A: If you are using the freely available evaluation version (i.e. available from Windows Update) it will, by design, only run for 1 hour and then needs to be re-plugged for use for another hour.
Q: What is meant by the terms “multi-frame networking” and “multiple frame capability”
A: Consider Network frames in the 802.3 context – Networking over USB implements an 802.3 network link. We refer to the sending of multiple network frames (datagrams in the NCM spec) via a single USB transfer. Which in turn typically lets us send more data across the USB per second .....
- in real life, most actual network packets sent are IP packets, and the packet length for these is capped at 64K, whereas the practical packet length for 802.3 is 1500 bytes (it can be increased, but it's tricky, and hardly ever done). This is the underlying reason for needing multiple packets -- the "real" data being sent is bigger than the 802.3 packet size.
Belcarra's USBLAN implementation of CDC-NCM, CDC-EEM and RNDIS support multiple Network Frames in a single Bulk Transfer.
Q: What is the advantage of using RNDIS over CDC-ECM ?
A: With the availability of drivers from Windows Update there really isn't any. If you want to use RNDIS you will need to either use Wndows Update or pre-install something - just like USBLAN or any other solution.
See Networking Over USB Protocol Comparisons for an overview of features and differences of USB protocols.
NOTE: RNDIS support NOW available in Belcarra USBLAN Release 2.4.1 available by request from firstname.lastname@example.org
Q: What is a VID/PID?
A: When a USB device is plugged into a host computer it will identify itself using a distinct and unique VID/PID number (16 bit each). The VID/PID combination is then used by the PC to locate and use the correct driver for that particular USB device. VID is short for Vendor ID and PID for Product ID.
Vendor ID's are available from the USB Implementers Forum ( http://www.usb.org/developers/vendor/ ). There is an administration fee of $2000 USD.
Belcarra has its own Vendor ID and can provide a subset Product ID to licensed customers.
Q: The Belcarra USBLAN 2.4 driver does not install for me from Windows Update. More precisely, no matching driver is found and the install wizard is not launched. I am certain I have the VID/PID on the device configured correctly. Is there a particular Windows 7 machine setup needed to get drivers from Windows Update?
A: - Follow these steps to find out, and optionally enable Windows Update if it is currently disabled.
1. Bring up the System Manager in Control Panel (Figure 1).
|Figure 1 - Control Panel Home|
|Figure 2 - System Properties|
|Figure 3 - Windows Update set to be used automatically|
|Figure 4 - Windows Update never to be used|
Q: Why does an Android device connect with a Mac using the CDC-ECM protocol but not to a Windows computer with Belcarra USBLAN.
A: The standard Android device offers a composite USB device consisting of several gadget devices, including g_ether. The activation of a component function (like g_ether) is done dynamically. The g_ether component is called "RNDIS" and this means that the RNDIS configuration of g_ether is always active when g_ether itself is. CDC ECM is only available as the second configuration, and is therefore never used by Windows which only considers the first configuration. The solution we use (internal test purposes) is to disable the Android gadget and to use the "standard" g_ether gadget, which allows us the flexibility of disabling RNDIS.
Q - question about how the pseudo network interfaces are set up and torn down - In one application we have multiple devices connected to the PC, each with a TCP connection to the PC. This works fine unless we unplug the first device that was plugged into the PC. It appears that in that case the network interface is torn down and re-established, which is fine except that the TCP connections to all of our other devices are torn down too.
A - this is a limitation of the Windows NDIS layer. When you unplug the device associated with the Primary interface we assign a new one from the other NDIS interfaces. From our perspective the network does not go away (to the other devices at least) but Windows propagates a reset notice to all of the TCP connections.
Note - this is a behavior unique to Windows, in Linux or Mac/OS unplugging a network cable does not do this.
Q - Do you have a suggestion for a free utility that will help with debugging a USB driver?
A - You can capture a view of the USB traffic with Snoopy Pro.. Although it doesn't see the bus it will give you a snapshot at what the host controller is doing.
Q: If I install a driver package using "setup.bat" (which invokes DPInst) , I cannot find the driver package listed in the Control Panel->Add/Remove Programs list. Where is it?
A: The item in the Add/Remove Programs is called "Windows Driver Package - (Customer) (CustomerUSBLan) Net (Date & build)". Look for that instead.