Setting up a bridge

I'm thinking about setting up a point to point bridge so that I can get
internet access to another building.

What additional hardware do I need to plug into the remote bridge, and how
is it connected? I'm thinking I need to plug an access point into the
remote bridge using an ethernet cable. Is this correct?

Would it be possible for the remote bride to also be an access point,
eliminating the need for the AP at the remote end?

Thanks.

"Jim" <(E-Mail Removed)> hath wroth:

>I'm thinking about setting up a point to point bridge so that I can get
>internet access to another building.

What's the distance and how fast (thruput) were you expecting?
Do you have line of sight?
Can you install high gain antennas?
Any potential for 2.4GHz interference along the line of sight?
Got a price limit?
Need roof access, building permits, landlords permission, etc?

>What additional hardware do I need to plug into the remote bridge, and how
>is it connected?

Nothing but power and ethernet. What I think you're describing is a
"transparent bridge" which will pass more than one MAC address. Wi-Fi
is all bridging so IP addresses and routeing are not involved. Some
of the bottom of the line bridges limit the number of MAC addresses
that can be bridged so count your boxes.

>I'm thinking I need to plug an access point into the
>remote bridge using an ethernet cable. Is this correct?

I'll assume that you want to redistribute the connection in the remote
building with wireless. This can be done if the added access point is
on a different channel (to avoid mutual inteference). A cross-over
ethernet cable and you're done.

>Would it be possible for the remote bride to also be an access point,
>eliminating the need for the AP at the remote end?

Yes. Google for WDS (Wireless Distribution Service) which allows an
access point or wireless router to simultanously allow client
connections and also act as a transparent bridge. The WDS feature is
not very well standardized so you'll need to have the same hardware on
both ends of the link. WDS also cuts the maximum throughput in half
for the wireless connections, so there may be a performance issue.

--
Jeff Liebermann (E-Mail Removed)
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

On Wed, 19 Jul 2006 08:10:44 -0700 Jeff Liebermann <(E-Mail Removed)> wrote:

| Yes. Google for WDS (Wireless Distribution Service) which allows an
| access point or wireless router to simultanously allow client
| connections and also act as a transparent bridge. The WDS feature is
| not very well standardized so you'll need to have the same hardware on
| both ends of the link. WDS also cuts the maximum throughput in half
| for the wireless connections, so there may be a performance issue.

Is that because it would be receiving, then retransmitting, taking twice
the bandwidth*time for each bit/packet?

In my case (already described better in another thread) it seems what I
need is something that can _be_ a client to talk to the wireless router
that connects to the DSL, and also talk _to_ a client (wireless printer)
but not actually interconnect those two. So there would not need to be
any retransmitting. That's why it seems WDS is overkill for me. But if
it's the only way to get one box that can talk _as_ a client in some cases
and talk _to_ a client in other cases, then I guess that's what I need.

If I have an office with staff working with laptops, each with a wireless
card, can those wireless cards talk _directly_ to each other? If not,
then does that mean everything is going in, and then back out, through an
access point, thus doubling the air time and being the same issue as the
WDS?

--
|---------------------------------------/----------------------------------|
| Phil Howard KA9WGN (ka9wgn.ham.org) / Do not send to the address below |
| first name lower case at ipal.net / spamtrap-2006-07-19-(E-Mail Removed) |
|------------------------------------/-------------------------------------|

phil-news-(E-Mail Removed) hath wroth:

>| WDS also cuts the maximum throughput in half
>| for the wireless connections, so there may be a performance issue.

>Is that because it would be receiving, then retransmitting, taking twice
>the bandwidth*time for each bit/packet?

Bingo. That's the problem. Only one transmitter can be on the air at
a time in a given airspace. So, everything gets sent over and over
again for each hop. That's why I really hate mesh networks. They're
very inefficient of scarce airtime.

However, it's not a horrible as it sounds. Let's say you have a
1.5Mbit/sec DSL connection. The wireless typically will connect at
perhaps 24Mbits/sec. That will yield about 12Mbit/sec thruput. If
the WDS repeater is stuffed in between, the maximum thruput drops from
12Mbits/sec to perhaps 6Mbits/sec (usually less). However, 6Mbits/sec
is still faster than 1.5Mbits/sec which is what limits the speed of
the connection.

--
Jeff Liebermann (E-Mail Removed)
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

On 19 Jul 2006 16:41:06 GMT, phil-news-(E-Mail Removed) wrote:

>In my case (already described better in another thread) it seems what I
>need is something that can _be_ a client to talk to the wireless router
>that connects to the DSL, and also talk _to_ a client (wireless printer)
>but not actually interconnect those two. So there would not need to be
>any retransmitting. That's why it seems WDS is overkill for me. But if
>it's the only way to get one box that can talk _as_ a client in some cases
>and talk _to_ a client in other cases, then I guess that's what I need.

Look at it this way. I can pull off a miracle and make an access
point or wireless router simultaneously act as an access point and
bridge. Unless you wanna deal with two seperate boxes at each end, it
can't be done without WDS.

>If I have an office with staff working with laptops, each with a wireless
>card, can those wireless cards talk _directly_ to each other?

Yes. It's called ad-hoc or peer to peer mode. No access point
required. Topology is where every client is directly connected to
every other client. The Microsoft incantation is limited to 9
devices.

The catch is that you cannot simultaneously run ad-hoc and
infrastructure (access point) mode unless you run experimental
software on each client.
http://research.microsoft.com/netres...s/virtualwifi/

>If not,
>then does that mean everything is going in, and then back out, through an
>access point, thus doubling the air time and being the same issue as the
>WDS?

Yes if you're moving data from laptop to laptop. Unless you're
running a game network, that's an unusual situation. More common is
to put the servers, printers, and internet connections on an ethernet
port connected to the access point. Going to/from a laptop to/from
one of these is only one hop.

--
# Jeff Liebermann 150 Felker St #D Santa Cruz CA 95060
# 831-336-2558 (E-Mail Removed)
# http://802.11junk.com (E-Mail Removed)
# http://www.LearnByDestroying.com AE6KS