On 17/04/2023 1:04 pm, David Lang wrote:
I think it is going to be fairly common, but the beauty of the idea is
that you don't have to risk much to try it. Long lived DNS answers
(and especially root servers and TLD servers) can trivially be
mirrored to the satellites, and you can experiment with caching to see
what sort of hit rate you get. Even if you don't cache a lot of the
CDN type traffic, it should still be a win to have the longer term
stuff there.
Yes - but root servers and TLD servers also get cached a long time at
the clients. If each of your clients needs a root server and a few TLD
lookups a day, it's not a huge gain in terms of performance.
It is however a significant step up in terms of complexity. E.g., your
satellite-based DNS would have to point you at the TLD server that is
topologically closest to your Starlink gateway, or risk a potentially
much longer RTT for the lookup. So you'd need to maintain a list of TLD
instances on your satellite-based DNS and return the one that
corresponds to what your gateway-based DNS would get. Sure possible but
more complex than a bog standard DNS server in a fixed network.
Practically speaking, we know from various sources that each Starlink
satellite provides - ballpark - a couple of dozen Gb/s in capacity,
and that active users on a "busy" satellite see a couple of dozen
Mb/s of that. "Busy" means most active users, and so we can conclude
that the number of users per satellite who use any site is at most
around 1000. The subset of users navigating to new sites among them
is probably in the low 100's at best. If we're excluding new sites
that aren't dynamic, we're probably down to a couple of dozen new
static sites being queried per satellite pass. How many of these
queries will be duplicates? Not a lot. If we're including sites that
are dynamic, we're still not getting a huge probability of cache
entry re-use.
I think that each user is typically going to use a lot less than the
'couple dozen MB' that is the limits that we see, so the number of
users in a cell would be much higher.
Yes, but these users aren't "active" in the sense that they will be
firing off DNS queries during the pass...
DNS data is not that large, getting enough storage into the
satellites to serve 90% of the non-dynamic data should not be a big
deal. The dynamic data expires fast enough (and can be detected as
being dynamic and expired faster in the satellite) that I'm not
worried about serving data from one side of the world to the other.
Yes, but the only advantage we'd get here is faster resolution for a
very small subset of DNS queries.
and while that's not as big a win as faster resolution of a larger
set, it's still a win.
Yes, but are we chasing diminishing margins here when there are much
bigger fish to fry?
There are various things that could be done if there is enough
interest in starlink users to improve the CDN traffic, and it's not
clear that misdirecting starlink users in some (or even many) cases
would be that horrible. Geolocation is very imprecise at best and
routinely misidentifies locations.
See my comments on geolocation in my response to David Reed's post - I
shouldn't have used that term.
--
****************************************************************
Dr. Ulrich Speidel
School of Computer Science
Room 303S.594 (City Campus)
The University of Auckland
[email protected]
http://www.cs.auckland.ac.nz/~ulrich/
****************************************************************
_______________________________________________
Starlink mailing list
[email protected]
https://lists.bufferbloat.net/listinfo/starlink
