The Internet - TCP/IP

Question 1

Internet Protocol Suite

Answer 1

• Internet protocol suite is the computer networking model and communications protocols used by the Internet and similar computer networks
• it is commonly known as TCP/IP, because its most important protocols, the Transmission Control Protocol (TCP) and the Internet Protocol (IP), were the first networking protocols defined in this standard

Question 2

IP Address

Answer 2

• every computer on the internet has an “IP address” that identifies it (like a phone number)
• the IP address is 4 bytes, written between dots, like “171.64.2.3”
• must be between 0-255
• the left part of the address encodes in part where that IP address is in the whole internet

Question 3

Domain Names

Answer 3

• alternate names for IP addresses
  
  • google.com
• easier for people to remember and type
• DNS looks up an IP address from a domain name

Question 4

Router

Answer 4

• most common way for a computer to be “on the internet” is to establish a connection with a “router” which is already on the internet
• handles traffic for a few local computers
• the routers at the ends have a trivial upstream/downstream configuration, so the next hop for a packet is pretty simple
• more central “core” routers tend to have several possible outgoing connections, so they have a more complicated choice about which link to use for the next hop

Question 5

Packet Routing

Answer 5

• The routing of a packet from your computer is like a capillary/artery system
  
  • your computer is down at the capillary level, your packet gets forwarded up to larger and larger arteries, makes its way over to the right area, and then down to smaller and smaller capillaries again, finally arriving at its destination
• forwards each packet one hop closer to its final destination
• The ultimate destination puts all the packets back together in the right order to recover the original file

Question 6

Special “Local” IP Addresss

Answer 6

• 10.x.x.x and 192.168.x.x addresses are special “local” IP addresses
• not valid out on the internet
• gets translated to a real IP address as a packet makes it way
• frequently given out by Wi-Fi routers

Question 7

DHCP

Answer 7

• Dynamic Host Configuration Protocol
• typically DHCP is used when you connect to a Wi-Fi access point
• facilitates connecting to a router; establishing a temporary connection, and the router gives your computer an IP address to use temporarily

Question 8

What does ping do?

Answer 8

sends a “are you there” packet to a computer, getting back a “yes” packet

Question 9

Device Connection Order

Answer 9

1. PC or wireless device
2. Router
3. Modem
4. ISP
5. Internet