What is Networking Hardware?

Networking hardware includes all computers, peripherals, interface cards and other equipment needed to perform data-processing and communications within the network.

1) File/Network Servers

One or more network servers is a part of nearly every local area network.These are very fast computers with a large amount of RAM and storage space, along with a one or more fast network interface card(s). The network operating system provides tools to share server resources and information with network users. A sophisticated permissions-handling system is included, so that access to sensitive information can be carefully tailored to the needs of the users. For small networks, a singe network server may provide access control, file sharing, printer sharing, email, database, and other services.
The network server may be responding to requests from many network users simultaneously. For example, it may be asked to load a word processor program to one workstation, receive a database file from another workstation, and store an e-mail message during the same time period. This requires a computer that can store and quickly share large amounts of information. When configuring such a server, budget is usually the controlling factor. The following guidelines should be followed:

• Fastest processor(s)
• Large amount of RAM
• multiple large, fast hard drives
• Extra expansion slots
• Fast network interface card(s) 

 

2) Workstations 

Computers that humans use are broadly categorized as workstations. A typical workstation is a computer that is configured with a network interface card, networking software, and the appropriate cables. Workstations do not necessarily need large storage hard drives, because files can be saved on the file server. Almost any computer can serve as a network workstation.

3) Laptops/Mobile Devices

Laptops and other mobile devices are becoming more and more common. These devices typically have modest internal storage, but enough power to serve as a workstation for users on the go. These machines nearly always have a wireless adapter to allow quick network connections without cumbersome cabling. In a school environment with good wireless coverage, a mobile device user can move about the campus freely, and remain continuously connected to the network.

4) Network Interface Cards

The network interface card (NIC) provides the physical connection between the network and the computer workstation. Most NICs are internal, and they are included in the purchase of most computers. Network interface cards are a major factor in determining the speed and performance of a network. It is a good idea to use the fastest network card available for the type of workstation you are using.
The most common network interface connections are Ethernet cards and wireless adapters.

5) Ethernet Cards

Ethernet cards are usually included with a computer, although additional ethernet cards can be purchased and installed on most computers,. Ethernet cards can contain connections for either coaxial or twisted pair cables (or both). If it is designed for coaxial cable, the connection will be BNC. If it is designed for twisted pair, it will have a RJ-45 connection. Some Ethernet cards also contain an AUI connector. This can be used to attach coaxial, twisted pair, or fiber optics cable to an Ethernet card. When this method is used there is always an external transceiver attached to the workstation. Only the RJ-45 connector is found on most modern ethernet cards.

6) Wireless Adapters

Wireless adapters are found in most portable devices, such as laptops, smart phones, and tablet devices. External wireless adapters can be purchased and installed on most computers having an open USB (Universal Serial Bus) port, or unused expansion slot.

 

7) Switches

An ethernet switch is a device that provides a central connection point for cables from workstations, servers, and peripherals. In a star topology, twisted-pair wire is run from each workstation to a central switch/hub. Most switches are active, that is they electrically amplify the signal as it moves from one device to another. The predecessor of the switch was the hub, which broadcasted all inbound packets out all ports of the device, creating huge amounts of unnecessary network traffic. Modern switches build a port map of all IP address which respond on each port, and only broadcasts on all ports when it doesn't have a packet's target IP address already in its port map. Switches are:

• Usually configured with 8, 12, or 24 RJ-45 ports
• Often used in a star or tree topology
• Available as "managed" or "unmanaged", with the later less expensive, but adequate for smaller networks
• direct replacements for hubs, immediately reducing network traffic in most networks
• Usually installed in a standardized metal rack that also may store network servers, bridges, or routers.

 

8) Repeaters

Since a signal loses strength as it passes along a cable, it is often necessary to boost the signal with a device called a repeater. The repeater electrically amplifies the signal it receives and rebroadcasts it. Repeaters can be separate devices or they can be incorporated into a concentrator. They are used when the total length of your network cable exceeds the standards set for the type of cable being used.
A good example of the use of repeaters would be in a local area network using a star topology with unshielded twisted-pair cabling. The length limit for unshielded twisted-pair cable is 100 meters. The most common configuration is for each workstation to be connected by twisted-pair cable to a multi-port active concentrator. The concentrator amplifies all the signals that pass through it allowing for the total length of cable on the network to exceed the 100 meter limit.

