Bandwidth

Performance

The maximum data transfer rate of a network link, measured in bits per second (Mbps, Gbps). Not the same as throughput—bandwidth is capacity, throughput is what you actually use.

Updated Mar 9, 2026

Full Explanation

Bandwidth is the size of the pipe. Throughput is how much water actually flows through it. A 10 Gbps link doesn't mean you'll transfer at 10 Gbps—congestion, protocol overhead, and distance all eat into that.

For CDNs, bandwidth matters in two places: the edge (how much you can serve to users) and the backhaul (how fast you can fill caches from origin). CDN providers price largely on bandwidth—either by peak usage (95th percentile billing) or total transfer (per-GB pricing).

A single 4K stream needs about 25 Mbps. A busy PoP serving 10,000 concurrent streams needs 250 Gbps just for video. That's why CDN PoPs are stuffed with 100GbE links and sit inside major IXPs.

Examples

Check bandwidth between your origin and CDN edge:

# Test with iperf3 between two endpoints
$ iperf3 -c cdn-origin.example.com
[ ID] Interval      Transfer    Bitrate
[  5] 0.00-10.00 sec  1.09 GBytes   938 Mbits/sec

# Or use curl to measure real HTTP throughput
$ curl -o /dev/null -w '%{speed_download}\n' https://cdn.example.com/bigfile.bin
# Output in bytes/sec

Video Explanation

Frequently Asked Questions

The maximum data transfer rate of a network link, measured in bits per second (Mbps, Gbps). Not the same as throughput—bandwidth is capacity, throughput is what you actually use.

Check bandwidth between your origin and CDN edge:

# Test with iperf3 between two endpoints
$ iperf3 -c cdn-origin.example.com
[ ID] Interval      Transfer    Bitrate
[  5] 0.00-10.00 sec  1.09 GBytes   938 Mbits/sec

# Or use curl to measure real HTTP throughput
$ curl -o /dev/null -w '%{speed_download}\n' https://cdn.example.com/bigfile.bin
# Output in bytes/sec

Related CDN concepts include:

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