Pairing 2 sets of bridges on one LAN for increased bandwidth

Hope I'm not being too blonde here...

We're a church and school (read: no money for real sophistication)
currently connecting a LAN that spans two buildings with two simple
D-Link 2200 APs (802.11g 108Mbps) operating in bridge mode. The two
bridges are about 50 feet apart, straight line-of-sight and the
performance has been generally more than adequate for our needs. The
buildings are separated by a city side street so there's no feasible
way to run wire. It's a BIG city and getting approval to do this would
be a futile effort.

The majority of the current traffic across this bridge is Internet
surfing from building A to and from a T1 in building B. Only rarely
have the individual computers in either building needed to cross the
bridge to each other, so to speak. That's about to change, however, and
5 administration computers in building B are now going to regularly
access a database on the server in building A. The users in building A
also need access to this same database. The program to manage this DB
has no inherent means of keeping two individual installations evergreen
so we have to find a way for both buildings to efficiently access this
single file.

We're concerned about a traffic slowdown and were wondering what
options there might be to increasing the throughput across this street.
One thought was to keep the Internet traffic that originates in
building A to the current bridge, and add another another 2 DLinks that
would provide a second bridge that would be specifically dedicated to
those 5 admin computers. We feel 802.11n is just too far away.

Is it even possible or feasible to run 2 pairs of bridge devices in
this scenario or are we just brainstorming ourselves into stupidity?
What brought up this concept was a fond recollection of pairing two
dial-up modems for blazing speed not so many years go.

To further complicate things we're also toying with the idea of adding
yet one more DLink in a 3rd building, and set up point-to-multi-point
on the existing bridge so that third building can also access the T1.
But by far the bigger issue is getting a dedicated pipe for those 5
admin computers to the server across the street.

Any other recommendations for separating/increasing the throughput in
this situation would be very welcome.

Thanks,
~Jacy

On 18 Jul 2006 18:55:57 -0700, (E-Mail Removed) wrote:

> Hope I'm not being too blonde here...
>
> We're a church and school (read: no money for real sophistication)
> currently connecting a LAN that spans two buildings with two simple
> D-Link 2200 APs (802.11g 108Mbps) operating in bridge mode. The two
> bridges are about 50 feet apart, straight line-of-sight and the
> performance has been generally more than adequate for our needs. The
> buildings are separated by a city side street so there's no feasible
> way to run wire. It's a BIG city and getting approval to do this would
> be a futile effort.
>
> The majority of the current traffic across this bridge is Internet
> surfing from building A to and from a T1 in building B. Only rarely
> have the individual computers in either building needed to cross the
> bridge to each other, so to speak. That's about to change, however, and
> 5 administration computers in building B are now going to regularly
> access a database on the server in building A. The users in building A
> also need access to this same database. The program to manage this DB
> has no inherent means of keeping two individual installations evergreen
> so we have to find a way for both buildings to efficiently access this
> single file.
>
> We're concerned about a traffic slowdown and were wondering what
> options there might be to increasing the throughput across this street.
> One thought was to keep the Internet traffic that originates in
> building A to the current bridge, and add another another 2 DLinks that
> would provide a second bridge that would be specifically dedicated to
> those 5 admin computers. We feel 802.11n is just too far away.
>
> Is it even possible or feasible to run 2 pairs of bridge devices in
> this scenario or are we just brainstorming ourselves into stupidity?
> What brought up this concept was a fond recollection of pairing two
> dial-up modems for blazing speed not so many years go.
>
> To further complicate things we're also toying with the idea of adding
> yet one more DLink in a 3rd building, and set up point-to-multi-point
> on the existing bridge so that third building can also access the T1.
> But by far the bigger issue is getting a dedicated pipe for those 5
> admin computers to the server across the street.
>
> Any other recommendations for separating/increasing the throughput in
> this situation would be very welcome.
>
> Thanks,
> ~Jacy

You don't mention what model hardware you are using.. but you can use quality of
service to prioritise traffic over the bridge.

You'd need a bridge/router that does this.. eg: Linksys WRT54GL - one at each
end with DD-WRT firmware - this has excellent QOS settings.

You could set file and print sharing to max and "other traffic" to a lesser
priority. (or break down the traffic by protocol eg: http - lowest)

That way when the link gets saturated with traffic you are guaranteed to get
your DB running at optimum with your "other" traffic resigned to waiting for a
slot.

Anyone else add to this ?

Doz

(E-Mail Removed) hath wroth:

>We're a church and school (read: no money for real sophistication)
>currently connecting a LAN that spans two buildings with two simple
>D-Link 2200 APs (802.11g 108Mbps) operating in bridge mode.

I'll assume a DWL-2000AP

>The two
>bridges are about 50 feet apart, straight line-of-sight and the
>performance has been generally more than adequate for our needs.

Please measure your thruput and convince me that it's adequate. At
50ft and presumeably with better than stock antennas, you should at
least get a 54Mbits/sec connection, which will give about 25Mbits/sec
throuput. Just copy a big file and use a stopwatch to estimate the
thruput. Do it in both directions. However, if you dont' have line
of sight, or are using junk antennas, the speed will be lower.

