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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 Info | Length |
Packet ID | Flags & Offset |
Protocol & TTL | Checksum |
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 Port | Dest. Port |
Sequence Number | |
Acknowledgement Number | |
Options | Length |
Checksum | Urgent |
Data... |
Transport - UDP
UDP Packet Structure | |
Source Port | Dest. Port |
Length | Checksum |
Data... |
TCP vs. UDP
TCP | UDP |
Connection Oriented | Connectionless |
Reliable | Unreliable |
Acknowledge | No 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.
Packet Switching Activity
DHCP Request
DHCP Response
DNS Lookup
DNS Response
HTTP Request
HTTP Response