bandwidth measures

One day (hopefully) lots of MP3, JPEG and perhaps even MPEG-files will be flying around our wireless home-network. But I didn’t have any idea of how much data I could cram through the Airport-connections. To estimate the available bandwith of a network there is a nice free tool around, iperf of which you can download binaries for almost any platform including OS X. So click on the MacOS X (Darwin 6.4) binary button half way on the iperf-page and you get a Desktop iperf-1.7.0-powerpc-apple-darwin6.4 Folder which you may rename to just iperf. Do this on two computers connected to the Airport-network you want to measure. Now, decide which of the two will play the ’server’ and which the ‘client’ (the end result does not depend on this choice). So fire up the Terminal of the serving computer and type

sudo ~/Desktop/iperf/iperf -s

and you will get a message saying that the server is listening on TCP port 5001. Go to the SystemPreferences/Network to obtain the IP-address of the server (say it is 10.0.1.5) . Walk over to the ‘client’-computer and type into its Terminal

sudo ~/Desktop/iperf/iperf -c 10.0.1.5
-r

and after a few moments it will compute the bandwidth of the connection for you. Here is a sample output of two Airport-card iMacs connected to the same Airport-Extreme base station :

iMacLieven:~/Desktop/iperf lieven$ ./iperf
-s ------------------------------------------------------------\r\
nServer listening on TCP port 5001 TCP window size: 64.0 KByte
(default) -----------------------------------------------------------
- [  4] local 10.0.1.2 port 5001 connected with 10.0.1.7 port
49245 [ ID] Interval       Transfer     Bandwidth [  4]  0.0-10.3
sec  2.77 MBytes  2.27
Mbits/sec -----------------------------------------------------------
- Client connecting to 10.0.1.7, TCP port 5001 TCP window size:
65.0 KByte
(default) -----------------------------------------------------------
- [  4] local 10.0.1.2 port 49515 connected with 10.0.1.7 port
5001 [ ID] Interval       Transfer     Bandwidth [  4]  0.0-10.2
sec  2.73 MBytes  2.23 Mbits/sec indicating a bandwidth of approximately
2.25Mbits/sec. If we replay the same game with two
AirportExtreme-card iMacs on the same network we can nearly
triple (!) the bandwidth : 

[eMacAnn:~] lieven% cd
Desktop/iperf [eMacAnn:~/Desktop/iperf] lieven% ./iperf
-s ------------------------------------------------------------\r\
nServer listening on TCP port 5001 TCP window size: 64.0 KByte
(default) -----------------------------------------------------------
- [  4] local 10.0.1.5 port 5001 connected with 10.0.1.6 port
49314 [ ID] Interval       Transfer     Bandwidth [  4]  0.0-10.0
sec  8.50 MBytes  7.11
Mbits/sec -----------------------------------------------------------
- Client connecting to 10.0.1.6, TCP port 5001 TCP window size:
65.0 KByte
(default) -----------------------------------------------------------
- [  4] local 10.0.1.5 port 49320 connected with 10.0.1.6 port
5001 [ ID] Interval       Transfer     Bandwidth [  4]  0.0-10.9
sec  7.07 MBytes  5.45 Mbits/sec

However, if these two AirportExtrame-card computers connect to each other via the Graphite-Airport base station the bandwidth drops to a meagre 1.9 Mbits/sec which is roughly the same as two Airport-card computers connecting (which gave me 2.45 Mbits/s). Anyway, there is no immediate problem with bandwidth on either network for what I have in mind. Another important number to know is the real speed of our internet-connection (for instance if I want to replace our old router by a better documented one and have a measure for the in/decrease of the connection-speed). Here, a good URL is performance.chello.at which offers two tests : String and String SSI. The later one has a graphical resulting page such as