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Definition: layer 3

In networking, the communications protocol that contains the logical address of a client or server station. It is called the "network layer" and contains the address (IP, IPX, etc.) inspected by a router that forwards it through the network. Layer 3 contains a type field so that traffic can be prioritized and forwarded based on message type as well as network destination. Since layer 3 provides more filtering capabilities, it also adds more overhead than layer 2 processing. See layer 3 switch, router and OSI.