I'm setting up a wireless point to point connection between two
locations, each of which has it's own Internet gateway (DSL
connection).  The primary purpose of the connection is to make it
possible to monitor security cameras without going via the Internet. 
A secondary purpose would be to enable backup Internet service in the
event that one or the other location had an problem with their
Internet service.  A major consideration is that the system should not
make things more complicated for the users and/or require ongoing
configuration changes to access different parts of the network, etc.
-- basically, it should be simple to use once it is set up.

With that in mind, I would be very interested in information that
explains how to properly configure a network for this kind of
arrangement.

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Request for Question Clarification by maniac-ga on 18 Sep 2005 17:29 PDT

Hello Mrfrog,

Could you clarify:
 - the distance between your two locations
 - the performance you need (e.g., 802.11b speed of 11 Mbps is adequate)
 - if you need an encryption solution as well
 - the number of systems you need to support at each site
 - if you have a budget to stay within
 - the brand / model of existing equipment you want to reuse (e.g., router)

The basic solution would be something like:

  Site A -- Wireless Link -- Site B

Inside Site A and Site B you have something like
  Systems -- Router -- Encryption? -- Wireless Link
               +--- DSL Link -- Internet

The router at each site can certainly be programmed to send the
security camera information on the wireless link (by a static route).
The internet backup access has a straight forward solution by
assigning a higher "cost" for the wireless link than the DSL links. I
can make other suggestions as well.

  --Maniac

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Clarification of Question by mrfrog-ga on 19 Sep 2005 09:10 PDT

- the distance between your two locations
About 3/4 of a mile.
 - the performance you need (e.g., 802.11b speed of 11 Mbps is adequate)
11 Mbps is sufficient.
 - if you need an encryption solution as well
No.
 - the number of systems you need to support at each site
Six to a dozen systems at each end.
 - if you have a budget to stay within
Yes and no -- would like to avoid spending an arm and a leg.
 - the brand / model of existing equipment you want to reuse (e.g., router)
Have two DLink routers with directional external antennas, plus normal
networking hardware at both locations.

Hello Mrfrog,

OK. Based on what you described, there basic solution should work and
there are a number of price points available for the antenna portion.
The rest of the equipment should be pretty similar once you decide on
the antenna set up. For what you describe, I suggest a directional
antenna but let me briefly outline the advantages / disadvantages of
each:
 - Directional - best distance, less loss of data. Harder to intercept
by others and should also have less interference from other sources.
Also harder to set up - must point in a relatively narrow direction
and if you have high wind gusts, the signal could drop out more
frequently. You mitigate the last disadvantage with a solid roof
mount.
 - Sector - good distance but has more chance for interference. The
"panel" antennas tend to be similar in performance as well.
 - Omnidirectional - shortest distance and something I would use only
if you are the only wireless network within range. If another wireless
user is within range, you could have real problems with interference.

EXTREME LOW COST ANTENNA

Perhaps you have heard of the "Cantenna". If not, and you are willing
to build it yourself, you can adapt a Pringles can to be your Antenna.
See
  http://www.netscum.com/~clapp/wireless.html
for the original article or
  http://www.oreillynet.com/cs/weblog/view/wlg/448
an article at O'Reilly describing how you can build two of them for
about $10 for a range of up to 10 miles or even pre built at
  http://tekgems.com/Products/et-16243-nwl-scb10.htm?adw.beta
(admittedly this last one is not extremely low cost...)

Search for
  cantenna
for more good references.

LOW COST ANTENNA

Pacific Wireless has a number of good products, direct from the
manufacturer or from a number of distributors.  For example:
  http://www.pacwireless.com/products/DC24.shtml
lists a number of directional antennas in the under $100 each range.
The directional performance is pretty good, see
  http://yanta.pair.com/jefatech/specsheets//PAWDCA-24-PLOT.pdf
for an example showing a +/- 20 degree range for the best performance.
[yes - that means you have to aim within 20 degrees between the two
antennas]

Other suppliers include (for antennas and other products)
  http://www.fab-corp.com/
  http://www.royalbusiness.com/
  (select wireless B/G then antennas)
  http://www.sureneeds.com/networking-networking--wireless-b--b-g.html
  (select antennas & cables)

HIGHER COST ANTENNA

For more money, you generally get better penetration (in case of non
line of sight. For example
  http://www.wirelessnetworkproducts.com/index.asp?PageAction=VIEWPROD&ProdID=744
or the spec page at
  http://www.connectronics.com/wifi_plus/82-5511.pdf
shows an antenna for roughly $200 which claims to "penetrate trees".

Also, for more money, you can get longer distance. For example:
  http://royalbusiness.com/product_info.php/products_id/152245/scs/1
is an antenna claimed to work up to 20 miles (for over $500).

I do not suggest a high cost antenna unless you do not have line of sight.

