Iperf 2 Files

See doc/DESIGN_NOTES for some description around the software design
See doc/CLOCKSYNC_NOTES for some description around synchronizing the
realtime clocks

2.2.1 (as of Oct 26th, 2024)
------------------------------
o man page updates
o support (alpha level) for --udp-l4s (linux only, requires ./configure --enable-udp-l4s)
o buffer overflow fixes (multiple places)
o support of udp summing enhanced outputs in sum reports with -P > 1
o SETABSTIME fix
o connection report errors ouput to stderr (vs stdout)
o fixes to --connectly-only regressions
o remove --tcp-cca and --reverse restriction
o fixes to ip_tos and cmsg
o remove setsockopt for ip tos, use sendmsg and ancillary messages instead
o sample tcp_info in the middle of a -i interval
o multiple fixes for TCP_TX_DELAY
o don't autoset --tcp-write-prefetch with --trip-times, warn instead
o Add Android NDK example, add mingw64 example
o set smallest prefetch to 256K
o print wait time on server side with --tx-starttime
o fix header code #if mismatch of (HAVE_DECL_SO_TIMESTAMP) && (HAVE_DECL_MSG_CTRUNC) per ticket 328
o fix client side bb summing
o fix format error in timestamps
o 1) Support CSV for isochronous, both UDP and TCP 2) Reorganise CSV report assignement to be more logical.
o support milliseconds and microseconds with iperf_formattime, also make sure the leading zeros are printed per the field width
o fix multiple pps regressions
o csv patches per ticket 320 and 322
o add per direction byte counts with bounceback on client (server side code yet to be done)
o fix summing init code per ticket 324
o tcp working load should use full capacity seeking behaviors
o fix csv compile breakage on MAC
o use append for --ouput vs w, ticket 321
o use --ipg units of seconds
o fix settings calculations when -b is given for --burst options
o improve port range / traffic thread count (-P) warning
o add transferid to recvmsg warning
o compute packet pps accounts for interval crossing using that timestamp vs packet timestamp
o use object setnow() method to set lastPackeTime in first packet delay
o pps calculation needs to include partial gap value with IPGsum ahead of PPS output
o minor fixes for DEBUG_PPS support
o fix initial udp write delay and reporting
o Rerun autoconf
o Remove unused ax_create_stdint_h
o move Socklen_t discovery entirely into dast.m4
o Remove unused DAST_REPLACE macros
o fix udp regression with high pps, sosndtimer needs to be set, don't use write select
o Remove obsolete web100 makefile support
o fix for windows enhanced writes with summing
o don't mix typecast with format specifiers, use %ld for (long) typecast
o use typecast for time_val seconds for portability, fix windows 64 cross compile
o Set default compiler and load flags without overiding user choice.
o Move packet and tuntap checks later so they don't execute before compiler checks.
o Use HAVE_GETIFADDRS instead of HAVE_IFADDRS_H for Android and any other OS that has the header file but might not enable the actual feature
o Remove code that is unused and deprecated
o Update defuns to comply with autoconf-2.72
o use netinet vs linux for ip.h and udp.h, add configure.ac checks for the header files, update dscp.h for new defines not in netienet per WFA/WMM inputs
o disable SO_REUSEPORT for server side
o various fixes in ReportOutputs including divide by zero test, segv fixes, and spacings
o fix for UDP 64b seq number detection per packet header
o fix configure.ac to support Win64 compiles
o ticket 314: eliminate the udp accept race between listener and server thread using a conditional signal
o ticket 313: remove support for configure --enable-static-bin, never worked and only misleads
o ticket 312: regression, fix for segv in UDP summing enhance outputs
o ticket 311: histogram worst timestamp needs proper formatting, didn't print leading zeros for the usec portion
o ticket 310: regression on client setting reports, too many with things like -P > 1
o ticket 309 (regression): udp summing is broken. Need to reset sum event counters after interval reports
o ticket 308: -P should be order independent
o ticket 305: add support for --skip-rx-copy w/tcp. Set recv flags to MSG_TRUNC when the payload isn't needed by iperf
o ticket 157 (regression since 2.1.4): remove AM_CONDITIONAL for TUN & TAP. Move the AF_PACKET AM_CONDITIONAL to its own scope. Rerun autoreconf automake
o fix output for tos on server side
o remove settings report for client threads when P > 1
o fix timeval outputs to use %06ld for usecs

