here's a little series of puzzlers, followed by an explanation of how i came to them.
- only 2/3 of the audio traffic between two Jacktrip-connected computers flows on the 4464 - 6100N pair of ports
- the remaining 500k of bandwidth is spread over a large number of other port-pairs
- those additional port pairs appear to be random when audio volume is high, but start to use known IP ports like 993 and 995 when the gain is reduced to zero
- the traffic-per-port-pair changes with audio volume
i was trying to diagnose a crackly connection a few days ago and decided to take a look at traffic by IP port just to see if a script-kiddie was interfering with our stream. that turned out to be a dead end, but i noticed this really interesting behavior that appears to be normal. i'm wondering whether Jacktrip or Jack is doing this, and whether it's normal/intended.
here's a little 30-second silent movie to show what i mean.
there are two computers. i'm running the IFTOP utility on both. the one on the left is the hub server, the one on the right is a hub client. there's a ton of traffic on port 5900 that you can ignore -- they're screen sharing. these are local Macs, but i've also run this test to a remote Linode with the same behavior. the three columns of the display are average traffic over 2, 10 and 40 second intervals
towards the top of the display you'll see the port 4464-61002 pipes. that port-pair stays really steady at 1 mbps.
at the beginning of the video, the volume on the audio-sending computer (the one on the right) is full on, with a fairly compressed signal that's peaking about -6 db.
as your eye goes down, you see a zillion other port pairs that look ephemeral. and they also look like random, non-assigned ports. i haven't explored how many of them there are, but since the overall bandwidth is 1.5 mbps, and they each have tiny traffic there must be a LOT of them. with a LOT of churn.
when i zero the volume on the audio, a couple interesting things happen.
- traffic starts to load up on a the non 4464 pairs
- the pairs are no longer anchored way up in the random range -- they're anchored in known ports like 256, 993 and 995
- some of the pairs aren't anchored in a port at all
can anybody point me in the right direction? i can't frame a good search query for this one.