Network components include nodes, links, clients, servers, and other devices that connect and allow communication between systems. Key components discussed include network interface cards, hubs, bridges, routers, switches, gateways, and wireless devices. Various media are used to physically transmit data between nodes on a network.

1. Topic TwoTopic Two
Network ComponentsNetwork Components
(Hardware & OS)(Hardware & OS)
BBC 2013/14BBC 2013/14
BWIRE SEDRICKBWIRE SEDRICK
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2. Network ComponentsNetwork Components
• Nodes: Special purpose devices
• Links: Connections between nodes
2
PC server switch bridge router
Optical fiber Coaxial cable wireless09/24/13 ENAM 2012

3. Parts of a NetworkParts of a Network
• Clients
– Computers that request or order information from
a server
– Usually desktop computers with their own local
storage and processing power
– Thin client – network computer with no local
storage
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4. • Servers
– Computers that work behind the scenes to provide
(serve) the resources requested by the clients
– Two types
•Non-dedicated – provides many different services to its
client computers such as file retrieval, printing, and
emailing
•Dedicated – provides only one type of resource to its
clients, such as printing
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5. Other network componentsOther network components
• Shared peripherals – a device that is connected
to a computer and controlled by its
microprocessor
• Media – physical pieces used to transport data
from one computer to another computer or
peripheral on the network
• Data - packets
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6. Network DevicesNetwork Devices
• As Organizations grow, so do their
networks
– Growth in number of users
– Geographical Growth
• Network Devices :
– Are products used to expand or connect
networks.
– Can control the amount of traffic on a network.
– Can speed up the flow of data over a network.
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7. Network Interface Card (NIC)Network Interface Card (NIC)
• NIC provides the physical interface between
computer and cabling.
• It prepares data, sends data, and controls the
flow of data. It can also receive and translate
data into bytes for the CPU to understand.
• The following factors should be taken into
consideration when choosing a NIC:
1. - Preparing data
2. - Sending and controlling data
3. - Configuration
4. - Drivers
5. - Compatibility
6. - Performance
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8. An Ethernet NICAn Ethernet NIC
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9. Connectivity DevicesConnectivity Devices
• Each topology and network architecture has its limits.
• Beyond a point networks can not be expanded by simple
adding more servers or cabling
• Connectivity devices are the basic building blocks of
network expansion
• Are used to connect separate segments of the network or
inter-network
• A segment is a portion of the network transmission
media that is assigned a network address
• Examples: Repeaters, Hubs, Bridges & Switches
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10. RepeatersRepeaters
• Repeaters are very simple devices. They allow a
cabling system to extend beyond its maximum
allowed length by amplifying the network voltages so
they travel farther.
• Repeaters are nothing more than amplifiers and, as
such, are very inexpensive. Repeaters can only be used
to regenerate signals between similar network
segments.
• For example, we can extend an Ethernet 10Base2
network to 400 meters with a repeater. But can’t
connect an Ethernet and Token Ring network
together with one.
• The main disadvantage to repeaters is that they just
amplify signals. These signals not only include the
network signals, but any noise on the wire as well.
• Operates at the physical layer of the OSI model09/24/13 10ENAM 2012

11. RepeatersRepeaters
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12. HubsHubs
• Hubs are devices used to link several computers
together. They repeat any signal that comes in on
one port and copy it to the other ports (a process
that is also called broadcasting).
• There are two types of hubs: active and passive.
• Passive hubs simply connect all ports together
electrically and are usually not powered.
• Active hubs use electronics to amplify and clean up
the signal before it is broadcast to the other ports.
• In the category of active hubs, there is also a class
called “intelligent” hubs, which are hubs that can be
remotely managed on the network.
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13. HubsHubs
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14. BridgesBridges
• They join similar topologies and are used to divide network
segments.
• For example, with 200 people on one Ethernet segment, the
performance will be mediocre, because of the design of
Ethernet and the number of workstations that are fighting
to transmit. If you divide the segment into two segments of
100 workstations each, the traffic will be much lower on
either side and performance will increase.
• If it is aware of the destination address, it is able to forward
packets; otherwise a bridge will forward the packets to all
segments. They are more intelligent than repeaters but are
unable to move data across multiple networks
simultaneously.
• Unlike repeaters, bridges can filter out noise.
• The main disadvantage to bridges is that they can’t connect
dissimilar network types or perform intelligent path
selection. For that function, you would need a router.
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15. BridgesBridges
A bridge is a Layer 2 (Data Link Layer) device.
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16. RoutersRouters
• Routers are highly intelligent devices that connect multiple
network types and determine the best path for sending data.
• The advantage of using a router over a bridge is that routers
can determine the best path that data can take to get to its
destination.
• Like bridges, they can segment large networks and can filter
out noise.
• However, they are slower than bridges because they are
more intelligent devices; as such, they analyze every packet,
causing packet-forwarding delays. Because of this
intelligence, they are also more expensive.
• Routers are normally used to connect one LAN to another.
Typically, when a WAN is set up, there will be at least two
routers used.
