Transcript Network Technology and the Internet

Network Technology
and the Internet
Unit E
Communications Network
The combination of hardware,
software and connecting links that
transport data (which is encoded,
sent to it’s destination and
decoded)
Noise
Encoded
Data
Source
Signal
Communications
Channel
Transmitter
Decoded
Data
Receiver
Destination
Communications Network
Source generates data, e.g. a microphone.
A signal is the physical representation of a
certain information.
Signals can be analog or digital. Analog signals
can have an infinite number of values in a
range; digital signals can have only a limited
number of values.
Communications Network
Transmitter converts the data into
electrical signals
A communication channel, or link, is the
physical path for signal transmission
from one point top another.
Noise is any polluting signal.
Receiver recovers the data.
Bandwidth of a channel is the
transmission capacity of a
communication channel.
Example a fiber optic cable can transmit
up to 20 trillions of bits per second, or 2
Gbps.
Communications Network
Communications system =
communications network.
There are two categories of
communications channels: wired and
wireless.
Data in wired network travels from
one device to another over cables.
Data in wireless networks travels
through the air.
Communication Channels
Node: each device connected
to network
Communications channel:
physical path for signal
transmission from one node
to another
– Wired
– Wireless
Wired Communication
Channels
Twisted-pair cables (phones)
– STP: shielded twisted pair
– UTP: unshielded twisted pair for small
networks
UTP is probably the most commonly used
transmission medium (or channel) for small
networks.
Wired Communication
Channels
Coaxial cable (television)
– High capacity
Wired Communication
Channels
Fiber-optic cable :thin tubes of
glass that transport light.
Wireless Communication
Channels
RF: radio frequency signals are sent
and receive by a transceiver with
antenna.
RF signals provide data transport for
small home networks, campus
networks, and business networks.
Microwaves
– More capacity than radio waves
– Need clear path between transmitter and
receiver
– Cannot penetrate metal objects
Bandwidths
The transmission capacity of a
communications channel measured
in bps (bits per second)
Low-bandwidth carries less data than
high bandwidth
– Telephone
– Narrowband
High-bandwidth
– Coaxial cable
– DSL lines
– Broadband
Types of Networks
Internet: global, public
Internetwork (internet): is a network that is
composed of many smaller networks.
An Intranet is a private network that
provides many of the same services as the
Internet, but has to differences;
– A intranet is owned by a private
business
– Typically an intranet does not provide
remote access
Types of Networks
An extranet is similar to an intranet, except
that it allows password-protected access by
authorized outside users
http://webmail.barry.edu/
A WAN (Wide Area Network) covers a large
geographical area and may consists of
several smaller networks. The Internet is
the largest example of a WAN.
A MAN (Metropolitan Area Network) is a
public high-speed network capable of voice
and data transmission within a range of 80
km.
A LAN (Local Area Network) is a network
that typically connects PCs within a very
limited geographical area, usually a single
building.
Network Topology
A physical topology refers to the layout of
devices, wires, and cables on a network.
A logical topology refers to the way messages
flow.
5 common topologies named for their shapes
– Star (central connection point)
– Ring (connects devices in a circle)
– Bus (common backbone)
– Mesh (each device connected to others)
– Tree (blend of star and bus)
Network Topology
Star topology
Ring topology
Network Topology
Bus topology
Mesh topology
Network Topology
Tree topology
Network Topology
Star
Bus
Ring
Interconnecting Networks
Two similar networks can be
connected by a bridge
– Transfers data without regard to format
Router
– Electronic device that connects 2 or more
networks
Gateway
– A device or software used to join dissimilar
networks by making data compatible
Network Hardware Overview
Network Hardware
Server (also called host computer)
– Distribute resources to network users
– Contains network management software
and files
Workstation (also called client)
– PC on a LAN
– Client is software that lets it talk to server
Network Hardware
Network Interface Card (NIC)
– Example: Ethernet card
Connection Devices
– Modem: converts PC digital signals
– Hub: connects nodes on a LAN
– Router: decides best way to route data
on network
– Gateway: entrance to another network
– Repeater: amplifies and regenerates
signals
Network Addresses
Physical address:
– Every node has one
– Built into circuitry of
network device
Logical address:
(Network address)
Transporting Data
The way data is
transported over a
network depends on
network topology, the
packet switching
technology, and
protocols.
Protocols are rules
that ensure the
orderly and accurate
transmission and
reception of data.
PROTOCOL
MAIN USE
TCP/IP
Internet
NetBIOS/NETB Microsoft
EUI
networks
AppleTalk
Macintosh
networks
IPX/SPX
Novell
networks
Transporting Data
When you send a file or an e-mail message over a network,
the file is actually broken up into small pieces called packets.
A packet is a piece of data that is sent across a computer
network.
Packet Switching Technology determines how data is broken
up so that it can be transported over a network.
Packet Switching Technology
Packet is a parcel of data on network
or a file broken into small, equal size
pieces
Contains
–
–
–
–
Sender address
Destination address
Sequence number
Data
Packet switching: packets sent
independently of each other
Communications Protocol
Allows two devices to negotiate
and agree on how data will be
transmitted
TCP/IP
– Transport Control Protocol/Internet
Protocol
– Most common
– TCP: breaks data into packets
– IP: addresses packets
Controlling Direction
of Data Flow
Simplex: one direction (TV)
Half duplex: can send and
receive data, but not at same
time (CB radio)
Full Duplex: can send and
receive data at same time on
same channel (Telephone)
IP Addresses
ISP gives unique IP address to
subscriber
Series of numbers in 4 parts
– 204.127.129.001
Static IP address: permanent, usually
servers
Dynamic IP address: temporary, for
one session
Network Technology
and the Internet
End