Internet protocols and network hardware Protocols are sets of rules or standards that are used for...
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Computer Networks
Internet protocols and network hardware Protocols are sets of rules or standards that are used for communication. They work together to help devices to
Internet protocols and network hardware Protocols are sets of
rules or standards that are used for communication. They work
together to help devices to communicate. The rules apply to
different layers used for communication purposes. A network
protocol is a standard method for transmitting data from one
computer to another.
Slide 3
Protocols/Services Physical layer-data is transmitted bit by
bit from one device to another e.g on modems Data Link Layer: It
acts upon requests for services from the physical and network layer
e.g wifi and ethernet Network/Internet layer: It is responsible for
forwarding packets and routing e.g internet protocol Transport
layer: It divides data to be transmitted and adds the address of
the source and destination address e.g UDP and TCP Application: It
consists of protocols that use the transport layer to deliver
services to the network or Internet layer.
Slide 4
Ethernet It refers to a basic set of protocols used to operate
a local area network(LAN). It is made up of the following: Devices
that send and receive data such as PCs, printers and servers.
Network devices such as hubs, switches and routers. Medium
connecting devices such as twisted pair, fibre optic and coaxial
cables.
Slide 5
TCP/IP Transmission Control Protocol(TCP) ensures that data is
delivered correctly Internet Protocol(IP) ensures that the data is
delivered to the correct address. An IP address consists of 4 bytes
which are given in decimal form Techniques such as subnetting and
local addressing are used to increase the number of addresses
Slide 6
TCP/IP TCP ensures that the correct number of packets reach the
destination and that there are no duplicates as a result of
retransmission. Any duplicates are deleted Each packet contains a
destination address, source address and a sequence number which
will be used for assembling the packets at the destination. It is
used on the www, e-mails and for file transfer.
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Handshaking It refers to the exchange of signals between
devices to establish a communication channel eg the rate of
transfer, parity checking and interrupts to be used. Parity can be
odd or even. It refers to the total number of bits within a
transmitted message. The number of bits is checked to make sure
that there are no errors in transmission
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UDP The UDP is a basic protocol. It is considered to be a
connectionless service. No handshaking is required. It has no
congestion control mechanisms. It is unreliable because packets of
data may fail to reach the destination. It is still better suited
for real-time transmissions e.g video on demand systems
Slide 9
FTP FTP is used for the transfer of files when downloading and
uploading files. FTP makes use of client-server systems. Clients
have to log on in order to download files. SSL and SSH are used to
enable encryption of files during transmission.
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HTTP HTTP is the protocol used for transmitting data across the
internet/intranets. It uses a client-server system in which a
browser makes a request using a URL. The URL is converted to an IP
address. The server will then provide the required resources
Slide 11
Telnet Telnet is a network protocol used on the internet or
within local area networks. It is used to enable a user to gain
access to another computer and use the resources provided there. It
works at the same layer as FTP. The remote compter should have
telnet client/server software. Telnet has major security problems
which has decreased its popularity. It is still used for network
diagnostics and troubleshooting problems.
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SSH It allows data to be shared between two computers. It
allows users to log in remotely and also uses encryption. It uses
uses public-key authentication. Its main purpose is to log into a
machine remotely and execute commands. It is therefore used by
administrators.
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Network Hardware
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Devices used in a computer network
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Network Hub A hub is a devices that has a number of network
devices or computers connected to it. When a hub receives data
packets it broadcasts them to all computers on that network
including itself. It does not read the data packets. Hubs that
amplify the signal are called active hubs and those that do not
amplify the signal are passive hubs.
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Switches A switch is more advanced than a hub. When hubs are
used congestion may occur when several computers are transmitting
data at the same time. The same packet of data is send to all the
ports on the hub. In a switch the data from any computer is sent
directly to its destination port without congesting the other ports
unnecessarily. A switch uses address tables to find the correct
port to send data packets. It stores the Media Access Control(MAC)
address. It is used for connecting local computers and
devices.
Slide 17
Routers A router enables data to be sent transmitted between
different networks e.g from a LAN to a WAN. It provides facilities
for protocol conversion. It may also have a firewall installed. The
router inspects packets of data and checks the IP address so that
it can forward it to the correct network. The first part of an IP
address is the network address which is then used for routing.
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Dedicated cabling Twisted pair: two conducting wires twisted
around each other which reduces magnetic interference and data loss
Coaxial: A conducting wire surrounded by a plastic non-conducting
layer, then conducting material and a PVC Fibre optic cable: Optic
fibres which are individually coated by a plastic resin and
sheathed in a plastic layer Networks that require fast speeds use
twisted pair and fibre optic cables.
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Servers File Servers- Store user data. Users must log on to use
the servers. Application Server-Distribute application software to
client machines e.g the isams servers Other servers include print
servers, e-mail servers, proxy servers etc One computer can be used
as multiple servers. File servers make use of groups and access
rights in order to manage security.
