Not every switch is the same, not every protocol stream the same [Flow control on switch solved dropouts]

[Paul_Kwan]

Just to share my experience on CAS streaming system troubleshooting experience on network related issue, where users may experience below problems :

1. your mobile app can not locate your server
2. stuttering sound output when streaming from a Roon server to a Roon bridge such as microRendu etc
   • above may happens consistently with a particular switch / network, or randomly with the same switch.
   • the problem often happen with HQP / NAA only, switch back to RAAT and problem gone

Anyway if you swap with another switch or network, or switch back to RAAT and the problem gone, then we can look into below.

Here I will use a low cost managed switch TP-LINK TL-SG108E, and a cheap unmanaged switch TL-SG1016D as example.

For problem 1, please check your switch / wifi router has IGMP snooping support and enabled, some device has no way to config, you can only check the spec or swap device to test it. By my testing, the unmanaged switch TL-SG1016D support this, and the higher model TP-LINK TL-SG108E has disabled this by default, I need to enable it manually to fix the problem

For problem 2, I got stuttering sound streaming NAA to mR suddenly, then I look at the monitor page for tips.

My Roon server is at port 5, mR at port 6. The “receive bad packet” keeping rising when I stream NAA, but not with RAAT. And task manager on Roon server shows this when streaming NAA by HQP to mR

The streaming speed is fluctuating a lot. Then I remember this piece of info I read here

mR and difference between RAAT / NAA

RAAT and NAA are completely different systems. I can answer any questions about RAAT, but I know nothing of NAA internals RAAT uses a TCP control channel for basic/management tasks, but the actual audio stream is transmitted over UDP. We also use UDP packets for clock synchronization and to manage resends of dropped/lost packets. The protocol is completely custom–i.e. it is not an application or adaptation of one of a pre-existing system like RTP/RTSP.

OK, Flow Control come to my mind, RAAT has it and seems work better than NAA on some network environment. I know model computer I seen all have flow control enabled at the network interface properties. But it need to be enabled at both end of the cables. I checked the manual my cheap unmanaged switch TL-SG1016D support 802.3x flow control, as it is unmanaged, so it must be enabled.

Then I check my TP-LINK TL-SG108E, it has Flow Control “Off” by default !!!

I enable it on port 5-8, which is for my Roon server, mR and NAS ports, actually enable them all is fine. Then problem 2 is gone, and the ethernet transfer becomes steady now.

During the troubleshooting, I also learn 2 things

• some network vendor recommend using flow control on switch depends on situation, as model computer has more CPU and RAM, so flow control may better handle in application layer instead of data link layer.
• managed switch may not perform better in the way you think if you don’t manage it