NDAA passed: Internet and Online Streaming Services Emergency Alert Study

Sun Jan 3 22:01:03 UTC 2021

At this point I would assume that nearly every device is persisting at 
least one long lived TCP connection.  Whether it's for telemetry or 
command and control, everything these days seems to have this 
capability.  As an example, I can hit a button in the Nintendo Switch 
parent app on my phone and my kid's Switch is reflecting changes a 
second later.  That's not even a platform I would have expected to have 
that capability.

If they have an existing connection then there lots of high connection 
count solutions in the IOT space that could easily handle this number of 
connections.  A single 12c 32G box running emqttd could handle 1.3M 
connections.  Just picking a random AWS EC2 size machine, m5.4xlarge, 
would run you about $0.003/year per device to keep that connection open 
and passing data.  I assume you could drive that down significantly from 
there.

On 01/03/2021 03:35 PM, Brandon Martin wrote:
> On 1/3/21 4:22 PM, Mark Delany wrote:
>> Creating quiescent sockets has certainly been discussed in the 
>> context of RSS where you
>> might want to server-notify a large number of long-held client 
>> connections very
>> infrequently.
>>
>> While a kernel could quiesce a TCP socket down to maybe 100 bytes or 
>> so (endpoint tuples,
>> sequence numbers, window sizes and a few other odds and sods), a big 
>> residual cost is
>> application state - in particular TLS state.
>>
>> Even with a participating application, quiescing in-memory state to 
>> something less than,
>> say, 1KB is probably hard but might be doable with a participating 
>> TLS library. If so, a
>> million quiescent connections could conceivably be stashed in a 
>> coupla GB of memory. And
>> of course if you're prepared to wear a disk read to recover quiescent 
>> state, your
>> in-memory cost could be less than 100 bytes allowing many millions of 
>> quiescent
>> connections per server.
>>
>> Having said all that, as far as I understand it, none of the 
>> DNS-over-TCP systems imply
>> centralization, that's just how a few applications have chosen to 
>> deploy. We deploy DOH to
>> a private self-managed server pool which consume a measly 10-20 
>> concurrent TCP sessions.
>
> I was thinking more in the original context of this thread w.r.t. 
> potential distribution of emergency alerts.  That could, if 
> semi-centralized, easily result in 100s of million connections to 
> juggle across a single service just for the USA.  While it presumably 
> wouldn't be quite that centralized, it's a sizable problem to manage.
>
> Obviously you could distribute it out ala the CDN model that the 
> content providers use, but then you're potentially devoting a sizable 
> chunk of hardware resources at something that really doesn't otherwise 
> require it.
>
> The nice thing is that such emergency alerts don't require 
> confidentiality and can relatively easily bear in-band, 
> application-level authentication (in fact, that seems preferable to 
> only using session-level authentication).  That means you could easily 
> carry them over plain HTTP or similar which removes the TLS overhead 
> you mention.
>
> Several GB of RAM is nothing for a modern server, of course.  It 
> sounds like you'd probably run into other scaling issues before you 
> hit memory limitations needed to juggle legitimate TCP connection state.