Bandwidth, Traffic, and Peak Billing: Making Sense of Cloud Server Network Pricing

When you buy a cloud server, the network column is often the most confusing part. Some plans sell by bandwidth (Mbps), others by traffic (GB/TB), and you'll run into terms like "95th percentile" and "shared vs. dedicated." Understanding them keeps you from overpaying or getting throttled.

Bandwidth vs. Traffic: A Pipe and the Water Through It

• Bandwidth is the maximum transfer rate per unit of time, measured in Mbps (megabits per second). Think of it as the width of a water pipe—it sets how fast data can flow at any instant.
• Traffic (or transfer) is the total volume of data moved over a period, measured in GB / TB. Think of it as how much water you used all month—it sets how much you can move in total.

Bandwidth caps the rate; traffic caps the total. A 50 Mbps dedicated line stays fast even if maxed out all month, while a 2 TB monthly quota can burst very fast but runs out quickly.

Bits vs. Bytes: That Factor of 8

Network speed is measured in bits (lowercase b), while file size is measured in Bytes (uppercase B), and 1 Byte = 8 bits. So to convert, divide by 8:

100 Mbps ÷ 8 = 12.5 MB/s

That's why a "100M connection" downloads files at only about 12.5 MB/s—nothing is being shortchanged, the units are simply different. Remember: Mbps is line speed, MB/s is disk-write speed, and they differ by 8x.

Three Common Billing Models

• Fixed bandwidth (dedicated, flat monthly): You buy a set number of Mbps and get exactly that, usually with unlimited traffic. Best for streaming, download servers, and other sustained-load use cases; pricing is the easiest to reason about.
• Pay-as-you-go (metered traffic): The bandwidth cap is high or unmetered, and you're billed only on the GB/TB you actually move. Ideal for low or spiky usage—an idle server costs almost nothing.
• 95th percentile: Your rate is sampled every 5 minutes (8,640 samples a month), the top 5% of peaks (432 samples) are discarded, and you're billed on the highest remaining value. It forgives brief spikes, making it a good fit for high-volume workloads with clear peaks and valleys.

Shared vs. Dedicated Bandwidth

• Dedicated: The line is yours alone. A 100 Mbps plan reliably reaches 100 Mbps, so performance is predictable.
• Shared: Several servers share one larger pipe, so the advertised number is a ceiling, not a guarantee—noisy neighbors can crowd you out at peak times. It's cheaper and fine when rock-solid stability isn't critical.

Check whether a plan says "dedicated" or "shared / up to"; the latter figure is usually a theoretical maximum.

Estimating What You Actually Need

Start with traffic: monthly traffic ≈ daily visits × average size per visit × 30. A small site with a few thousand daily visitors and pages of a few hundred KB often lands in the tens of GB per month, while video or download services easily hit TB territory.

Then bandwidth: required bandwidth (Mbps) ≈ peak concurrent connections × per-connection rate (MB/s) × 8. When in doubt, run a metered plan for a month or two to observe real numbers, then decide whether fixed bandwidth is cheaper.

Measuring Traffic with vnstat

vnstat is a lightweight Linux traffic monitor built on kernel counters, with almost zero overhead. Install on Ubuntu/Debian:

sudo apt update && sudo apt install -y vnstat
sudo systemctl enable --now vnstat

Everyday queries:

vnstat            # overview: today / this month / all time
vnstat -d         # daily breakdown
vnstat -m         # monthly breakdown
vnstat -h         # hourly breakdown
vnstat -tr 5      # live throughput, sampled over 5 seconds
vnstat -i eth0    # pick an interface (find names with: ip a)

After it's been running a while, the monthly figures from vnstat -m are the most reliable basis for choosing a plan.

Summary

Bandwidth governs rate (Mbps), traffic governs total volume (GB/TB), and never forget the 8x unit gap between them (100 Mbps ≈ 12.5 MB/s). Fixed bandwidth buys stability, pay-as-you-go buys savings, and 95th percentile tolerates spikes; dedicated is predictable, shared is cheaper. Don't guess your plan—run vnstat for a month or two and let the bill follow real usage.