[mythtv-users] how to troubleshoot network congestion problems with mythtv

[Simon Hobson]

Tim Coote wrote:

>I seem to have quite a nasty variation in the latency of my home 
>network (ethernet over power, using upa, Comtrend kit). I've got a 
>simple set up with two computers. However, the ping times have a std 
>dev of approx. 2x the mean ping time. With no traffic the ping time 
>is ~4ms, with peaks of 100ms+ every few seconds or so, when 
>streaming live or recorded tv, ping times go up to >20ms (I've not 
>yet measured the variation).

That would not surprise me at all - and my advise would be to invest 
in a real network cable. The cable put in for your power was never 
designed for any form of data transmission and presents a complex and 
changing path - every time a piece of equipment is plugged in, 
unplugged, switched on, or switched off ... the communications path 
alters. That doesn't just mean items on the same power circuit, but 
anything on the same supply phase (if you have more than one) in the 
house.

I strongly suspect these adapters have some significant error 
detection and correction built in - and that could account for the 
occasional high latency. Once you put some traffic on the network 
then I'd expect to see round trip latency go up considerably - you 
have a relatively slow network which is both shared and simplex (ie 
it's like going back to the days before network switches and 100mbps 
or more were common).

Also, some of those powerline network systems are really, really bad 
for the radio environment - and in the UK, the Radio Society of Great 
Britain (RSGB) is having "discussions" with our regulator (OfCom) 
trying to get them to take action against BT who are supplying kit 
that is marked as complying with standards but which wipes out large 
parts of the radio spectrum when used in real applications. Again, 
the power cable isn't designed for data transmission, but it makes a 
fairly effective antenna to leak the signals out.
Oh look, it was Comtrend kit they complained about :
http://www.rsgb.org/plt/
-- 
Simon Hobson

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