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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 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 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:
Packet Switching Activity
DHCP Request
DHCP Response
DNS Lookup
DNS Response
HTTP Request
HTTP Response