------------------------------------------------------------[&nbsp; 4] local &lt;IP Addr node4&gt; port 5001 connected with &lt;IP Addr node3&gt; port 13914[ ID] Interval&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Transfer&nbsp;&nbsp;&nbsp;&nbsp; Bandwidth[&nbsp; 4]&nbsp; 0.0- 2.3 sec&nbsp;&nbsp; 632 KBytes&nbsp;&nbsp; 2.1 Mbits/sec<B><FONT color=#ff0000>WARNING: Path MTU Discovery may not be enabled.</FONT></B>[&nbsp; 4] <B><FONT color=#ff0000>MSS size 536 bytes (MTU 576 bytes, minimum)</FONT></B>[&nbsp; 4] Read lengths occurring in more than 5% of reads:[&nbsp; 4]&nbsp;&nbsp; 536 bytes read&nbsp;&nbsp; 308 times (58.4%)[&nbsp; 4]&nbsp; 1072 bytes read&nbsp;&nbsp;&nbsp; 91 times (17.3%)[&nbsp; 4]&nbsp; 1608 bytes read&nbsp;&nbsp;&nbsp; 29 times (5.5%)</PRE></BLOCKQUOTE>Iperf supports other tuning options, which were added for exceptional network situations like HIPPI-to-HIPPI over ATM. <BR><HR><!-- ----- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- --><H2><A name=tuningudp></A>Tuning a UDP connection</H2>Iperf creates a constant bit rate UDP stream. This is a very artificial stream, similar to voice communication but not much else. <P>You will want to adjust the datagram size (-l) to the size your application uses. <P>The server detects UDP datagram loss by ID numbers in the datagrams. Usually a UDP datagram becomes several IP packets. Losing a single IP packet will lose the entire datagram. To measure packet loss instead of datagram loss, make the datagrams small enough to fit into a single packet, using the -l option. The default size of 1470 bytes works for ethernet. Out-of-order packets are also detected. (Out-of-order packets cause some ambiguity in the lost packet count; Iperf assumes they are not duplicate packets, so they are excluded from the lost packet count.) Since TCP does not report loss to the user, I find UDP tests helpful to see packet loss along a path. <P>Jitter calculations are continuously computed by the server, as specified by RTP in RFC 1889. The client records a 64 bit second/microsecond timestamp in the packet. The server computes the relative transit time as (server's receive time - client's send time). The client's and server's clocks do not need to be synchronized; any difference is subtracted out in the jitter calculation. Jitter is the smoothed mean of differences between consecutive transit times. <BLOCKQUOTE><PRE><B>node2&gt;</B> iperf -s -u -i 1------------------------------------------------------------Server listening on UDP port 5001Receiving 1470 byte datagramsUDP buffer size: 60.0 KByte (default)------------------------------------------------------------[&nbsp; 4] local &lt;IP Addr node2&gt; port 5001 connected with &lt;IP Addr node1&gt; port 9726[ ID] Interval&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Transfer&nbsp;&nbsp;&nbsp;&nbsp; Bandwidth&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Jitter&nbsp;&nbsp; Lost/Total Datagrams[&nbsp; 4]&nbsp; 0.0- 1.0 sec&nbsp;&nbsp; 1.3 MBytes&nbsp; 10.0 Mbits/sec&nbsp; 0.209 ms&nbsp;&nbsp;&nbsp; 1/&nbsp; 894 (0.11%)[&nbsp; 4]&nbsp; 1.0- 2.0 sec&nbsp;&nbsp; 1.3 MBytes&nbsp; 10.0 Mbits/sec&nbsp; 0.221 ms&nbsp;&nbsp;&nbsp; 0/&nbsp; 892 (0%)[&nbsp; 4]&nbsp; 