Abstract: A method and apparatus are disclosed for determining the starting location and starting protocol of LAN data in a WAN frame. A list of offsets and a list of LAN protocols are maintained. For each offset in the offset list, the WAN frame is parsed beginning at the offset and each LAN protocol in the LAN protocol list is looked for, one at a time. If no LAN protocol is recognized to begin at this offset, the next offset in the offset list is chosen and all of the LAN protocols are tried once again beginning at the newly-chosen offset. This process is repeated until all of the LAN protocols are tried at all of the offsets, or until a LAN protocol is recognized. If a LAN protocol is recognized, the offset at which the protocol was recognized is reported, together with the identity of the LAN protocol that was recognized at the offset. If a LAN protocol is not recognized, an appropriate error message is reported.