Messages are sent by calling sendmessage(), which routes by destination address. Messages for other pvmds or tasks are linked to packet descriptors and attached to a send queue. If the pvmd addresses a message to itself, sendmessage() passes the whole message descriptor to netentry(), avoiding the packet layer entirely. This loopback interface is used often by the pvmd. During a complex operation, netentry() may be reentered several times as the pvmd sends itself messages.
Messages to the pvmd are reassembled from packets in message reassembly buffers, one for each local task and remote pvmd. Completed messages are passed to entry points (Section ).