bwctl
Section: User Commands (1)
Updated: $Date: 2009-02-23 08:08:04 -0500 (Mon, 23 Feb 2009) $
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NAME
bwctl - Client application to request throughput tests.
SYNOPSIS
bwctl
[options] -c recvhost -s sendhost
bwctl
[options] -c recvhost
bwctl
[options] -s sendhost
DESCRIPTION
bwctl is a command line client application that is used to
initiate throughput tests.
- This version of bwctl is capable of initiating Iperf, Nuttcp, and Thrulay tests.
-
bwctl
works by
contacting a bwctld daemon on both the receiving host and
the sending host. bwctld manages and schedules the resources
of the host it runs on.
In the case where only one of the receiving host or
sending host is specified, bwctl assumes the local host is the
other endpoint. bwctl will attempt to contact a local bwctld
if it can. If there is no local bwctld running, bwctl assumes
the local host does not require policy controls and will execute the
bwctld functionality required to run the test directly.
If cases where bwctl is directly running the throughput test
on the host, there are several configuration options that are shared
with bwctld. Those configuration options
can be set using the bwctlrc(5) configuration file in a way very similar
to the way they are specified in the bwctld.conf(5) file.
The bwctl client is used to request the desired type of throughput
test. Furthermore, it requests when the test is wanted.
bwctld on each endpoint either responds with a tentative
reservation or a test denied message. Once bwctl is able to get
a matching reservation from both bwctld processes (one for each
host involved in the test), it confirms the
reservation. Then, the bwctld processes run the test and return the
results. The results are returned to the client from both sides of the
test from the respective bwctld processes. Additionally, the
bwctld processes share the results from
their respective side of the test with each other.
BWCTL (bwctl and bwctld) is used to enable
non-specific throughput tests
to hosts without having to give full user accounts on the given systems.
Users want the ability to run throughput tests to determine the achievable
or available bandwidth between a pair of hosts. It is often useful to test
to multiple points along a network path to determine the network
characteristics along that path. Typically, users who want to do this path
decomposition have to directly contact the network/system administrators
who control the hosts along the path. The administrator needs to either
run half of the test for the user or give them a user account on the host.
Also, network paths of interest are typically controlled by
multiple administrators. These hurdles have made this kind of testing
difficult in practice.
BWCTL was designed to help with this problem. It allows an
administrator to configure a given host as an Iperf, Thrulay, or
Nuttcp endpoint. The endpoint can be a packet sender (e.g. Iperf
client) or a packet receiver (e.g. Iperf server). It can be shared by
multiple users without concern that those users will interfere with each other.
Specific policy limits can be applied to specific users, and individual tests
are scheduled so they will not interfere with each other. Additionally, full
user accounts are not required for the users running the tests.
BWCTL allows the administrator to classify incoming connections
based upon a user name and AES key combination or, alternatively, based
upon an IP/netmask.
Once the connection is classified, the bwctld can determine the
exact type and intensities of througput tests that will be allowed.
More information on the policy controls can be found in the bwctld(8)
man page.
BWCTL makes use of a distributed scheduling algorithm. Each host
maintains a schedule independently. As a client requests a test, the two
endpoints are contacted and each bwctld server responds with the first
available open schedule slot. This enables on-demand tests to co-exist
with regularly scheduled tests since regularly scheduled tests are implemented
by having the client request tests on regular intervals. Different
priorities can be implemented using the event_horizon configuration
directive to bwctld. (By allowing clients that implement regularly scheduled
tests to reserve their time slots further into the future.)
ARGUMENTS
Connection/Authentication Arguments:
- -A authmethod
-
authmethod is used to specify the authentication method the
bwctl client is willing to use for communication with the bwctld
on the sendhost and recvhost.
The authentication options of
bwctl are intended to be extensible. The communication from the
bwctl client to each bwctld server may take different options
for different types of authentication.
If the authmethod option is specified for either the -s,
or the -c argument, it overrides the authmethod specified
with the -A option for communication with that particular host.