>The buildings are separated by a city side street so there's no feasible
>way to run wire. It's a BIG city and getting approval to do this would
>be a futile effort.

Go through the sewers with fiber. There are lots of other pipes
available under a street. Just look for them in the manholes. You
can also piggyback on the CATV if there's a common cable.

>The program to manage this DB
>has no inherent means of keeping two individual installations evergreen
>so we have to find a way for both buildings to efficiently access this
>single file.

Also, check how well the program responds to data loss and
disconnects. Wireless is not like wired ethernet in that it will have
fades, higher packet loss, disconnects, and such. I've seen far too
many database engines that blow up with the slightest hickup.

>We're concerned about a traffic slowdown and were wondering what
>options there might be to increasing the throughput across this street.

You should be getting 25Mbits/sec thruput with your wireless. A wired
ethernet 10baseT-HDX will do perhaps 7Mbit/sec. 100baseTX-FDX will do
about 80Mbits/sec. You're already in the ballpark.

>One thought was to keep the Internet traffic that originates in
>building A to the current bridge, and add another another 2 DLinks that
>would provide a second bridge that would be specifically dedicated to
>those 5 admin computers. We feel 802.11n is just too far away.

Barf. Yeah, it can be done and can be made to work. The traffic load
will NOT magically distribute itself between the two wireless links.
You'll need some manner of load balancer or just live with seperate
paths for seperate connections. I don't see if justified unless you
have *SUSTAINED* high traffic through the wireless slink.

>Is it even possible or feasible to run 2 pairs of bridge devices in
>this scenario or are we just brainstorming ourselves into stupidity?

Both. It is possible to do this and yes, it's a dumb idea.

>What brought up this concept was a fond recollection of pairing two
>dial-up modems for blazing speed not so many years go.

Yeah, but that was with a multilink protocol that required the
cooperation of the ISP. It can't be done with off the shelf, bottom
of the line, wireless hardware. See:
http://www.edimax.com/html/english/p...-PRIrouter.htm
for load balancers.

>To further complicate things we're also toying with the idea of adding
>yet one more DLink in a 3rd building, and set up point-to-multi-point
>on the existing bridge so that third building can also access the T1.

Three options depending on line of sight:
1. WDS (wireless distribution service) network.
2. Point to Multipoint bridge network. I think your DWL-2200AP
supports this:
http://support.dlink.com/emulators/d...gAPMode.html?1
Yep. PtMP is supported.
3. Seperate link between 3rd building and whatever.
It all depends on line of sight and what you are connecting.

>But by far the bigger issue is getting a dedicated pipe for those 5
>admin computers to the server across the street.

No, the real issue is performance. Estimate how much data you're
gonna move and how fast. Measure what you have now. Then decide if
you actually need more bandwidth. I really doubt it.

--
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

> That's about to change, however, and
> 5 administration computers in building B are now going to regularly
> access a database on the server in building A. The users in building A
> also need access to this same database. The program to manage this DB
> has no inherent means of keeping two individual installations evergreen
> so we have to find a way for both buildings to efficiently access this
> single file.

Put the admin computers on a different subnet and use a different wifi link.
That way you'll keep their traffic separate and, in theory, give better
performance. The trick being in structuring your wired setups such that
it's possible to have these machines on a different subnet and/or VLAN. I
designed and ran a campus-wide network doing just this, but using fibre
between the buildings. Worked quite well to have the traffic segregated,
both from a performance AND a security perspective.

> Any other recommendations for separating/increasing the throughput in
> this situation would be very welcome.

It all depends on what you've got on the in-building networking side of
things. What switches and routers are in use now?

-Bill Kearney

On Wed, 19 Jul 2006 13:34:56 -0400, "Bill Kearney"
<(E-Mail Removed)> wrote in
<(E-Mail Removed)> :

>> That's about to change, however, and
>> 5 administration computers in building B are now going to regularly
>> access a database on the server in building A. The users in building A
>> also need access to this same database. The program to manage this DB
>> has no inherent means of keeping two individual installations evergreen
>> so we have to find a way for both buildings to efficiently access this
>> single file.
>
>Put the admin computers on a different subnet and use a different wifi link.
>That way you'll keep their traffic separate and, in theory, give better
>performance. The trick being in structuring your wired setups such that
>it's possible to have these machines on a different subnet and/or VLAN. I
>designed and ran a campus-wide network doing just this, but using fibre
>between the buildings. Worked quite well to have the traffic segregated,
>both from a performance AND a security perspective.

Good suggestion. Make sure the two wireless networks are on different
channels with minimal overlap (1, 6, 11). Check first for possible
interference, although directional antennas may be able to overcome it.

--
Best regards, FAQ for Wireless Internet: <http://Wireless.wikia.com>
John Navas FAQ for Wi-Fi: <http://wireless.wikia.com/wiki/Wi-Fi>
Wi-Fi How To: <http://wireless.wikia.com/wiki/Wi-Fi_How_To>
Fixes to Wi-Fi Problems: <http://wireless.wikia.com/wiki/Wi-Fi_Fixes>