I decided to create this thread to talk and possibly share experience with the community about these three items on wireless networking. Im looking initialy for specifications arround hardware limits and technology limits. Furthermore, this thread may become a useful reference to the mentioned subject above on this forum.
I did some measurements on my wireless network and would be nice if people point out corrections/measurements about the whole topic, including post references, benchmarks, etc.
Lets say, the main table to start: Technology and hardware. 802.11b show limits arround 200 pps, while in 802.11a I can see about 4000 pps. Apart the physical limitations in packets, there are known bandwidth and throughput limitations. I mean, if you have 11mb bandwidth limit, does not exactly mean that you will have 200 pps limit or even a corresponding limit on throughput. Of course, there are other variables included like tcp, udp, framing policy, queues, qos, traffic shaping, etc.
The main reason behind this post is about wireless network performance on different ways to acomplish it, i.e: l2tp, dual nstreme, ap, cpe, ppp and routed/bridged devices as well. Many people perhaps are basicly interested in QoS together with p2p, traffic shaping and specialy those using APs in 802.11b.
We have some scenarios to start talk, but first, let me tell you some history. We got specific problems on clients using old 802.11b cards when changing the AP hw to Atheros a/b/g cards, but only when using the AP for 802.11b only. We also got problems on APs that share 802.11b with many different card types on the client side, i.e: AP Atheros a/b/g -> Client Atheros a/b/g + 802.11b only cards.
A MT Wireless Access Point box with about 78 clients in 802.11b. Atheros a/b/g card at the AP side, few MT box with Atheros a/b/g and the rest are a mix of cards for 802.11b and some of them b/g cards, including realtek, d-link, ralink, orinoco, etc... All hidden stations. A side note: On this case, seems that MT to MT get very high priorities over the whole 200 pps limits. Lets say, you can barely see about 300 pps from time to time. Also, this AP have a mix pppoe/static IP clients. So, its difficulties on traffic shaping/qos are not so easy to beat. Most of all complaints are clients with static IP addresses, but are not atheros cards. The total throughput under this conditions does not get more than 2.5mbits/s. Clients with MT boxes can get a CIR of 80-95% easy, all over the rest. We use WRAP router boards and the CPU get less than 25% to do the job.
I was looking for some way to deal with the 200 pps limit, but seems the best way (easy as well) is to turn the AP from 802.11b to 802.11a. Then we get problems at the client side. Well, about 200 clients that use this tower must thrown out the 802.11b cards and then start using 802.11a cards. Queues, specialy the PCQ one or traffic shapping seems does not solve the problem with packets per second and also increase latency a lot. The situation get really worse when the client side (atheros a/b/g cards) are infected with viruses. Otherwise, we need a lot more AP units to do a ressonable coverage with about 25 clients max limit per AP.
I am sure that maybe a good samaritan could give us a great fine tune possible to better handle the situation without leave the 802.11b.
Please, all comments are welcome.