[jrockway]

To some extent, this already happens. My cable modem adds about 30ms latency no matter the destination. I think this is a combination of buffer bloat (wait for buffer to fill before talking on the network) and waiting for a transmit time slot (shared access to the physical layer). I haven't looked at it in detail, but it is very surprising to me that I get 60ms RTT to Blizzard's servers in Chicago (a speed of light distance of 4ms one way) and 25-40ms ping to Google (in what they call "lga15", which is somewhere in Manahttan, probably 60 Hudson).

I realize that ping is a very poor benchmark as most routers do not handle ping in their fast path, but it's not adding 40ms of latency. So I suspect my modem.

[dannyw]

This is extremely unusual to me. Personally I notice it when my ping to local game servers go from 5 to 25.

I’d recommended you look into it, and potentially get another modem. If all my requests started taking another 30ms, I’d consider my network degraded.

[lxgr]

On a congested upstream, DOCSIS unfortunately seems to behave like this due to contention for and the insufficient granularity of upsteam transmission timeslots.

This effectively means that even if your share of the total upstream link of a network "collision domain" (shared coaxial medium really) is low (i.e you're using less than 1/n and accordingly should not be experiencing queueing in the modem), you might be seeing latency spikes due to having to compete and wait for transmission timeslots.

My local DOCSIS link is experiencing anything between 0 and 60 milliseconds of latency which I suspect is mostly due to this (since it's inversely correlated to upstream bandwith).

[jrockway]

Seems like everyone with any cable ISP has this problem. It could be a modem problem, but it's happened with a variety of modems. It could be an ISP problem, but both Comcast and Spectrum users see the same thing in my experience.

I'd be interested in hearing counterexamples, but I imagine that people with good experiences are on DSL or Fiber.

[zrm]

I can ping 1.1.1.1 right now at 12-15ms, or Google at around 20ms, via Comcast. Less than 10ms to either one on Optimum. But it's 25-30ms to ping Optimum from Comcast.

[lxgr]

> buffer bloat (wait for buffer to fill before talking on the network)

That's not buffer bloat (but might nevertheless be something that happens on DOCSIS modems, although I haven't heard of buffering several packets before contending for an upstream send grant).

Buffer bloat, while also rampant especially in shitty CPE like most DOCSIS modem/router combinations, would only occur when your upstream is saturated.

Supposedly though, on DOCSIS, the upstream access contention algorithm used can sometimes add the latency you describe, adding latency even for single packets.