Provided by: irtt_0.9.0-2ubuntu0.24.04.3_amd64 
NAME
irtt-client - Isochronous Round-Trip Time Client
SYNOPSIS
irtt client [args]
DESCRIPTION
irtt client is the client for irtt(1) (irtt.html).
OPTIONS
-d duration
Total time to send (default 1m0s, see Duration units below)
-i interval
Send interval (default 1s, see Duration units below)
-l length
Length of packet (default 0, increased as necessary for required headers), common values:
• 1472 (max unfragmented size of IPv4 datagram for 1500 byte MTU)
• 1452 (max unfragmented size of IPv6 datagram for 1500 byte MTU)
-o file
Write JSON output to file (use `-' for stdout). The extension used for file controls the gzip be‐
havior as follows (output to stdout is not gzipped):
Extension Behavior
──────────────────────────────────────────────────
none extension .json.gz is added, output
is gzipped
.json.gz output is gzipped
.gz output is gzipped, extension changed
to .json.gz
.json output is not gzipped
-q Quiet, suppress per-packet output
-Q Really quiet, suppress all output except errors to stderr
-n No test, connect to the server and validate test parameters but don't run the test
--stats=stats
Server stats on received packets (default both). Possible values:
Value Meaning
───────────────────────────────────────────────
none no server stats on received packets
count total count of received packets
window receipt status of last 64 packets
with each reply
both both count and window
--tstamp=mode
Server timestamp mode (default both). Possible values:
Value Meaning
─────────────────────────────────────────────────
none request no timestamps
send request timestamp at server send
receive request timestamp at server receive
both request both send and receive time‐
stamps
midpoint request midpoint timestamp (send/re‐
ceive avg)
--clock=clock
Clock/s used for server timestamps (default both). Possible values:
Value Meaning
─────────────────────────────────
wall wall clock only
monotonic monotonic clock only
both both clocks
--dscp=dscp
DSCP (ToS) value (default 0, 0x prefix for hex). Common values:
Value Meaning
─────────────────────────────────
0 Best effort
8 CS1- Bulk
40 CS5- Video
46 EF- Expedited forwarding
DSCP & ToS (https://www.tucny.com/Home/dscp-tos)
--df=DF
Setting for do not fragment (DF) bit in all packets. Possible values:
Value Meaning
─────────────────────────
default OS default
false DF bit not set
true DF bit set
--wait=wait
Wait time at end of test for unreceived replies (default 3x4s). Possible values:
Format Meaning
───────────────────────────────────────────────────
#xduration # times max RTT, or duration if no
response
#rduration # times RTT, or duration if no re‐
sponse
duration fixed duration (see Duration units
below)
Examples:
Example Meaning
────────────────────────────────────────────────
3x4s 3 times max RTT, or 4 seconds if no
response
1500ms fixed 1500 milliseconds
--timer=timer
Timer for waiting to send packets (default comp). Possible values:
Value Meaning
─────────────────────────────────────────────────
simple Go's standard time.Timer
comp Simple timer with error compensation
(see -tcomp)
hybrid:# Hybrid comp/busy timer with sleep
factor (default 0.95)
busy busy wait loop (high precision and
CPU, blasphemy)
--tcomp=alg
Comp timer averaging algorithm (default exp:0.10). Possible values:
Value Meaning
──────────────────────────────────────────────
avg Cumulative average error
win:# Moving average error with window #
(default 5)
exp:# Exponential average with alpha # (de‐
fault 0.10)
--fill=fill
Fill payload with given data (default none). Possible values:
Value Meaning
───────────────────────────────────────────────────
none Leave payload as all zeroes
rand Use random bytes from Go's math.rand
pattern:XX Use repeating pattern of hex (default
69727474)
--fill-one
Fill only once and repeat for all packets
--sfill=fill
Request server fill (default not specified). See values for –fill. Server must support and allow
this fill with –allow-fills.