2.2.0 (as of April 9th, 2024)
------------------------------
o new ./configure --enable-summing-debug option to help with summing debug
o select ahead of writes slow down UDP performance. support ./configure --disable-write-select
o support fo -b 0 with UDP, unlimited load or no delay between writes
o support for --sync-transfer-id so client and server will match the ids and give a remap message
o support --dscp command line option
o support for application level retries and minimum retry interval of the TCP connect() syscall via --connect-retry-time and --connect-retry-timer, repsectively
o support for --ignore-shutdown so test will end on writes vs the BDP drain and TCP close/shutdown, recommended not to use this but in rare cases
o support for --fq-rate-step and --fq-rate-step-interval
o CCAs per --tcp-cca, --tcp-congestion, etc neeed to be case sensitive
o support for both packets and bytes inflight taken from tcp_info struct amd pkt calc of (tcp_info_buf.tcpi_unacked - tcp_info_buf.tcpi_sacked - tcp_info_buf.tcpi_lost + tcp_info_buf.tcpi_retrans)
o man page updates and -h to reflect new options, better descriptions
o lots of work around summing with parallel threads, new implementation based on interval or slot counters, hopefully should work reliably
o --bounceback tests are much more reliable and robust
o Improve event handling around select timeouts, helps with larger -P values and summing
o use the getsockopt IP_TOS for the displayed output, warn when set and get don't match
o better tos byte output, include dscp and ecn fields individually
o better tos setting code for both v6 and v4, so they behave the same around checks and warnings
o much better NULL events to help with reporter processing even when traffic is not flowing
o support for a new string report
o python flows work around CDF based tests
o rate limit fflush calls to a max of one every millisecond or 1000 per sec
o remove superfulous fflush calls
o reports when P = 1 and --sum-only need sum outputs
o enable summing with --incr-dstip
o add macro TIME_GET_NOW to set a struct timeval in a portable manner
o code readability improvements with enums, bools, etc.
o fix for TCP rate limited and -l less than min burst size
o only use linux/tcp.h when absolutely needed, otherwise use netinet/tcp.h
o print bounceback OWD tx/rx in interval reports
o add flows Makefiles for tarball or make dist-all
o support interval reports for bounceback histograms
o support for TCP working loads and UDP primary flows, including UDP isochronous, per ticket 283
o fix working-load with isoch so working-load streams are capacity seeking
o exit when CCA not supported or read of the current CCA doesn't match requested CCA
o add more make check tests
o add support for omit string (omit code not ready for this release)
o pyflows qdisc settings and outputs
o add first send pacing with --tx-starttime so listener threads udp_accept has time to perform udp_accept() between the client threads
o adjust the sender time per the client delay and the client first write, i.e. subtract out this delay in the calculations
o fixes for small packets and --tx-starttime
o use more modern multicast socket options (now in src/iperf_multicast_api.c)
o warn on bind port not sent with --incr-srcport
o display fq-rate values in outputs when --fq-rate is used
o add support for --test-exchange-timeout
o fixes around wait_tick
o add support for TCP_TX_DELAY via --tcp-tx-delay <val ms> option on both client and server
o pass the CCA from client to server
o support burst-size with different write sizes and don't require --burst-period
o output traffic thread send scheduling error stats in final ouput
o output clock unsync stats with --bounceback
o add warn message on MSG_CTRUNC
o UDP select fixes
o enable TCP_NOTSENTLOWAT and set to a default small value with --tcp-write-times
o default histogram max binning to 10 seconds
o add a max timestamp to histogram outputs so user can find packets in pcaps or equivalent
o autoconf change for struct ip_mreqn
o print errno on writen fail