(Therefore, the -A argument is really only useful if the same
authentication can be used with both hosts.)
-
Allowing different authentication methods for each connection should allow
a client to use different authentication methods with different servers
which should in turn allow cross-domain tests to occur more easily.
The format for authmethod is:
authmode [authscheme schemeopts]
- authmode
-
Specifies the authentication mode the client is willing to speak with
a server. It must be set as a character string with
any or all of the characters "AEO". The modes are:
-
- A
-
[A]uthenticated. This mode encrypts the control connection.
- E
-
[E]ncrypted. This mode encrypts the control connection. If the
test supports encryption, this mode will additionally encrypt the test
stream. (Encryption of the test stream is not currently supported, so
this mode is currently identical to authenticated.)
- O
-
[O]pen. No encryption of any kind is done.
The client can specify all the modes with which it is willing to communicate.
The most strict mode that both the server and the client are willing to use
will be selected.
- Default:
-
"AEO"
- authscheme schemeopts
-
authscheme indicates the authentication scheme that should be used to
achieve the authenticated or encrypted modes.
schemeopts are a list of arguments specific to each particular
authentication scheme. Supported authscheme values follow
(listed with the schemeopts each scheme requires):
-
- AESKEY userid [keyfile]
-
This is the initial "simple" shared secret (AES key) model. userid
is required to identify which shared secret the server and client should
use. keyfile optionally specifies a file to retrieve the AES key
from. If keyfile is not specified, the user will be prompted for a
passphrase. keyfile can be generated using the aespasswd(1)
application.
- Default:
-
Unauthenticated
authscheme and schemeopts are only needed if authenticated
communication (A or E modes of authmode)
is wanted with sendhost and recvhost.
- -B srcaddr
-
Bind the local address of the client socket to srcaddr. srcaddr
can be specified using a DNS name or using standard textual notations for
the IP addresses.
-
- Default:
-
Unspecified (wild-card address selection).
- -c recvhost[:port] [authmethod]
-
Specifies the host that will run the Iperf, Thrulay or Nuttcp server.
The :port suffix is optional
and is only needed if bwctld is being run on a non-default
port number. If an IPv6 address is being specified, note that the accepted
format contains the recvhost portion of the specification in square
brackets as: [fe80::fe9f:62d8]:4823.
This ensures the port number is distinct from the address specification, and
is not needed if the :port suffix is not being used.
-
At least one of the -c or -s options must be specified. If
one of them is not specified, it is assumed to be the local host.
authmethod is a specifically ordered list of keywords that
is only needed if authenticated communication is wanted with recvhost.
These keywords are used
to describe the type of communication and authentication that should be
used to contact the recvhost.
If recvhost and sendhost share
the same authentication methods and identities, it is possible to
specify the authmethod for both recvhost and sendhost
using the -A argument.
An authmethod specified with
the -c option will override an authmethod specified
with the -A argument for communication with the recvhost.
The format for authmethod and a description of the
currently available authentication
methods are described with the -A argument.
- -k
-
This option has been deprecated. Originally, it was used to specify the
keyfile for authentication.
All authentication options can now be specified
using the -A argument.
For the next several versions this option will
report an error. Eventually, it may be reclaimed for another purpose.
- -s sendhost[:port] [authmethod]
-
Specifies the host that will run the Iperf, Thrulay or Nuttcp client.
The :port suffix is optional
and is only needed if bwctld is being run on a non-default
port number. If an IPv6 address is being specified, note that the accepted
format contains the sendhost portion of the specification in square
brackets as: [fe80::fe9f:62d8]:4823.
This ensures the port number is distinct from the address specification, and
is not needed if the :port suffix is not being used.
-
At least one of the -c or -s options must be specified. If
one of them is not specified, it is assumed to be the local.
authmethod is a specifically ordered list of keywords that
is only needed if authenticated communication is wanted with sendhost.
These keywords are used
to describe the type of communication and authentication that should be
used to contact the sendhost.
