Layer 3 Switching
Just thought this maybe useful information - and nice and short?
The Network Layer provides the functional and procedural means of transferring variable length data sequences from a source to a destination via one or more networks, while maintaining the quality of service requested by the Transport Layer. The Network Layer performs network routing functions, and might also perform fragmentation and reassembly, and report delivery errors. Routers operate at this layer—sending data throughout the extended network and making the Internet possible. This is a logical addressing scheme – values are chosen by the network engineer. The addressing scheme is hierarchical.
Careful analysis of the Network Layer indicated that the Network Layer could have at least 3 sublayers. Subnetwork Access - that considers protocols that deal with the interface to networks, such as X.25; Subnetwork Dependent Convergence, when it is necessary to bring the level of a transit network up to the level of networks on either side; and Subnetwork Independent Convergence, which handles transfer across multiple networks. The best example of this latter case is CLNP, or IPv7 ISO 8473. It manages the connectionless transfer of data one hop at a time, from end system to ingress router, router to router, and from egress router to destination end system. It is not responsible for reliable delivery to a next hop, but only for the detection of errored packets so they may be discarded. In this scheme IPv4 and IPv6 would have to be classed with X.25 as Subnet Access protocols because they carry interface addresses rather than node addresses.
A number of layer management protocols, a function defined in the Management Annex, ISO 7498/4, belong to the Network Layer. These include routing protocols, multicast group management, Network Layer information and error, and Network Layer address assignment. It is the function of the payload that makes these belong to the Network Layer, not the protocol that carries them. Cisco are major players in this field - cisco 3 layer.