Commit bb6aaf53 authored by chris's avatar chris
Browse files

""

parent 9e3d1e08
......@@ -18,20 +18,18 @@ iftop - display bandwidth usage on an interface by host
if none is specified, and displays a table of current bandwidth usage by pairs
of hosts.
When run, \fBiftop\fP displays, for each pair of hosts, the rate at which data
is sent and received averaged over 2, 10 and 40 second intervals. The direction
of data flow is indicated by arrows, <= and =>. In addition, a simple bar graph
shows the 10-second average. The pairs of hosts which consume the most bandwidth
are displayed at the top of the screen, and totals for all hosts are shown at
the bottom of the screen.
By default, \fBiftop\fP will look up the hostnames associated with addresses it
finds in packets. This can cause substantial traffic of itself, and may result
in a confusing display. You may wish to suppress display of DNS traffic by
using filter code such as \fBnot port domain\fP, or switch it off entirely,
by using the \fB-d\fP option or by pressing \fBR\fP when the program is running.
By default, \fBiftop\fP shows all IP packets that pass through the filter, and the direction of the packet is determined according to the direction the packet is moving across the interface. Using the \fB-n\fP option it is possible to get \fBiftop\fP to show packets entering and leaving a given network. For example, \fBiftop -n 10.0.0.0/255.0.0.0\fP will analyse packets flowing in and out of the 10.* network.
By default, \fBiftop\fP shows all IP packets that pass through the filter, and
the direction of the packet is determined according to the direction the packet
is moving across the interface. Using the \fB-n\fP option it is possible to
get \fBiftop\fP to show packets entering and leaving a given network. For
example, \fBiftop -n 10.0.0.0/255.0.0.0\fP will analyse packets flowing in and
out of the 10.* network.
\fBiftop\fP must be run as root.
......@@ -47,6 +45,51 @@ Count web traffic only, unless it is being directed through a local web cache.
How much bandwith are users wasting trying to figure out why the network is
slow?
.SH DISPLAY
When running, \fBiftop\fP uses the whole screen to display network usage. At
the top of the display is a reminder of keys which control \fBiftop\fP in
operation. Below that is a logarithmic scale for the `bar chart' visual display
of traffic.
The main part of the display lists, for each pair of hosts, the rate at which
data has been sent and received over the preceding 2, 10 and 40 second
intervals. The direction of data flow is indicated by arrows, <= and =>. In
addition, a simple bar graph shows the 10s average. For instance,
.nf
foo.example.com => bar.example.com 1K 500b 100b
<= 2M 2M 2M
.Sp
.fi
shows, on the first line, traffic from \fBfoo.example.com\fP to
\fBbar.example.com\fP; in the preceding 2 seconds, this averaged 1Kbit/s,
around half that amount over the preceding 10s, and a fifth of that over the
whole of the last 40s. During each of those intervals, the data sent in the
other direction was about 2Mbin/s. On the actual display, part of each line
would be inverted to give a visual indication of the 10s average of traffic.
You might expect to see something like this where host \fBfoo\fP is making
repeated HTTP requests to \fBbar\fP, which is sending data back which saturates
a 2Mbit/s link.
All rates are displayed in bits per second and multiples thereof. The pairs of
hosts responsible for the most traffic are displayed at the top of the list.
At the bottom of the display, various totals are shown, for instance:
.nf
total: 3.1K TX: 0.3M peaks: 64b 64b 30b 10b
peak: 4.5K RX: 8M 4.5K 4.5K 0.1M 5K
.Sp
.fi
The first column of numbers shows the total rate of received plus transmitted
traffic, and its peak value over the past 40s. The next column shows the
total amount of traffic observed during this session, \fIin bytes, not bits\fP.
The next column shows the peaks in received and transmitted traffic, and the
remaining colums show the 2, 10 and 40 second averages. As with the per-host
displays, the top line shows transmitted and the bottom line received traffic.
.SH OPTIONS
......@@ -72,6 +115,8 @@ counted, so the specified code is evaluated as \fB(\fP\fIfilter code\fP\fB) and
Specifies a network for traffic analysis. If specified, iftop will only
include packets flowing in to or out of the given network, and packet direction
is determined relative to the network boundary, rather than to the interface.
You may specify \fImask\fP as a dotted quad, such as /255.255.255.0, or as a
single number specifying the number of bits set in the netmask, such as /24.
.SH SEE ALSO
.BR tcpdump (8),
.BR pcap (3),
......
......@@ -77,7 +77,7 @@ static void usage(FILE *fp) {
" -i interface listen on named interface (default: eth0)\n"
" -f filter code use filter code to select packets to count\n"
" (default: none, but only IP packets are counted)\n"
" -n network/netmask show traffic flows in/out of network\n"
" -n net/mask show traffic flows in/out of network\n"
"\n"
"iftop, version " IFTOP_VERSION " copyright (c) 2002 Paul Warren <pdw@ex-parrot.com>\n"
);
......
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