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Manual Reference Pages  -  OWAMPD (8)


owampd - One-way latency server.


Environment Variables
See Also


owampd [options]


owampd is a server program specifically designed to run one side of one-way latency tests. The client program owping is available to run the other side of the test.

Aside from actually running the tests, the main function of owampd is to determine which tests are allowed, based upon the policy restrictions configured by the system administrator.

owampd was designed to be run as a stand-alone daemon process. It uses the classic accept/fork model of handling new requests.

Most of the command line options for owampd have analogous options in the owampd.conf file. The command line takes precedence.


-a authmode
  Specify the authentication modes the server is willing to use for communication. authmode 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 and encrypts part of each test packet.
E [E]ncrypted. This mode encrypts the control connection and encrypts each test packet in full. (This mode forces an encryption step between the fetching of a timestamp and when the packet is sent. This adds more computational delay to the time reported by OWAMP for each packet.)
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".
-c confdir
  Specify the directory that holds the owampd configuration files: owampd.conf, owampd.limits and owampd.pfs.
Default: Current working directory.
-d datadir
  Specify the directory that holds the buffered data files. The data files are the result of one-way latency tests where the server is the receiving host. The data files are used to buffer the data, at least until a client downloads the file. Policy restrictions can be used to set how much disk space a given connection can use, as well as to determine when each file is deleted. (See the owampd.limits(5) manual page.)
Default: Current working directory.
-e facility
  Syslog facility to which messages are logged.
-f Disables the requirement that owampd be run with non-root permissions. There are legitimate reasons to run owampd as root, but it is more risky. (For example, some operating systems require root permissions to set the TOS bits used by the -D option of owping.) This additional option was added to ensure that root permissions are only used when explicitly intended.
-G group
  Specify the gid for the owampd process. group can be specified using a valid group name or by using -gid. This option is only used if owampd is started as root.

This option can be useful to limit logfile permissions to only users in this group.

-h Print a help message.
-P 0 | lowport-highport
  Specify the specific port range to use on the local host for OWAMP-Test packets. This can be specified in two ways. First, as 0 which would indicate owampd 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
-R vardir
  Specify the directory to hold the file.
Default: Current working directory
-S nodename:port
  Specify the address and port on which owampd 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, simply by leaving off the ’:’ and port specification. Likewise, a non-default port can be specified for all system addresses (wildcard) by starting the specification string with a ’:’. If an IPv6 address is specified, note that the accepted format contains nodename in square brackets, such 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 861.
-U user Specify the uid the owampd process should run as. user can be specified using a valid user name or by using -uid. This option is only used if owampd is started as root.

In the default case, owampd should be started as root so it can bind the protected port 861. (See -S option.) owampd will release root permissions shortly after binding to this protected port and requests will be serviced by processes running with permissions defined by the user.

-v Set verbose output. Messages will still only go to syslog unless the -Z option is specified.
-Z Run the master owampd process in the foreground. In this mode, error messages are printed to STDERR as well as being sent to syslog. Also, normal terminal controls are available. (i.e., <Cntr-C> will cause the daemon to kill it’s child processes and exit.) This is useful for debugging.


The owampd daemon requires a very well synchronized and stable clock. owampd requires that NTP be running to synchronize the system clock. NTP needs to be setup in a more methodical way than on most systems for the results to be meaningful. Please see the OWAMP web site  ( for details concerning proper configuration of NTP for OWAMP.


owampd uses syslog to output error messages including access information. The facility configuration option is used to determine what syslog facility is used. The levels used are as follows:
LOG_ERR Used for messages indicating fatal errors. The requested action will not be performed.
LOG_WARNING Used for messages indicating an unexpected or dangerous condition.
LOG_INFO Used for access messages.
LOG_DEBUG Used to indicate reasons for actions. For example, if an access is denied due to policy choices that will be noted with this log level.
These levels were chosen to give the system-administrator the ability to separate access log information from error log information in a straight forward manner.


The owampd process makes use of a number of signals to perform IPC between the various processes involved:
  Used throughout to set timers where appropriate.
  Used to keep track of the state of child processes.
SIGHUP Used to terminate any owampd process. These signals are caught by the parent daemon and it manages the complete shutdown of all the owampd processes.
  Disabled throughout owampd.
  Used to tell a spawned off receiver/sender process that all control setup interaction is complete and the test can continue at the determined time. (This is an indication that the StartSessions message was received for those familiar with the OWAMP protocol.)
  Used to tell a spawned off receiver/sender process to terminate a session early. (This is an indication that a StopSessions message was received for those familiar with the OWAMP protocol.)



OWAMP uses environment variables for some debugging options.

OWAMP Environment VariableDescription
OWAMP_DEBUG_TIMEOFFSETOffset time by this amount (seconds)


There are more details on configuring the owampd daemon in the owampd.conf(5) manual page. Details on configuring the policy are in the owampd.limits(5) and owampd.pfs(5) manual pages. Information on the client is in the owping(1) manual page. For more of an overview of the full functionality and architecture, see the web site.


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.
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