It’s the latency, stupid!

While working on some bandwidth-related stuff (my bandwidth calculator), I came across an excellent article on “latency vs. bandwidth” by Stuart Cheshire. It was originally written in 1996, so focuses a lot on modems, but Fact 1, 2 and 4 are still valid.

His points:

The following calculation is eye-opening:

The distance from Stanford to Boston is 4320km.
The speed of light in vacuum is 300 x 10^6 m/s.
The speed of light in fibre is roughly 66% of the speed of light in vacuum.
The speed of light in fibre is 300 x 10^6 m/s * 0.66 = 200 x 10^6 m/s.
The one-way delay to Boston is 4320 km / 200 x 10^6 m/s = 21.6ms.
The round-trip time to Boston and back is 43.2ms.
The current ping time from Stanford to Boston over today’s Internet is about 85ms:

[cheshire@nitro]$ ping -c 1
PING ( 56 data bytes
64 bytes from icmp_seq=0 ttl=238 time=84.5 ms

So: the hardware of the Internet can currently achieve within a factor of two of the speed of light.

Definitions of latency:

Latency, a synonym for delay, is an expression of how much time it takes for a packet of data to get from one designated point to another -

Latency is the time a message takes to traverse a system -

💬 bandwidth 🏷 network 🏷 latency