Method and apparatus providing network communications between devices using frames with multiple formats

Abstract

A method and an apparatus providing data communications among network devices using tagged and untagged frame formats. In one embodiment, a virtual local area network (VLAN) is implemented using frames that may be transferred among network devices in both tagged and untagged formats. In one embodiment, the frames are transferred among network switches in an untagged format, independent of whether the source devices sent the frames in a tagged or untagged format. In addition, destination devices may receive frames in either a tagged or an untagged format, independent of whether the source devices originally send the frames a tagged or untagged format. Cyclic redundancy check (CRC) code information contained in the frames as originally sent is left unchanged when transferred among the switches of the VLAN, even though the frames may have been modified prior to transfer among switches. New CRC code information is generated for reformatted frames in the switches containing the outbound ports such that reformatted frames with valid CRC codes are forwarded to destination devices. In the event that a switch receives a corrupt frame from a source device, a corresponding corrupt reformatted frame is forwarded to the destination device from the switch.