LLP

from The Free On-line Dictionary of Computing (8 July 2008)

Lower Layer Protocol
LLP

   <networking, protocol> (LLP, or lower-layer protocol)
   Any {protocol} residing in {OSI} layers one to four.

   These protocols package, {route}, verify and transmit
   {datagrams}.  A prime example would be {TCP/IP}.  Lower layer
   protocols support the {upper layer protocols}.

   (1999-02-17)