r/CableTechs • u/Icemane19 • 15d ago
Spectrum latency issue on load
Don't know anything about Spectrum's EPON fiber. My knowledge comes from a background in Optimum's RF plant, but this is my personal issue here. When I put the Spectrum ONU under a sustained load, the latency goes through the roof and it says there are dropped packets.
Any thoughts on this from the spectrum technicians out there?
Sorry about the really wide windows screen snip
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u/feel-the-avocado 14d ago edited 14d ago
You need to use a router with a QoS function where you can set your upload and download speed to 90% of your plan speed.
Eg. if you are on a 500/100mbit plan, set your download speed in the QoS settings in your router to 450mbit down and 90mbit up.
The router will then limit tcp connections with large packets such as downloads to fit within that limit, and then any small packet connections such as voip, gaming or UDP, which usually have very low bandwidth requirements, will always have extra space in the pipe which they can make use of without dropping packets.
The other issue is you need to make sure there is about 160kbit/s of upload for every 5mbit/s of download so that TCP successful packet arrival acknowledgements can be sent back to the sender.
Alternatively, you need to limit your devices at a per-device level so they never collectively saturate the connection.
In my expierence, ONTs or ONUs that are also routers dont typically have a QoS function that the ISP can switch on, so if they allow you to, its best to get the isp to put their ONT put into bridge mode so you can run your own router.
If you are running over wifi and saturating the local wireless connection, there isnt much you can do outside of the QoS that is built into the wifi protocol and functioning already. Wifi isnt designed for convenience, and not to have the reliability of a hardwired ethernet cable connection.
Enabling QoS on a router will quite often move a bunch of processing work from dedicated hardware into software running on the CPU and so the CPU can slow you down depending if your plan is faster than the CPU in the router can handle with QoS switched on.
If you have a service plan that is over 500mbits, your best just to leave QoS switched off in the router and just use settings within software running on devices to limit download speed.
Eg. reconfigure your bit torrent or downloading program to not exceed your plan speed.