• Internetwork connectivity device
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17. RoutersRouters
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18. SwitchSwitch
• A network switch is a computer networking device that connects
network segments.
• Low-end network switches appear nearly identical to network hubs,
but a switch contains more "intelligence" (and a slightly higher price
tag) than a network hub.
• Network switches are capable of inspecting data packets as they are
received, determining the source and destination device of that packet,
and forwarding it appropriately.
• By delivering each message only to the connected device it was
intended for, a network switch conserves network bandwidth and
offers generally better performance than a hub.
• A vital difference between a hub and a switch is that all the nodes
connected to a hub share the bandwidth among themselves, while a
device connected to a switch port has the full bandwidth all to itself.
• For example, if 10 nodes are communicating using a hub on a 10-Mbps
network, then each node may only get a portion of the 10 Mbps if other
nodes on the hub want to communicate as well. But with a switch,
each node could possibly communicate at the full 10 Mbps.
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19. SwitchSwitch
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20. GatewaysGateways
• A gateway is a network point that acts as an entrance
to another network. On the internet, in terms of
routing, the network consists of gateway nodes and
host nodes.
• Host nodes are computer of network users and the
computers that serve contents (such as Web pages).
• Gateway nodes are computers that control traffic
within your company’s network or at your local
internet service provider (ISP)
• Internetwork connectivity device
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21. Security DevicesSecurity Devices
• Increased Internet and extranet connections
• More telecommuters
• Mobile users
• Security Devices:
– Firewalls:
•Software or Hardware
•Only valid traffic can enter or leave the network
– AAA Servers
•Authentication, Authorization, and Accounting Servers
– VPN Concentrators
•Remote access and site-to site VPN capabilities
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22. Wireless DevicesWireless Devices
• Wireless NICs
– Provide wireless connectivity
– PCMCIA and PCI cards to provide
• Wireless Access Points
– It is a wireless LAN transceiver
– Acts as a hub or as a bridge
– Multiple Access Points – Roaming Functionality
• Wireless Bridges
– Provide long-range connectivity – 25 miles
– Line of sight wireless09/24/13 22ENAM 2012

23. Wireless LAN TopologyWireless LAN Topology
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•Allow computers to communicate over a telephone line
•Enable communication between networks or connecting to
the world beyond the LAN
•Cannot send digital signal directly to telephone line
•Sending end: MODulate the computer’s digital signal into
analog signal and transmits
•Receiving end: DEModulate the analog signal back into
digital form
Modems
Remote Access devicesRemote Access devices
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25. Communication MediaCommunication Media
• A path through which information are
transmitted from one place to another is called
communication media. It is also referred to as
communication medium or link.
• In network communication, the
communication media’ are wires, cables and
other means through which information travels
from its source to its destination.
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26. Features of a communication MediaFeatures of a communication Media
• Transmission speed (measured in bps)
• Band width (capacity of communication media,
measure is Hertz or bps)
• Transmission mode
–Asynchronous transmission
–Synchronous transmission
• Transmission direction
• Simplex
• Half duplex
• Full-duplex
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27. Con’tCon’t
• Data is transmitted in the form of signals (analog signal).
• The data transmission is measured in bandwidth.
• Bandwidth measures the amount of information that can
be transmitted through the media within the given
period of time.
• For analog signals bandwidth is represented in hertz
(Hz).
• For digital signals, it is represented in bits per second
(bps).
• The higher the bandwidth of the transmission media, the
more information can be transmitted.
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28. Asynchronous and SynchronousAsynchronous and Synchronous
transmissiontransmission
• Asynchronous transmission is where data is
transmitted one character at a time, where each
character is five to eight bits in length.
• The most common transfer rates in these are btn 1200
& 19200 bits per second.
• This is used mainly to transfer medium quantities of
data over a long distances.
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29. Synchronous transmissionSynchronous transmission
• Synchronous transmission is a mode of
transmission where data is transferred in a block
of bits at ago without a start and stop.
• It is amore efficient mode of transfer used mainly
to transfer large quantities of data e.g. contents
in disk already assembled.
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30. Transmission directionTransmission direction
• Simplex transmission: Where by data can
travel in only one direction at all times.
• These systems are often employed in
broadcast networks, where the receivers do
not need to send any data back to the
transmitter/broadcaster. eg radio stations and
TV
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31. Half-duplexHalf-duplex
• A half-duplex system allows communication in
both directions, but only one direction at a time
(not simultaneously).
• Any radio system where you must use "Over" to
indicate the end of transmission, or any other
procedure to ensure that only one party
broadcasts at a time would be a half duplex.
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32. Full-duplexFull-duplex
• A full-duplex system allows communication in
both directions, and unlike half-duplex allows
this to happen simultaneously.
• Most telephone networks are full duplex as they
allow both callers to speak at the same time.
• A good analogy for a full-duplex system would be
a two lane road with one lane for each direction.
Example: Telephone, Mobile Phone, etc.
