Network Intelligence

How Network Performance Actually Works

A speed test checks the physical limits of cables, routing protocols, and hardware queues. When you run a test, you check the entire route from your computer to a globally distributed edge server.

Here is exactly what these metrics mean, why they matter, and the technology behind them.

1. Download and Upload Speed (Throughput)

What it is:

Throughput is the raw volume of data your connection can process in one second, measured in Megabits per second (Mbps).

Why you need it:

• Download: Needed for fetching large files. 4K video streaming requires about 25 Mbps.
• Upload: Needed for sending data. WebRTC video calls (Zoom, Google Meet) and live streaming require 10-20 Mbps upload speeds.

How it works:

• Data is split into small units called packets using the Transmission Control Protocol (TCP).
• The receiving device must acknowledge (ACK) these packets.
• If the TCP Window Size (the amount of unacknowledged data allowed) is too small, the transfer stops to wait for acknowledgments, capping your speed.

2. Latency (Ping)

What it is:

Latency is the exact time it takes for a single data packet to travel from your device to the server and back. It is measured in milliseconds (ms).

Why you need it:

• Web Browsing: Low latency means DNS lookups and TLS handshakes finish instantly, making websites load faster.
• Gaming: A ping under 50ms ensures your actions register immediately on the server.

How it works:

• Data travels through fiber optic cables at the speed of light in glass (about 200,000 km/s).
• Packets pass through multiple routers. Each router uses the Border Gateway Protocol (BGP) to read the packet and forward it.
• More router hops equal higher latency.
• Content Delivery Networks (CDNs) use Anycast routing to answer your request from a server in your own city, dropping latency to under 15ms.

3. Jitter and Bufferbloat

What it is:

Jitter is the variance in your latency. If your ping jumps rapidly between 20ms and 150ms, you have high jitter.

Why it matters:

• Video calls and online games use the User Datagram Protocol (UDP).
• UDP requires packets to arrive in a strict sequence.
• High jitter causes packets to arrive out of order. This creates robotic audio, frozen video frames, and game stuttering.

The hardware problem (Bufferbloat):

• When a network is busy (e.g., downloading a large file), routers store incoming packets in large memory queues instead of dropping them.
• Your small, real-time VoIP packets get stuck at the back of this queue, causing massive latency spikes. This is called Bufferbloat.
• High-end routers use Active Queue Management (AQM) algorithms like fq_codel to prioritize small, real-time packets over bulk downloads.

4. Packet Loss

What it is:

Packet loss happens when data fails to reach its destination.

Why it matters:

• For TCP (Websites/Downloads): The protocol detects the missing packet and asks the server to resend it. This halves your download speed.
• For UDP (Gaming/Video): The packet is gone forever. You experience visual glitches or teleporting in games.
• Packet loss is usually caused by failing hardware, bad coaxial cables, or interference on 2.4GHz Wi-Fi networks.