Definitions for "Layer 3"
Network Layer - Addresses & Routing
The physical layer in the OSI Model. For TCP/IP, this applies to the IP packet that contains the IP destination address, IP source address and ToS byte. See also Layer 2.
the path control layer, which routes packets through an inter-network and can subdivide datagrams and reassemble them to accommodate the transmission facilities.
Keywords:  application, see
See Application layer.