Latency and Jitter

[!NOTE] This module explores the core principles of Latency and Jitter, deriving solutions from first principles and hardware constraints to build world-class, production-ready expertise.

1. Latency (Delay)

Latency is the time it takes for a packet to travel from the source to the destination. It is usually measured as Round Trip Time (RTT).

Components of Latency

  1. Propagation Delay: The time it takes for the signal to travel through the physical medium (Limited by the speed of light).
  2. Serialization Delay: The time it takes to push the bits onto the wire.
  3. Queuing Delay: The time a packet spends waiting in a router’s buffer during congestion.
  4. Processing Delay: The time a router takes to read the header and decide where to send the packet.

2. Jitter (Delay Variation)

Jitter is the variation in the delay of received packets.

  • If packets arrive at 10ms, 10ms, 10ms, jitter is 0.
  • If packets arrive at 10ms, 40ms, 5ms, jitter is High.

Why it matters: High jitter is the enemy of real-time communication (VoIP, Video Calls). It causes “choppy” audio or “lagging” video because the receiver can’t predict when the next piece of data will arrive.

3. Interactive: Jitter Visualizer

Watch how inconsistent arrival times break the stream.

Low Jitter (Smooth)
High Jitter (stutter)

4. Mitigation: The Jitter Buffer

To handle jitter, receivers use a Jitter Buffer.

  • The receiver collects received packets in a small buffer and waits a short time before playing them out.
  • This “smooths out” the arrivals, but adds a small amount of fixed latency.
  • If the jitter is greater than the buffer size, packets are discarded (leading to gaps in audio).