If recvhost and sendhost share
the same authentication methods and identities, it is possible to
specify the authmethod for both recvhost and sendhost
using the -A argument.
An authmethod specified with
the -s option will override an authmethod specified
with the -A argument for communication with the sendhost.
The format for authmethod and a description of the
currently available authentication
methods are described with the -A argument.
- -U
-
This option has been deprecated. Originally, it was used to specify the username
to identify the AES key for authentication.
All authentication options can now be specified
using the -A argument.
For the next several versions this option will
report an error. Eventually, it may be reclaimed for another purpose.
Throughput Test Arguments:
The arguments were named to match their counterparts in Iperf
as closely as possible.
Some of the options are not available for some of the
throughput testers. BWCTL does not support UDP tests, changing the output format or
changing the output units for either Nuttcp or Thrulay.
- -T
-
Specify which throughput tester to use:
-
- iperf
-
- thrulay
-
- nuttcp
-
- Default:
-
None. Selects a tool that the client and server have in common
- -b bandwidth
-
Limit UDP send rate to bandwidth (bits/sec).
-
- Default:
-
1 Mb
- -i interval
-
Report interval (seconds).
-
- Default:
-
unset (no intervals reported)
- -l len
-
length of read/write buffers (bytes).
-
- Default:
-
8 KB TCP, 1470 bytes UDP
- -P nStreams
-
Number of concurrent streams for the test. See the -P option
of Iperf for details.
- -S TOS
-
Set the TOS (See RFC 1349) byte in packets.
-
- Default:
-
0 (not set)
- -t time
-
Duration of test (seconds).
-
- Default:
-
10
- -u
-
UDP test.
-
- Default:
-
TCP test
- -W window
-
Same as the -w option, except that the value is advisory. bwctl
will attempt to dynamically determine the appropriate TCP window, based upon
RTT information gathered from the control socket. If bwctl is unable
to dynamically determine a window, the value window will be used.
-
- Default:
-
Unset (system defaults)
- -w window
-
Socket buffer sizes (bytes). For TCP, this sets the TCP window size. For UDP,
this sets the socket receive buffer size.
-
- Default:
-
Unset (system defaults)
Scheduling Arguments:
- -a syncfuzz
-
Allow bwctl to run without a synchronized system clock. Use this to
specify how far off the local clock is from UTC. bwctl
prefers to have an NTP synchronized system clock to ensure the two
endpoints of the test are actually agreeing to the same scheduled time window
for test execution.
-
If two systems do NOT have a close enough notion of time, then
the throughput test will eventually fail because one endpoint of the test
will attempt to run at a different time than the other.
If the operating system supports the NTP system calls, and the system
clock is determined to be unsynchronized, error messages will still
be reported depending upon the value of the -e flag.
When calculating the time errors, this value will be aded in to account for the
difference. The maximum time offset can be bounded on the server side, using
the max_time_error directive, to prevent a denial of service attack. If set,
the server will reject any requests to test with a peer that has too high a
timestamp error.
- Default:
-
Unset (Defaults to Set for systems without the NTP system calls)
- -I interval
-
Specifies that bwctl should attempt to run a throughput test every
interval seconds.
-
- Default:
-
Unset. If it is unset, bwctl only runs the test once.
- -L longest
-
Specifies the longest amount of time the client is willing to wait for a
reservation window. When bwctl requests a test from the bwctld
server, it specifies the earliest time and the latest time it is willing
to accept. The latest time is determined by adding this longest
option to the earliest time. The earliest time is essentially 'now'.
The longest time is specified as a number of seconds.
-
- Default:
-
If interval is set, the default is 50% of interval. Otherwise,
the default is twice the test duration time but no smaller than
5 minutes. (See -t.)
- -n nIntervals
-
Number of tests to perform if the -I option is set.
-
- Default:
-
Continuous
- -R alpha
-
Randomize the start time of the test within this alpha percent of the
interval. Valid values for alpha are from 0-50. bwctl
will attempt to run the test every interval +/- alpha percent.
