[walrus01]

Note that the measurement on geostationary is almost certainly performed on a contended (tdma) 32:1 consumer grade oversubscribed link or worse.

Actual 1:1 dedicated geostationary which is very expensive in $/Mbps is a fixed, flat 492 to 495ms rtt latency, plus or minus a tiny bit either way, depending on modem encode and decode FEC type.

Consumer grade geostationary could be anywhere from 495ms in the middle of the night local time to 1350ms or worse.

Re: the figure for terrestrial fiber service, I'm curious how the presumed residential last mile "fiber" link in Geoff's example which is not real gigabit service would compare to one of the symmetric gigabit last mile operators that exist in some cities. Where you can see actual 980 x 980Mbps speed test results from fast.com or speedtest.net in a browser.

I'm always very suspicious of anything that says it's fiber but is limited to like 25Mbps up, either it's a totally artificial limit or in reality it's some vdsl2 link, or "fiber" delivered over docsis3 copper cable with limited upstream rf channel allocation, etc.

[formerly_proven]

> Re: the figure for terrestrial fiber service, I'm curious how the presumed residential last mile "fiber" link in Geoff's example which is not real gigabit service would compare to one of the symmetric gigabit last mile operators that exist in some cities. Where you can see actual 980 x 980Mbps speed test results from fast.com or speedtest.net in a browser.

Well if you pay for gigabit over GPON it means you have at worst a 2:1 split, which gives you 1.2/1.2 Gbps. Even assuming they're still using an MPoA/ATM transfer layer like they did on DSL (keep in mind, these are ITU standards - GPON is not Ethernet - though there are fiber networks which are Ethernet, these are AONs by definition (no splitters possible), and use 1000BASE-BX10), that doesn't have nearly enough overhead to reduce 1.2 Gbps to below 1 Gbps.

[walrus01]

The exact likelihood of being able to max out your lan side 1GbE interface to a home gpon terminal also depends on some factors you can't know unless you are the ISP, such as the usage patterns and traffic volumes moved by your neighbours on the same port. Could be wildly different if you happen to be in a condo with some person that is seeding popular torrents or if you're in a neighborhood of mostly retirees for instance.

Not sure what you mean by at worst a 1:2 split since GPON last mile can be implemented at the physical fiber level as many possible configurations such as a 8:1, 16:1, 32:1 split. Your ISP isn't likely to tell you or share with you the optical link budget and split of your segment.