Protocol 139?

Dear all,

in my SOHO network I have two RB2011UiAS-2HnD-IN routers connected to each other via ethernet.
Looking at the winbox ip firewall connections tab I find entries that show connections with source address 0.0.0.0 (no port) and destination address 255.255.255.255 (no port) using protocol 139.

What is protocol 139, please? I cannot find anything about it.
Protocol 139.JPG

it is HID (host identity protocol)