For example, if the interval is 300 seconds and alpha is
set to 10 percent, then bwctl will attempt to run a test every
270-330 seconds. This option is only useful with the -I option.
-
- Default:
-
0 (no randomness)
Output Arguments:
- -d dir
-
Specifies directory for results files if the -p option is set.
- -e facility
-
Syslog facility to log messages to.
-
- Default:
-
LOG_USER
- -f units
-
Specify the units for the tool to use when displaying the results. The accepted values for units are tool specific.
-
- Iperf:
-
-
- k
-
Kilobits per second
- K
-
Kilobytes per second
- m
-
Megabits per second
- M
-
Megabytes per second
- -h
-
Print a help message.
- -p
-
Place test results in files. Print the filenames to stdout when
results are complete.
- -q
-
Quiet output. Output as little as possible.
- -r
-
Send syslog messages to stderr. This is the default unless the -q
option is specified so this option is only useful with the -q
option.
- -V
-
Print version information and exit.
- -v
-
Verbose output. Specifying additional -v's increases the verbosity.
- -x
-
Output sender (client) results as well as receiver results.
By default, sender results are not output. If the -p option is
specified, the sender results are placed in an additional file.
- -y format
-
Specify the output format of the tool. The accepted values for format are tool specific.
-
- Iperf:
-
-
- c
-
[c]omma-separated output
ENVIRONMENT VARIABLES
bwctl Environment Variable | use | default
|
|
|
|
BWCTLRC | Config file | ~/.bwctlrc
|
BWCTL_DEBUG_TIMEOFFSET | Offset | 0.0(seconds)
|
LIMITATIONS
Only tested with versions 1.7.0 and 2.0.b of Iperf.
EXAMPLES
bwctl -c somehost.example.com
-
Run a default 10 second TCP test as soon as possible with
local as the sender and somehost.example.com as the receiver, using
whichever tools they have in common. Return the results from the receive side
of the test.
bwctl -x -c somehost.example.com
-
Like the previous test, but also return the results from the sender
side of the test.
bwctl -x -c somehost.example.com -s otherhost.example.com
-
Like the previous test, but with otherhost.example.com as the
sender instead of local.
bwctl -t 30 -T iperf -s somehost.example.com
-
Run a 30 second TCP Iperf test with somehost.example.com as the sender
and local as the receiver.
bwctl -I 3600 -R 10 -t 10 -u -b 10m -s somehost.example.com
-
Run a 10 second UDP test about every hour (3600 +/- 360 seconds) with
the sender rate limited to 10 Mbits per second from somehost.example.com to
local.
bwctl -s somehost.example.com AE AESKEY someuser
-
Run the default 10 second TCP test. Authenticate using
the identity someuser. bwctl will prompt for a passphrase
that will be used to create an AES key.
SEE ALSO
bwctld(8) and the http://e2epi.internet2.edu/bwctl/ web site.
For details on Iperf, see the http://sourceforge.net/projects/iperf
web site.
For details on Nuttcp, see the http://www.wcisd.hpc.mil/nuttcp/Nuttcp-HOWTO.html
web site.
For details on Thrulay, see the http://e2epi.internet2.edu/thrulay/
web site.
ACKNOWLEDGMENTS
This material is based in part on work supported by the National Science
Foundation (NSF) under Grant No. ANI-0314723. Any opinions, findings, and
conclusions or recommendations expressed in this material are those of
the author(s) and do not necessarily reflect the views of the NSF.
Index
- NAME
-
- SYNOPSIS
-
- DESCRIPTION
-
- ARGUMENTS
-
- Connection/Authentication Arguments:
-
- Throughput Test Arguments:
-
- Scheduling Arguments:
-
- Output Arguments:
-
- ENVIRONMENT VARIABLES
-
- LIMITATIONS
-
- EXAMPLES
-
- SEE ALSO
-
- ACKNOWLEDGMENTS
-
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Time: 22:37:05 GMT, May 19, 2010