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LAN switching is a form of packet switching used in local area networks (LAN). Switching technologies are crucial to network design, as they allow traffic to be sent only where it is needed in most cases, using fast, hardware-based methods. LAN switching uses different kinds of network switches. Basic switch is marked as ''layer 2 switch'' and could be found in nearly all LAN around. ''Layer 3'' or ''layer 4'' switch requires advanced technology (see managed switch) and are more expensive, and thus could be found in larger LAN or in the special network environment. == Layer 2 switching == Layer 2 switching uses the media access control address (MAC address) from the host's network interface cards (NICs) to decide where to forward frames. Layer 2 switching is hardware-based,〔(Techsoft Computing )〕 which means switches use application-specific integrated circuit (ASICs) to build and maintain filter tables (also known as MAC address tables or CAM tables). One way to think of a layer 2 switch is as a multiport bridge. Layer 2 switching provides the following * Hardware-based bridging (MAC) * Wire speed / non-blocking forwarding * Low latency Layer 2 switching is highly efficient because there is no modification to the data packet and the frame encapsulation of the packet changes only when the data packet is passing through dissimilar media (such as from Ethernet to FDDI). Layer 2 switching is used for workgroup connectivity and network segmentation (breaking up collision domains). This allows a flatter network design with more network segments than traditional networks joined by repeater hubs and routers. Layer 2 switching has helped develop new components in the network infrastructure. * Server farms — Servers need no longer be distributed to physical locations because virtual LANs can be created to create broadcast domains and network proximity in a switched internetwork. This means that all servers can be placed in a central location, yet a certain server can still be part of a workgroup in a remote branch, for example. * Intranets — Allows organization-wide client/server communications based on a Web technology. These new technologies allow more data to flow off from local subnets and onto a routed network, where a router's performance can become the bottleneck. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「LAN switching」の詳細全文を読む スポンサード リンク
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