[Starlink] It’s the Latency, FCC

[Colin_Higbie]

David,

Just on that one point that you "don't think developers think about latency at all," what developers (en masse, and as managed by their employers) care about is the user experience. If they don't think latency is an important part of the UX, then indeed they won't think about it. However, if latency is vital to the UX, such as in gaming or voice and video calling, it will be a focus. 

Standard QA will include use cases that they believe reflect the majority of their users. We have done testing with artificially high latencies to simulate geosynchronous satellite users, back when they represented a notable portion of our userbase. They no longer do (thanks to services like Starlink and recent proliferation of FTTH and even continued spreading of slower cable and DSL availability into more rural areas), so we no longer include those high latencies in our testing. This does indeed mean that our services will probably become less tolerant of higher latencies (and if we still have any geosynchronous satellite customers, they may resent this possible degradation in service). Some could call this lazy on our part, but it's just doing what's cost effective for most of our users. 

I'm estimating, but I think probably about 3 sigma of our users have typical latency (unloaded) of under 120ms. You or others on this list probably know better than I what fraction of our users will suffer severe enough bufferbloat to push a perceptible % of their transactions beyond 200ms. 

Fortunately, in our case, even high latency shouldn't be too terrible, but as you rightly point out, if there are many iterations, 1s minimum latency could yield a several second lag, which would be poor UX for almost any application. Since we're no longer testing for that on the premise that 1s minimum latency is no longer a common real-world scenario, it's possible those painful lags could creep into our system without our knowledge.

This is rational and what we should expect and want application and solution developers to do. We would not want developers to spend time, and thereby increase costs, focusing on areas that are not particularly important to their users and customers. 

Cheers,
Colin


-----Original Message-----
From: David Lang <david at lang.hm> 
Sent: Saturday, March 16, 2024 7:06 PM
To: Colin_Higbie <CHigbie1 at Higbie.name>
Cc: Dave Taht via Starlink <starlink at lists.bufferbloat.net>
Subject: RE: [Starlink] It’s the Latency, FCC

On Sat, 16 Mar 2024, Colin_Higbie wrote:

> At the same time, I do think if you give people tools where latency is 
> rarely an issue (say a 10x improvement, so perception of 1/10 the 
> latency), developers will be less efficient UNTIL that inefficiency 
> begins to yield poor UX. For example, if I know I can rely on latency 
> being 10ms and users don't care until total lag exceeds 500ms, I might 
> design something that uses a lot of back-and-forth between client and 
> server. As long as there are fewer than
> 50 iterations (500 / 10), users will be happy. But if I need to do 100 
> iterations to get the result, then I'll do some bundling of the 
> operations to keep the total observable lag at or below that 500ms.

I don't think developers think about latency at all (as a general rule)