How may hops are too many?

[kishvet]

Question for the experts.

With good signal strengths, minimal interference, Agere cards, distances less than 20 miles (~32km) between hops, routing instead of bridging, and no omni antennas (pause for breathe); how many wireless "hops" can I expect to be able to use until the signal becomes unusable? Will ping times become the killer? Which of the above (or what else) will hurt me the most in trying to maximize the number of hops. Trying to plan for the future. Thanks in advance.

Grant
EA Media

[lonnie]

What will kill you is the latency at each hop. If you can have your average ping less than 30 msec I think you'll be OK. The ideal is under 15 and that will happen at around the third or fourth hop.

[redfeaag]

Just out of interest, I am running 4 hops at 8ms.

Some key things I have found here:

1. Keep all the 'hop' connections at 11 meg. It really does dramatically increase not so much the performance but reduce the delays and lag.

2. I originally had a single box at each AP that had 3 cards. 2 AP's and one backhaul. This gave 300-400ms across the network. OUCH!

I took Tony's advice and put an extra box in as a dedicated backhaul, ie. I have one box with the two AP's and another linked via ethernet as the backhaul.

The results speak for themselves.

[tbutcher]

We currently have a setup where each WRAP board has 2 cards in it, one for the AP and one for the backhaul. However performance seems to be effected as per the above posts. Is anybody else having the same problems with the new versions. Do people use seperate boards for the backhaul connections?

Also what subnet masks are people using for their PTP links we currently use /24 and I think that is wrong.

Thanks.

Tim

[Stratolinks]

Our system is currently made up of industrial PCI single board computers equipped with dual Atheros mini PCI cards on PCI adapters. The computers are 1.1GHz Celerons with 128Megs RAM running Mikrotik for the backhaul. An Ethernet cable goes from the on-board ethernet to the StarOS on WRAP as the access points (some are still Orinoco AP-1000 but we are replacing them with Star-OS over time). Yes we tried the Mikrotik as an AP, but Star-OS blows it away. Mikrotik on the backhaul supports more choices on the computer boards and chipsets. Each router is powered by a 12V battery via a custom DC-DC converter, with the battery being charged by a switching power supply whenever AC power is present.

Our longest chain is 7 hops. The ping times from the first router on the chain to the last router on the chain is typically 12 to 16 ms. And right now only the very first link on the chain is 5GHz, everything else is 2.4GHz @ 11Mb. There is no bridging, only routing. Correction, the Star-OS access points bridge the data from the Prism AP radio to the ethernet port on the Mikrotik router. All bandwidth control happens on the Mikrotik router (it has the horsepower for it). The PTP links use a subnet of 4 or /30. The PTP links are also 104bit WEP encryped and use a shared secret and a hidden SSID. This keeps then out of reach of all but the most experienced hackers.

We have a few "hotspots" that are completely Star-OS that use an Atheros radio to link back to the nearest access point and a Prism card to provide access in the local area.

[go.fast]

Our system is currently made up of industrial PCI single board computers equipped with dual Atheros mini PCI cards on PCI adapters. The computers are 1.1GHz Celerons with 128Megs RAM running Mikrotik for the backhaul.

Couple questions I have, if you don't mind.
Do you have a url for these boards?
How much are these boards?
Do they work with star-os?
Thanks

I have 6 hops to my furthest customer with star-os and wraps, and see speeds at about 3 megs most of the time.
George

[tbutcher]

The reason why I am asking is that I have some strange performance on our connections. The layout I am testing is as follows

NOC <--Ethernet--> AP1 <--P2P 802.11b--> AP2 <--P2M 802.11b--> Customer

Throughput test results are as follows

AP2 to Customer 296KB/sec
AP1 to Customer 302KB/sec
NOC to Customer 109KB/sec
NOC to AP1 3466KB/sec

All APs are WRAP boards with CM9s for backhauls connections and Prism for the AP. My concern is the speed from the NOC to the customer which doesn't seem right especially since the speed seems to be lost over an ethernet connection.

Tim

[lonnie]

Do you have your routes OK? What does tracert show from the customer?

[tbutcher]

All the routes look fine, we are currently using just static routes. I will check the tracert shortly. In the meantime should we be seperating the backhaul into a different WRAP board? Also will changing the /24 subnet mask to a /30 mask gives us any performance advantages on the backhaul connections?

Thanks.

Tim

EDIT: I have just check tracert and everything looks as it should be.

[tbutcher]

Any more ideas?

[mp3turbo]

RF optimalization. Definitely. With enough CPU power (what you should obviously have), there should be no drop in performance.

[lonnie]

What are the speeds from NOC to AP2?

[tbutcher]

1719KB/sec.

Tim

[Stratolinks]

Couple questions I have, if you don't mind.
Do you have a url for these boards?
How much are these boards?
Do they work with star-os?
Thanks

I have 6 hops to my furthest customer with star-os and wraps, and see speeds at about 3 megs most of the time.
George

The boards are from Advantech, most of them are the older model PCI-6771 (intel 440bx chipset) but a few are the newer PCI-6870 (intel 815 chipset). http://www.advantech.com/products/Model_Detail.asp?model_id=1-TQLSW&BU=ACG&PD=
Even this one has now been replaced with newer models with different chipsets. If I recall correctly they were about $375 about 1.5 years ago.

All are equipped with 128Megs PC100 RAM, and a 256Meg Compact Flash with the Mikrotik OS, on a 4 slot PCI backplane with 2 PCI to Mini PCI adapters with Atheros radios.

Yes Star-OS loads and works OK on the PCI-6771, but I have not actually tried it on the PCI-6870.

We can reliably get 3Megs at the far end of the system. At the first 2.4Gig hop, we get very close to 5 Megs.