Re: Wireless Network in Public Places Options

From: Smowk (SmowkOne_at_Yahoo.com)
Date: 02/11/05 

Date: Fri, 11 Feb 2005 12:31:23 -0600

Jeff Liebermann <jeffl@comix.santa-cruz.ca.us> wrote in
news:kmrp01djlp9jgj3h4qiqjbuk5rd2mj3dp6@4ax.com:

> On Thu, 10 Feb 2005 17:49:22 -0600, Smowk <SmowkOne@Yahoo.com> wrote:
>
>>Jeff Liebermann <jeffl@comix.santa-cruz.ca.us> wrote in
>>news:eq2n01drgkhb3el6draacn7usklfifk33u@4ax.com:
>>
>>> Well, the way this is done is to disable the dynamic bridging table
>>> feature of the switch, and implement a static bridging table. Each
>>> wireless MAC address goes to a specific ethernet port, which only
>>> allows traffic to one other ethernet port, which conveniently happens
>>> to be that of the router.
>
>>yea, but we would have to register all of the mac addresses of the
>>guests who use the hotels wifi and set it up manually for each new user
>>(around 20 or so per day peak season).
>>right?
>>other than that, i agree with phil...VERY GOOD EXPLANATION
>>smowk
>
> Nope. Here's where I get on thin ice as I'm not sure how existing
> implementations do such things. I'm also not too good on the protocol
> thing. Therefore, I'll guess(tm) how I would implement such a scheme.
>
> The bridging algorithm needs a bit of tweaking. For example, the
> bridge would still automatically sniff for 802.3 ethernet packets
> source MAC addresses. However, instead of allowing multiple MAC
> addresses per port and multiple MAC addresses per destination, it
> would have a fixed destination MAC address pointing at the router
> port. Any other MAC destination addresses or other source addresses
> would simply be ignored. The switch (multi-port bridge) would still
> be able to connect new wireless MAC addresses to the router port after
> a disconnect, but destination MAC addresses other than the router
> would be ignored.
>
> Packets with no destination addresses such as broadcasts and DHCP
> requests would also need to be handled. Broadcasts have a source, but
> no destination MAC address. So, the switch sends them to every port.
> Not good. So, the broadcast mechanism has to restricted to pass
> broadcasts only to the port in the bridging table. Broadcasts from
> the router port go to every port and wireless connection.
>
> As I vaguely recall, that's the way some ancient access point firmware
> worked. I do recall the constant complaints in the mailing lists that
> some access points would not allow communications between wireless
> clients, or between wireless clients and wired LAN ports. For WISP
> (wireless ISP), hot spot, and neighborhood LAN service, it's the
> desired mode of operation.
>
> Again, this cannot be done at the IP level by tweaking the routing
> table even if every client were trustworthy. There would be nothing
> to prevent a client from turning your access point into their private
> game network, which never sees the router or goes to the internet.
> Also, without any control, everyone would also get everyone else's
> broadcasts. Therefore, it has to be one at with a bridge/switch at
> the MAC level.
>
>

this is good if i'm building my own access point...but...

lol

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