LtG wrote:
I'm not sure what changes in the "core infra" you are referring to and how they affect routing congestion?
What kind of delays are you referring to? Ballpark figure?
A ping from Europe to Australia (au.archive.ubuntu.com) takes 300-400ms. The geodesic distance from Europe to Australia is somewhere from 13Mm to 16Mm. The speed of light in optical fiber is about 200Mm per second. So the roundtrip time for the signal itself should be about 160 ms on a straight line or about 220ms on a "diagonal" (non-optimal path, steering up to 45 degrees from the geodesic). So the remaining 100-200ms delay, I assume, should be routing latency. Which seems strange to me, considering that top of the line core routers are capable of sub microsecond routing table lookups, but this is only when the packet doesn't have to wait in a queue. That is why I assume that the remaining 100-200ms are effects from congestion or deep packet queueing at the core internet routers. It should also be mentioned that the icmp packets are handled differently from conventional payloads, so the ping latency may be misleading me. I have to test the latency with some actual tcp or udp application protocol.
LtG wrote:
Also, I'm pretty sure they already use wireless links from cell towers when it makes more sense, but in urban areas I would expect using wires will continue. Though haven't really studied that.
I believe that what you are referring to is the backhaul traffic, which connects the access sites to the internet core routers. But the core infrastructure, I believe, is the same one that is used for wired subscriptions. I speculated in my previous post that in order to take advantage of the reduced access latency of 5g at the access sites, the network operators would have to somehow upgrade the core infrastructure as well, or otherwise this point would be moot. If they did deploy wireless infrastructure for the entire end to end communication, this would allow them to form the intermediate connections dynamically and may be reduce the congestion and queueing effects. Because, when it comes to wired communication, the variety of electrical paths available to be taken by the payload on its way to the destination are inherently restricted. This is largely speculation on my part though. If someone here has already read something about the transition and could pass a few words of wisdom on how the overall latency will be handled by 5g, I would appreciate the hint.
LtG wrote:
And remember, electricity doesn't travel 1km/3.3usec, it depends on the wire how fast it travels. It can be significantly lower, like less than half of speed of light in a vacuum (~300 Mm/s). Not sure if really relevant here, but though I'd mention it anyway.
I said 1km/3.3usec, because for wireless, the signal will be traveling through air. You are right that for optical fiber, this is about 2/3rds the speed.
LtG wrote:
Of course other devices in the path (switches, routers, amplifiers, etc) tend to add quite a bit of delay also.
Exactly the kind of latency I was wondering about.