recommendations. For example, consider avoiding spaces in computer names: Windows 98 and other older versions of Windows will not support file sharing with computers having spaces in their name. The length of computer names, the case (upper and lower) of names and the use of special characters must also be considered.
2. Name Each Workgroup (or Domain) Correctly
Each Windows computer belongs either to a workgroup or a domain. Home networks and other small LANs utilize workgroups, whereas larger business networks operate with domains. Whenever feasible, ensure all computers on a workgroup LAN have the same workgroup name. While sharing files between computers belonging to different workgroups is possible, it is also more difficult and error-prone. Similarly, in Windows domain networking, ensure each computer is set to join the correct named domain.
3. Install TCP/IP on Each Computer
TCP/IP is the best network protocol to use when setting up a Windows LAN. In some circumstances, it's possible to use the alternative NetBEUI or IPX/SPX protocols for basic file sharing with Windows. However, these other protocols normally don't offer any additional functionality beyond what TCP/IP provides. Their presence also can create technical difficulties for the network. It is strongly recommended to install TCP/IP on each computer and uninstall NetBEUI and IPX/SPX whenever possible.
4. Set up Correct IP Addressing and Subnetting
On home networks and other LANs having a single router or gateway computer, all computers must operate in the same subnet with unique IP addresses. First, ensure the network mask (sometimes called "subnet mask") is set to the same value on all computers. The network mask "255.255.255.0" is normally correct for home networks. Then, ensure each computer possesses a unique IP address. Both the network mask and other IP address settings are found in the TCP/IP network configuration.
5. Verify File and Printer Sharing for Microsoft Networks is Installed
"File and Printer Sharing for Microsoft Networks" is a Windows network service. This service must be installed on a network adapter to enable that computer to participate in file sharing. Ensure this service is installed by viewing the adapter's properties and verifying that a)this service appears in the list of installed items and b)the checkbox next to this service is checked.
6. Temporarily or Permanently Disable Firewalls
The Internet Connection Firewall (ICF) feature of Windows XP computers will interfere with peer-to-peer file sharing. For any Windows XP computer on the network that needs to participate in file sharing, ensure the ICF service is not running. Misconfigured third-party firewall products can also interfere with LAN file sharing. Consider temporarily disabling (or lowering the security level of) Norton, ZoneAlarm and other firewalls as part of troubleshooting file sharing problems.
7. Verify Shares are Correctly Defined
To share files on a Windows network, ultimately one or more network shares must be defined. Share names that end with a dollar sign ($) will not appear in the list of shared folders when browsing the network (although these can still be accessed). Ensure shares have been defined on the network appropriately, following the Microsoft recommendations for share naming.
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Processors
Configurator