2.1.9 (as of February 13th, 2023)
------------------------------
o fixed traffic setitimer to use uintmax_t vs int, supporting large values
o --bounceback officially supported (including Windows) for repsonsiveness test scenarios
o deprecated --bounceback-congest introduced in 2.1.8, replaced by --working-loads
o --working-loads support generalized; works with --bounceback, --connect-only & --burst-period
o default TCP_NOTSENT_LOWAT with the --working-loads concurrent traffic
o add support for GMT time formatting via --utc option
o --trip-times will auto set TCP_NOTSENT_LOWAT
o CSV output fixes for reverse
o CSV output regressions fixed per sum outputs using negative transfer ids
o CSV output support with --enhanced
o Fix to isoch wait_tick with Windows
o fix support for --txstart-time with --bounceback
o Add support for summing histograms in histogram sum outputs
o Multiple sum report fixes per threading & needing mutex protections
o Jitter packet IPG calcluations ignore inter frame gaps
o Isoch jitter output to use running value vs sampled value
o Add support for --jitter-histograms
o man page content updates
o output isoch scheduling errors at end of isoch run
o PRIdMAX fix for ARM systems
o better work around in isochronous with Windows per early return of WaitForSingleObject()
o fix SO_BINDTODEVICE regression
o fix v6 source port parsing with -B and brackets
o fix malloc error with --hideips
o fixes for rate limited TCP with --trip-times
o add support for TCL_NOTSENT_LOWAT with rate limited TCP
o permit key now supports -P using listen() with a backlog, no longer single thread limited
o fixes for zero valued permit-key
o fixes for multiple permit-key regressions
o fix token bucket delay with TCP await write
o fix isMulticast test for ipv4 - previous logic indicate true for 240.x.x.x which is not multicast
o fix regression on jitter calc - starts on second transit time
o add cmsg for loop with UDP rx timestamp, cmsg processing best to use loop w/test
o use stdout and exit(0) for -h and -v (vs stderr and exit(1))
o add python facetime scripts
o Fix single thread compile breakage
o fix windows cross compile
o multiple spelling error fixes in comments and man page


2.1.8 (as of August 5th, 2022)
------------------------------
o Add support for --bounceback to perform a repsonsiveness test (see man page for other options)
o add support for working loads with --bounceback
o Fix to wait_tick with Mac OS X
o Various python pyflows commits
o add support for client side tcp-write-time histograms and mean/min/max
o add support for human readable dscp or -T values (see man page)
o udp_accept no longer accepts packets from a previous run as a new connection, this can occur with long network delays
o multiple isoch bug fixes for both UDP and TCP
o isoch server provides mean/min/max/stdev for both frames and packets
o UDP max MTU discovery, requires configure.ac will support --enable-discover-defaultlen prior to compile


2.1.7 (as of April 5th, 2022)
----------------------------
o Support for tcp bounceback test
o Code clean up
o Regression fixes (see git-log)

2.1.6
-----
o Fix to major 2.1.5 regeressions

2.1.5 change set as of (December 3, 2021)
--------------------------------------
o fix some HAVE_IPV6 conditional changes
o fix SO_TIMEOUT regressiony
o ren sockets.c to socket_io.c
o fix compile breakage per abs() returning an int instead of float
o support for gettcpinfo on Mac OS X (tested on both M1 and x86 silicon)
o move setsock_blocking from sockets into PerfSocket.cpp
o don't require -V for v6, instead try v6 when v4 hostname lookup fails, client only
o add assert in writen
o add tcp RTT variance to client output
o use setsockopt to get the nagle status
o show Nagle and TOS settings on client
o more on connect-only testing
o sample and output the initial rtt and cwnd in the connect report
o fix multiple fullduplex regressions
o fix for HAVE_TCP_STATS in configure, then linux compile
o writen can have more than one write, fix accounting when this occurs
o fix tos with --reverse and --full-duplex
o add support for --tos-override <value> on server
o add support for  --tcp-drain, add mmm stats, histograms - experimental feature
o multiple man page updates
o fix partial histogram print to not show (f)
o some new scripts in python flows
o fixes to incr-srcport
o fixes for --incr-dstport
o fix regression on very first UDP packet having transit latency of zero
o fix --reverse and --isochronous when --trip-times not set
o fix client_init regression, pull out tcp_shutdown
o fix reporter startup race and one second delay by setting the threads ready predicate and issuing the signal under a lock
o fix first send accounting for small -n
o fix configure.ac to use '=' instead of '=='


2.1.4 change set as of (August 12, 2021)
--------------------------------------
o fix TCP isoch regression
o fix regression in UDP header exchange for tests like --reverse
o Add support for TCP_NOTSENT_LOWAT vi --tcp-write-prefetch and select() before write()
o Add support for TCP_WINDOW_CLAMP
o Rework recvn() and writen() for when SO_SNDTIMEO and SO_RCVTIMEO are enabled
o Add support for --histograms on select with --tcp-write-prefetch
o Add support for bind to device on the listener, i.e. iperf -s -i 1 -e -B 0.0.0.0%eth0, will only accept/receive on the eth0 interface
o Add support for virtual/tap interfaces
o Add support for --hide-ips (don't show the ip addresses in the report outputs)
o Fix units of -pps with --reverse, --fullduplex, -r and -d
o Remove use of MSG_PEEK by moving the mBuf buffer from client/server object to settings context
o Use MSG_WAITALL in recvn (collided with MSG_PEEK on Windows)

