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A typical wireless router
A wireless router is a network device that performs the functions of a router but also includes the functions of a wireless access point. It is commonly used to allow access to the Internet or a computer network without the need for a cabled connection. It can function in a wired LAN (local area network), a wireless only LAN, or a mixed wired/wireless network. Most current wireless routers have the following characteristics:
LAN ports, which function in the same manner as the ports of a network switch
A WAN port, to connect to a wider area network. The routing functions are filtered using this port. If it is not used, many functions of the router will be bypassed.
Wireless antennae. These allow connections from other wireless devices (NICs (network interface cards), wireless repeaters, wireless access points, and wireless bridges, for example). WAP functions
The wireless functions operate as a separate nested "mini-LAN" within the router. The devices that connect wirelessly use the wireless router as their hub, and the wireless router presents that "mini-LAN" as a single device to the rest of the LAN. This mini-LAN has the same features as discrete WAPs have.
Wireless routers, access points, and bridges are available that utilize each of the commonly used wireless frequencies (used in the Wireless-B, Wireless-A (and -G), and Wireless-N standards). The frequency bands for these wireless standards can be used license-free in most countries.
Wireless routers can work with devices in a point-to-point mode, but more commonly functions in a point to multipoint mode.
Wireless devices used that communicate with the wireless router must be set to the same service set identifier (SSID) and radio channel

Network switch
From Wikipedia, the free encyclopedia




Typical SOHO network switch.


Back view of Atlantis network switch Ethernet Port.
A network switch is a broad and imprecise marketing term for a computer networking device that connects network segments.
The term commonly refers to a Network bridge that processes and routes data at the Data lin layer (layer 2) of the OSI model. Switches that additionally process data at the Network layer (layer 3 and above) are often referred to as Layer 3 switches or Multilayer switches.
The term Network switch does not generally encompass unintelligent or passive network devices such as hubs and repeaters.
The first Ethernet switch was introduced by Kalpana in 1990.


Function
As with hubs, Ethernet implementations of network switches support either 10/100 Mbit/s or 10/100/1000 Mbit/s ports Ethernet standards. Large switches may have 10 Gbit/s ports. Switches differ from hubs in that they can have ports of different speed.
The network switch, packet switch (or just switch) plays an integral part in most Ethernet local area networks or LANs. Mid-to-large sized LANs contain a number of linked managed switches. Small office, home office (SOHO) applications typically use a single switch, or an all-purpose converged device such as gateway access to small office/home office broadband services such as DSL router or cable, Wi-Fi router. In most of these cases, the end user device contains a router and components that interface to the particular physical broadband technology, as in the Linksys 8-port and 48-port devices. User devices may also include a telephone interface to VoIP.
In simple terms, in the context of a standard 10/100 Ethernet switch, a switch operates at the data-link layer of the OSI model to create a different collision domain per switch port. This basically says that if you have 4 computers A/B/C/D on 4 switch ports, then A and B can transfer data between them as well as C and D at the same time, and they will never interfere with each others' conversations. That is the basic idea. In the case of a "hub" then they would all have to share the bandwidth, run in half-duplex and there would be collisions and retransmissions. Using a switch is called micro-segmentation - it allows you to have dedicated bandwidth on point to point connections with every computer and to therefore run in full duplex with no collisions.
Role of switches in networks
Network switch is a marketing term rather than a technical one. Switches may operate at one or more OSI layers, including physical, data link, network, or transport (i.e., end-to-end). A device that operates simultaneously at more than one of these layers is called a multilayer switch, although use of the term is diminishing.
In switches intended for commercial use, built-in or modular interfaces make it possible to connect different types of networks, for example Ethernet, Fibre Channel, ATM, and 802.11. This connectivity can be at any of the layers mentioned. While Layer 2 functionality is adequate for speed-shifting within one technology, interconnecting technologies such as Ethernet and token ring are easier at Layer 3.
Interconnection of different Layer 3 networks is done by routers. If there are any features that characterize "Layer-3 switches" as opposed to general-purpose routers, it tends to be that they are optimized, in larger switches, for high-density Ethernet connectivity.
In some service provider and other environments where there is a need for much analysis of network performance and security, switches may be connected between WAN routers as places for analytic modules. Some vendors provide firewall, network intrusion detection and performance analysis modules that can plug into switch ports. Some of these functions may be on combined modules.
In other cases, the switch is used to create a "mirror" image of data that can go to an external device. Since most switch port mirroring provides only one mirrored stream, network hubs can be useful for fanning out data to several read-only analyzers, such as intrusion detection systems and packet sniffers.