UDP - Dleifnesor/NET-215 GitHub Wiki
UDP and Ports
Overview
User Datagram Protocol (UDP) is a transport layer protocol in the OSI model that provides a connectionless communication method between devices. Unlike TCP (Transmission Control Protocol), UDP does not guarantee delivery, ordering, or error correction, making it faster and more efficient for applications that require low latency.
How UDP Works
- UDP sends packets, called datagrams, without establishing a connection.
- It does not retransmit lost packets, which reduces overhead.
- It relies on the application layer to handle potential data loss or ordering issues.
- UDP is commonly used for applications that require speed over reliability, such as VoIP, online gaming, video streaming, and DNS queries.
UDP vs TCP Comparison Table
| Feature | UDP (User Datagram Protocol) | TCP (Transmission Control Protocol) |
|---|---|---|
| Connection | Connectionless | Connection-oriented (3-way handshake) |
| Reliability | Unreliable (no error checking or retransmission) | Reliable (error checking, retransmission) |
| Ordering | No ordering guarantee | Ensures packet order |
| Speed | Faster due to low overhead | Slower due to reliability mechanisms |
| Error Checking | Yes (basic checksum) | Yes (checksum, acknowledgments) |
| Data Flow Control | No | Yes (uses congestion control) |
| Use Cases | Streaming, VoIP, DNS, gaming | Web browsing, file transfer, emails |
Common UDP Ports
| Port | Protocol | Description |
|---|---|---|
| 53 | DNS | Domain Name System queries |
| 67, 68 | DHCP | Dynamic Host Configuration Protocol |
| 69 | TFTP | Trivial File Transfer Protocol |
| 123 | NTP | Network Time Protocol |
| 161, 162 | SNMP | Simple Network Management Protocol |
| 500 | IKE | IPsec Key Exchange |
| 1701 | L2TP | Layer 2 Tunneling Protocol |
| 4500 | IPsec NAT-T | IPsec over NAT |
Advantages of UDP
- Low latency: No connection setup, making it ideal for real-time applications.
- Efficient: Less overhead compared to TCP.
- Broadcast and Multicast support: Suitable for services that send data to multiple clients.
Disadvantages of UDP
- No reliability: Packets may be lost without notice.
- No congestion control: Can lead to packet loss during high traffic.
- Not ideal for data integrity-critical applications.
When to Use UDP?
- Online gaming (e.g., FPS games, real-time multiplayer)
- Streaming services (e.g., YouTube, Netflix, Twitch)
- VoIP (Voice over IP) (e.g., Skype, Zoom, Discord calls)
- DNS resolution (quick domain name lookups)
- Broadcast & Multicast applications
Conclusion
UDP is an essential protocol for fast, low-latency communication where speed is prioritized over reliability. While it lacks built-in error recovery, its efficiency makes it the preferred choice for streaming, gaming, and real-time communications.
For applications needing data integrity and reliability, TCP remains the preferred choice.