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CIS 115

How the Internet Works

Circuit Switching

Image Source: Wikipedia







Packet Switching - Paul Baran

Image Source: Wikipedia

7 Layer OSI Network Model

Encapsulation

Image Source: Wikipedia

Physical - 100BASE-T

Image Source: Wikipedia

Data Link - Ethernet

Image Source: Wikipedia

Network - IPv4

IPv4 Packet Structure
Version InfoLength
Packet IDFlags & Offset
Protocol & TTLChecksum
Source IP Address
Destination IP Address
Data...

IPv4 vs. IPv6

IPv4: 32 bit Addresses
232 = 4,294,967,296

IPv6: 128 bit Addresses
2128 = 340,282,366,920,938,463,463,
374,607,431,768,211,456
or 340 Undecillion addresses

Network - IPv6

Image Source: Wikipedia

Image Source: XKCD

Transport - TCP

TCP Packet Structure
Source PortDest. Port
Sequence Number
Acknowledgement Number
OptionsLength
ChecksumUrgent
Data...

Transport - UDP

UDP Packet Structure
Source PortDest. Port
LengthChecksum
Data...

TCP vs. UDP

TCPUDP
Connection OrientedConnectionless
ReliableUnreliable
AcknowledgeNo Acknowledge

Applications

Domain Name System (DNS)
"Phonebook for the Internet"

Image Source: Wikipedia

DNS Lookup

Image Source: Wikipedia

Dynamic Host Configuration Protocol (DHCP)

Image Source: Tech Juice

HyperText Transfer Protocol (HTTP)

Image Source: Wikipedia

Image Source: Wikipedia

HTTP Commands

HTTP Status Codes

HTTP Status Codes

Assignments

Blog 8: How has the Internet Influenced You?

The internet has been a major force in our lives for several decades now. Write about how the internet has influenced you as a person. Try and think about ways that you would be a different person if you didn’t have the internet. Things you can think about:

DHCP Request

DHCP Response

DNS Lookup

DNS Response

HTTP Request

HTTP Response