Internet & World Wide Web, E-Commerce Video Lecture | E-Commerce - B Com

hey we're going to be looking at the
Internet in this video this might be a
somewhat typical setup you might have so
all of this excluding the incident here
might be a local area network so we've
got some devices connected to a switch
perhaps I've is wise being nearly
Ethernet maybe copper cables you've ever
had maybe some devices would connect
wirelessly to a wireless root of root is
what connects directly to the internet
both to what was in a sec and the cables
between me Internet as a whole or her
the ISP but between routing might be
fiber-optic and obviously the air is for
transmission medium for wireless so this
might be a somewhat typical set up
essentially the point of me showing you
this is that everything has to go
through a router doesn't have to
wireless but has to go through a router
so no we'll come back to that but first
of all let's just define what the
internet is so the internet is the
worldwide collection of networks that
use a protocol suite called the Internet
Protocol suite a Miss is written as
tcp/ip four slash IP and we're looking
with a more detailed breakdown the
layers of this protocol suite a
difference we need to establish early on
is for difference between the internet
and for worldwide web so for water web
is virtual collection of web pages
hosted on web servers so stored on web
servers and web runs using in our
protocol which will also look at HTTP so
the difference is the internet is for
Hardware so for Reuters for connections
between networks whereas the web is not
quite software but more the resources
hosted on the Internet in order to get
resources you have to address from and
this is done through URLs Uniform
Resource locators and so they're dress
specific web resources so this is an
example one a generic one so first we
have your protocol specifying services
while our webseal running HTTP then you
have what is known as with the main name
so sometimes the main name is just
considered to be example.com or door
whatever but sometimes includes this
this is actually the host so world wide
web when he sorry when you do www miss
specifies that you're wanting to access
its web server so if you leave this out
if you just typed in youtube.com/
without
ww it would just blow due to normally
but you can also if it had a different
host you could also write different host
name here so there might be news
youtube.com or upload youtube.com and
this is addressing a different server
Avenue across specify the folders and
the files you know dot PHP dot hatred
amount so on for these web resources are
stored on the server as so says we would
talk about Reuters and here we go let's
leave for web for now we'll come back to
it we look at protocols but going back
to the Internet in terms of a physical
connections internet it hair looks like
a much more complicated version of this
we have a current normal Reuters they
sit in their houses but look like these
and we also have industrial sized
routers which we don't ever see but
these are owned by four people bind
owned by ISPs so you know you've got
these very large companies like sky and
BT and bigger ones and rows but
virtually owned for connect remain
connections between continents for
high-speed links but transfer you know a
massive amount of data and the
connections between ISPs are considered
of a backbone of the Internet so the
purpose of router is just a forward
packets between networks because
remember the Internet is a collection of
networks as a network of networks so as
a discusses Verve we need to introduce
IP addresses and an IP address uniquely
identifies a device on a network and
defines where it's located
geographically so both parts of its
definition are very important let's say
the first one first uh-huh so an IP
address is unique on the network for
devices connected to so it doesn't mean
it's unique worldwide because you could
be connected to just your office network
and your IP address is going to be
unique on that network but doesn't have
to be unique worldwide whereas as soon
as you connect to the internet your IP
address then has to be unique on the
internet which is a much larger pool of
IP addresses that you've gotta avoid so
you kind of - IP just you can have a
private one and a public one which of
public one refers to the Internet so the
second part of definition the fact for
VIP just defines where it's located
geographically is really important so
you can look at an IP address and go
okay it's an
or it's in America and so on so you
actually look in IP address and it tells
you works like a to geographically so it
helps with this routing of packets it
needs to know roughly where it is so it
can contact you know this Rooter in
services in Russia and China this will
say it'll take an IP address no got ok
it's in South America it knows it needs
to then go to the truth in South America
so you need that kind of geographical
nature in order to be able to actually
route across such a large distance and
with so many IP addresses so as I say
the route to use is this destination IP
address of a packet so a packet has a
destination IP address in it as we'll
talk about a sec and so it uses beside
us to define to determine where it is
and where it needs to send it and it
will use routing algorithms to determine
the best route to get it there so
Reuters contain a table of IP addresses
so this is what a I purchase might look
like this is expressed in decimal
notation and obviously corresponds to
binary values throw different versions
actually of IP addresses because they
ran out of space effectively evade
previously in ipv4 I only had so many
combinations and spent creased the size
of an IP address so if it they could
have more combinations as more and more
devices got connected to the Internet
obviously they need to be unique quad
wide so they needed more combinations we
don't necessarily need to know that but
it reinforces a point this would be
unique and this map is showing you these
are different organizations it's their
job to assign IP addresses to the kind
of ISPs in their locations so the
European service providers will get a
set amount of IP addresses and they have
to assign to their customers so having
these organizations helps it to be
unique first of all and also helps it
kind of be linked to the geographic
location so this method of route is
passing along or forwarding data packets
is actually called packet switching and
in this no fixed path is created between
the two communication devices server
device with sending the data and the
devices receiving the data each
individual packet that comprises the you
know the hub entire data being sent can
take a different routes in order to
reach his destination this contrast from
something called so
switching we're actually a single path
is created and all the data sent on that
path which isn't actually as efficient
it makes more sense to do this way
because for example if for connection
drops there's always another way it can
reroute however packets so speaking of
package let's talk about what they are
in more detail so we actually have three
sections
you have four header and you have the
actual data services the data bits part
of a larger database getting sent and
you also have a trailer and these names
do very little bit but the header
contains information about the data so
this is really important like for packet
number services the number in the
sequences in services of a fifth packet
being sent misses the tenth packet being
sent and the numbers used to reassemble
the data if you ever end if there wasn't
a packet on but it wouldn't know which
data was which because the fact that we
can take a different route means that
they may arrive at different times so it
needs to be able to reassemble it when
all the data arrives
it also contains addresses so the MAC
address and the IP address of the sender
and receiver and the IP address is used
to send it as we've talked about to the
correct location of a world of a MAC
address is used to identify on the
individual local area network the device
is actually on so MAC address isn't a
geographic address it's there to locate
a device on the individual network
whereas an IP address as we've talked
about is a geographic address among
other bits information also contains
details of a protocol being used the
trailer is less important but may
contain something called a checksum and
this is a way of validating the data to
determine if an error has been
introduced in transmission which just
happened quite a lot it's very easy you
know the Internet is so so complicated
but it's very easy for errors to kind of
creep in a checksum is just a value that
the sender and receiver both calculates
using some function applied to the data
so this isn't how it works but it's in
binary say they can add up all the ones
in binary and create this checksum and
then they can be compared or for senders
determines Weaver checksum and what for
receivers determined to be the checksum
and if they match then the data hasn't
been corrupted if they're different then
the packet needs to be resent because
some something's gone wrong in which
mission