--local=addr
Local address (default from OS). Possible values:
Value Meaning
──────────────────────────────────────────────────
:port Unspecified address (all IPv4/IPv6
addresses) with port
host Host with dynamic port, see Host for‐
mats below
host:port Host with specified port, see Host
formats below
--hmac=key
Add HMAC with key (0x for hex) to all packets, provides:
• Dropping of all packets without a correct HMAC
• Protection for server against unauthorized discovery and use
-4 IPv4 only
-6 IPv6 only
--timeouts=durations
Timeouts used when connecting to server (default 1s,2s,4s,8s). Comma separated list of durations
(see Duration units below). Total wait time will be up to the sum of these Durations. Max pack‐
ets sent is up to the number of Durations. Minimum timeout duration is 200ms.
--ttl=ttl
Time to live (default 0, meaning use OS default)
--loose
Accept and use any server restricted test parameters instead of exiting with nonzero status.
--thread
Lock sending and receiving goroutines to OS threads
-h Show help
-v Show version
Host formats
Hosts may be either hostnames (for IPv4 or IPv6) or IP addresses. IPv6 addresses must be surrounded by
brackets and may include a zone after the % character. Examples:
Type Example
──────────────────────────────────────
IPv4 IP 192.168.1.10
IPv6 IP [2001:db8:8f::2/32]
IPv4/6 hostname localhost
Note: IPv6 addresses must be quoted in most shells.
Duration units
Durations are a sequence of decimal numbers, each with optional fraction, and unit suffix, such as:
“300ms”, “1m30s” or “2.5m”. Sanity not enforced.
Suffix Unit
──────────────────────
h hours
m minutes
s seconds
ms milliseconds
ns nanoseconds
OUTPUT
IRTT's JSON output format consists of five top-level objects:
1. version
2. system_info
3. config
4. stats
5. round_trips
These are documented through the examples below. All attributes are present unless otherwise noted.
version
version information
"version": {
"irtt": "0.9.0",
"protocol": 1,
"json_format": 1
},
• irtt the IRTT version number
• protocol the protocol version number (increments mean incompatible changes)
• json_format the JSON format number (increments mean incompatible changes)
system_info
a few basic pieces of system information
"system_info": {
"os": "darwin",
"cpus": 8,
"go_version": "go1.9.2",
"hostname": "tron.local"
},
• os the Operating System from Go's runtime.GOOS
• cpus the number of CPUs reported by Go's runtime.NumCPU(), which reflects the number of logical rather
than physical CPUs. In the example below, the number 8 is reported for a Core i7 (quad core) with hy‐
perthreading (2 threads per core).
• go_version the version of Go the executable was built with
• hostname the local hostname
config
the configuration used for the test
"config": {
"local_address": "127.0.0.1:51203",
"remote_address": "127.0.0.1:2112",
"open_timeouts": "1s,2s,4s,8s",
"params": {
"proto_version": 1,
"duration": 600000000,
"interval": 200000000,
"length": 48,
"received_stats": "both",
"stamp_at": "both",
"clock": "both",
"dscp": 0,
"server_fill": ""
},
"loose": false,
"ip_version": "IPv4",
"df": 0,
"ttl": 0,
"timer": "comp",
"waiter": "3x4s",
"filler": "none",
"fill_one": false,
"thread_lock": false,
"supplied": {
"local_address": ":0",
"remote_address": "localhost",
"open_timeouts": "1s,2s,4s,8s",
"params": {
"proto_version": 1,
"duration": 600000000,
"interval": 200000000,
"length": 0,
"received_stats": "both",
"stamp_at": "both",
"clock": "both",
"dscp": 0,
"server_fill": ""
},
"loose": false,
"ip_version": "IPv4+6",
"df": 0,
"ttl": 0,
"timer": "comp",
"waiter": "3x4s",
"filler": "none",
"fill_one": false,
"thread_lock": false
}
},
• local_address the local address (IP:port) for the client
• remote_address the remote address (IP:port) for the server
• open_timeouts a list of timeout durations used after an open packet is sent
• params are the parameters that were negotiated with the server, including:
• proto_version protocol version number
• duration duration of the test, in nanoseconds
• interval send interval, in nanoseconds
• length packet length
• received_stats statistics for packets received by server (none, count, window or both, --stats flag
for irtt client)
• stamp_at timestamp selection parameter (none, send, receive, both or midpoint, --tstamp flag for irtt
client)
• clock clock selection parameter (wall or monotonic, --clock flag for irtt client)
• dscp the DSCP (https://en.wikipedia.org/wiki/Differentiated_services) value
