User Datagram Protocol (UDP)

A communication protocol used across the internet especially for time-sensitive transmissions.

It’s best for situations where speed is critical and error handeling can be done by the application or is not that nessecary.

known for

low latency

reducd processing overhead

it’s at layer 4.

tcp 3 way handshake ≠ UDP

Source dest port numbers, legenth field, check sums

packets are 8 bytes vs 20-60 for TCP. no error checking or recovery, but it is faster.

UDP’s Stateless natuere

does not maintain the stae of the connection or keep track of the packers, fire and forget.

udp does not ned an acknowledgement from the recier, to may not arive or be out of synquence.

Udp IS use where the SPEED is the most important thing. online gaming VOIP, sttreaming.

UDP relies on ports to help diffenerate between multiple services or appicatons

UCP includes a chucksum to provide som minimal protection against data corruption during transsion.

⚡ UDP – User Datagram Protocol (Layer 4)

Lightweight, connectionless protocol used when speed and low latency are more important than reliability.

✅ Core Characteristics

| Feature | Description | | --- | --- | | Connectionless | No handshake or connection tracking | | Unreliable Delivery | No acknowledgments, no retransmissions | | Low Overhead | Only 8 bytes per header (vs TCP’s 20–60 bytes) | | Stateless | Doesn’t maintain session state — “fire and forget” | | Faster | Ideal for real-time applications | | Minimal error checking | Includes a checksum, but no recovery or sequencing |

🔧 UDP Header Fields (8 bytes total)

| Field | Purpose | | --- | --- | | Source Port | Identifies sender’s port | | Destination Port | Identifies receiving app/service | | Length | Total length of UDP header + data | | Checksum | Optional error detection (basic integrity check) |

🧠 Key Differences: TCP vs UDP

| Feature | TCP | UDP | | --- | --- | --- | | Handshake | 3-way handshake | No handshake | | Reliability | Reliable (ACKs, retries) | Unreliable (no ACKs) | | Header Size | 20–60 bytes | 8 bytes | | Speed | Slower (more overhead) | Faster (low overhead) | | Use Cases | Web, Email, File Transfer | Streaming, VoIP, Gaming | | Stateful | Maintains connection state | Stateless |

🚀 When to Use UDP

Use UDP when:

Speed > Accuracy
Some data loss is acceptable
App handles its own error correction (if needed)

🔊 Common UDP Use Cases:

VoIP (Voice over IP)
Streaming video/audio
Online multiplayer gaming
DNS queries

⚡ Rapid Review Questions

What layer does UDP operate on?

→ Layer 4 (Transport)
What makes UDP faster than TCP?

→ No handshake, smaller header, no tracking or retransmissions
Does UDP guarantee delivery?

→ No
What’s a key reason UDP is used in streaming?

→ Low latency – dropped packets don’t halt the stream

🧠 Memory Trick:

"U Don’t Persist"

UDP doesn’t care about acknowledgment — it just sends and moves on.