 

9) Bridges

A bridge is a device that allows you to segment a large network into two smaller, more efficient networks. If you are adding to an older wiring scheme and want the new network to be up-to-date, a bridge can connect the two.
A bridge monitors the information traffic on both sides of the network so that it can pass packets of information to the correct location. Most bridges can "listen" to the network and automatically figure out the address of each computer on both sides of the bridge. The bridge can inspect each message and, if necessary, broadcast it on the other side of the network.
The bridge manages the traffic to maintain optimum performance on both sides of the network. You might say that the bridge is like a traffic cop at a busy intersection during rush hour. It keeps information flowing on both sides of the network, but it does not allow unnecessary traffic through. Bridges can be used to connect different types of cabling, or physical topologies. They must, however, be used between networks with the same protocol.

10) Routers

Routers are the traffic directors of the global internet. All routers maintain complex routing tables which allow them to determine appropriate paths for packets destined for any address. Routers communicate with each other, and forward network packets out of or into a network. Here's an example:
You want to search for something on the internet using a search engine. You open a browser on your workstation. The browser opens to a blank page (not usually the default, but appropriate for this example). You type "http://www.google.com" into the URL (Universal Resource Locator) address line of the browser. The browser software packages up the URL you typed, and sends it with a request for an IP address to the DNS (Domain Name Server) that has been set in your network adapter's configuration. The domain server returns an IP, such as 74.125.67.103 (actual address returned by DNS for google.com on June 7th, 2011). The browser ships the request for that IP address off to the network card, which bundles the request into an ethernet packet, destined for 74.125.67.103. The network card sends the packet to the gateway of your network, which opens the header of the packet, and makes a determination that the packet is traveling out of your network, in search of 74.125.67.103. Your network's router has routing tables which it has been building from communicating with other routers, and potentially augmented with "static routes", which are specific paths added by your network's administrators to make the task of accessing certain networks easier, or faster, or in some cases, not possible. In this case, I find that my router knows about another router at my ISP(Internet Service Provider), which in turn has several more routers that are all on networks of which I am just a small node, much like finding an atom of a molecule of a piece of dust on a rock on a moon of a planet of a sun of a galaxy of the universe. In any case, the packet gets passed from router to router, each time moving out of the subnets of the packet sender, towards a router that will know where the desired server is. The packet finally reaches the router of the network at 74.125.67.103, which dutifully delivers the packet to the server at that IP address. The server carefully crafts a response, and sends a reply back, which follows the same process to get the response "Yes. Go ahead" back to the requester. Whew. And that's just the initial request.
While bridges know the addresses of all computers on each side of the network, routers know the addresses other routers which in turn know about their own networks. Routers can even "listen" to entire networks to determine which sections are busiest -- they can then redirect data around those sections until traffic congestion clears.
So, routers are network gateways. They move network packets from one network to another, and many can convert from one network protocol to another as necessary. Routers select the best path to route a message, based on the destination address of the packet. The router can direct traffic to prevent head-on collisions, and is smart enough to know when to direct traffic along back roads and shortcuts.
If you have a school LAN that you want to connect to the Internet, you will need to purchase a router. In this case, the router serves as the forwarder between the information on your LAN and the Internet. It also determines the best route to send the data over the Internet.

 

11) Firewalls

A firewall is a networking device that is installed at the entrance to a LAN when connecting a networks together, particularly when connecting a private network to a public network, such as the internet. The firewall uses rules to filter traffic into and out of the private network, to protect the private network users and data from malevolent hackers.
Firewalls are either hardware or software, depending on their intended use. A firewall used to protect a network is a hardware device that should be installed in the network between the router and the network. Almost all hardware firewalls will have at least two ports, labeled "Trusted" and "Untrusted". These terms imply the true nature of the firewall's responsibility to the private network. The public network is connected to the untrusted network port, and the private network is connected to the trusted port.
Firewall rules are usually simple, consisting of a verb, either allow or deny, the direction of the traffic, either inbound or outbound, and an address or other network traffic identifier. Firewall rules are cumulative, so general rules may be specified, and exceptions added as necessary. Some examples are:

• Allow outbound all (all private network users can do anything on the public network)
• Deny inbound all (default setting to prevent all traffic from the public or untrusted port, to the private port)
• Allow inbound port 80 (allow internet web traffic to come into network to find web servers)
• Allow inbound port 80 destined to 170.200.201.25 (allow inbound web traffic to a specific web server on your private network)
• Deny inbound from 201.202.1.1/24 (deny all inbound traffic from a specific IP address or range of addresses)

ABOUT TOPOLOGY...