2.0- 3.0 sec&nbsp;&nbsp; 1.3 MBytes&nbsp; 10.0 Mbits/sec&nbsp; 0.277 ms&nbsp;&nbsp;&nbsp; 0/&nbsp; 892 (0%)[&nbsp; 4]&nbsp; 3.0- 4.0 sec&nbsp;&nbsp; 1.3 MBytes&nbsp; 10.0 Mbits/sec&nbsp; 0.359 ms&nbsp;&nbsp;&nbsp; 0/&nbsp; 893 (0%)[&nbsp; 4]&nbsp; 4.0- 5.0 sec&nbsp;&nbsp; 1.3 MBytes&nbsp; 10.0 Mbits/sec&nbsp; 0.251 ms&nbsp;&nbsp;&nbsp; 0/&nbsp; 892 (0%)[&nbsp; 4]&nbsp; 5.0- 6.0 sec&nbsp;&nbsp; 1.3 MBytes&nbsp; 10.0 Mbits/sec&nbsp; 0.215 ms&nbsp;&nbsp;&nbsp; 0/&nbsp; 892 (0%)[&nbsp; 4]&nbsp; 6.0- 7.0 sec&nbsp;&nbsp; 1.3 MBytes&nbsp; 10.0 Mbits/sec&nbsp; 0.325 ms&nbsp;&nbsp;&nbsp; 0/&nbsp; 892 (0%)[&nbsp; 4]&nbsp; 7.0- 8.0 sec&nbsp;&nbsp; 1.3 MBytes&nbsp; 10.0 Mbits/sec&nbsp; 0.254 ms&nbsp;&nbsp;&nbsp; 0/&nbsp; 892 (0%)[&nbsp; 4]&nbsp; 8.0- 9.0 sec&nbsp;&nbsp; 1.3 MBytes&nbsp; 10.0 Mbits/sec&nbsp; 0.282 ms&nbsp;&nbsp;&nbsp; 0/&nbsp; 892 (0%)[&nbsp; 4]&nbsp; 0.0-10.0 sec&nbsp; 12.5 MBytes&nbsp; 10.0 Mbits/sec&nbsp; 0.243 ms&nbsp;&nbsp;&nbsp; 1/ 8922 (0.011%)<B>node1&gt;</B> iperf -c node2 -u -b 10m------------------------------------------------------------Client connecting to node2, UDP port 5001Sending 1470 byte datagramsUDP buffer size: 60.0 KByte (default)------------------------------------------------------------[&nbsp; 3] local &lt;IP Addr node1&gt; port 9726 connected with &lt;IP Addr node2&gt; port 5001[ ID] Interval&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Transfer&nbsp;&nbsp;&nbsp;&nbsp; Bandwidth[&nbsp; 3]&nbsp; 0.0-10.0 sec&nbsp; 12.5 MBytes&nbsp; 10.0 Mbits/sec[&nbsp; 3] Sent 8922 datagrams</PRE></BLOCKQUOTE>Notice the higher jitter due to datagram reassembly when using larger 32 KB datagrams, each split into 23 packets of 1500 bytes. The higher datagram loss seen here may be due to the burstiness of the traffic, which is 23 back-to-back packets and then a long pause, rather than evenly spaced individual packets. <BLOCKQUOTE><PRE><B>node2&gt;</B> iperf -s -u -l 32k -w 128k -i 1------------------------------------------------------------Server listening on UDP port 5001Receiving 32768 byte datagramsUDP buffer size:&nbsp; 128 KByte------------------------------------------------------------[&nbsp; 3] local &lt;IP Addr node2&gt; port 5001 connected with &lt;IP Addr node1&gt; port 11303[ ID] Interval&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Transfer&nbsp;&nbsp;&nbsp;&nbsp; Bandwidth&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Jitter&nbsp;&nbsp; Lost/Total Datagrams[&nbsp; 3]&nbsp; 0.0- 1.0 sec&nbsp;&nbsp; 1.3 MBytes&nbsp; 10.0 Mbits/sec&nbsp; 0.430 ms&nbsp;&nbsp;&nbsp; 0/&nbsp;&nbsp; 41 (0%)[&nbsp; 3]&nbsp; 1.0- 2.0 sec&nbsp;&nbsp; 1.1 MBytes&nbsp;&nbsp; 8.5 Mbits/sec&nbsp; 5.996 ms&nbsp;&nbsp;&nbsp; 6/&nbsp;&nbsp; 40 (15%)[&nbsp; 3]&nbsp; 2.0- 3.0 sec&nbsp;&nbsp; 1.2 MBytes&nbsp;&nbsp; 9.7 Mbits/sec&nbsp; 0.796 ms&nbsp;&nbsp;&nbsp; 1/&nbsp;&nbsp; 40 (2.5%)[&nbsp; 3]&nbsp; 3.0- 4.0 sec&nbsp;&nbsp; 1.2 MBytes&nbsp; 10.0 Mbits/sec&nbsp; 0.403 ms&nbsp;&nbsp;&nbsp; 0/&nbsp;&nbsp; 40 (0%)[&nbsp; 3]&nbsp; 4.0- 5.0 sec&nbsp;&nbsp; 1.2 MBytes&nbsp; 10.0 Mbits/sec&nbsp; 0.448 ms&nbsp;&nbsp;&nbsp; 0/&nbsp;&nbsp; 40 (0%)[&nbsp; 3]&nbsp; 5.0- 6.0 sec&nbsp;&nbsp; 1.2 MBytes&nbsp; 10.0 Mbits/sec&nbsp; 0.464 ms&nbsp;&nbsp;&nbsp; 0/&nbsp;&nbsp; 