• server_fill the requested server fill (--sfill flag for irtt client)
• loose if true, client accepts and uses restricted server parameters, with a warning
• ip_version the IP version used (IPv4 or IPv6)
• df the do-not-fragment setting (0 == OS default, 1 == false, 2 == true)
• ttl the IP time-to-live (https://en.wikipedia.org/wiki/Time_to_live) value
• timer the timer used: simple, comp, hybrid or busy (irtt client --timer flag)
• waiter the waiter used: fixed duration, multiple of RTT or multiple of max RTT (irtt client --wait
flag)
• filler the packet filler used: none, rand or pattern (irtt client --fill flag)
• fill_one whether to fill only once and repeat for all packets (irtt client --fill-one flag)
• thread_lock whether to lock packet handling goroutines to OS threads
• supplied a nested config object with the configuration as originally supplied to the API or irtt com‐
mand. The supplied configuration can differ from the final configuration in the following ways:
• local_address and remote_address may have hostnames or named ports before being resolved to an IP and
numbered port
• ip_version may be IPv4+6 before it is determined after address resolution
• params may be different before the server applies restrictions based on its configuration
stats
statistics for the results
"stats": {
"start_time": "2017-10-16T21:05:23.502719056+02:00",
"send_call": {
"total": 79547,
"n": 3,
"min": 17790,
"max": 33926,
"mean": 26515,
"stddev": 8148,
"variance": 66390200
},
"timer_error": {
"total": 227261,
"n": 2,
"min": 59003,
"max": 168258,
"mean": 113630,
"stddev": 77254,
"variance": 5968327512
},
"rtt": {
"total": 233915,
"n": 2,
"min": 99455,
"max": 134460,
"mean": 116957,
"median": 116957,
"stddev": 24752,
"variance": 612675012
},
"send_delay": {
"total": 143470,
"n": 2,
"min": 54187,
"max": 89283,
"mean": 71735,
"median": 71735,
"stddev": 24816,
"variance": 615864608
},
"receive_delay": {
"total": 90445,
"n": 2,
"min": 45177,
"max": 45268,
"mean": 45222,
"median": 45222,
"stddev": 64,
"variance": 4140
},
"server_packets_received": 2,
"bytes_sent": 144,
"bytes_received": 96,
"duplicates": 0,
"late_packets": 0,
"wait": 403380,
"duration": 400964028,
"packets_sent": 3,
"packets_received": 2,
"packet_loss_percent": 33.333333333333336,
"upstream_loss_percent": 33.333333333333336,
"downstream_loss_percent": 0,
"duplicate_percent": 0,
"late_packets_percent": 0,
"ipdv_send": {
"total": 35096,
"n": 1,
"min": 35096,
"max": 35096,
"mean": 35096,
"median": 35096,
"stddev": 0,
"variance": 0
},
"ipdv_receive": {
"total": 91,
"n": 1,
"min": 91,
"max": 91,
"mean": 91,
"median": 91,
"stddev": 0,
"variance": 0
},
"ipdv_round_trip": {
"total": 35005,
"n": 1,
"min": 35005,
"max": 35005,
"mean": 35005,
"median": 35005,
"stddev": 0,
"variance": 0
},
"server_processing_time": {
"total": 20931,
"n": 2,
"min": 9979,
"max": 10952,
"mean": 10465,
"stddev": 688,
"variance": 473364
},
"timer_err_percent": 0.056815,
"timer_misses": 0,
"timer_miss_percent": 0,
"send_rate": {
"bps": 2878,
"string": "2.9 Kbps"
},
"receive_rate": {
"bps": 3839,
"string": "3.8 Kbps"
}
},
Note: In the stats object, a duration stats class of object repeats and will not be repeated in the indi‐
vidual descriptions. It contains statistics about nanosecond duration values and has the following at‐
tributes:
• total the total of the duration values
• n the number of duration values
• min the minimum duration value
• max the maximum duration value
• mean the mean duration value
• stddev the standard deviation
• variance the variance
The regular attributes in stats are as follows:
• start_time the start time of the test, in TZ format
• send_call a duration stats object for the call time when sending packets
• timer_error a duration stats object for the observed sleep time error
• rtt a duration stats object for the round-trip time
• send_delay a duration stats object for the one-way send delay (only available if server timestamps are
enabled)
• receive_delay a duration stats object for the one-way receive delay (only available if server time‐
stamps are enabled)
• server_packets_received the number of packets received by the server, including duplicates (always
present, but only valid if the ReceivedStats parameter includes ReceivedStatsCount, or the --stats flag
to the irtt client is count or both)
• bytes_sent the number of UDP payload bytes sent during the test
• bytes_received the number of UDP payload bytes received during the test