For additional antenna references, try searches like
  http://froogle.google.com/froogle?q=802.11+2.4+Ghz+miles
or searching with phrases like
  802.11 2.4 Ghz miles
  802.11 long distance antenna

MOUNTING / LIGHTNING PROTECTION

There are plenty of good mounts - choose one that you can install
easily in your facility. See
  http://www.jefatech.com/category/f100/
for some specific examples or
  http://froogle.google.com/froogle?q=antenna%20mount
for several other examples from Froogle.

Do not forget lightning protection. Many of the sites I already
referenced have lightning protection as either built in to the antenna
or as a separate item.

CABLES

Good cables will help make or break this installation. See
  http://www.jefatech.com/product/ll400
for a possible supplier and a brief explanation of the line losses you
can expect. For the product mentioned at 2.4 Ghz, the loss is 6.65 db
per 100 feet. If you mount the wireless router within a reasonable
distance of the antenna (certainly within 100 feet if possible) you
should not have a problem with the antennas suggested above.

For additional references, try searches like
  2.4 Ghz cable jumper
  2.4 Ghz cable outdoor
  2.4 Ghz cable jumper (your wireless interface brand)

ROUTER SET UP

This part is going to vary based on the specific model of wireless
access point. For example, the description at
  http://www.wirelessnetworkproducts.com/index.asp?PageAction=VIEWPROD&ProdID=602
indicates this DLINK product can be set up in one of five modes
including a point to point bridge - confirmed with the manual at
DLINK's site
  ftp://ftp.dlink.com/Wireless/dwl2100AP/Manual/DWL-2100ap_manual_06292005.zip
What I cannot confirm however is a way to establish a static route
with this product nor could I find that capability in the similar
Linksys products. Based on this, you will need a router as well -
something like

  local systems -- Router -- Wireless AP -- Antenna
  local DSL link ----+

at each site and specify the static route in the router (you did not
mention the model of router you had - it probably has this capability
already). The static route is describe briefly at (with Cisco
examples)
  http://www.inetdaemon.com/tutorials/internet/ip/routing/static/
but you can find out more for your router with a search like
  static route (your router model here)
or indicate the router model and I can search for it as well - make a
clarification request.

OTHER REFERENCES
A good description of really long distance connections (5 & 20+ mile).
  http://www.oreillynet.com/pub/a/wireless/2001/05/03/longshot.html

Complete kits are available at
  http://www.wirelessnetworkproducts.com/index.asp?PageAction=VIEWCATS&Category=228
or for example
  http://www.wirelessnetworkproducts.com/index.asp?PageAction=VIEWPROD&ProdID=793
  (showing all the items included)

I also suggest you ask the vendor about FCC approvals related to the
equipment you purchase. Some of the solutions may use power levels in
excess of FCC guidelines and require special approval.

Please make a clarification request if some part of the answer is
unclear or incomplete in any way.

Good luck.
  --Maniac

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Request for Answer Clarification by mrfrog-ga on 24 Sep 2005 07:58 PDT

Hello!  Thanks for the extensive answer.  I'm still trying to track
down the model numbers for the routers in question, but I see where I
can get more information once I have that.

One area that I'm still a little confuse with is the idea of the
'static route'.  Is there a chance that you could point me to some
resources that explain this concept a little more fully?  As I
understand it, it would be item in the routing table of the routers
that would say: "route all traffic to this range of IP addresses out
through my antenna".  Any additional explanations or resources
appreciated.

Thanks,

mrfrog

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Clarification of Answer by maniac-ga on 24 Sep 2005 10:39 PDT

Hello Mrfrog,

What you said...
  it would be item in the routing table of the routers
  that would say: "route all traffic to this range of IP
  addresses out through my antenna"
is correct. It is pretty much as simple as that.

It is unfortunate, that an explanation of a static route is not
readily available in highly ranked pages (e.g., search for static
route IP).  There are a couple definitions:
  ://www.google.com/search?q=define:Static+route
but they basically say the same as what you already know. There are
some good tutorials and explanations on routing in general. See
  http://www.comptechdoc.org/independent/networking/guide/netrouting.html
  http://www.sangoma.com/fguide.htm
  http://www.webopedia.com/TERM/T/TCP_IP.html
  (on this last one - not the page per se, but the links near the end)
or search for
  IP routing tutorial
  IP routing explanation
  explain IP routing
for several other sites.

  --Maniac

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Request for Answer Clarification by mrfrog-ga on 24 Sep 2005 17:35 PDT

Great!  That has helped me along.  Still a bit mysterious, but will
just require some testing.

I did track down the model number of the routers I'm planning to use:
D-Link DI-624.  I think they should do the trick, although I don't see
anything in D-Links site that provides more information.

Thanks again,

Tor

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Clarification of Answer by maniac-ga on 25 Sep 2005 13:45 PDT

Hello Mrfrog,

Glad to help. I don't have personal experience with the D-Link DI-624
but there are a few reviews that rate it highly. If you intend to use
this on the point to point link, I suggest you confirm with D-Link
that it is capable (I don't see the menu option like available on the
DWL-2100AP).

  --Maniac

Very helpful.  Wish there where more examples out there, but I think
maniac did a great job assembling the information that is available. 
mrfrog.