Re: [rtcweb] Network times . was SDP Security Descriptions (RFC 4568) and RTCWeb

[Cullen Jennings <[e-mail]>]

On May 1, 2013, at 12:30 PM, Randell Jesup <[e-mail]> wrote:

> On 5/1/2013 9:01 AM, Justin Uberti wrote:
>> This doesn't match what we are seeing. I pulled some Chrome stats on average RTT seen across various network connections; on 3G, close to half of users had RTTs > 250 ms. 4G is somewhat better. 2G is considerably worse.
>> 
>> India continues to be especially bad, partially because of the above, partially because of use of satellite links, which due to physics incur 500 ms RTTs.
> 
> Those are all RTT measurements, so One Way Delay's of roughly half of that?  speed-of-light for a one-way satellite link would be around 280ms in theory - and of course that's just for that one physical link.

By one way here, you mean up to the satellite link, then back down to the ground again which the satellite people often don't call one way but I agree it is the network latency measurement from browser to browser we are looking for. You are of course correct that, for geosync satellites that are at somewhere around 42,000 km up, we get around 240 to 280 ms depending on your relative location to the satellite. But, keep in mind the preferred satellites for this type of stuff are globalstar at 1400 km or iridium at less than 800 km which have way less latency than geosync. 

I'm still looking for the elusive 1500 ms. 


> 
> -- 
> Randell Jesup
> [e-mail]
> 
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