• duplicates the number of packets received with the same sequence number
• late_packets the number of packets received with a sequence number lower than the previously received
sequence number (one simple metric for out-of-order packets)
• wait the actual time spent waiting for final packets, in nanoseconds
• duration the actual duration of the test, in nanoseconds, from the time just before the first packet
was sent to the time after the last packet was received and results are starting to be calculated
• packets_sent the number of packets sent to the server
• packets_received the number of packets received from the server
• packet_loss_percent 100 * (packets_sent - packets_received) / packets_sent
• upstream_loss_percent 100 * (packets_sent - server_packets_received / packets_sent) (always present,
but only valid if server_packets_received is valid)
• downstream_loss_percent 100 * (server_packets_received - packets_received / server_packets_received)
(always present, but only valid if server_packets_received is valid)
• duplicate_percent 100 * duplicates / packets_received
• late_packets_percent 100 * late_packets / packets_received
• ipdv_send a duration stats object for the send IPDV (https://en.wikipedia.org/wiki/Packet_delay_varia‐
tion) (only available if server timestamps are enabled)
• ipdv_receive a duration stats object for the receive IPDV (https://en.wikipedia.org/wiki/Packet_de‐
lay_variation) (only available if server timestamps are enabled)
• ipdv_round_trip a duration stats object for the round-trip IPDV (https://en.wikipedia.org/wiki/Pack‐
et_delay_variation) (available regardless of whether server timestamps are enabled or not)
• server_processing_time a duration stats object for the time the server took after it received the pack‐
et to when it sent the response (only available when both send and receive timestamps are enabled)
• timer_err_percent the mean of the absolute values of the timer error, as a percentage of the interval
• timer_misses the number of times the timer missed the interval (was at least 50% over the scheduled
time)
• timer_miss_percent 100 * timer_misses / expected packets sent
• send_rate the send bitrate (bits-per-second and corresponding string), calculated using the number of
UDP payload bytes sent between the time right before the first send call and the time right after the
last send call
• receive_rate the receive bitrate (bits-per-second and corresponding string), calculated using the num‐
ber of UDP payload bytes received between the time right after the first receive call and the time
right after the last receive call
round_trips
each round-trip is a single request to / reply from the server
"round_trips": [
{
"seqno": 0,
"lost": false,
"timestamps": {
"client": {
"receive": {
"wall": 1508180723502871779,
"monotonic": 2921143
},
"send": {
"wall": 1508180723502727340,
"monotonic": 2776704
}
},
"server": {
"receive": {
"wall": 1508180723502816623,
"monotonic": 32644353327
},
"send": {
"wall": 1508180723502826602,
"monotonic": 32644363306
}
}
},
"delay": {
"receive": 45177,
"rtt": 134460,
"send": 89283
},
"ipdv": {}
},
{
"seqno": 1,
"lost": false,
"timestamps": {
"client": {
"receive": {
"wall": 1508180723702917735,
"monotonic": 202967099
},
"send": {
"wall": 1508180723702807328,
"monotonic": 202856692
}
},
"server": {
"receive": {
"wall": 1508180723702861515,
"monotonic": 32844398219
},
"send": {
"wall": 1508180723702872467,
"monotonic": 32844409171
}
}
},
"delay": {
"receive": 45268,
"rtt": 99455,
"send": 54187
},
"ipdv": {
"receive": 91,
"rtt": -35005,
"send": -35096
}
},
{
"seqno": 2,
"lost": true,
"timestamps": {
"client": {
"receive": {},
"send": {
"wall": 1508180723902925971,
"monotonic": 402975335
}
},
"server": {
"receive": {},
"send": {}
}
},
"delay": {},
"ipdv": {}
}
]
Note: wall values are from Go's time.Time.UnixNano(), the number of nanoseconds elapsed since January 1,
1970 UTC
Note: monotonic values are the number of nanoseconds since the start of the test for the client, and
since start of the process for the server
• seqno the sequence number
• lost the lost status of the packet, which can be one of false, true, true_down or true_up. The
true_down and true_up values are only possible if the ReceivedStats parameter includes Received‐
StatsWindow (irtt client --stats flag). Even then, if it could not be determined whether the packet
was lost upstream or downstream, the value true is used.