What is a Topology?

The physical topology of a network refers to the configuration of cables, computers, and other peripherals. Physical topology should not be confused with logical topology which is the method used to pass information between workstations. Logical topology was discussed in the Protocol chapter.

Linear Bus  

A linear bus topology consists of a main run of cable with a terminator at each end. All nodes (file server, workstations, and peripherals) are connected to the linear cable.

Advantages of a Linear Bus Topology

• Easy to connect a computer or peripheral to a linear bus.
• Requires less cable length than a star topology.

 Disadvantages of a Linear Bus Topology

• Entire network shuts down if there is a break in the main cable.
• Terminators are required at both ends of the backbone cable.
• Difficult to identify the problem if the entire network shuts down.
• Not meant to be used as a stand-alone solution in a large building. 

Star

A star topology is designed with each node (file server, workstations, and peripherals) connected directly to a central network hub, switch, or concentrator.
Data on a star network passes through the hub, switch, or concentrator before continuing to its destination. The hub, switch, or concentrator manages and controls all functions of the network. It also acts as a repeater for the data flow. This configuration is common with twisted pair cable; however, it can also be used with coaxial cable or fiber optic cable.

Advantages of a Star Topology

• Easy to install and wire.
• No disruptions to the network when connecting or removing devices.
• Easy to detect faults and to remove parts.

Disadvantages of a Star Topology

• Requires more cable length than a linear topology.
• If the hub, switch, or concentrator fails, nodes attached are disabled.
• More expensive than linear bus topologies because of the cost of the hubs, etc. 

Tree or Expanded Star

A tree topology combines characteristics of linear bus and star topologies. It consists of groups of star-configured workstations connected to a linear bus backbone cable (See fig. 3). Tree topologies allow for the expansion of an existing network, and enable schools to configure a network to meet their needs.

Advantages of a Tree Topology

• Point-to-point wiring for individual segments.
• Supported by several hardware and software venders.

Disadvantages of a Tree Topology

• Overall length of each segment is limited by the type of cabling used.
• If the backbone line breaks, the entire segment goes down.
• More difficult to configure and wire than other topologies. 

Definition you should know...

 10Base2 - Ethernet specification for thin coaxial cable, transmits signals at 10 Mbps (megabits per second) with a distance limit of 185 meters per segment.

10Base5 - Ethernet specification for thick coaxial cable, transmits signals at 10 Mbps (megabits per second) with a distance limit of 500 meters per segment.

 
10BaseF - Ethernet specification for fiber optic cable, transmits signals at 10 Mbps (megabits per second) with a distance limit of 2000 meters per segment.
 
10BaseT - Ethernet specification for unshielded twisted pair cable (category 3, 4, or 5), transmits signals at 10 Mbps (megabits per second) with a distance limit of 100 meters per segment.
 
100BaseT - Ethernet specification for unshielded twisted pair cabling that is used to transmit data at 100 Mbps (megabits per second) with a distance limit of 100 meters per segment.
 
1000BaseTX -Ethernet specification for unshielded twisted pair cabling that is used to transmit data at 1 Gbps (gigabits per second) with a distance limitation of 220 meters per segment.
 
Asynchronous Transfer Mode (ATM) - A network protocol that transmits data at a speed of 155 Mbps and higher. It is most often used to interconnect two or more local area networks.
 
Backbone - A cable to which multiple nodes or workstations are attached.
 
Bit - Binary digit in the binary numbering system. Its value can be 0 or 1. In an 8-bit character scheme, it takes 8 bits to make a byte (character) of data.
 
BNC Connector (Bayone-Neill-Concelman) - Standard connector used to connect 10Base2 coaxial cable.
 