40 (0%)[&nbsp; 3]&nbsp; 6.0- 7.0 sec&nbsp;&nbsp; 1.2 MBytes&nbsp; 10.0 Mbits/sec&nbsp; 0.442 ms&nbsp;&nbsp;&nbsp; 0/&nbsp;&nbsp; 40 (0%)[&nbsp; 3]&nbsp; 7.0- 8.0 sec&nbsp;&nbsp; 1.2 MBytes&nbsp; 10.0 Mbits/sec&nbsp; 0.342 ms&nbsp;&nbsp;&nbsp; 0/&nbsp;&nbsp; 40 (0%)[&nbsp; 3]&nbsp; 8.0- 9.0 sec&nbsp;&nbsp; 1.2 MBytes&nbsp; 10.0 Mbits/sec&nbsp; 0.431 ms&nbsp;&nbsp;&nbsp; 0/&nbsp;&nbsp; 40 (0%)[&nbsp; 3]&nbsp; 9.0-10.0 sec&nbsp;&nbsp; 1.2 MBytes&nbsp; 10.0 Mbits/sec&nbsp; 0.407 ms&nbsp;&nbsp;&nbsp; 0/&nbsp;&nbsp; 40 (0%)[&nbsp; 3]&nbsp; 0.0-10.0 sec&nbsp; 12.3 MBytes&nbsp;&nbsp; 9.8 Mbits/sec&nbsp; 0.407 ms&nbsp;&nbsp;&nbsp; 7/&nbsp; 401 (1.7%)<B>node1&gt;</B> iperf -c node2 -b 10m -l 32k -w 128k------------------------------------------------------------Client connecting to node2, UDP port 5001Sending 32768 byte datagramsUDP buffer size:&nbsp; 128 KByte------------------------------------------------------------[&nbsp; 3] local &lt;IP Addr node2&gt; port 11303 connected with &lt;IP Addr node1&gt; port 5001[ ID] Interval&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Transfer&nbsp;&nbsp;&nbsp;&nbsp; Bandwidth[&nbsp; 3]&nbsp; 0.0-10.0 sec&nbsp; 12.5 MBytes&nbsp; 10.0 Mbits/sec[&nbsp; 3] Sent 401 datagrams</PRE><PRE></PRE></BLOCKQUOTE><P><A name=multicast></A><B><FONT size=+1>Multicast</FONT></B> <P>To test multicast, run several servers with the bind option (-B, --bind) set to the multicast group address. Run the client, connecting to the multicast group address and setting the TTL (-T, --ttl) as needed. Unlike normal TCP and UDP tests, multicast servers may be started after the client. In that case, datagrams sent before the server started show up as losses in the first periodic report (61 datagrams on arno below). <BLOCKQUOTE><PRE><B>node5&gt;</B> iperf -c 224.0.67.67 -u --ttl 5 -t 5------------------------------------------------------------Client connecting to 224.0.67.67, UDP port 5001Sending 1470 byte datagramsSetting multicast TTL to 5UDP buffer size: 32.0 KByte (default)------------------------------------------------------------[&nbsp; 3] local &lt;IP Addr node5&gt; port 1025 connected with 224.0.67.67 port 5001[ ID] Interval&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Transfer&nbsp;&nbsp;&nbsp;&nbsp; Bandwidth[&nbsp; 3]&nbsp; 0.0- 5.0 sec&nbsp;&nbsp; 642 KBytes&nbsp;&nbsp; 1.0 Mbits/sec[&nbsp; 3] Sent 447 datagrams<B>node5&gt;</B> iperf -s -u -B 224.0.67.67 -i 1------------------------------------------------------------Server listening on UDP port 5001Binding to local address 224.0.67.67Joining multicast group&nbsp; 224.0.67.67Receiving 1470 byte datagramsUDP buffer size: 32.0 KByte (default)------------------------------------------------------------[&nbsp; 3] local 224.0.67.67 port 5001 connected with &lt;IP Addr node5&gt; port 1025[ ID] Interval&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Transfer&nbsp;&nbsp;&nbsp;&nbsp; Bandwidth&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Jitter&nbsp;&nbsp; Lost/Total Datagrams[&nbsp; 3]&nbsp; 0.0- 1.0 sec&nbsp;&nbsp; 131 KBytes&nbsp;&nbsp; 1.0 Mbits/sec&nbsp; 0.007 ms&nbsp;&nbsp;&nbsp; 0/&nbsp;&nbsp; 91 (0%)[&nbsp; 3]&nbsp; 1.0- 2.0 sec&nbsp;&nbsp; 128 KBytes&nbsp;&nbsp; 1.0 Mbits/sec&nbsp; 