I have already know what you mean and thanks for your advice. Now, the rate result is about 24Mbps~
Best Regards, Qing --- 11年3月30日，周三, Jon Dugan <jdu...@es.net> 写道： 发件人: Jon Dugan <jdu...@es.net> 主题: Re: [Iperf-users] Bandwidth Question in Iperf 收件人: "清 廖" <liaoqin...@yahoo.com.cn> 抄送: "iperf-users" <iperf-users@lists.sourceforge.net>, "Xiaojun Feng" <fight...@gmail.com> 日期: 2011年3月30日,周三,上午4:16 Excerpts from 清 廖's message of Mon Mar 28 11:14:18 -0500 2011: > Hi all, I use two PCs and one router to establish a 802.11b network in my > lab. And I let a client use 54M udp bandwidth(-b 54M) to send data to > another pc through router. But the result is only 13MBytes/sec. > Furthermore, I use "iwconfig wlan0 rate 1M" to set the client wireless > adapter rate. But the result of iperf is not be influenced by this command. > > Could anyone tell me how to let the iperf result reach to the 54M, because > the interference between two pc is not large through the spectrum analyzer > examination. And why the rate setting doesn't influence the bandwidth? > Thanks very much! There are many things that will limit your throughput on 802.11 networks. It is important to understand that the advertised rate (eg 54Mb/s or 108Mb/s for 802.11g) is the theoretical maximum of the physical layer without taking any of the protocol overhead into account. Competing traffic (are there other users on the wireless network?) will slow you down. RF interference may slow you down. Also, if you have any 802.11b clients you will be limited to 802.11b rates. Finally for a given channel there can only be one transmitter at a time. If both hosts in your are sending traffic at the same time you'll end up spending a lot of time switching between the senders. This is different than full-duplex wired ethernet where two parties could be sending at the same time without causing contention. Somewhere in 20Mb/s range is about what you can expect out of an 802.11g network. The Wikipedia article touches on this: http://en.wikipedia.org/wiki/IEEE_802.11#802.11g I haven't done much with iwconfig so I can't answer your questions about it's behavior. Hope that helps, Jon
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