Bridge - Devices that connect and pass packets between two network segments that use the same communications protocol.
 
Byte - an 8-bit long binary value, which originally mapped to text character values (between 0 and 255 decimal). For example, a decimal value of 65, represented in a binary byte is "01000001" and represents the capital letter "A". A byte also is the atomic value of data storage, so a megabyte is the amount of memory required to store a million bytes.
 
Cable - Transmission medium of copper wire or optical fiber wrapped in a protective cover.
 
Client/Server - A networking system in which one or more file servers (Server) provide services; such as network management, application and centralized data storage for workstations (Clients)
 
Coaxial Cable - Cable consisting of a single copper conductor in the center surrounded by a plastic layer for insulation and a braided metal outer shield.
 
E-mail - An electronic mail message sent from a host computer to a remote computer.
 
End User - Refers to the human executing applications on the workstation.
 
Ethernet - A network protocol invented by Xerox Corporation and developed jointly by Xerox, Intel and Digital Equipment Corporation. Ethernet networks use CSMA/CD and run over a variety of cable types at 10 Mbps (megabits per second).
 
Fast Ethernet - An Ethernet standard that supports 100 Mbps using category 5 twisted pair or fiber optic cable.
 
Fiber Distributed Data Interface (FDDI) - A network protocol that is used primarily to interconnect two or more local area networks, often over large distances.
 
Fiber Optic Cable - A cable, consisting of a center glass core surrounded by layers of plastic, that transmits data using light rather than electricity. It has the ability to carry more information over much longer distances.
 
File Server - A computer connected to the network that contains primary files/applications and shares them as requested with the other computers on the network. If the file server is dedicated for that purpose only, it is connected to a client/server network. An example of a legacy client/server network is Novell Netware. All the computers connected to a peer-to-peer network are capable of being the file server. Most modern operating systems can operate as servers or as clients, greying the distinction in the server architecture.
 
Firewall - A security device which inspects traffic entering and leaving a network, and allows or disallows the traffic, depending on rules describing acceptable use of the network, by filtering out unwanted packets. The firewall is usually positioned as the gateway device to another network, such as the internet. Many routers now contain firewalls. A personal firewall is usually software that runs on a workstation or server to filter unwanted traffic at the individual machine.
 
Gigabit Ethernet - An Ethernet protocol that raises the transmission rates to 1 Gbps (gigabits per second). Most school, corporate, and household networks provide gigabit ethernet to the workstations via cabled connections.
 
Gigabyte (GB) - One billion bytes of information. One thousand megabytes.
 
Hub - A hardware device that contains multiple independent but connected modules of network and internetwork equipment. Hubs can be active (where they repeat signals sent through them) or passive (where they do not repeat but merely split signals sent through them).
 
Infrared - Electromagnetic waves whose frequency range is above that of microwaves, but below that of the visible spectrum.
 
Intranet - Network internal to an organization that uses Internet protocols.
 
Internet - A global network of networks used to exchange information using the TCP/IP protocol. It allows for electronic mail and the accessing ad retrieval of information from remote sources.
 
LAN (Local Area Network) - A network connecting computers in a relatively small area such as a building.
 
Linear Bus - A network topology in which each node attaches directly to a common cable.
 
LocalTalk - Apple Corporation proprietary protocol that uses CSMA/CA media access scheme and supports transmissions at speeds of 230 Kbps (Kilobits per second).
 
MAN (Metropolitan Area Network) - A network connecting computers over a large geographical area, such as a city or school district.
 
MAU (Multistation Access Unit) - A Token Ring wiring hub.
 
Modem (Modulator/Demodulator) - Devices that convert digital and analog signals. Modems allow computer data (digital) to be transmitted over voice-grade telephone lines (analog).
 
Multiplexer - A device that allows multiple logical signals to be transmitted simultaneously across a single physical channel.
 
Network Modem - A modem connected to a Local Area Network (LAN) that is accessible from any workstation on the network.
 
Network Interface Card (NIC) - A board that provides network communication capabilities to and from a computer.
 
Network Operating System (NOS) - Operating system designed to pass information and communicate between more than one computer. Examples include Linux/Unix and Windows Server.
 
