Specifications

Appendix 2
Iperf commands and options
Command line
option
Environment variable
option
Description
Client and Server options
-f, --format
[bkmaBKMA]
$IPERF_FORMAT
A letter specifying the format to print bandwidth numbers in.
Supported formats are
'b' = bits/sec 'B' =
Bytes/sec
'k' = Kbits/sec 'K' =
KBytes/sec
'm' = Mbits/sec 'M' =
MBytes/sec
'g' = Gbits/sec 'G' =
GBytes/sec
'a' = adaptive bits/sec 'A' =
adaptive Bytes/sec
The adaptive formats choose between kilo- and mega- as
appropriate. Fields other than bandwidth always print bytes, but
otherwise follow the requested format. Default is 'a'.
NOTE: here Kilo = 1024, Mega = 1024^2 and Giga = 1024^3
when dealing with bytes. Commonly in networking, Kilo =
1000, Mega = 1000^2, and Giga = 1000^3 so we use this when
dealing with bits. If this really bothers you, use -f b and do the
math.
-i, --interval
#
$IPERF_INTERVAL
Sets the interval time in seconds between periodic bandwidth,
jitter, and loss reports. If non-zero, a report is made every
interval seconds of the bandwidth since the last report. If zero,
no periodic reports are printed. Default is zero.
-l, --len
#[KM]
$IPERF_LEN
The length of buffers to read or write. Iperf works by writing an
array of len bytes a number of times. Default is 8 KB for TCP,
1470 bytes for UDP. Note for UDP, this is the datagram size and
needs to be lowered when using IPv6 addressing to 1450 or less
to avoid fragmentation. See also the
-n and -t options.
-m, --
print_mss
$IPERF_PRINT_MSS
Print the reported TCP MSS size (via the TCP_MAXSEG
option) and the observed read sizes which often correlate with
the MSS. The MSS is usually the MTU - 40 bytes for the
TCP/IP header. Often a slightly smaller MSS is reported because
of extra header space from IP options. The interface type
corresponding to the MTU is also printed (ethernet, FDDI, etc.).
This option is not implemented on many OSes, but the read sizes
may still indicate the MSS.
-p, --port # $IPERF_PORT
The server port for the server to listen on and the client to
connect
to This should be the same in both client and server
36