Low Latency DOCSIS (LLD - DOCSIS means “cable”) aims to implement a low-latency path on cable networks. That low-latency path can be used by traffic that does not slow down due to loss/congestion (e.g. real-time gaming traffic), or protocols (e.g. “L4S services”) that are designed to run over it. The latter has yet to see widespread adoption, so for now, the benefit is limited to those incompressible flows. LDD is what Comcast has activated on their network.
Today’s cable networks exhibit sky-high latency during congestion. Congestion is also much more frequent than in PON networks like Sonic’s, as far more customers share a much smaller pipe. Technologies like LLD can bring a meaningful decrease in latency to some traffic types in cases of congestion. Fundamentally, though, the best approach to congestion is to … not have congestion, and it is very rare at Sonic.
LLD can also provide a faster path in steady-state operation for those same types of prioritized traffic. This concept is just as applicable to DOCSIS as it is to PON, but again, of far less importance to the latter. Non-LLD DOCSIS equipment may add 10ms or more of steady-state latency, and LLD is said to improve latency to ~1-2ms. That’s a big improvement – but Sonic’s PON network has had steady-state latency in the ~1-2ms range for years.
Bottom line, there is a potential improvement from implementing a low-latency queue in our PON infrastructure, but it’s small. We are investigating what it would take to deploy, especially with an eye to future L4S services. Any benefits, though, will be much less dramatic than in DOCSIS, and our products remain top-of-the-heap when compared to anything else out there.
For those technically inclined, take a peek at the following, which goes over the gory details of LLD:
https://tinyurl.com/3zsv3hcd
-Nathan