0.008 ms&nbsp;&nbsp;&nbsp; 0/&nbsp;&nbsp; 89 (0%)[&nbsp; 3]&nbsp; 2.0- 3.0 sec&nbsp;&nbsp; 128 KBytes&nbsp;&nbsp; 1.0 Mbits/sec&nbsp; 0.010 ms&nbsp;&nbsp;&nbsp; 0/&nbsp;&nbsp; 89 (0%)[&nbsp; 3]&nbsp; 3.0- 4.0 sec&nbsp;&nbsp; 128 KBytes&nbsp;&nbsp; 1.0 Mbits/sec&nbsp; 0.013 ms&nbsp;&nbsp;&nbsp; 0/&nbsp;&nbsp; 89 (0%)[&nbsp; 3]&nbsp; 4.0- 5.0 sec&nbsp;&nbsp; 128 KBytes&nbsp;&nbsp; 1.0 Mbits/sec&nbsp; 0.008 ms&nbsp;&nbsp;&nbsp; 0/&nbsp;&nbsp; 89 (0%)[&nbsp; 3]&nbsp; 0.0- 5.0 sec&nbsp;&nbsp; 642 KBytes&nbsp;&nbsp; 1.0 Mbits/sec&nbsp; 0.008 ms&nbsp;&nbsp;&nbsp; 0/&nbsp; 447 (0%)<B>node6&gt;</B> iperf -s -u -B 224.0.67.67 -i 1------------------------------------------------------------Server listening on UDP port 5001Binding to local address 224.0.67.67Joining multicast group&nbsp; 224.0.67.67Receiving 1470 byte datagramsUDP buffer size: 60.0 KByte (default)------------------------------------------------------------[&nbsp; 3] local 224.0.67.67 port 5001 connected with &lt;IP Addr node5&gt; port 1025[ ID] Interval&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Transfer&nbsp;&nbsp;&nbsp;&nbsp; Bandwidth&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Jitter&nbsp;&nbsp; Lost/Total Datagrams[&nbsp; 3]&nbsp; 0.0- 1.0 sec&nbsp;&nbsp; 129 KBytes&nbsp;&nbsp; 1.0 Mbits/sec&nbsp; 0.778 ms&nbsp;&nbsp; 61/&nbsp; 151 (40%)[&nbsp; 3]&nbsp; 1.0- 2.0 sec&nbsp;&nbsp; 128 KBytes&nbsp;&nbsp; 1.0 Mbits/sec&nbsp; 0.236 ms&nbsp;&nbsp;&nbsp; 0/&nbsp;&nbsp; 89 (0%)[&nbsp; 3]&nbsp; 2.0- 3.0 sec&nbsp;&nbsp; 128 KBytes&nbsp;&nbsp; 1.0 Mbits/sec&nbsp; 0.264 ms&nbsp;&nbsp;&nbsp; 0/&nbsp;&nbsp; 89 (0%)[&nbsp; 3]&nbsp; 3.0- 4.0 sec&nbsp;&nbsp; 128 KBytes&nbsp;&nbsp; 1.0 Mbits/sec&nbsp; 0.248 ms&nbsp;&nbsp;&nbsp; 0/&nbsp;&nbsp; 89 (0%)[&nbsp; 3]&nbsp; 0.0- 4.3 sec&nbsp;&nbsp; 554 KBytes&nbsp;&nbsp; 1.0 Mbits/sec&nbsp; 0.298 ms&nbsp;&nbsp; 61/&nbsp; 447 (14%)</PRE><PRE><HR width="100%"></PRE></BLOCKQUOTE><P><A name=ipv6></A><DL>  <DT><B><FONT size=+2>IPv6 Mode</FONT></B>   <DD>Download the IPv6 version of this release.<BR>Get the IPv6 address of the node using the 'ifconfig' command.<BR>Use the <FONT color=#000099>-V</FONT> option to indicate that you are using an IPv6 address Please note that we need to explicitly bind the server address also.   <P>Server side:<BR><FONT color=#000099> $ iperf -s -V</FONT>  <P>Client side:<BR><FONT color=#000099>$ iperf -c &lt;Server IPv6 Address&gt; -V </FONT>  <P>Note: Iperf version 1.6.2 and eariler require a IPv6 address to be explicitly bound  with the <A HREF="#bind">-B</A> option for the server.</P></DD></DL><HR><P><A name=repmode></A><DL>  <DT><B><FONT size=+2>Using Representative Streams to measure   bandwidth</FONT></B>   <DD>Use the -F or -I option. If you want to test how your network performs   with compressed / uncompressed streams, just create representative streams and   use the -F option to test it. This is usually due to the link layer   compressing data.   <P>The -F option is for file input.<BR>The -I option is for input from stdin.   <P>E.g. <BR>Client: $ <FONT color=#000099> iperf -c &lt;server address&gt; -F &lt;file-name&gt;<BR></FONT>          <BR>Client: $ <FONT color=#000099> iperf -c &lt;server address&gt; -I </FONT></P></DD></DL><P><A name=daemon></A><HR><DL>  <DT><B><FONT size=+2>Running the server as a daemon</FONT></B>   <DD>Use the -D command line option to run the server as a daemon. Redirect the   output to a file.