• timestamps the client and server timestamps
• client the client send and receive wall and monotonic timestamps (receive values only present if lost
is false)
• server the server send and receive wall and monotonic timestamps (both send and receive values not
present if lost is true), and additionally:
• send values are not present if the StampAt (irtt client --tstamp flag) does not include send time‐
stamps
• receive values are not present if the StampAt (irtt client --tstamp flag) does not include receive
timestamps
• wall values are not present if the Clock (irtt client --clock flag) does not include wall values or
server timestamps are not enabled
• monotonic values are not present if the Clock (irtt client --clock flag) does not include monotonic
values or server timestamps are not enabled
• delay an object containing the delay values
• receive the one-way receive delay, in nanoseconds (present only if server timestamps are enabled and
at least one wall clock value is available)
• rtt the round-trip time, in nanoseconds, always present
• send the one-way send delay, in nanoseconds (present only if server timestamps are enabled and at
least one wall clock value is available)
• ipdv an object containing the IPDV (https://en.wikipedia.org/wiki/Packet_delay_variation) values (at‐
tributes present only for seqno > 0, and if lost is false for both the current and previous round_trip)
• receive the difference in receive delay relative to the previous packet (present only if at least one
server timestamp is available)
• rtt the difference in round-trip time relative to the previous packet (always present for seqno > 0)
• send the difference in send delay relative to the previous packet (present only if at least one serv‐
er timestamp is available)
EXIT STATUS
irtt client exits with one of the following status codes:
Code Meaning
──────────────────────────────────────
0 Success
1 Runtime error
2 Command line error
3 Two interrupt signals received
WARNINGS
It is possible with the irtt client to dramatically harm network performance by using intervals that are
too low, particularly in combination with large packet lengths. Careful consideration should be given
before using sub-millisecond intervals, not only because of the impact on the network, but also because:
• Timer accuracy at sub-millisecond intervals may begin to suffer without the use of a custom kernel or
the busy timer (which pins the CPU)
• Memory consumption for results storage and system CPU time both rise rapidly
• The granularity of the results reported may very well not be required
EXAMPLES
$ irtt client localhost
Sends requests once per second for one minute to localhost.
$ irtt client -i 200ms -d 10s -o - localhost
Sends requests every 0.2 sec for 10 seconds to localhost. Writes JSON output to stdout.
$ irtt client -i 20ms -d 1m -l 172 --fill=rand --sfill=rand 192.168.100.10
Sends requests every 20ms for one minute to 192.168.100.10. Fills both the client and server pay‐
load with random data. This simulates a G.711 VoIP conversation, one of the most commonly used
codecs for VoIP as of this writing.
$ irtt client -i 0.1s -d 5s -6 --dscp=46 irtt.example.org
Sends requests with IPv6 every 100ms for 5 seconds to irtt.example.org. Sets the DSCP value (ToS
field) of requests and responses to 46 (Expedited Forwarding).
$ irtt client --hmac=secret -d 10s “[2001:db8:8f::2/32]:64381”
Sends requests to the specified IPv6 IP on port 64381 every second for 10 seconds. Adds an HMAC
to each packet with the key secret.
SEE ALSO
irtt(1) (irtt.html), irtt-server(1) (irtt-server.html)
IRTT GitHub repository (https://github.com/peteheist/irtt/)
v0.9.0 February 11, 2018 IRTT-CLIENT(1)