Regarding EthType ( Last two bytes of ethernet header ) usage...

NTDEV
1

Hello ,

I was wondering how the value of ethType ( the two byte value on the ethernet header of NDIS_PACKET ) is used. On a 802.11 wireless network, does the whole ethernet header including the ethType is sent as a part of data ?

I see the following code in NDISUIO sample which deals with EthType. Could someone explain me about the usage of this field ?

Thanks
Srikanth

// Check the EtherType. If the Ether type indicates presence of

// a tag, then the “real” Ether type is 4 bytes further down.

//

if (pEthHeader->EthType == NUIO_8021P_TAG_TYPE)

{
USHORT UNALIGNED *pEthType;
pEthType = (USHORT UNALIGNED *)((PUCHAR)&pEthHeader->EthType + 4);
if (*pEthType != Globals.EthType)
{

Status = NDIS_STATUS_NOT_ACCEPTED;
break;

}

}
else if (pEthHeader->EthType != Globals.EthType)
{
Status = NDIS_STATUS_NOT_ACCEPTED;
break;
}