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CIS 115

Lecture 13: 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 6: Web Technologies

While many people regard the internet as a single entity that is incomprehensible, we as computer scientists understand that it is actually made up of lots of underlying technologies and systems all combined together to bring life to the internet. Choose a technology related to the internet and tell us more about it. Try to think outside the box and find a technology no one else will write about. Here are some questions to ask yourself as you research it:

DHCP Request

DHCP Response

DNS Lookup

DNS Response

HTTP Request

HTTP Response