<BR>E.g. <FONT color=#000099>iperf -s -D &gt;   iperfLog</FONT>. <FONT color=#000000>This will have the Iperf Server running   as a daemon and the server messages will be logged in the file iperfLog. </DD></DL><HR><P><A name=service></A><DL>  <DT><B><FONT size=+2>Using Iperf as a Service under Win32</FONT></B>   <DD>There are three options for Win32:   <P>  <DL>    <DT>-o outputfilename     <DD>output the messages into the specified file     <DT>-s -D     <DD>install Iperf as a service and run it     <DT>-s -R     <DD>uninstall the Iperf service </DD></DL>  <P>Examples:   <DL>    <DT><FONT color=#3366ff>iperf -s -D -o iperflog.txt</FONT>     <DD>will install the Iperf service and run it. Messages will be reported     into "%windir%\system32\iperflog.txt"     <P></P>    <DT><FONT color=#3366ff>iperf -s -R</FONT>     <DD>will uninstall the Iperf service if it is installed.     <P>Note: If you stop want to restart the Iperf service after having killed     it with the Microsoft Management Console or the Windows Task Manager, make     sure to use the proper OPTION in the service properties dialog.   </P></DD></DL></DD></DL><HR><!--<P><A name=multicast></A><DL>  <DT><B><FONT size=+2>Running the multicast server and client</FONT></B>   <DD>Use the -B option while starting the server to bind it to a multicast   address.<BR>E.g. :-<FONT color=#3366ff>iperf -s -u -B 224.0.55.55</FONT>.   <P>This will have the Iperf server listening for datagrams (-u) for the   address 224.0.55.55(-B 224.0.55.55).   <P>Now, start a client sending packets to this multicast address.   <P>E.g. : <FONT color=#3366ff>iperf -c 224.0.55.55 -u</FONT>.   This will have a UDP client (-u) sending to the multicast address   224.0.55.55(-c 224.0.55.55).   <P><FONT color=#000000>Start multiple clients or servers as explained above,   sending data to the same multicast server. (If you have multiple servers   listening on the multicast address, each of the servers will be getting the data) </P></DD></DL><HR>--><!--<A name=adaptive></A><DL>  <DT><B><FONT size=+2>Adaptive window sizes</FONT></B>   <DD>Use the -W option on the client to run the client with the adaptive window   size. Ensure that the server window size is fairly big for this   option.<BR>E.g.. If the server TCP window size is 8KB, it does not help having   a client TCP window size of 256KB.<BR>256KB Server TCP Window Size should   suffice for most high bandwidth networks.   <P>Client changes the TCP window size using a binary exponential   algorithm. This means that you may notice that TCP window size suggested may   vary according to the traffic in the network, Iperf will suggest the best   window size for the current network scenario. </DL><HR width="100%">--><P><!-- ----- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- --><CENTER><P>Copyright 1999,2000,2001,2002,2003,2004 <BR>The Board of Trustees of the University of Illinois <BR>All rights reserved <BR>See <A href="ui_license.html">UI License</A> for complete details.</CENTER></BODY></HTML>