Re:Meta's Hyperscale Infrastructure: Overview and Insights
by dijit on Tuesday February 11, 2025 @05:49AM
(#43011317)
DC-to-DC networking is typically much higher throughput, and often lower latency (due to fewer hops).
Consider also that the CDN can fetch the whole image async after the first request, but the nature of TCP (that you'll be using to fetch objects) is serial, meaning you can only fetch about 1k each round-trip.
Now, in reality the situation is way more complex, because various hacks have been added over the years, for example your browser might grab the size header and just create a bunch of download threads for your image with various offsets, the TCP scaling window might come into play; but largely most people set 1500b for their MTU on consumer hardware, and there's some overhead from TCP/IP and so on.
Consider also that the CDN can fetch the whole image async after the first request, but the nature of TCP (that you'll be using to fetch objects) is serial, meaning you can only fetch about 1k each round-trip.
Now, in reality the situation is way more complex, because various hacks have been added over the years, for example your browser might grab the size header and just create a bunch of download threads for your image with various offsets, the TCP scaling window might come into play; but largely most people set 1500b for their MTU on consumer hardware, and there's some overhead from TCP/IP and so on.