single ip bandwidth from a lan

I think you are looking for the

System.Net.NetworkInformation.NetworkInterface

You can get all the adapters on your system by using

NetworkInterface.GetAllNetworkInterfaces()

. From every adapter you can request the Speed.

If you need to know it from a specific IP Address you can use something like:

foreach (NetworkInterface networkInterface in NetworkInterface.GetAllNetworkInterfaces())
{
   if (networkInterface.OperationalStatus == OperationalStatus.Up)
   {
      foreach (UnicastIPAddressInformation unicastIPAddressInformation in     
                  networkInterface.GetIPProperties().UnicastAddresses)
      {
         if ((null != unicastIPAddressInformation.IPv4Mask) &&
             (unicastIPAddressInformation.Address.AddressFamily ==
               AddressFamily.InterNetwork))
         {
             IPAddress theAddress = unicastIPAddressInformation.Address;
             IPAddress theMask = unicastIPAddressInformation.IPv4Mask;
         }
      }
   }
}