DESCRIPTION

The bwctlrc file is a configuration file for the bwctl(8) program. If a test is requested using bwctl, and there is not a local bwctld(8) running, bwctl will spawn its own copy of bwctld. This configuration file is used to configure the basic operation of the automatically spawned server. For example, it can be used to configure whether to allow the local clock to be unsynchroznied, or where the iperf command is located.

This file can be placed in ~/.bwctlrc, where it will be automatically read by bwctl when it spawns off a bwctld. If the file is put elsewhere, the BWCTLRC environmental variable can be set to the path to the file and bwctl will read it.

The format of this file is:

• Comment lines are any line where the first non-whitespace character is '#'. These lines are counted for the purposes of returning line numbers in error messages but are otherwise ignored by the spawned bwctld.
• Lines may be continued using the semi-standard '\' character followed immediately by a newline character. This is the only valid place for the '\' character. If it is found elsewhere, a syntax error is reported.
• Blank lines are treated as comment lines.
• All other lines are used to set configuration options. The format of these lines is an initial keyword followed by a variable list of arguments, separated by whitespace.

CONFIGURATION OPTIONS

access_priority priority

Syslog priority to log access messages.

Default:

LOG_INFO

allow_unsync

Directs bwctld to continue accepting valid requests for throughput tests when the system clock is not synchronized. bwctld 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. This option is used to bypass this requirement for systems that either do not have the NTP system calls, or prefer not to configure NTP.

Note: if the difference between the system clocks on the two endpoints is too great, the eventual throughput test will fail when the endpoints attempt to run the test at different times. The threshold for this difference is controlled using the sync_fuzz option. (If you set allow_unsync, you should set sync_fuzz to a reasonable value for your system.)

Default:

unset (set if the operating system does have the NTP system calls)

auth_mode authmode

Specify the authentication modes the server is willing to use for communication. auth_mode should 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 server 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"

bottleneck_capacity bottleneckcapacity

This value is used in the algorithm to dynamically set the TCP send/recv window sizes. This option is likely to be removed in the future once a dynamic bottleneck_capacity algorithm is incorporated into the code. (This option only really works when the local NIC is the bottleneck.) If this option is not specified, the dynamic window calculation requested by the -W option to bwctl is not done and the advisory value is used.

Default:

unset

control_timeout controltimeout

Number of seconds to wait for protocol messages before timing out. This value should be significantly larger than what typical users specify for the -I flag of bwctl or bwctl will have to open a new control connection for each new test it requests.

Default:

7200 (Picked to be the same as the default for TCP keepalive)

die_by dieby

Number of seconds to wait for child processes to gracefully terminate before killing them with SIGKILL. This is in response to the master process receiving SIGTERM or SIGHUP.

Default:

5

disable_iperf

Prevent bwctl from executing Iperf tests

Default:

unset

disable_iperf3

Prevent bwctl from executing Iperf3 tests

Default:

unset

disable_nuttcp

Prevent bwctl from executing Nuttcp tests

Default:

unset

disable_owamp

Prevent bwctl from executing Owamp tests

Default:

unset

disable_ping

Prevent bwctl from executing Ping tests

Default:

unset

disable_tracepath

Prevent bwctl from executing Tracepath tests

Default:

unset

disable_traceroute

Prevent bwctl from executing Traceroute tests

Default:

unset

facility facility

Syslog facility to log messages.

Default:

LOG_DAEMON

group group

Specifies the gid the bwctld process should run as. group can be specified using a valid group name on the system or by using -gid. This option is only used if bwctld is started as root.

Default:

unset

iperf_cmd iperfcmd

The path to the Iperf command on the system. If the iperf_cmd does not contain a '/' character, then the PATH of the bwctld environment will be searched to find the Iperf executable.

Default:

iperf

iperf_port iperfport

The port number(s) that Iperf receivers will use. Currently, bwctld simply cycles through this range linearly. iperf_port can be specified as a single valid port number or as a range as low-high. The range must be specified as two valid port numbers with the '-' character separating them. Whitespace is not allowed within the iperf_port. For example, "5001-5004" would be valid, but "5001 - 5004" would be invalid.

