TCP Meltdown - Computerphile

TL;DR

VPNs often use UDP instead of TCP to communicate, as UDP is better suited for the unreliable nature of the internet.

Transcript

so we're going to follow up a bit on the vpn video we did the other day one of the things i mentioned in that video is how vpns often use udp or raw ip sockets to send the data rather than using tcp to communicate which is what lots of other protocols like http and so on use to communicate i thought it'd be a good idea to follow up on why they use ... Read More

Key Insights

• 🚚 IP is an unreliable network that does not guarantee packet delivery or order.
• 🏛️ TCP is built on top of IP to provide reliability and ordered delivery of data.
• 😒 VPNs that use TCP can suffer from performance issues due to conflicting algorithms.
• ❓ UDP, being more aligned with the nature of IP, is a preferred choice for VPNs to ensure better performance.
• 💦 TCP works well when used within its intended environment but can cause problems when used in a VPN context.
• ❓ VPNs using UDP sacrifice reliability for better performance.
• 🌸 TCP and UDP have different mechanisms to handle packet loss and reordering.

Questions & Answers

Q: Why do VPNs often use UDP instead of TCP?

VPNs use UDP because UDP aligns with the unreliable nature of the underlying IP network. TCP can cause performance issues due to conflicting algorithms when used within a VPN.

Q: How does TCP ensure reliable data delivery?

TCP guarantees reliable data delivery by using sequence numbers to reorder packets that arrive out of order and sending acknowledgments to ensure all packets are received. It also includes mechanisms for retransmitting lost packets.

Q: What is the primary advantage of using UDP in VPNs?

The main advantage of using UDP in VPNs is that it allows VPN traffic to align with the unreliable nature of the underlying IP network, which results in better performance compared to using TCP.

Q: How does UDP differ from TCP?

UDP does not provide reliability or guarantee ordered delivery like TCP. It simply multiplexes data packets between two machines. UDP is more lightweight and faster than TCP but sacrifices reliability.

Summary & Key Takeaways

• IP is the underlying protocol of the internet, which is designed to send data packets anywhere but doesn't guarantee their reliability.

• TCP is built on top of IP and provides a reliable connection between two machines, ensuring ordered delivery of data.

• VPNs that use TCP experience performance issues due to the conflicting algorithms of TCP and the underlying IP network.

• VPNs use UDP instead of TCP as UDP aligns with the unreliable nature of IP, allowing for better performance.