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CIS 115

Lecture 17: 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: Are We Too Connected?

In today’s world it seems that we are always connected to something. Instead of taking vacations away from everything, we take along our phones and computers and still answer email and post on Facebook as if we had never left home. It is becoming more and more difficult to truly go “off the grid” and be disconnected from the world (though it is easier to do that in parts of Kansas than other places in the U.S.). Do you feel that we are too connected as a society? Or are we not nearly connected enough? Draw from your own experiences and give concrete examples to explain your position on the topic.

DHCP Request

DHCP Response

DNS Lookup

DNS Response

HTTP Request

HTTP Response