2.1.3 change set as of (July 13, 2021)
--------------------------------------
o relax cli errors a bit to WARN instead of ERROR
o fix TCP read fatal error macro
o fix UDP server to not fatal error on EINTR, use macro
o handle and warn on failed read of tcp test flags
o redesign of tcp retry (2.1.2 fix was incomplete)
o thread exit signals reporter thread condition var for timely exits of the tool


2.1.2 change set (as of June 25th, 2021)
----------------------------------------
o fix TCP retry regression per interval reporting

2.1.1 change set (as of June 23rd, 2021)
----------------------------------------
o isochronous bug fix
o -P and -B src port will increment for unique quintuple
o support for port ranges, e.g. -p 6000-6008
o double free fix per memory corruption when -l is less than 244
o don't use pthread_join on the client --reverse, symptom hung client
o fixes for --trip-times and small 64 byte packets
o udp fail on reverse should exit
o support for low duty cycle bursts (--burst-period and --burst-size)
o final report fixes
o full duplex ouput fixex
o support for --incr-scrip
o multicast setsockopt fixes


2.1.0 change set (as of January 5th, 2021)
----------------------------------------
o scaling improvements for -P, i.e. improved support for large numbers of traffic threads
o major code refactoring (see doc/DESIGN_NOTES) for maintainability, extensibilty, performance, scaling, memory usage
o support for full duplex traffic using --full-duplex
o support for reverse traffic using --reverse
o support for role-reversal character of asterisk in the transfer id
o transfer id now an incrementing integer and no longer the socket id
o support for TCP connect only tests with --connect-only
o isochronous support compiled in by default, must use config to disable
o support --isochronous for both UDP or TCP traffic to simulate video streams
o support for low duty cycle traffic patterns via --burst-period and --burst-size
o use of clock_nanosleep when supported to schedule isochronous burst starts, otherwise use nanosleep delay
o support for --trip-times indicating the client and server clocks are synchronized to an accuracy sufficient, note: consider the use of precision time protocol as well as ask your data center to provide access to a GPS disciplined reference time source
o support for --trip-times with -d and -r bidirectional tests
o output TCP connect times (3WHS) in connect reports
o support for application level tcp connect retries via --connect-retries n
o rate-limited options of -b and --fq-rate supported for unidirectional, full duplex and reverse traffic
o reporter thread designed to automatically cause packet reports to aggregate - mitigating and hopefully removing thread thrashing
o support for frame or burst based reporting or sampling vs time based via -i [f|F] (experimental)
o support for UDP traffic only from client to server with --no-udp-fin
o support for write to read latencies (UDP and TCP) with --trip-times
o support for sum only outputs with --sum-only
o support for little's law calculations in --trip-time outputs
o support for --txstart-time <epoch-time> to schedule client traffic start, timestamp support microseconds, e.g. unix $(expr $(date +%s) + 1).$(date +%N)
o support for --txdelay-time to insert delay between TCP three way handshake (3WHS) and data transfer
o support for --no-connect-sync which disables transmit traffic start synchronization when -P is used, defaults to synchronized
o option of --full-duplex implementation uses a barrier on the client side to synchronize full duplex traffic
o no limits to group sum reports, i.e. all clients will get its own sum report per a server
o improved report timestamps, e.g. end to end or client and server based timestamps with --trip-times
o improved settings messaging
o improved messaging for --tcp-congestion or -Z
o re-implemented -U for single UDP server with minimal threading interactions
o re-implemented -1 or --singleclient where server will serialize traffic runs
o warning message if the test were likely CPU bound instead of network i/o bound
o fix the case when -P <value> is set on the server such that summing output is displayed
o multicast listener will autoset -U (single server), e.g -P > 1 not supported for multicast
o multicast listener no longer busy drops multicast packets during traffic test, i.e. only server thread receives them
o immediate bail out on mutually exclusive command line options
o getaddrinfo bug with -static linkage workaround and DNS lookup one time in setttings context vs twice in Settings and client traffic thread
o fix -o or --output using freopen to redirect stdout and stderr to a file
o support for --local-only which sets SO_DONTROUTE on a socket to limit traffic to local hosts (default is off)
o support compile time option of --local-only to set on by default via ./configure --enable-default-localonly
o support for date and time of in connect messages,
  e.g. [  0] local 192.168.1.108%eth0 port 5001 connected with 192.168.1.62 port 36724 (MSS=453) (sock=5) on 2020-12-22 19:43:42 (PST)
o support for feature of --permit-key and permit-key-timeout (defaults to 20 seconds.) The permit-key must match for the server to accpet the client's traffic. It also sets the transfer id. TCP only.
o support for experimental feature of --near-congestion (tcp only)
o man page updates with examples
o tested with 1000's of traffic streams, WiFi, 10G and 100G