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33. Classes of Transmission MediaClasses of Transmission Media
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GUIDED MEDIAGUIDED MEDIA
Guided media: Are those that provide a conduit from oneGuided media: Are those that provide a conduit from one
device to another, include twisted-pair cable, coaxialdevice to another, include twisted-pair cable, coaxial
cable, and fiber-optic cable.cable, and fiber-optic cable.
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Twisted Pair WireTwisted Pair Wire
•Two or more pairs of single conductor wires that have
been twisted around each other.
•Twisted pair wire is classified by category. Twisted pair
wire is currently Category 1 through Category 6.
•Twisting the wires helps to eliminate electromagnetic
interference between the two wires.
•Shielding can further help to eliminate interference.
•Two types; shielded and Un shielded twister pair wire
•It uses RJ 45 connectors
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Coaxial CableCoaxial Cable
A single wire wrapped in a foam insulation surrounded by
a braided metal shield, then covered in a plastic jacket.
Cable can be thick or thin.
Baseband coaxial technology uses digital signaling in which
the cable carries only one channel of digital data.
Broadband coaxial technology transmits analog signals and
is capable of supporting multiple channels of data.
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37. Coaxial CableCoaxial Cable
• Coaxial cable is also referred to as Coax. It carries signals of
higher frequency ranges than twisted-pair cable.
• Coaxial cable can be used for telephone lines for voice and
data transmission with very high frequency. The bandwidth of
coaxial cable is 80 times greater than twisted pair media,
Coaxial cable is also widely used in local area network (LAN).
It is more expensive than twisted-pair wire.
• It creates less noise and protects the cable from interference of
external electromagnetic waves. Has low transmission error
rates.
• These cables can transmit data over longer distances than that
of twisted pair. Transmission speed is from 10 Mbps to 200
Mbps.
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Fiber Optic Cable
•A thin glass cable approximately a little thicker than a human hair
surrounded by a plastic coating and packaged into an insulated
cable. A fiber optic cable consists of tubes of glass (or thin glass
fibers) through which data is transmitted as pulses of light. The
core is surrounded by a concentric layer of glass called Cladding
•The data transmission speed is very high because fiber-optic cable
uses light to transmit data. Transmission speed is up to billions bits
per second.
•It has high level of security.
•It is not affected by electromagnetic waves.
•It is more reliable and has lower data transmission errors.
Disadvantages
•It is more costly.
•It is difficult to install and modify
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It is very common to mix fiber with twisted pair in LANs.
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Data Communications and Computer Networks
Chapter 3
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Radio, satellite transmissions, and infrared light
are all different forms of electromagnetic waves
that are used to transmit data.
•LANs use radio waves
•WANs use microwave signals
Wireless Media
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•Land-based, line-of-sight transmission
•Approximately 20-30 miles maximum between towers
•Transmits data at hundreds of millions of bits per
second
•Popular with telephone companies and business to
business transmissions
Terrestrial Microwave
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Similar to terrestrial microwave except
the signal travels from a ground station on
earth to a satellite and back to another
ground station.
Satellites can be classified by how far out
into orbit each one is (LEO, MEO, GEO,
and HEO).
Satellite Microwave
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Data Communications and Computer Networks
Chapter 3
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•LEO - Low Earth Orbit - 100 miles to 1000 miles. Used for pagers,
wireless e-mail, special mobile telephones, spying,
videoconferencing.
•MEO - Middle Earth Orbit - 1000 to 22,300 miles. Used for GPS
and government.
•GEO - Geosynchronous Orbit - 22,300 miles. Used for weather,
television, and government operations.
•HEO – Highly Elliptical Orbit A fourth type of orbit used by the
military for spying and by scientific organizations for
photographing celestial bodies.
When satellite is far out into space, it takes photos. When
satellite is close to earth, it transmits data.
Satellite Microwave
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Mobile TelephoneMobile Telephone
Wireless telephone service, such as cellular
telephone and PCS (personal communication
system).
To support multiple users in a metropolitan area
(market), the market is broken into cells.
Each cell has its own transmission tower and set
of assignable channels.
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(MTSO) Mobile Telephone Switching Office
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Special transmissions that use a focused ray of light in the
infrared frequency range. Very common with remote control
devices, but can also be used for device-to-device transfers, such
as PDA to computer.
Bluetooth is a Radio Frequency specification for short-range,
point-to-multipoint voice and data transfer. Bluetooth can
transmit through solid, non-metal objects. Its typical link range
is from 10 cm to 10 m, but can be extended to 100 m by
increasing the power.
Infrared & Bluetooth Transmissions
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This technology transmits data between
workstations and local area networks using high
speed radio frequencies.
Current technologies allow up to 54 Mbps data
transfer at distances up to hundreds of feet.
Wireless LAN (IEEE 802.11)
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•Cost – Initial, maintenance/support cost
•Speed – Data transfer, propagation speed
•Distance and expandability
•Environment – Noise level
•Security – Wiretap possible? Need
encryption?
Communication Media Selection CriteriaCommunication Media Selection Criteria
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