[App_rpt-users] RTCM Inbound (Eth Rx) packet out of bounds

Jesse Lloyd ve7lyd at gmail.com
Sat Sep 23 22:46:28 EDT 2017


Here's how I do it, seems to work...
Calculate the maximum latency in network. If its less than 60 ms use 60ms for the calculations. 
For RTCM Tx Buffer length, take latency * 8. Minimum therefore is 480 (this value is in packets (8 packets per ms))
For buflen in voter.conf, take latency + 100. Minimum therefore is 160 (this value is in ms)
The delay of the system is RTCM Tx Buffer Length /8 + tx buffer length in Asterisk. Minimum therefore is 220ms
If you have voter.conf set to 250 the RTCM should be set to 1200. This should make the system able to handle latency spikes to 150ms.  
Note: If your GPS is weak on the RTCM which is connected to your Asterisk server it'll cause lots of problems. I've also had better luck using a dedicated RTCM for the server timing and using a different one for the radio/repeater, even if they are in the same building. I suspect the UDP TX audio stream combined with the 10Mbps 1/2 duplex RTCM ethernet causes packet collisions which messes up the server timing packets (this is a hunch at this point).

Cheers,
Jesse

> On Sep 23, 2017, at 5:41 PM, Hayden Honeywood <haydenph91 at gmail.com> wrote:
> 
> More testing last night and today.
> 
> I set the TX Buffer to 1200 last night, rebooted both RTCM units and it was working fine last night. 
> 
> Switched off one of the sites (at home) overnight. Came back this morning, powered up and getting the packet out of bounds issues again. Changed up to 1600 and rebooted both units, worked again. buflen set to 250.
> 
> Is it just a matter of increasing these up and up until it's stable even after a power reset?
> 
> I've been swapping out ethernet cables too just checking to make sure that is not the issue... Could still be a hardware problem. Next thing to change is the port from 667 to make sure there is no limiting down at the ISP level.
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