Computer Networks: Packets and Topology

Study Notes

Messages or data are broken down into fixed-sized packets of data and metadata (e.g., P1, P2, P3) before being sent over the Internet.
Each packet is sent to its destination independently, which may cause them to take different paths.
Packets are re-assembled at the destination to form the original message or data, which may arrive in the correct order, out of order, or not at all.

The original motivation for sending packets of data was to create a network that could withstand a nuclear attack by decentralizing and having multiple paths between two computers.
Dividing data into small packets prevented the entire data set from being intercepted before reaching its destination.
Each router along the path forwards the packets to another router until it reaches the final destination.

Local Area Network (LAN) connects computers within a small geographic location, such as a school or home.
Wide Area Network (WAN) connects computers across a broad geographic region, such as a telephone network.

The layout or topology of a network can affect its output and reliability.
Token Ring is a wired LAN that connects workstations in a ring, where a signal called a "Token" is sent to a computer, authorizing it to send data.
Ethernet Protocol is a more efficient wired LAN that allows computers to send data at a rate of a gigabit per second.
Ethernet Cables are used to connect workstations, preventing data from colliding, and are backward compatible with old and new technologies.
WiFi Protocol is a wireless LAN that uses radio waves to connect computer workstations and devices, also known as a star topology.

WiFi Protocol has become the most commonly used WAN, but WAN stands for "Wide Area Network", not "Wireless Area Network".
The "L" in LAN and "W" in WAN represent the physical distance between computers/devices on a network, not the method of connection.
Modern networks often combine Ethernet and WiFi connections, depending on individual needs.

Bus topology uses a single cable to connect all peripheral devices, but if one computer stops working, the entire network stops.
Star topology uses a central hub, making it more difficult to create, but more reliable, and works well with large numbers of computers.

When messages are sent from one computer to another via the Internet, they are broken down into fixed-sized packets of data and metadata.
Each packet is sent to its destination independently via the Internet and may take different paths.
Packets are re-assembled at the destination to form the original message or data.

In the 1960s, the driving motivation was to create a network that could withstand a nuclear attack by decentralizing and having multiple paths between computers.
Dividing data into small packets prevents the entire data set from being intercepted before reaching its destination.

Local Area Network (LAN) connects computers within a small geographic location, such as a school or home.
Wide Area Network (WAN) connects computers across a broad geographic region, such as a telephone network.

Token Ring Protocol is a wired LAN that connects workstations in a ring shape, with a signal called a "Token" authorizing computers to send data.
Token Ring is inefficient due to waiting for tokens, slowing down communication.
Ethernet Protocol is a more efficient wired LAN that allows data to be sent at a rate of a gigabit per second.
Ethernet Protocol uses a bus topology, with computers connected through a single cable.
WiFi Protocol is a wireless LAN (WLAN) that uses radio waves to connect computer workstations and devices, with a star topology.
WiFi Protocol is also commonly used in WANs.

Bus topology: single cable connects all peripheral devices, simple to create, uses less cable length, and is more economical.
Bus topology: if one computer in the network stops working, the entire network stops working.
Star topology: utilizes a central hub, more difficult to create, uses more cable length, and is more expensive.
Star topology: if one computer in the network is damaged, the network continues to function.