How Packet Switching Sends Data Across a Network
What is Packet Switching?
Definition
Packet switching
Packet switching is a method of transmitting data by dividing it into smaller units called packets.
Each packet is sent independently across the network and reassembled at the destination.
Note
Packet switching is the foundation of the internet, enabling efficient and reliable data transmission across complex networks.
The Process of Packet Switching
- Data Segmentation: Large data is broken into smaller packets.
- Encapsulation: Each packet is wrapped with a header containing routing and control information.
- Independent Transmission: Packets are sent independently, taking different routes if necessary.
- Routing: Routers direct packets based on current network conditions.
- Reassembly: Packets are reassembled at the destination in the correct order.
Tip
- Think of packet switching like sending a book by mail, one page at a time.
- Each page (packet) has an address (header) and can take different routes to reach the destination, where they are reassembled into the complete book.
Data Segmentation and Encapsulation
- Data Segmentation: Large data is divided into smaller packets.
- Encapsulation: Each packet is wrapped with a header containing:
- Source and destination addresses
- Sequence numbers for reassembly
- Error-checking codes
Example
- Consider sending a photo via email.
- The photo is broken into packets, each with a header specifying its order and destination.
- This ensures the photo can be reassembled correctly at the recipient's end.
Independent Transmission and Routing
- Independent Transmission: Packets are sent separately, allowing for flexibility in routing.
- Routing: Routers use routing tables to determine the best path for each packet based on:
- Network traffic
- Availability of links
- Current network conditions
Note
Routers make dynamic decisions for each packet, ensuring efficient use of network resources and adaptability to changes like congestion or link failures.
Reassembly at the Destination
- Reassembly: Packets are reassembled in the correct order using sequence numbers.
- Error Handling: If packets are missing or corrupted, the destination requests retransmission.
Tip
- When analyzing an algorithm's time complexity, always consider the worst-case scenario first.
- Then evaluate average-case performance, which often provides a more realistic assessment of practical efficiency.
The Role of Switches and Routers
- Switches:
- Operate within a local network (LAN)
- Forward packets based on MAC addresses
- Reduce network congestion by directing packets to specific devices
- Routers:
- Connect different networks
- Forward packets based on IP addresses
- Use routing tables to determine the most efficient path
Note
Switches handle data within a local network, while routers manage data between networks, making them essential for global connectivity.
Why Packet Switching Matters
- Efficiency: Packets can take different routes, optimizing network usage.
- Reliability: If one path fails, packets can be rerouted.
- Scalability: Supports large, complex networks like the internet.
