Following up a little on population statistics:
I came across a note that Comm Bouys are supposed to handle communications from trillions of people at once. One particular methodology made the assumption of two trillion, and a sort of hub and spoke model.
Now, they also make some assumptions on how internet traffic would have been handled, but I think there are a few solutions that might address this, caching systems that would help websites especially media platforms to improve response times, and lower actual traffic through Comm Buoys, but sending email and calling should represent the majority of data sent. We can likely ignore text-based communication, since text-based data should have a negligible effect on data transfer times, but calls and similar communications, especially in near-realtime should overlap. The call times used on the other thread were 1:30 for paid calls and 4:00 for free ones, which might make sense, but given calls are, by default near-realtime, we can't really differentiate between paid and free calls. Delayed communications would likely be routed through the free queues in order to save cost the vast majority of the time, but real-time communication are likely always charged at a priority unless it is at non-peak hours.
Of course, it's also relatively unlikely that all a system's traffic needs to go through a buoy. Planets are large, and unless they are involved in space travel somehow, it's relatively unlikely that people will be calling others outside their planet or at least system for the most part.
Consider it similar to people calling internationally, relatively limited, all told, though VOIP has been making that more available but that's due to the removal of international calling charges, something that we can't consider to be available.
However, for a lowball estimate, let's say that the Comm Bouys operate on a hub-and-spoke system, one that tends to route traffic through a few central systems for the sake of reasonable calculations, and that all comm buoys are standard, which actually makes sense. Most of the cost is likely bound up in the Eezo needed to establish inter-system zero-mass corridors, so the computational equipment needed to handle the communications is probably a relatively minor cost to the system, and something that might well be standardised to help with mass production.
The estimation in the other thread suggests that the core spoke should serve an eighth of the citadel population, but I believe this to be faulty, for one reason.
The Citadel.
The Citadel acts as the hub for galactic politics, and thus would likely be a major hub for inter-system communication. I've considered a number of possibilities for other inter-system trade, but between the use of in-system contractors (at least at hub-systems) for things like customer and technical support as well as the relatively low likelihood of family being split across multiple systems (outside of spacers, but these people are likely a smaller proportion) it makes sense that the majority of the traffic going through these systems will be business, politically or military focused. The last is likely fairly well distributed as a load across the network, but the former two are likely to be focused through the citadel, being the centre of politics and the economy.
With that in consideration, I'd estimate that if the Citadel has the single greatest load for the system, it handles somewhere in the neighbourhood of 30% of the load.
Using the low-end estimate of 2 trillion, that would mean that it's somewhere in the neighbourhood of 6-7 trillion sapients.
Further tweaking notes: The Comm buoy network isn't new. It's probably older than the Krogan Rebellions, and this is important.
If the System was built with Krogans in mind, it might have been overbuilt, perhaps not overbuilt enough, but the trillions may be reflecting a time when there were just so many Krogan that things needed to take account for that. The krogan may even have contributed more than one of those trillions.
Now, bringing back the population graph I put together earlier (again very rough) but let's figure out how different groups play into it.
Asari, Batarian, Drell, Elcor, Hanar, Human, Krogan, Quarian, Salarian, Turian, Volus, Vorcha?
Eleven, I guess if we drop the Vorcha, I don't remember them using any tech.
Humans have 13,000,000,000 which doesn't really dent that 6-7 trillion number, but it's actually within a fifth of a tenth that number - which would be useful if there are equal numbers of the other races. Unlikely, overall though.
It's not actually clear how many Krogans there are, but I'd actually suspect that there are more than you would think. They did overpopulate several entire planets not too long ago - for them. Krogans can live to at least 1400, if not longer assuming that they don't kill themselves off in battle (which they probably do) but they are hard to kill. I wouldn't be surprised to hear that they actually outnumber humans, and that too by a decent degree. If anything, I'd rank them at... perhaps a decent fraction of the turian population? not more than 25% but I think that number should work. Though would it be better to compare them at the time of Comm Buoy peak use? At that level I'd put them at equal to the Turians in number.
Drell are another easy one to knock off the list, a few hundred thousand two hundred years ago? not worth much. I don't think their population would be back over ten million let alone a billion.
We have numbers on Quarians, 17 million, another relatively superfluous number. However, this does not include quarians that were exiled from the fleet though that number would be minor. Though, if we are considering the Quarians prior to the Morning War... Might actually rate higher. Perhaps equal to the Asari?
And now we get to the harder ones.
Batarians are likely to be relatively large. An economy as inefficient as theirs (slavery is inherently inefficient) being able to out-power humans in a relatively deniable manner suggests that they have the more powerful economy despite it being worse pound for pound. A quick estimate suggests that they may have 10 to twenty times as many batarians as humans. I'd say that Batarians probably equal the Turians in sheer numbers... in the modern day. Back when the Buoys were being made, they were probably a smaller player, maybe not worth more than half of the Turian population? I expect the Batarian numbers to grow faster than the Turians, all things told.
Elcor probably outnumber the Asari, but basically no one else. They have an effective rate four times as long as anyone else, but twice that of an Asari. I'd say they rate 1.5 Asari.
Hanar are a bit of a mystery, but for the purposes of keeping things simple, let's give them the average population of the council races. The Asari should pull that down enough to make that a reasonable number.
Next up is the Volus. They actually predate the Turians, and it's unsure how exactly they became a client race the the Turians. It could be the fanfic favourite of Turians putting the boot on them, but I find that unlikely. Possible, the Turians were the primary military power and were new entrants to the council and thus likely to push things, but I could also see the Volus doing this in order to be able to spend less on their military in favour of expanding their economy in other ways. Overally, I'd put them at more populous than the Turians, unless their atmosphere has a serious impact on their ability to colonize. Perhaps 2 times the turian populaiton.
Now onto the big three.
If we make the assumption that 6 Trillion is spread out among
A + 1.5A + A + T + 2T + T + 0.5T + S + ((A+S+T)/3) = 3.5A + 4.5T + S + ((A+S+T)/3) = (11.5A + 14.5T + 4S)/3
For when the comm buoy network was designed
We can plug in some tweaked growth rates for the others and well...
A set of numbers that work for a growth rate in this situation is about a 1% growth rate for the Asari, a 0.34% growth rate for the Salarians and a 0.35% growth rate for the Turians.
This gives a rough estimate as to the Council race numbers at :
Asari : 71 Billion
Salarian : 2.2 Trillion
Turian : 480 Billion
And a total Citadel alliance population at about 5.3 billion
Lower than the six above I know, but these numbers are so rough that anything in the right order of magnitude should be just as accurate as anything else in the same order of magnitude
EDIT: Those numbers may have to be an order of magnitude bigger, since I forgot to account for distribution of call times across the entire working day, and this doesn't include the people who are unlikely to spending extra on priority inter-system traffic.
Of course, these assume the Comm buoy numbers are accurate, and that could mean as little as the buoys are future proofed to handle a population of trillions or the number is just a hyperbole, reflecting the network as a whole handling the whole population which is in the trillions.