Node - End point of a network connection. Nodes include any device attached to a network such as file servers, printers, or workstations.
 
Node Devices - Any computer or peripheral that is connected to the network.
 
PCMCIA - (later versions were PCMCIA2 and PC Card) An expansion slot found in many laptop computers. Largely replaced by USB in the 2000-2010 period.
 
Peer-to-Peer Network - A network in which resources and files are shared without a centralized management source.
 
Physical Topology - The physical layout of the network; how the cables are arranged; and how the computers are connected.
 
Point-to-Point - A direct link between two objects in a network.
 
Ports - A connection point for a cable.
 
Protocol -A formal description of a set of rules and conventions that govern how devices on a network exchange information.
 
RAID (Redundant Array of Inexpensive Disks) - A configuration of multiple disks designed to preserve data after a disk casualty.
 
RAM (Random Access Memory) - The working memory of a computer where data and programs are temporarily stored. RAM only holds information when the computer is on.
 
Repeater - A device used in a network to strengthen a signal as it is passed along the network cable.
 
RJ-45 - Standard connectors used for unshielded twisted-pair cable.
 
Router -A device that routes information between interconnected networks. It can select the best path to route a message, as well as translate information from one network to another. Many routers now contain firewalls. Home routers can contain firewall, router, switching (for cabled connections), and a wireless access point.

SCSI (Small Computer Serial Interface) - An interface controller that allows several peripherals to be connected to the same port on a computer.

Segment - Refers to a section of cable on a network. In Ethernet networks, two types of segments are defined. A populated or trunk segment is a network cable that has one or more nodes attached to it. A link segment is a cable that connects a computer to an interconnecting device, such as a repeater or concentrator, or connects a interconnecting device to another interconnecting device.

Sneaker-Net - Refers to a manual method of sharing files in which a file is copied from a computer to a floppy disk, transported to a second computer by a person physically walking (apparently wearing sneakers) to the second computer, and manually transferring the file from floppy disk to the second computer.

Speed of Data Transfer - The rate at which information travels through a network, usually measured in megabits per second.

Star Topology - LAN topology in which each node on a network is connected directly to a central network hub or concentrator.

Star-Wired Ring - Network topology that connects network devices (such as computers and printers) in a complete circle.
 
Switch - A "intelligent" type of hub, in that it sends packets only to the intended ports, rather than all computers on the network.
 
Tape Back-Up - A common server or network peripheral which allows copying data and programs from a computer system to magnetic tape. On tape, data is stored sequentially. When retrieving data, the tape is searched from the beginning of tape until the data is found.
 
Terminator - A device that provides electrical resistance at the end of a transmission line. Its function is to absorb signals on the line, thereby keeping them from bouncing back and being received again by the network. 

Thicknet - A thick coaxial cable that is used with a 10Base5 Ethernet LAN.
 
Thinnet - A thin coaxial cable that is used with a 10Base2 Ethernet LAN.
 
Token - A special packet that contains data and acts as a messenger or carrier between each computer and device on a ring topology. Each computer must wait for the messenger to stop at its node before it can send data over the network.

Token Ring - A network protocol developed by IBM in which computers access the network through token-passing. Usually uses a star-wired ring topology.

Topology - There are two types of topology: physical and logical. The physical topology of a network refers to the configuration of cables, computers, and other peripherals. Logical topology is the method used to pass the information between workstations. Issues involving logical topologies are discussed on the Protocol chapter

Transceiver (Transmitter/Receiver) - A Device that receives and sends signals over a medium. In networks, it is generally used to allow for the connection between two different types of cable connectors, such as AUI and RJ-45.

Tree Topology - LAN topology similar to linear bus topology, except that tree networks can contain branches with multiple nodes.

Twisted Pair - Network cabling that consists of four pairs of wires that are manufactured with the wires twisted to certain specifications. Available in shielded and unshielded versions.

USB/ USB2 Port - A hardware interface for peripherals from keyboards to hard drives, widely used on all computers.

WAN (Wide Area Network) - A network connecting computers within very large areas, such as states, countries, and the world.

Workgroup - A collection of workstations and servers on a LAN that are designated to communicate and exchange data with one another.

Workstation - A computer connected to a network at which users interact with software stored on the network.