Discarded bytes

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trigger
Posts: 27
Joined: Sun Jan 19, 2014 10:03 pm

Discarded bytes

Post by trigger » Wed Dec 17, 2014 10:03 am

I'm feeding VRS-World and FR24. The stats show that I get no discarded bytes at all with FR24 but with VRS-World they rack up at about 10 million per hour. I upload data from my weather station every 10 minutes and whilst this is happening the buffered bytes rises to 150,000 on both feeds but VRS-World discards them all.

My upload speed is 448Kbps.

Any thoughts?

agw
Posts: 2247
Joined: Fri Feb 17, 2012 3:20 am

Re: Discarded bytes

Post by agw » Thu Dec 18, 2014 1:07 am

The discarded bytes count is an indication of how many bytes were buffered up for transmission to the remote side but, by the time they got to the top of the queue and were ready to be sent, they were so old that they were deemed to be stale and were discarded. That can happen if either the remote side is slow in taking bytes from the feed or you're on a slow link and there isn't enough bandwidth to send the feed in a timely fashion. My guess is that the combination of weather data and the two feeds exceeds your upload bandwidth and the VRS World feed gets clobbered. However I don't know why it would be getting clobbered while the FR24 feed is unaffected. Is the FR24 feed sending to a remote site or is it sending to another program that's on the same PC or on the local network, which in turn repackages the feed to send on to FR24? If it's the latter then the feeder program is probably just buffering up the feed from VRS as fast as it can take it and then suffering from the same lack of bandwidth problem when it comes to send the feed on to FR24.

One workaround would be to increase the duration that a message can sit in the queue before it's considered to be stale. It's the "Max message age" option in the rebroadcast server settings, which by default is 3 seconds... i.e. if a message doesn't get sent to the remote side within 3 seconds of it being buffered then it's thrown away and not sent. Three seconds might be a little optimistic, you could try bumping that up a bit.

trigger
Posts: 27
Joined: Sun Jan 19, 2014 10:03 pm

Re: Discarded bytes

Post by trigger » Fri Dec 26, 2014 1:32 pm

Happy New Year to everyone. :D :D :D

I've done a bit more investigation. I have upped the max message age to 6 seconds but the buffering still happens.

I've installed a free network analyser (Networx) which gives stats for uploading and downloading speeds and volumes and looked at the figures for the laptop running RTL1090, VRS etc.

With FR24 RBS running, the stats show 1.5Mb download and 1.8Mb upload in 1 hour.
With VRS RBS running, the stats show 0.6Mb download and 11Mb upload in 10 minutes so in an hour VRS RBS download is 3.6Mb and upload 66Mb.

I've attached an image showing when VRS RBS turns on. I'm using the "Push" version.
I wondered why my broadband usage has gone through the roof!
Any thoughts?
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agw
Posts: 2247
Joined: Fri Feb 17, 2012 3:20 am

Re: Discarded bytes

Post by agw » Sun Dec 28, 2014 2:34 pm

Which format is the rebroadcast server using?

trigger
Posts: 27
Joined: Sun Jan 19, 2014 10:03 pm

Re: Discarded bytes

Post by trigger » Sun Dec 28, 2014 7:49 pm

It was BaseStation in the above graph. I've since swapped to Compressed VRS as suggested by Jon. The throughput has dropped to about a tenth (2 to 3 KB/s)

I'm still looking at the amount of data uploaded to VRS and FR24 so will report back shortly.

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