This is a tale of someone who was, and still is, extremely happy with
their Logitech Touch but who had one nagging problem for which there
was a work around, but for which the cause was, nonetheless, not
understood.

Under certain conditions the Touch would start ‘rebuffering’ to the
extent that it was not possible to listen to the music.  Changing
tracks exacerbated the problem.  Rebuffering could very occasionally
happen at any time, but it would reliably occur when playing 24 bit
96Khz FLAC tracks and sending PCM to the Touch (by setting the
appropriate options in the File Types section of the SB server settings
so that FLAC – FLAC and FLAC – MP3 were disabled, and FLAC - PCM was
flac).  Sending the tracks as ‘native’ FLACs almost completely solved
the problem, but the cause was still unknown and kept me awake.

There are, no doubt, dozens of reasons why one might get such problems.
You might or might not have the same problem as I did.  I have tried to
give a few hints below as to how you might narrow the problem down to
see if the cause of your problem is the same as mine.

In my case the setup consists of:
•       a 2cpu 2Ghz PC with 3GB memory running XP SP3, with SB version 7.5.3
or 7.5.4 – the SB version made no difference
•       a network consisting of 3 gigabit switches, several wall sockets, and
sundry lengths of Cat 5 or better Ethernet cable of varying ages
•       a Touch running 7.5.4, 7.5.4 or 7.6.0 r9441 – the version made no
difference

To cut a long story shorter, several things had to be done to locate
the problem.  I shall simplify what I actually did and explain what I
should have done in an orderly fashion, to avoid long tales of going
down long and totally mistaken routes in an attempt to find the source
of the problem.

First, and simplest, was to use Task Manager in Windows to view the
Network Traffic.  This gives a visual feel for the traffic being sent
to the Touch.  In my case using PCM and 24/96 recordings, the traffic
was a bit erratic, but hovered around 6 to 8% of the network capacity. 
The network speed was 100Mbps.  The CPU was low at only a few %. See
'network traffic fixed 2.jpg' attached to this post (the first of the
images below).

Secondly, I wanted a way of looking at the network traffic in more
detail. I’m no TCP/IP expert, but have some knowledge of computer
protocols.  I installed Microsoft Network Monitor from
http://www.microsoft.com/downloads/en/details.aspx?familyid=983b941d-06cb-4658-b7f6-3088333d062f&displaylang=en
. I captured a few seconds of traffic when sending data as PCM from the
PC to the Touch, and then sending as FLAC.  The program showed, in
plain English, many ‘retransmit’ packets being sent in both cases, such
as:

4860    13:34:35
09/05/2011      10.4931640      SQUEEZ~3.EXE    192.168.1.2     192.168.1.9     
TCP     TCP:[ReTransmit
#4838][Continuation to #4833]Flags=...A...., SrcPort=9000,
DstPort=33584, PayloadLen=1460, Seq=2798448564 - 2798450024,
Ack=1411749148, Win=64226 (scale factor 0x2) = 256904   {TCP:28,
IPv4:26}

4861    13:34:35
09/05/2011      10.4931640      SQUEEZ~3.EXE    192.168.1.2     192.168.1.9     
TCP     TCP:[ReTransmit
#4839][Continuation to #4833]Flags=...A...., SrcPort=9000,
DstPort=33584, PayloadLen=1460, Seq=2798450024 - 2798451484,
Ack=1411749148, Win=64226 (scale factor 0x2) = 256904   {TCP:28,
IPv4:26}

This was a surprise, and indicated a network issue of some form.

Third, I connected the Touch directly to the PC using my most recent
piece of Cat 6 Ethernet cable and no switch, to see if the problem was
due to the physical network.  To make this work the Touch had to have a
fixed IP address. In my case the problem was, if anything, worse than
over my full network.

I now knew I had a problem either with the Touch itself or the PC. 
There’s little I could do about the Touch, other than note that other
people successfully send 24/96 PCM to their Touch with no difficulty. 
PCs are a different matter, since no two are the same.

If it is not the network, work back from there into the PC itself.  How
about the network card?  My PC has a built-in Nvidia nForce 10/100/1000
Mbps Ethernet NIC.  Looking at the device properties, under the
Advanced tab there are many options.  I tried several.  Turning ‘flow
control’ on seemed to help, but after listening for an hour the problem
came back.  I won’t bore you with the other options I tried, none of
which helped.  However, one option completely fixed the problem.

On this NIC there is an option to set the speed/duplex settings for the
NIC.  Options include fixed speeds of 10 or 100 Mbps at full or half
duplex (FD or HD), 10 or 100Mbps with ‘autoneg’ full or half duplex, or
Autonegotiation.  My NIC was set at ‘100Mbps full duplex’ following
advice given elsewhere.  This was my mistake.

Setting my NIC to ‘Autoneg for 100FD’ solved my problem completely.  I
also did a few tests with ‘Autonegotiation’ and had no problems.

For details of why a fixed speed might be a bad idea for some systems,
see http://en.wikipedia.org/wiki/Autonegotiation

Going back to my small kit of tools, using Task Manager the network
traffic is now much smoother, and stable at around 4-5%.  Using
Microsoft Network Monitor, I could find almost no retransmissions.  See
See 'network traffic autoneg 2.jpg' attached to this post (the second of
the images below).

I know that other people have reported using fixed speed NICs
successfully.  I can only guess that in such cases their network,
switches and PC are either capable of handling the retransmission
loads, or their switches or NIC are in some way avoiding the speed
negotiation problems that bedevilled my system.

Now I can sit back and enjoy the music without that nagging doubt in my
mind.


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PasTim
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