Do I need WDS for a mesh network?

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tedm
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PostPosted: Wed Jul 21, 2021 22:52    Post subject: Do I need WDS for a mesh network? Reply with quote
I have a house with a lot of heavy wood and commercial drywall in it. wifi signals die in there.

I have 3 points in the house, spaced equally from each other that I have ethernet run to from a central switch. At the central switch is a dd-wrt system that is running as a router/dhcp server/etc.

I have 3 Netgear WNDR3400 routers configured as access points, plugged into the 3 ethernet points, running K2.6 r46239 code

I configured all wifi parameters identically on all APs for both the 2.5 and 5 Ghz bands.

wireless clients get good signal now anywhere in the house, and are able to connect.

Now my question is this - according to wikipedia:

https://en.wikipedia.org/wiki/Wireless_distribution_system

There is a statement:

"The notable advantage of WDS over other solutions is that it preserves the MAC addresses of client frames across links between access points.[1]"

This references the dd-wrt wiki here:

https://wiki.dd-wrt.com/wiki/index.php?title=WDS_Linked_router_network

However, no such statement actually exists on the dd-wrt wiki on WDS

Now, on a commercial Ubiquity solution with multiple meshed access points that are all on a single Ethernet backbone, IF those are setup as a mesh on a single SSID, then according to a utility called "Wifi Anlyzer" that runs on Android, in such an environment, there is only ONE SSID advertisement, one MAC address and (basically) one "virtual" access point. When a client connects, they connect to this and then as they move around the building they hop from access point to access point.

This sort of SEEMS to be the behavior that the wikipedia article is implying that will happen and that implication comes from the dd-wrt wiki.

However, in actual practice, the DD-wrt WDS configuration DOES NOT seem to work like this at all.

Instead, if you attempt to setup WDS, the radios will show each other in the "WDS Node" area but they will randomly show either 0 signal strength or some ridiculous amount like -75db

It does not matter if the radios are setup using WPA2 or no encryption. And more fun is that sometimes if you change configuration in such a setup the radios will lock up or otherwise go crazy, spitting out billions of packets and locking the entire network up until the offending radio is rebooted.

And if you get them setup then Wifi Analyzer does NOT show a single SSID it shows multiple SSID's all named the same, all on the same channel. And the AP list shows independent MAC addresses.

If you turn all of this off, and just set the AP's up identically to each other, same SSID and all of that, then it APPEARS to me that the clients are able to dynamically jump from AP to AP without losing association. I can login to an AP, verify my laptop's MAC is showing as a connected client, reboot the AP, and my laptop does not disconnect. Instead, the association immediately shows up on another AP in the network.

Beyond this - I cannot find really squat on WDS. The wikipedia article says:

"WDS may be incompatible between different products (even occasionally from the same vendor) since the IEEE 802.11-1999 standard does not define how to construct any such implementations or how stations interact to arrange for exchanging frames of this format. The IEEE 802.11-1999 standard merely defines the 4-address frame format that makes it possible."

In other words - translation - "don't ask the IEEE we don't know how the F it's supposed to work"

Virtually all other sources on the Internet I've been able to find seem to reference that Wikipedia article when discussing "how WDS works" And the wikipedia article says squat, and references dd-wrt which doesn't even say what the wikipedia article thinks it says.

My conclusion is that as-implemented in DD-wrt, on the Broadcom radios, that WDS is more intended as a "network extender" that is, you have a dd-wrt AP that's connected to a real Ethernet cable, and a dd-wrt AP that's connected to nothing, and just hanging out in mid-air, and you can interconnect those via WDS, then connect clients to either of them. I've used it before like that back in the WRT54g days and it worked for that. And the dd-wrt wiki on WDS appears to be written with that as a goal.

But it definitely does NOT appear to work the way that commercial "meshed" systems appear to work.

So either I am completely screwed up in my configuration of this - or the documentation is full of hand-waving and guesstimates.

Can anyone shed any light on this?
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Per Yngve Berg
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PostPosted: Thu Jul 22, 2021 16:08    Post subject: Reply with quote
WDS is for connecting APs wireless together. As you have cables between them you just set them up as AP.

Cables are better as bandwidth are not used on the wifi to transfer traffic between routers.
tedm
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Joined: 13 Mar 2009
Posts: 554

PostPosted: Tue Jul 27, 2021 15:03    Post subject: Reply with quote
Thanks, that confirms my observations.

In the early days of wifi the client systems did not take kindly to being yanked off one AP and pasted into another even if the SSID's and passwords were identical. One of the features of vendor mesh "WDS" networks was that the meshed SSID's could have a single MAC and so as the client device was moved from AP to AP, the AP's would pass the association around in between themselves.

But it appears this is no longer an issue with modern client operating systems. They seem to operate fine when moving around in this sort of environment, dropping the association with one access point and re-establishing it with another without the user realizing anything has changed. As long as the SSIDs are all the same and the passwords, and radio channels, channel widths, and encryption is all the same with each AP, it appears the re-association and key renegotiation with the new AP occurs fast enough that the operating system doesn't see an "interface down" event, which would kill all TCP connections though the interface.

I'm thinking of writing a wiki entry on meshing wifi for the dd-wrt wiki and editing the WDS wiki entry a bit to clarify this.

The confusion seems to be the IEEE basically allowing an "anything goes" mentality under the banner of "WDS" By defining a spot for a WDS tag but completely ignoring any other standards for WDS, it turned WDS into more of a marketing term than anything else.

The problem with the Wikipedia article is that it's seeking standardization for the WDS term where none actually exists. So the author ran into the same thing I did - could not find any real information on what WDS was other than the dd-wrt wiki, but instead of just explaining it's a vendor-defined term, he or she just assumed that what the DD-WRT wiki on WDS said was how WDS works.
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