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THG
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Daisy chained WDS nodes (halved speed after every hop)

Sun Feb 13, 2011 7:22 pm

All over the internet, I can read that every hop in a daisy chained WDS network will be halved.

Basicly they claim that the speed will be cut in half, cut in half, cut in half, cut in half, cut in half and cut in half, until there is no bandwith left in the last hop. :)

Please, can anyone sheer some light here? :?
Last edited by THG on Sun Feb 13, 2011 9:14 pm, edited 1 time in total.
 
SurferTim
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Re: Daisy chained WDS nodes (half speed after every hop)

Sun Feb 13, 2011 8:12 pm

Maybe. WDS is old. It has been around for a while. It is a protocol that is the answer to "I have two networks that I cannot connect with CAT5 cable, but I want it to act like it is."

Every hop, it must distribute (the 'D' in WDS) all packets on all interfaces, as if it were connected by a CAT5 cable. So it takes exactly twice the time to "distribute" the packets to all interfaces if there are twice as many interfaces...and on, and on...
 
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THG
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Re: Daisy chained WDS nodes (half speed after every hop)

Sun Feb 13, 2011 9:10 pm

So if I have six 108 Mbps nodes, the speed will be like this if I transmit data from WDS Node 1 to WDS Node 6? Sorry, but I don't understand why the speed would be cut after WDS Node 3. :?

First hop = 108 Mbps

Second hop = 54 Mbps

Third hop = 27 Mbps

Fourth hop = 13.5 Mbps

Fifth hop = 6.75 Mbps
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sup5
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Re: Daisy chained WDS nodes (halved speed after every hop)

Mon Feb 14, 2011 3:04 am

Every Node receives data.
It has to buffer this data.
Then it will transmit the previously received data with the SAME antenna it has received the data.
This results in a theoretical 50% loss in throughput.
 
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THG
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Re: Daisy chained WDS nodes (halved speed after every hop)

Wed Feb 16, 2011 5:23 pm

I don't believe that the speed will be cut to half after ever hop. I'm quite sure that the speed will be the same from WDS Node 1 to WDS Node 6 (at least if you only transmit data in one direction, otherwise it wil be cut to 25%).
 
mhoppes
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Re: Daisy chained WDS nodes (halved speed after every hop)

Mon Mar 28, 2011 11:15 pm

Can anyone confirm this?
 
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colebert
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Re: Daisy chained WDS nodes (halved speed after every hop)

Tue Mar 29, 2011 4:13 pm

I have a six hop PTP system that consisted of 12 RBs each with one XR5 connected back to back over about 300 miles. When I used WDS to bridge them all together speeds were much lower than when I used straight up bridge/client and routed them.

I cannot explain the problem in technical terms like you are requesting but my throughput for each hop (e.g., RB1 to RB2) was perfect but my throughput from RB1 to RB12 was abysmal even though taken individually each hop had perfect stats (CCQ, good fade margins, appropriate settings, etc.)

Best-practice is to minimize your use of WDS. It is the simple beginner way to get wireless links working in Mikrotik but you quickly run into problems when you try to scale it up like you are doing (and I did.)
 
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ne0031
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Re: Daisy chained WDS nodes (halved speed after every hop)

Tue Mar 29, 2011 5:53 pm

Not to disagree Colebert....

Against our advice, we have deployed multiple 4-6 hop paths for a customer, using WDS, CM9s, 433s (3.30), and using 20mhz channels get 36-40mb consistently. When using 40mhz channels we typically run about 62mb. We do not use separate RBs, we place 2-3 radios (1 ap, 2 bh) on each RB.

Recently we have made some inroads into having them segment their network, but for now, it is what is is.

Our longest string of WDS hops is 8. This one even has a 12,000 foot copper segment just to make it more interesting.
 
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Re: Daisy chained WDS nodes (halved speed after every hop)

Sun Apr 03, 2011 4:49 pm

WDS with multiple cards should not have the same issues as a single card WDS repeater.

You would still have network broadcasts going however far just to get to the guy literally next door, but...

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