But How Does the Internet
Work?
Presented by Rebecca Meinhold
Let’s get started with
the basics
First thing you need to
know is that every
computer has an IP
address
There are TWO ways in which a computer gets
an IP address:
A computer administrator will
manually set the IP address to the
machine
The Dynamic Host Control
Protocol (DHCP) server is
responsible for assigning IP
addresses to all computers on
the network
There are two
different types of IP
addresses
Servers typically use public
IP addresses
Personal computers are
usually assigned private
IP, which is then
connected to a router
with a public IP
google.com
Your computer
HTTP GET
request
Your router/ domain
name server
Google’s IP address
74.125.224.72
• A request is sent to the router to find out the IP address
of the domain name
• Here is where the domain name is converted into it’s IP
address
• Once the IP is known, the DNS server sends an HTTP
GET request to Google’s particular IP
HTTP GET
Application
Layer
request
Presentation Layer
Session Layer
Transport
PacketLayer
Packet
Network
Layer
DataPacket
Link Layer
Physical Layer
Requests are
encapsulated in the
form of transport
layer packets and
then are sent to the
network layer
In the network later,
information related to
source & destination IP
addresses are are
added and then are sent
to the Data Link layer
MAC addresses are
added in the data link
layer before the
packet heads to the
physical layer
Two protocols operate in the Transport Layer:
TCP
Transmission Control Protocol
Ensures that the packet
is not larger than the
largest protocol data
unit in the path located
between your computer
and the destination
UDP
User Datagram Protocol
Offers a limited
amount of service
when messages are
exchanged between
computers in a
network that uses IP
Packet
Your computer
When the packet leaves
your computer, the MAC
Address of the router in
which your packet is being
transferred to is used as
the packets destination
MAC Address
Packet
Router
The router searches
it’s cache for the
packets host address,
when found, it
forwards the packet to
it’s destination
Destination
The following slide will show the
process that the packet goes
through while traveling to it’s
destination
Application Layer
Presentation Layer
The MAC address is
checked to see if the
packet is at the
correct destination
Session Layer
Packet
Transport
Layer
PacketLayer
Network
DataPacket
Link Layer
PacketLayer
Physical
IP address checks
and check-sum
verifications are done
before passing to the
transport layer
HTTP GET
Request is passed
to the application
listening on the
port
The response is then formed and
transmitted back in the same way
that it came in