2.0.13 change set (as of January 22, 2019)
----------------------------------------
o Set the listening socket backlog to a large value, let os control the max, better operations with FreeBSD
o Fix breakage to -r and -d options
o Fix so ctrl-c works with -r and -d
o Fix ctrl-c on server to have a graceful exit including print report
o Fix freebsd compile breakage per multicast support
o The UDP final server report may be larger than the client's -l length, fix the client to read maximum packet length for that instead of using -l as the read size
o Minor code clean up around write errors
o Added netpower to TCP client enhanced output (throughput/RTT)
o Display TCP client connect time in the connected to message
o use IPV6_TCLASS for ipv6 (-V) dscp/tos (-S) if available
o Add support for --txstart-time <value> where value is epoch/unix format, e.g. iperf -c 192.168.100.33 --txstart-time 1536090358.515
o Add support for socket option SO_MAX_PACING_RATE using --fq-rate
o Add configure support for --enable-fastsampling, allowing 100 microsecond report intervals
o Add support for --trip-time on the client.  Measures client's 3WHS done to client's fin+fin-ack, reported on the server requires -e and synchronized clocks
o Support for 64 bit sequence numbers on by default, no longer requires --udp-counters-64bit, inter-operates with 2.0.5 32 bit sequence numbers
o Integer fixes for 64 bit, int max, printf,  etc.
o Obsolete the need for include/slim_headers.h
o Update man page to have some example usages

2.0.12 change set (as of June 25th 2018)
----------------------------------------
o Change the unicast TTL default value from 1 to the system default (to be compatible with previous versions.)   Multicast still defaults to 1.
o adaptive formatting bug fix: crash occurs when values exceed 1 Tera.  Add support for Tera and Peta and eliminate the potential crash condition
o configure default compile to include isochronous support (use configure --disable-isochronous to remove support)
o replace 2.0.11's --vary-load option with a more general -b option to include <mean>,<stdev>, e.g. -b 100m,40m, which will pull from a log normal distribution every 0.1 seconds
o fixes for windows cross compile (using mingw32)
o compile flags of -fPIE for android
o configure --enable-checkprograms to compile ancillary binaries used to test things such as delay, isoch, pdf generation
o compile tests when trying to use 64b seq numbers on a 32b platform
o Fix GCC ver 8 warnings


2.0.11 change set (as of May 24th, 2018)
----------------------------------------
o support for -b on server (read rate limiting)
o honor -T (ttl) for unicast.  (Note: the default value is 1 so this will impact unicast tests that require routing)
o support for --isochronous traffic with optional frames per second, mean and variance uses a log normal distribution (requires configure w/-enable-isochronous and compile)
o support for --udp triggers (requires configure w/ --enable-udptriggers, early code with very limited support)
o support for --udp-histogram with optional bin width and number of bins (default is 1 millisecond bin width and 1000 bins)
o support for  frame (burst) latency histograms when --isochronous is set
o support for --tx-sync with -P for synchonrized writes.  Initial use is for WiFi OFDMA latency testing.
o support for --incr-dstip with -P for simultaneous flows to multiple destinations (use case is for OFDMA)
o support for --vary-load with optional weight, uses log normal distribution (requires -b to set the mean)
o support for --l2checks to detect L2 length errors not detected by v4 or v6 payload length errors (requires linux, berkeley packet filters BPFs and AF_PACKET socket support)
o support for server joining mulitcast source specific multicast (S,G) and (*,G) for both v4 and v6 on platforms that support it
o improved write counters (requires -e)
o accounting bug fix on client when write fails, this bug was introduced in 2.0.10
o slight restructure client/server traffic thread code for maintainability
o python: flow example script updates
o python: ssh node object using asyncio
o python: histograms in flows with plotting (assumed gnuplot available)
o python: hierarchical clustering of latency histograms (early code)
o man pages updates
o Note: latency histograms require client and server system clock synchronization.   A GPS disciplined oscillator using Precision Time Protocol works well for this.

