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I just learnt the theoretical basics about network switching and forwarding with the aid of some connection diagrams but then it got me to wonder how the switching actually happen on a wireless router/switch since both the router and the NIC has to broadcast/probe constantly, making it appear to resemble a hub (shared bus) setup.

So, how does a wireless switching work?

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Can you provide a link to a 'wireless switch'? I don't believe I have seen one. I have seen combo devices that are a wired switch and a wireless AP, but I have never seen a wireless switch. –  Zoredache Nov 15 '10 at 18:33
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Got to agree with Zoredache - most of the time when you see people talking about a "wireless switch" they're often talking about the central controller for a managed wireless infrastructure. –  RobM Nov 15 '10 at 18:46
    
Sorry, I think you are getting too far ahead for a newbie like me. I meant to ask about those consumer "wireless routers" that are bought off the shelf. Since they are routers, and routers do switching, so then how does the "wireless switching" work? Not sure if it makes sense? –  Jake Nov 15 '10 at 18:55
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The wireless NIC in the router works basically just like any other Network port on the router. I believe you're misunderstanding the relative simplicity of wireless NICs/APs. –  Chris S Nov 15 '10 at 19:11
    
Thanks everyone for the replies and clearing my doubts. –  Jake Nov 17 '10 at 11:39

2 Answers 2

up vote 4 down vote accepted

I meant to ask about those consumer "wireless routers" that are bought off the shelf. Since they are routers, and routers do switching, so then how does the "wireless switching" work?

If you are talking about standard wireless it is like a hub and is a shared bus as you mentioned.

Every wireless adapter sees every packet on the network it is associated with, the adapter will ignore packets not address to it unless promiscuous mode is available for that adapter and enabled. No method of point-to-point communication exists with standard hardware.

If you want to understand a consumer wifi device imagine a Ethernet switch with a HUB attached to one port. In the case of our wireless switch that HUB is the wireless AP feature of the device. Switching is not done devices attached to the wireless AP, since it really isn't possible, given the way the technology currently works.

To say it differently, the switching features of a consumer 'wireless switch' only apply to the wired ports.

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The devices you are talking about (standard consumer grade WiFi routers that enable WiFi access to an ISP's DSL or cable service) have multiple integrated functions that act at different layers and it may help you understand if you think about that layering.

The Wireless Interface is Layer 1 - the physical carrier that is in this case a shared RF environment. There are a host of standards (802.11 abgnhw...) that deal with the specifics. This is by its very nature a shared medium, possibly with multiple concurrent channels, possibly with individually encrypted sessions, but where communications are almost always directly between individual end points and the wireless access point. The Wifi protocols handle the physical signalling that are used to encapsulate the next layer, which is typically ethernet. While wireless AP's do switch traffic in the sense that a processor coordinates the stream of traffic between two nodes rather than relying on dumb rebroadcasting the fact remains that the WiFi environment is a shared medium and many of the characteristics of switching in the wired world simply do not apply to WiFi.

That leads to the next part of the system - a wired Ethernet switch. This is a layer 2 device that allows Ethernet packets to be sent directly from a source to a destination as identified by MAC addresses. The Ethernet packets received by the WiFi radios in the AP are fed into the same switch and can be switched (not routed yet) to any other port on that switch, that may be one of the wired interfaces or another wireless client.

The final layer involved is the router part - this may be more or less a basic ethernet router that allows traffic to be moved from the switch to the external network and vice versa. You will see that most of these devices default to a private address space for the WiFi and switch connected devices (e.g. 192.168.1.x) and traffic has to be routed to move from that network to the external interface (DSL\cable modem, whatever) that will have a public ip-address provided by an ISP or some other upstream network.

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