This value should be set to a range because it can take a few minutes for a port to become free after a test has run. If the port is not free when the next test starts, the test will fail. If set to a range, the daemon will cycle through them when starting tests, decreasing the chance that a port will still be open when the test starts. For best results, ensure that this range is different from that of nuttcp_port and thrulay_port.

Default:

unset

iperf3_port iperf3port

The port number(s) that Iperf3 receivers will use. Currently, bwctld simply cycles through this range linearly. iperf3_port can be specified as a single valid port number or as a range as low-high. The range must be specified as two valid port numbers with the '-' character separating them. Whitespace is not allowed within the iperf3_port. For example, "5001-5004" would be valid, but "5001 - 5004" would be invalid.

This value should be set to a range because it can take a few minutes for a port to become free after a test has run. If the port is not free when the next test starts, the test will fail. If set to a range, the daemon will cycle through them when starting tests, decreasing the chance that a port will still be open when the test starts. For best results, ensure that this range is different from that of nuttcp_port and thrulay_port.

Default:

unset

log_location

Directs the bwctld process to report source code file and line number information with error messages. This is a particularly useful option to set when sending in messages as part of a bug report.

Default:

unset

nuttcp_cmd nuttcpcmd

The path to the Nuttcp command on the system. If the nuttcp_cmd does not contain a '/' character, then the PATH of the bwctl environment will be searched to find the Nuttcp executable.

Default:

nuttcp

nuttcp_port nuttcpport

The port number(s) that Nuttcp receivers will use. Currently, bwctld simply cycles through this range linearly. nuttcp_port can be specified as a single valid port number or as a range as low-high. The range must be specified as two valid port numbers with the '-' character separating them. Whitespace is not allowed within the nuttcp_port. For example, "5001-5004" would be valid, but "5001 - 5004" would be invalid.

This value should be set to a range because it can take a few minutes for a port to become free after a test has run. If the port is not free when the next test starts, the test will fail. If set to a range, the daemon will cycle through them when starting tests, decreasing the chance that a port will still be open when the test starts. For best results, ensure that this range is different from that of iperf_port and thrulay_port.

Default:

unset

owamp_cmd owampcmd

The path to the owping command on the system. If the owamp_cmd does not contain a '/' character, then the PATH of the bwctl environment will be searched to find the owping executable.

Default:

owping

owamp_server_cmd owampservercmd

The path to the owampd command on the system. If the owamp_server_cmd does not contain a '/' character, then the PATH of the bwctl environment will be searched to find the owampd executable.

Default:

owampd

owamp_port owampport

The port number(s) that Owamp receivers will use. Currently, bwctld simply cycles through this range linearly. owamp_port must be specified as a range as low-high. The range must be specified as two valid port numbers with the '-' character separating them. Whitespace is not allowed within the owamp_port. For example, "5001-5004" would be valid, but "5001 - 5004" would be invalid.

This value must be set to a range because it is used for both the Owamp communication and test ports.

Default:

unset

peer_port 0 | lowport-highport

Specify the port range that will be used on the local host for peer connections to other bwctld servers. These connections are used to verify clock timing between the servers and to exchange test results. This is a required part of the protocol used by BWCTL to run tests. However, this option allows system administrators to limit these connections to a specific port range, which should allow BWCTL to work in a firewall environment. This option can be specified in two ways. First, as a 0, which would indicate that bwctld should allow the system to pick the port (ephemeral). Second, as a range. lowport must be a smaller value than highport and both numbers must be valid port values. (16-bit unsigned integer values)

Default:

0

ping_cmd pingcmd

The path to the ping command on the system. If the ping_cmd does not contain a '/' character, then the PATH of the bwctl environment will be searched to find the ping executable.