Slide 20
Network cards A network interface card is a card that fits onto
a computers motherboard. A network interface card may allow both
wired and wireless communication.
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Network Types Local Area Networks- These are house within a
building or the same geographical area e.g schools, offices etc The
networks normally use switches/hubs The switch is in turn connected
to a broadband modem in order to connect to the internet.
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Network Topologies There are 3 main types of network
topologies: The Ring Network The Bus Network The Star Network
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Network Topologies The Ring Network: Computers are connected
together to form a ring shape so that none of them is more
important than any of the others.
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Network Topologies The Ring Network: Advantages: They are cheap
to expand. The data flows around the network in one direction so it
is fast. It performs better than a star network when traffic is
heavy. There is no reliance on a central computer. Disadvantages:
If there are a lot of users on the network, it could slow down as
all the data is sent along a single line. If one computer in the
ring stops working, the whole network stops. Adding a new computer
may cause disruptions to the network.
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Network Topologies The Bus (or line) Network: Computers are
connected like bus stops on a main road. None of them is more
important than any of the others. The spine has cables which
connect to each network.
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Network Topologies The Bus (Line) Network: Advantages: It is
cheap as it uses the least amount of cable. More computers can be
added without disruption. If one of the devices fails the network
will continue to function as normal No hubs/switches are required
Disadvantages: With a lot of users, the network will be slow as
data has to travel through the same central cable. Failure of the
central cable will stop the network from working. It is difficult
to troubleahoot when the whole network breaks down.
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Network Topologies The Star Network: Computers are connected
like a star to a central hub/switch/serve r/router.
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Network Topologies The Star Network: Advantages: If a cable
fails, it will only affect one workstation. More computers can be
added without disruption. Disadvantages: It is more expensive as it
uses the most cabling. Failure of the central computer/network
device will stop the network from working.
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Hybrid Networks It is made up of star networks where each
hub/switch is connected to one backbone. The backbone cable forms a
bus-type network. The switches may also connect to each other
forming multiple interconnected star networks.
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Network Topologies The Hybrid Network: Advantages: It employs
the advantages of a star network and bus network More computers can
be added without disruption. Disadvantages: Sections can stop
working if a hub/switch breaks down. The whole network will not
work if there is a fault in the spine.
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Intranets Local Area Networks are used for creating intranets.
An intranet can be defined as a private company network that makes
use of internet technology. It is for the use of members of that
organisation. Users are given usernames and passwords Dedicated
telecommunication links may also be used for linking different
locations such as fibre optic cable and telephone lines. It uses
internet protocols.
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Uses of Intranets Providing local e-mail Video conferences
Sharing information Fast access to documents and statistics Sharing
diaries Organising meetings Discussion forums Policy
information
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Local e-mail and Business Networks Intranets are very secure
and businesses use them put up information that employees need to
access. Intranets reduce paper costs Lan-based e-mail reduces the
cost of printing An ISP can be used for providing the e-mail
service
Slide 34
WLANs A WLAN uses either spread spectrum( a signal with an
initially low bandwidth is spread to have a wider bandwidth) radio
waves or infrared signals for communication. Computers or devices
must have WNICs Devices can be added easily to the network problems
with the WLANs include security issues, interference and poor
speeds
Slide 35
Wi-fi Wifi is short for wireless fidelity. Data is transmitted
into radio signals and then transmitted. The wireless router
decodes the signal. The following hardware devices are used:
Wireless Network Cards Wireless Routers Wireless Access Points
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Wireless Network Cards It transmits data as radio waves. Most
laptops a fitted with WNICs by manufacturers Desktop computers can
also have these fitted Most mobile devices have wireless NICs
Slide 37
Wireless Router It converts data signals into radio signals as
well as radio signals back to data signals. Features include: Wifi
protected access(WPA), a complexi encryption system MAC address
filtering and IP address filtering Invisible mode
Slide 38
Wireless Access Points They are used for connecting wireless
devices to a wired network. They cover a limited area and number of
computers. List Devices that have wireless capabilities:
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Methods of Data transmission Spread spectrum radio waves are
used for transmitting data by increasing its bandwidth.
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Methods of Data transmission contd. The same random number
generators are used by the receiver and sender to generate random
frequencies and stay synchronised. It allows computers and other
devices to communicate through walls. Another method is to use
infrared signals. As it pulses on and off it willl be transmitting
data in bits. It is secure because it cannot be used across walls.
There is also no interference. The main disadvantage of the system
is the lack of range.
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WPAN Pg 141-143 Dont have to do network security.
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Network Security Network security is there to ensure that
unauthorised users do not view data or understand it if they manage
to intercept/access the data.
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Physical Security This prevents users from gaining physical
access to computers. This can be achieved by: -Securing Computer
Rooms- All doors and windows should be locked when computers are
not in use. Burglar alarms may also be used. Some Servers are
lockable. CCTVs can also be used for deterring thieves. Pass cards
can be used for giving users different times and levels of access.
