Remove Juniper header: trace files captured on certain Juniper devices may contain a special header preceding the Ethernet header, making it hard to open the file in a couple of network analysis tools that do not understand that header. This option will remove the Juniper header and change the link layer type with standard Ethernet.
Add Pseudo L2 header if not present: in some cases there may not be a layer 2 header. With this option a generic header will be created and inserted, with zero values for the MAC addresses.
Add a frame comment explaining the zero header: adds a PCAPng frame comment explaining the modification
Remove GRE header: some packets may contain multiple IP layers when using GRE encapsulation. With this option TraceWrangler will remove everything between the Ethernet layer and the layer following the GRE layer.
Remove GTP-U header: GTP-U is used to tunnel IP over GPRS (mobile traffic). With this option you can cut away the layers between Ethernet and the tunneled IP layer.