Default:

ping

ping6_cmd ping6cmd

The path to the ping6 command on the system. If the ping6_cmd does not contain a '/' character, then the PATH of the bwctl environment will be searched to find the ping6 executable.

Default:

ping6

post_hook /path/to/script

Specifies a script to run after each bwctl session has finished. These hooks can be used to save the results into a database, track usage or any number of other tasks. You can specify as many hooks as you want by including multiple post_hook entries.

priority priority

Syslog priority to log error messages.

Default:

LOG_ERR

root_folly

Disables the checks that disable bwctld if it is run with root permissions. There are legitimate reasons to run bwctld as root, but it is risky. Forcing this additional option will make it less likely root permissions are accidently used.

Default:

unset

src_node nodename:port

Specify the address and port on which bwctld will listen for requests. nodename can be specified using a DNS name or using the textual representation of the address. It is possible to set the source address without setting the port by simply leaving off the ':' and port specification. If an IPv6 address is specified, note that the accepted format contains nodename in square brackets as: [fe80::fe9f:62d8]. This ensures the port number is distinct from the address specification.

Default:

nodename is wildcarded as any currently available address
port is 4823

sync_fuzz syncfuzz

This value is added to the NTP error estimates to increase the tolerance of bwctld to incomplete NTP configurations, or if the NTP system calls are not available. If NTP is unavailable to bwctld it assumes the clock is accurate to within one second plus the value of sync_fuzz. This option is specified as a floating point number in seconds. For example, to indicate that the system is synchronized within one second, you could specify this option as 1.0.

Practically, this option is used to determine the size of the time window buffer before and after each throughput test.

Default:

0.0

test_port testport

The port number(s) that receivers of all test types will use, unless otherwise set using one of the other port variables. Currently, bwctld simply cycles through this range linearly. test_port must be specified as a range as low-high. The range must be specified as two valid port numbers with the '-' character separating them. Whitespace is not allowed within the test_port. For example, "5001-5004" would be valid, but "5001 - 5004" would be invalid.

This value must be set to a range because it is used for both the Owamp communication and test ports.

Default:

5001-5900

thrulay_port thrulayport

The port number(s) that Thrulay receivers will use. Currently, bwctld simply cycles through this range linearly. thrulay_port can be specified as a single valid port number or as a range as low-high. The range must be specified as two valid port numbers with the '-' character separating them. Whitespace is not allowed within the thrulay_port. For example, "5001-5004" would be valid, but "5001 - 5004" would be invalid.

This value should be set to a range because it can take a few minutes for a port to become free after a test has run. If the port is not free when the next test starts, the test will fail. If set to a range, the daemon will cycle through them when starting tests, decreasing the chance that a port will still be open when the test starts. For best results, ensure that this range is different from that of iperf_port and nuttcp_port.

Default:

unset

tracepath_cmd tracepathcmd

The path to the tracepath command on the system. If the tracepath_cmd does not contain a '/' character, then the PATH of the bwctl environment will be searched to find the tracepath executable.

Default:

tracepath

tracepath6_cmd tracepath6cmd

The path to the tracepath6 command on the system. If the tracepath6_cmd does not contain a '/' character, then the PATH of the bwctl environment will be searched to find the tracepath6 executable.

Default:

tracepath6

traceroute_cmd traceroutecmd

The path to the traceroute command on the system. If the traceroute_cmd does not contain a '/' character, then the PATH of the bwctl environment will be searched to find the traceroute executable.

Default:

traceroute

traceroute6_cmd traceroute6cmd

The path to the traceroute6 command on the system. If the traceroute6_cmd does not contain a '/' character, then the PATH of the bwctl environment will be searched to find the traceroute6 executable.

Default:

traceroute6

user user

Specifies the uid the bwctld process should run as. user can be specified using a valid user name on the system or by using -uid. This option is only used if bwctld is started as root. If the given user has root permissions, the root_folly option must also be specified.

Default:

unset

var_dir vardir

Directory path where the bwctld.pid file will be placed.

Default:

Current directory

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.