Technicolor TG582n – Any tips to achieve low latency (lag)?

[#1]

Apologies if this perhaps is not the right section of the forum.
I am not a gamer, in reality.
I am a musician, and I use an application called Jacktrip, a client/server solution which passes through  port 4464 as default, and allows to stream audio bidirectionally.
Basically, it allows to play music with somebody else online.
Of course, to play together latency must be very low, under 30ms for sure, but ideally 10/15ms.
Given gamers need low latency too when playing online, I figured out that perhaps somebody could  give me some tips about network settings.
I am forwarding the port (UDP, as that' what we use) on the modem and I connect directly to it with a LAN cable. My latency at the moment is very bad, I use a linux distro pre-optimized for  low latency, so the problem shouldn't be a software one.
Do the options “Use Extended Security” and “Use UpnP” affect latency?
Does plus net apply any traffic shaping?
Any other tips?
Thanks!

[#2]

I don't think the UPnP settings will affect latency, they only affect how programs are able to automatically open ports they need.
I suppose you could try disabling the power saving options as described here: http://npr.me.uk/telnet.html#cpu - however I expect any differences in performance would be very small. Also, turning off all the power saving features might make it run hotter when idle.
On current tariffs, Plusnet apply traffic prioritisation, this should only make a difference if there are other activities using your Internet connection at the same time as you're playing music.
The main way you can ensure you're getting the lowest possible latency, is to make sure you're getting the best out of your ADSL line, so you need to post the ADSL stats from the 582n for anyone on the forum to comment on that.

[#3]

Thanks so much.
For stats do you mean an speedtest such as ookla or some logs from the modem admin interface?


Product Name: TG582n
Serial Number: CP1333VFNVL
Software Release: 10.2.2.B
Software Variant: EH
Boot Loader Version: 1.0.5
Product Code: 3701603C
Board Name: DANT-T

[#4]

The DSL stats from the admin interface - see http://www.plus.net/support/broadband/hardware/technicolor-582n-faqs.shtml#lineStats - make sure you click "View more" under "DSL Connection"

[#5]

Thanks, I could not find View More, but I clicked on Details, hopefully with the same result

DSL Connection
Link Information

Uptime: 74 days, 6:57:45
DSL Type: ITU-T G.992.5
Bandwidth (Up/Down) [kbps/kbps]: 1,219 / 12,543
Data Transferred (Sent/Received) [GB/GB]: 41.88 / 316.35
Output Power (Up/Down) [dBm]: 12.3 / 0.0
Line Attenuation (Up/Down) [dB]: 15.8 / 32.0
SN Margin (Up/Down) [dB]: 6.1 / 6.8
System Vendor ID (Local/Remote): TMMB / ----
Chipset Vendor ID (Local/Remote): BDCM / IFTN
Loss of Framing (Local/Remote): 70 / 0
Loss of Signal (Local/Remote): 8 / 0
Loss of Power (Local/Remote): 0 / 0
Loss of Link (Remote): -
Error Seconds (Local/Remote): 190,895 / 0
FEC Errors (Up/Down): 0 / 0
CRC Errors (Up/Down): 3,120 / 227,697
HEC Errors (Up/Down): 3,648 / 1,962,290

[#6]

Yes, those are the required details. The zero FEC errors indicate that interleaving is off, interleaving would increase latency, so that's not part of the problem. The other errors, CRC and HEC, are perhaps a little higher than ideal, but I don't think they're too bad either. Too many CRC or HEC errors would result in the packet loss becoming noticeable, as glitches in the audio, or the latency momentarily increasing if Jacktrip uses TCP which would automatically re-transmit lost packets.
How are you measuring the latency? Using the ping command from the command line should be fairly reliable. Ping times around 10-15 ms are possible on ADSL if you live in South East England. All the datacentres where customers connect to Plusnet's network, and to the rest of the Internet, are in London. If you live at the other end of the country, your latency will always be a bit higher, and there won't be much you can do about that.
I probably should have asked earlier - what is your current latency, from commands like ping ntp.plus.net or ping google.co.uk? Also, is your latency better or worse at different times of the day? If your latency gets worse in the evenings when the network is busiest (especially 8pm to 10pm), then there might be congestion at your exchange which Plusnet could look into.

[#7]

My latency, on LAN cable
--- google.co.uk ping statistics ---
17 packets transmitted, 17 received, 0% packet loss, time 16025ms
rtt min/avg/max/mdev = 6.898/7.431/8.060/0.300 ms
I did several, and the figures remained stable around 7-8ms
I have run the test before, I don't think there was significant variability dependently on the time of  the day, but I could  check again.
Thing is, jacktrip, the application I need to use , needs UDP rather than TCP.
Basically, it is a bidirectional flow and errors are not corrected, they simply determine pops and general deterioration of audio quality.
So I have been testing mainly with iperf, and of course I can only do that with somebody online willing to start an iperf server.
Results were very variable, but there are so many parameters involved, on my side and their side, that it is difficult to tell.
Also, I just found out that there are public iperf servers, but I could not connect to any of these with the -u option (UDP).

[#8]

Well those are really good ping times. Of course for us google is actually a plusnet server as you may have noticed already (depending on which ping you(r distro) uses.
What bandwidth and packet size are you using for the UDP iperf tests?
If you push it too close to your or your peers upstream then it is going to fall apart. ADSL has a lot of overheads so you will need to stay well below any sync rates as shown by routers.

[#9]

Thanks
I would need to double check to confirm the iperf settings.
Unfortunately I could only run iperf with a colleague from a low latency audio course I am taking, and that was a few weeks ago now.
I'll see if I can dig my command line history to see what I used.

[#10]

You could also use wireshark to check the prioritisation Plusnet assign Jacktrip data:
What to do if you suspect a game is being incorrectly traffic shaped
Probably this program is so uncommon that it is not classified as anything apart from "Other". I've just checked the current traffic management page, even Other gets prioritised as Gold now.

[#11]

Yep, that makes sense.
Thanks for the link, if I run into problems with the application I'll give it a go with wireshark.
But, like you say, it is unlikely to be scheduled for traffic shaping, if that is the way it is implemented.
Thanks so much for your help!