-Security Guards for patrolling and responding to alarms.
Slide 44
Software Security Most computer threats come from hackers who
access computer systems remotely. The following methods may be used
for preventing access: Firewall Encryption Digital Certification
Authentication Techniques Anti-virus Software
Slide 45
Firewalls A firewall can be in the form of hardware or software
or a combination of both. Firewalls prevent unwanted network
traffic from accessing a computer network. Packets of data are
inspected and if their ip address/network address is not wanted
then they are prevented from accessing the computer network.
Domains, words, phrases can be filtered out. Packets with these
phrases are prevented from entering the system. At school we have a
firewall that does this.
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Encryption Encryption refers to encoding data by scrambling or
encoding it. This is for preveting hackers from understanding data
sfter intercepting it. The sending computer uses an encryption key
for encoding data. The receiving computer has a decryption key for
decoding it. Public key/Private key encryption is used. The sender
computer uses the public key for encrypting data and the receiver
will use a private key for decoding it.
Slide 47
Digital Certification Digital certificates are issued by a
certification authority. The authority certifies that both
receiving and sending computers are who they say they are. Once
certified each one may get the public key of the other.
Slide 48
Authentication Techniques This can be achieved by using a for
example a username and password, card and pin code, biometrics such
as facial recognition and finger print scanners.
Slide 49
Anti-virus software It is used to find viruses and remove them.
The anti-virus software has a database to remove known viruses. One
way is to scan the hard disk or monitor ports for suspicious
behaviour. Actions taken by viruses include the following: -Repair
the files -Quarantine the file by not allowing any program to
access it. -Delete the file Anti-virus software must be updated
regularly. Antivirus definitions are becoming longer
Slide 50
Other Types Of Viruses Trojan horses Worms
Slide 51
User ID These are used for identifying users and must match a
password in the database. Users can also be grouped and be given
privileges. Users are given a limited number of attempts when
logging in usually three attempts Good password policies must be
maintained such as ?
Slide 52
Chip and PIN cards Chip and pin card readers are slotted into
keyboards
Slide 53
Anti-spam This is software for rejecting unsolicited
e-mails
Slide 54
Anti-pop-up software Pop up blockers are usually incorporated
into the browser. It identifies part of html code that will open
another window and prevents it from being executed.
Slide 55
Anti-spyware software Spyware software allows people to access
and control your computer. It allows pop ups, changes browser
settings. In its worst form it searches for user names and
passwords. Anti-spyware software searches the hard disk for known
spyware software and removes it. It needs constant updating. Key
logging software may also be used to detect the keys presssed.
Slide 56
Wired Equivalent Privacy of information(WEP) and Wi-fi
Protected Access(WPA) WEP is used for encrypting data on wireless
networks but uses a weak key WPA uses stronger encryption keys and
also includes user authentication
Slide 57
Electronic conferencing Hardware Requirements Electronic
conferencing requires additional hardware such as microphones,
earphones/speakers, webcams including in some cases phone
handsets.
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Software Requirements Conference Software VOIP software Instant
messaging
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Coference Software Compression Decompression software is used
to reduce the size of the packets of data transmitted. The packets
of data must be transmitted in real time. Echo cancellation
software is used for keeping communication synchronised VOIP
software may also be used for conducting telephone
conferences.
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VOIP Software It is cheaper than using conventional telephone
lines. The software coverts the speech into digital data and
compresses the audio data so that it can be transmitted in real
time.
Slide 61
Instant Messaging It is the exchange of text messages across
the internet in real time. Businesses and Institutions can also
make use of IM on Local Area Networks.
Slide 62
Video Conferencing Advantages Meetings can be called at short
notice No time spend on travelling No money spend on travelling No
money spend on booking facilities It is environmentally friendly
Meetings are kept shorter It is safer No payments for travelling
time
Slide 63
Video Conferencing Disadvantages Confidential documents may
need to be seen in their original form There is no direct eye
contact Delegates may be put off by the camera Quality of the video
depends on the bandwidth Transmission breakdowns may occur
Environmental factors such as power cuts may also affect the video
conference
Slide 64
Phone Conference Advantages Cheaper than a video conference
because there are no webcams ot large screens Less bandwidth No
need to worry about appearance
Slide 65
Phone Conference Disadvantages Documents cannot be seen Facial
expressions cannot be seen Number of participants is limited Power
cuts may interrup services
Slide 66
Instant messaging Advantages It is instant Saves time and money
when resolving problems Easy to use
Slide 67
Instant messaging Disadvantages Users may be exposed to
dangerous people It may lead to obescity It is disruprive in
workplaces when used for socialising It may also pose a security
risk when files are sent.
Slide 68
Uses Of Electronic Conferencing Businesses Schools Research
Meetings