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/e...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.