In communications technology, the Lower Layer Protocols (LLP) are the protocols for the transport-oriented layers of the OSI reference model
, i.e. for layers 1 to 4.The protocols for the application-oriented layers are
According to other interpretations, the Lower Layer Protocols are about protocols and their relation to other protocols. According to this interpretation, protocols that are one layer above another are called Upper Layer Protocols (ULP) and those that are one layer below another are called Lower Layer Protocols (LLP). According to this interpretation, the TCP protocol would be the Upper Layer Protocol of the IP protocol, and vice versa, the IP protocol is the Lower Layer Protocol of the TCP protocol.