On Wed, 30 Apr 2008, Eric Sooter wrote:
I thought that pseudobridge had better performance in p-t-multipoint. On the Mikrotik forum, I noticed alot of complaining about WDS performance dropping when you get over 5 or 6 WDS sessions on an AP. Is this true?
Let's say that you have an AP with 10 client devices connected. If these 10 are all running with station-wds, then you will have some performance hit for that. If you only need station-wds on 2 of them, then you will not suffer noticably. Alternatively, you can run all 10 with pseudobridge and performance will not suffer. HOWEVER, because of the way 802.11 functions, you will have other issues. Let me give a specific scenario.
You have a customer that needs the public IP on their own gear (so they can control the port forwarding or whatever). You can build that customer's radio connection in one of 3 ways (more, actually, but for this example, we'll just discuss the 3 main ways).
1. You can assign an IP to the radio card on their MT radio and route their subnet via that IP. This will cost nothing in terms of performance of the AP, and the customer's IP will be 100% reachable.
2. You can set the MT radio in station-wds mode and assign their public IP on their equipment (the gateway IP would be on your AP). This will only cause a performance hit if you have to do this for more than about 7-10 customers. This performance hit will not be dramatic, even with 10-15 customers, unless the AP is already pretty loaded.
3. You can use pseudobridge. Like #2, you would assign the customer's public IP to their equipment and their gateway IP would be assigned to your AP. When the customer generates traffic toward the Internet, your AP would find their MAC address to be that of the radio card on their MT running pseudobridge. All traffic generated by the customer would be properly delivered. However, if the customer's equipment has not sent any packets for a bit, then you will have a problem because when the AP (which considers their IP to be available local) cannot determine their MAC address with an ARP broadcast. SO..the customer can send traffic to the internet with no problems, but if a connection is initiated from the internet side, and their device has been quiet for some time, that connection will fail. This is due to the reality of how 802.11 was defined and the way that pseudobridge "fools" the network into thinking the end user IP actually exists on the wireless network. I can't cover this in enough detail to make it clear WHY this is true, because I'm short on time, but if there is enough interest, I can try to provide some information later.
-- ******************************************************************** *Butch Evans *Professional Network Consultation * *Network Engineering *MikroTik RouterOS * *573-276-2879 *ImageStream * *http://www.butchevans.com/ *StarOS and MORE * *Mikrotik Certified Consultant *Wired or Wireless Networks * ********************************************************************
