Computer networks--networking hardware

Agenda
 Basic LAN Definition
 Network Hardware
 Network Media
 Sample LAN Implementation

LANs
 Definition – LAN
 "local area network"
 Is a group of computers and associated devices that share a
common communications line or wireless link and typically share
the resources of a single processor or server within a small
geographic area (for example, within an office building).
 Usually, the server has applications and data storage that are
shared in common by multiple computer users.
 A local area network may serve as few as two or three users (for
example, in a home network) or many as thousands of users.

LANs
 Definition – Wireless LAN
 A local area network that transmits over the air typically in an
unlicensed frequency such as the 2.4GHz band.
 A wireless LAN does not require lining up devices for line of sight
transmission.
 Wireless access points (base stations) are connected to an
Ethernet hub or server and transmit a radio frequency over an
area of several hundred to a thousand feet which can penetrate
walls and other non-metal barriers.
 Roaming users can be handed off from one access point to
another like a cellular phone system.
 Laptops use wireless network cards that plug into an existing
PCMCIA slot or that are self contained on PC cards, while stand-
alone desktops and servers use plug-in cards (ISA, PCI, etc.).

LANs
Characteristics – LAN
 Topology
 The geometric arrangement of devices on the network or
the shape of a local-area network (LAN) or other
communications system.
 Protocols
 The rules and encoding specifications for sending data. The
protocol defines the format and meaning of the data that is
exchanged. The protocols also determine whether the network
uses a peer-to-peer or client/server architecture.
 Media
 Devices can be connected by twisted-pair wire, coaxial cables,
or fiber optic cables. Some networks do without connecting
media altogether, communicating instead via radio waves.

LANs
 Topology types
 bus topology: All devices are connected to a central cable, called the bus
or backbone. Bus networks are relatively inexpensive and easy to install
for small networks. Ethernet systems use a bus topology.
 star topology: All devices are connected to a central hub. Star networks
are relatively easy to install and manage, but bottlenecks can occur
because all data must pass through the hub. This is not much of a
problem anymore with the widespread deployment of switches.
 ring topology: All devices are connected to one another in the shape of a
closed loop, so that each device is connected directly to two other
devices, one on either side of it. Ring topologies are relatively expensive
and difficult to install, but they offer high bandwidth and can span large
distances.

Network Hardware
 Hub
 An unintelligent network device that sends one
signal to all of the stations connected to it.
 All computers/devices are competing for
attention because it takes the data that comes
into a port and sends it out all the other ports in
the hub.
 Traditionally, hubs are used for star topology
networks, but they are often used with other
configurations to make it easy to add and
remove computers without bringing down the
network.
 Resides on Layer 1 of the OSI model
OSI Model Layers
7 Application
6 Presentation
5 Session
4 Transport
3 Network
2 Data Link
1 Physical

Network Hardware
 Switch
 Split large networks into small segments,
decreasing the number of users sharing the
same network resources and bandwidth.
 Understands when two devices want to talk to
each other, and gives them a switched
connection
 Helps prevent data collisions and reduces
network congestion, increasing network
performance.
 Most home users get very little, if any,
advantage from switches, even when sharing a
broadband connection.
 Resides on Layer 2 of the OSI model.
OSI Model Layers
7 Application
6 Presentation
5 Session
4 Transport
3 Network
2 Data Link
1 Physical

Network Hardware
 Bridge
 Connects two LANs and forwards or filters data
packets between them.
 Creates an extended network in which any two
workstations on the linked LANs can share
data.
 Transparent to protocols and to higher level
devices like routers.
 Forward data depending on the Hardware
(MAC) address, not the Network address (IP).
OSI Model Layers
7 Application
6 Presentation
5 Session
4 Transport
3 Network
2 Data Link
1 Physical

Network Hardware
 Repeater
 Used to boost the signal between two cable
segments or wireless access points.
 Can not connect different network architecture.
 Does not simply amplify the signal, it
regenerates the packets and retimes them.
OSI Model Layers
7 Application
6 Presentation
5 Session
4 Transport
3 Network
2 Data Link
1 Physical

Network Hardware
 Router
 A device that connects any number of LANs.
 Uses standardized protocols to move packets
efficiently to their destination.
 More sophisticated than bridges, connecting
networks of different types (for example, star
and token ring)
 Forwards data depending on the Network
address (IP), not the Hardware (MAC) address.
 Routers are the only one of these four devices
that will allow you to share a single IP address
among multiple network clients.
OSI Model Layers
7 Application
6 Presentation
5 Session
4 Transport
3 Network
2 Data Link
1 Physical

Network Hardware
 Additional Network Hardware Devices
 Network Interface Cards (NICs)
 Puts the data into packets and transmits packet onto the network.
 May be wired or wireless.
 Gateway
 Connects networks with different protocols like TCP/IP network and IPX/SPX
networks.
 Routers and Gateways often refer to the same device.
 Proxy server
 Isolates internal network computers from the internet.
 The user first access the proxy server and the proxy server accesses the internet
and retrieves the requested web page or document. The user then gets a copy of
that page from the proxy server.
Source:
http://www.camas.wednet.edu/chs/tech/computer_tech/info/routers_hubs_bridges.htm

Common Network Media
•Electrical (copper)
•Coaxial Cable
•Single copper conductor in the center surrounded by a plastic layer for
insulation and a braided metal outer shield.
•Twisted pair
•Four pairs of wires twisted to certain specifications.
•Available in shielded and unshielded versions.
•Fiber-optic - A cable, consisting of a center glass core surrounded by layers of
plastic, that transmits data using light rather than electricity.
•Atmosphere/Wireless – Uses Electromagnetic waves. whose frequency
range is above that of microwaves, but below that of the visible spectrum.
•Choose Media based on :
•Wiring configurations
•Distance and location limitations
•Speed
•Reliability
•Security
•Budget

Copper - Twisted Pair
 Dialup over telephone line.
 DSL (Digital Subscriber Line)
 High-speed (256 Kbps – 55 Mbps), Full-duplex.
 Asymmetric Digital Subscriber Line (ADSL) and
High-bit-rate Digital Subscriber Line (HDSL)
 CAT5
 Ethernet cable standard defined by the Electronic
Industries Association and Telecommunications
Industry Association (EIA/TIA).
 Speeds up to 100 Mbps.
 Connector
 RJ-45 - Standard connectors used for unshielded
twisted-pair cable.

Ethernet Specifications
 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.
 10BaseF
 Ethernet specification for fiber optic cable, transmits signals at 10 Mbps (megabits per
second) with a distance limit of 2000 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.

•Infrared light is transmitted through fiber and confined
due to total internal reflection.
•Fibers can be made out of either plastic or glass.
•Used for high speed backbones and pipes over long
distances.
•Comparatively expensive.
Optical Fiber

Computer networks--networking hardware

Wireless Media
•Wireless LAN or WLAN
• Wireless local area network that uses radio
waves as its carrier
•Wi-Fi ("Wireless Fidelity“)
•A set of standards for WLANs based on
IEEE 802.11
•Wi-Max
•Emerging technology that can cover ranges
up to 10 miles or more
•Satellite/Microwave
•High speed media used for longer
distances and remote locations

Sample LAN Implementation
Home Configuration

Sample LAN Implementation
Business Configuration

Computer networks--networking hardware

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