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Wet / Wds / Wds+ap

Discussion in 'Tomato Firmware' started by fyellin, Jun 4, 2008.

  1. fyellin

    fyellin LI Guru Member

    I'm trying to summarize another thread in which different modes were compared. Lots of information was given and contradicted. The following is what I think was the final consensus. Corrections appreciated.

    I'm assuming that Router #1 (192.168.1.1) is attached to the WAN. Router #2 (192.168.1.2) is a secondary router that I'm trying to use to extend the wireless network. There may be other secondary routers.

    Case 1: Router #1: Access Point. Router #2: Wireless Ethernet Bridge
    • No special configuration needed on Router #1. Bridges can be added and removed at will.
    • All encryption modes except WPA2 supported.
    • Wired devices attached to the LAN ports of Router #2 are on the same LAN as Router #1. Machines wired to Router #2 and those attached (wired or wireless) to Router #1 can talk freely.
    • All devices wired to Router #2 appear to have the MAC address of Router #2 to devices upstream. This confuses the "device list" page of Tomato, but DNS works correctly.
    • The WAN port of Router #2 is unused. Hacking can make it into a LAN port.
    • Every secondary router in this mode must be visible to Router #1.

    Case 2: Router #1: Access Point. Router #2: Wireless Client
    • No special configuration needed on Router #1. Bridges can be added and removed at will.
    • All encryption modes supported.
    • Wired devices attached to the LAN ports of Router #2 are on their own subnetwork. All communication with upstream clients must use Router #2 as a gateway. All communications from upstream clients must go through some sort of port forwarding.
    • The WAN port of Router #2 is unused. Hacking can make it into a LAN port.
    • Every secondary router in this mode must be visible to Router #1.

    Case 3: Router #1: Access Point + WDS. Router #2: WDS
    • Router #1 and #2 must be told each other's wireless MAC address. (Not strictly true for some encryption modes.)
    • Not all encryption modes supported.
    • Wired devices attached to the LAN ports of Router #2 are on the same LAN as Router #1.
    • All devices appear on the LAN with their own MAC address.
    • The WAN port of #2 is unused. Hacking can make it into a LAN port.
    • Routers in WDS mode can be set up into complex communication topologies. Communication between a particular WDS router and Router #1 may involve multiple hops. If there are any loops, you must enable Spanning Tree Protocol.
    With one secondary router (or with all secondary routers talking only to Router #1), this mode is functionally equivalent to Case 1, although the implementation is quite different. Testing by Kiwi8 indicates that this mode is just slightly slower. HennieM hypothesizes that this is because WDS has to deal with four hardware addresses rather than three.

    The speed by which any particular secondary router can talk to the WAN is inversely proportional to the number of wireless hops required from the secondary router to the main router. Each intermediate router needs to listen to a packet and then rebroadcast it, and it cannot do both simultaneously.

    Case 4: Router #1: Access Pointer + WDS: Router #2: WDS + AP

    The same as Case #3, except that wireless clients can talk to either router.

    The speed by which a wireless client can talk to the WAN is inversely proportional to the number of wireless hops, including the first hop from the client to its WDS.

    [Edited to include comments]
     
  2. Kiwi8

    Kiwi8 LI Guru Member

    My answers in red. :smile:
     
  3. HennieM

    HennieM Network Guru Member

    All good.
    One slight case of not truely comparing apples with apples:

    "Talking to the WAN via Router #2 requires two separate wireless communications."

    Should read

    "A wireless client talking to the WAN via Router #2 requires two separate wireless communications[, as the single radio in Router #2 needs to say what it heard, and it cannot listen and talk at the same time]." (A wired client connected to Router #2 still only requires 1 wireless comm).

    On the point of speed of WDS vs. WET: As Kiwi8's testing indicated, WET mode is a tad faster than WDS, but not so as you'd notice. The reason for this IMO is that:

    In WET-to-AP comms, the wireless deals with 3 MAC addresses as per normal wireless comms (client, AP, destination).

    In WDS-to-WDS comms, the wireless deals with 4 MAC addresses (the 3 above, plus a WDS address).

    So in WDS mode, and in WDS-to-WDS comms, this 4th address gets send along - and needs to be "handled" by WDS nodes - with every frame going over wireless links, which slows the comms down that tiny bit.
     

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