Transcript PPP - Ivailo Chakarov

Introduction to IT and
Communications Technology
Networking Fundamentals
CE00378-1
Justin Champion
C208 – 3292
Content
LANS
 WANS
 Technology which keeps them operating

Sneakernet

Earliest example of networking
 As
more work was done on computers, the
need to share this information became greater
Multiple people working on the same item for
example
 A need to print a document but there is no printer
attached to your network
 This network was not connected, it involved a person
copying the files to a removable medium and
physically going to that computer and doing the work
 Therefore sneakernet

Sneakernet
LANS

Local Area Network (LAN)
 As
computers got more powerful and were relied
upon to do more work moving around the office
became less desirable
 Problems were
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Time involved
Limit on the distance that could be travelled
Data got corrupted
Undue replication of Data
Expense in physical media
 Users wanted all
 Printers
 Data files
 Internet Access
functionality at THERE machine
LANS

Local Area Network (LAN)
 These
were the solution to the problem
Locally connecting multiple computers together
 Allowing sharing of

Data files
 Printers
 Central storage areas

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All companies now with more than one machine
will use a LAN of some sort to reduce the costs
and improve productivity
LAN’s
LAN
WANS

Wide Area Network (WAN)
 With
the introduction of LANS in companies there
needed to be a method of allowing communications
across multiple LANS
 For example a company who has 4 offices

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All of these may want to share central data files
Backup all of the data on the local LAN to a central location
 For
this a WAN is needed, which uses different
technology
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The WAN will allow communications across a wider distance
The Internet is an example of a WAN
Companies like Hewlett Packard, will use WANs to connect
offices, but smaller companies will also use this technology
WAN
Other Network Types

Metropolitan Area Network (MAN)
 This
is a network which allows resources to be shared
across an area larger than a LAN and smaller than a
WAN.
 Services across a town, like Stafford for example

Storage Area Network (SAN)
 This
is a high speed network, where a number of
servers will be connected
 These servers will be able to provide a high speed
service
 In the event of more higher speed being needed an
additional server can be added to the SAN
Metropolitan area network
Other Network Types

Virtual Private Networks (VPN)
 These
are networks which are usually setup
by companies
 They allow someone who is not connected to
a network to be able to use the network as
though they were connected

Example would be a business person on the road
using a Internet connection in Starbucks to
connect into the VPN of the company to read
emails or replicate a data source
 These
work with a combination of software
and hardware
VPN connections
Other Network Types

VPNs
 Other parts of the same company
 Can then use the relative cheap access to a network via the
Internet
 Using the VPN removes the worry of people stealing your
data or gaining illegal access
 Other users
 Can also be used to allow other companies access to your
network
 If you have a company that needs to share some of your
data, the VPN can be configured to allow them access
 This can be restricted so that they can only access the parts
of the network you need.

i.e. it is highly unlikely that you would a external supplier access
to your printers
Intranet and extranet VPN
History of Networking

Networking Technology

Did not just happen

There were stages which contributed to this development to get
where we are now
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1890’s Bell invents the telephone
1948 Claude Shannon Publishes “A mathematical theory of
communications”
1962 Paul Baran at RAND works on “Packet Switching”
1969 ARPANET is established
1972 Ray Tomlinson creates a email program to send messages
1973 work begins on TCP/IP
1981 The term Internet is first used
1983 TCP/IP becomes the default language for the Internet
1984 Cisco Systems is founded
1990 ARPANET becomes the Internet
1991 World Wide Web is created by Sir Tim Berners-Lee
1993 First Graphical browser Mosaic is created
Symbols

Throughout this course a number of symbols will be
used
 These
are a quick way to recognise different elements of
a network
 Below are the end user symbols
Network device icons
Symbols

Quick overview of the symbols

Repeater


Switch

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Based on the IP Address this node will forward the data to the correct
host/machine
Bridge
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Based on the Ethernet MAC address this node will forward the data to the
correct host/machine
Router
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
This receives a signal from the network and then repeats it. After a
distance an electrical signal will lose power. This node increases the
power of the signal again
Connects two segments of a network together. Only allowing data to pass
if the destination host/machine is located on the other segment
More information will be given on all of these terms during the
course
Bridges
Physical Setup

