Network

1. Network Interface Controllers (NIC) and MAC Addresses

• NICs can connect a computer to different physical mediums, such as: Ethernet (wired), Wi-Fi (wireless)

• Every NIC in the world has a unique MAC (Media Access Control) address

  • 48 bits total (manufacturer + device ID)
  • 28 trillion possible address
  • some devices randomly change their MAC address for privacy

• Find Linux Machines’ NIC and MAC

  

  

  loopback (lo) device a virtual interface (not actual hardware) connecting to a mini network containing just your computer, no communication with outside network.

• Add NICs to Google Virtual Machine: Create Instance > Advanced Options > Networking

2. Rules

• A network has nodes that send bytes to other nodes by MAC address
• Node (Computer) send out a packet with destination MAC, Node (Switch) figure out where the destination and send the packet to the destination.
• The whole network uses same physical tech (Wi-Fi, Ethernet, etc).
• Computers can have multiple NICs, which can be on multiple networks (2 ethernets, ethernet+Wi-FI, etc).
• Computers can't send to a MAC address in another network without a NIC there.

Internets

1. Definitions

• Internet: routers connect networks together to form internets.

• “Internet”: the global internet we all use is the.

  

• Packets: some bytes with an address and other info, which can be forwarded along a path from point A to point B.

• Forwarding Tables: routers contain forwarding tables that help them (routers) decide which direction to send along a packet.

  Problem: those tables would be too big if a router had to know where every MAC address existed in the Internet.