The network has wires, which are used to transfer
the information
 Wireless

communications will be covered in other courses
These machines can then be wired in different ways
depending on
 The
level of reliability needed
 The network technology being used
 Money available to invest in the infrastructure
Physical topology
Bandwidth

There are two measures of the amount of data that
can be transferred on a network
 Throughput
 Bandwidth

These are often used interchangeably, but they do
indicate different measures
 Bandwidth

This is the amount of data that can be physically supported on your
network
 Throughput

This is the amount of data that is actually moved in a period of time

This time interval is usually in seconds
Why is bandwidth important?

For a successful network you must ensure you have
enough bandwidth
 Even
for a simple network at home you ensure you have
enough

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If you are downloading multimedia, you would replace your 56
Kbps modem with cable or ADSL
You have now increased your available bandwidth
 Points to remember
 Bandwidth is limited by the technology used and the physics of the
medium used
 Bandwidth is not free
 Bandwidth requirements are always growing

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You can never have enough bandwidth
Bandwidth is crucial to the performance of your network
Highway analogy
Units of bandwidth
Max bandwidth and length
WAN services and bandwidths
Variables effecting throughput

So why are bandwidth and throughput different
values ?
 A number
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of factors may effect the throughput of a device
The available speed/power of the requesting machine (Client)
The available speed/power of the responding machine (server)
Routing delays within the network
Design and topology of the networks transferring the data
Type of data being transferred
Time of day (other users on the network)

Email servers are usually slow first thing in the morning as a lot of
people are checking them
Transfer time calculation
Typical
S = 20000 Bits (size of the file)
P = 5640 Bps (actual throughput at the time)
= 3.54 seconds transfer time
Network layers
Network Flows

Data on the network must flow correctly
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This is from the source to the destination
If this happens correct communication can take place
This is the same that happens in real-life with other networks
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i.e. phone call
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Spoken language is the protocol (the information to be transferred)
Flow control takes place with politeness i.e. two people should not speak at
the same time. One speaks when the other stops
Physical medium for the transfer of information is the telephone and electrical
wires.
This same set of rules happens within computer networks using
software protocols, which both parties agree on before starting
Layer based communications

Networks use protocols to transfer information
 The
information which is transferred is sent through a
number of processes called layers before transmission

The destination then reverse the processes to get the information
back again
OSI Layer based communications

All network communications are based
on these layers
 As
long as the source and destination use
the same layers in the same sequence the
information can be transferred successfully
 The standard for the layers is referred as the
OSI model
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The benefits of using this standard model are
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Reduces complexity
Facilitates modular engineering
Standardises interfaces
Accelerates evolution
Simplifies teaching and learning 
The OSI model

Each of the layers has a specific task to perform
 The
OSI model was developed by the International
Standards Organisation (ISO)
Peer-to-peer communications

In the OSI model
 The
information is passed from layer
7 to 1 at the source

Each layer will add some additional
information needed for the successful
transfer i.e. layer 3 adds the IP address
of the destination
 The
destination then receives the
data

The data is transferred from layer 1 to 7

Each layer removes and process
information and passes the remaining
data to the layer above
Peer-to-peer communications

In the OSI model
 Only
the layer which created a piece
of information can process it

So if Layer 4 (transport) adds some
transport information at the source

Only layer 4 (transport) can remove this
information at the destination
TCP/IP

The most widely used protocols for the transfer of
information is Transport Control Protocol (TCP) /
Internet Protocol (IP)
 TCP/IP
does not use all of the OSI layers
 It combines layers 5,6 and 7 into a single Application layer
 Layers 1and 2 are combined into Network Access
Common TCP/IP protocols
Main protocols
Data encapsulation
Data encapsulation example
Conclusion

What we have covered today
 A lot
!