2.0.10 change set (as of August 11, 2017)
-----------------------------------------
o clean up help and man page for -V option
o UDP IPv6 : Default the mBuf size to 1450 for the client, default the Listener/server to 1470
o Display read/write buffer size in the report header (only when -e enhanced)
o Add -S and --tos to man page and help, and format options to same
o Reject --ipv6_domain (-V) option if HAVE_IPV6 is not defined, rather than silently ignoring it.
o Clean up settings/command line parsing code including removing oder dependencies
o Use strtok (instead of strtok_r) for better portability
o Fix 'format string is not a string literal' warnings on Mac OS X
o Use SOCKET type on Windows instead of int to clean up signed/unsigned warnings
o Fix WIN32 timeout paste errors
o man page updates to describe format characters, improve BUGS sections
o Fix autoconf IPV6 check for case where configure is not called from srcdir
o Add support for v6 link local, e.g. 'iperf -V -c fe80::428d:5cff:fef7:5a73%eno1'
o Fix ClientHdrXchange when gettimeofday() is used
o Fix for -l, -W and -n to support format characters, also fix -n for -d and -r
o Fixes -for -d (dual) honoring -b on remote
o Fix for -t and -r
o Support for 64 bit sequence numbers (--udp-counters-64bit)
o Update config to support new platforms, eg --host=aarch64-linux
o Fixes to header xchange, length messages, and packing
o Server thread mbuf length checks
o remove trailing whitespace across all files in the git repository
o Support peer version detection and exchange with -X option
o Add UDP buffer size minimum checks and warnings prior to peer test exchange
o 2.0.5 interop testing and fixes (assume lots of 2.0.5 servers in the field)
o Fix thread settings per hdr xhcange fixes
o Fix for -P and -d used together
o Error on client and -D
o Fix local port binding on client to support both v4 and v6
o Fix more on use clock_gettime() over gettimeofday() when available
o Treat ENOBUFS as transient, i.e. don't exit on this error
o Python: add flows directory and skeleton flows code using asyncio
o Python: Support flows stats in dictionary for pandas

2.0.9 change set (as of June 2016)
----------------------------------
o Apply SO_SNDTIMEO for both UDP and TCP per both -t and -i
o Server (and listener) threads won't block forever when -t set (uses select() with non-blocking accept())
o Remove need for <cmath> to improve portability
o Fix report interval bug so single threaded mode no works
o Skeleton code for Python based flows which will be use Pythnon 3's asyncio module
o configure script check for struct tcp_info code fix and uses netinet/tcp.h

2.0.8 change set (as of 1/12/2015)
----------------------------------
o Fix portability, compile and test with Linux, Win10, Win7, WinXP, MacOS and Android
o Client now requires -u for UDP (no longer defaults to UDP with -b)
o Maintain legacy report formats
o Support for -e to get enhanced reports
o Support TCP rate limited streams (via the -b) using token bucket
o Support packets per second (UDP) via pps as units, (e.g. -b 1000pps)
o Display PPS in both client and server reports (UDP)
o Support realtime scheduler as a command line option (--realtime or -z)
o Improve client tx code path so actual tx offerred rate will converge to the -b value
o Improve accuracy of microsecond delay calls (in platform independent manner)
o (Use of Kalman filter to predict delay errors and adjust delays per predicted error)
o Display target loop time in initial client header (UDP)
o Fix final latency report sent from server to client (UDP)
o Include standard deviation in latency output
o Suppress unrealistic latency output (-/-/-/-)
o Support SO_SNDTIMEO on send so socket write won't block beyond -t (TCP)
o Use clock_gettime if available (preferred over gettimeofday())
o TCP write and error counts (TCP retries and CWND for linux)
o TCP read count, TCP read histogram (8 bins)
o Server will close the socket after -t seconds of no traffic

2.0.7 change set (rjmcmahon@rjmcmahon.com) August 2014
------------------------------------------------------
o Linux only version which supports end/end latency (assumes clocks synched)
o Support for smaller report interval  (5 milliseconds or greater)
o End/end latency with UDP (mean/min/max), display in milliseconds with resolution of microseconds
o Socket read timeouts (server only) so iperf reports occur regardless of no received packets
o Report timestamps now display millisecond resolution
o Local bind supports port value using colon as delimeter (-B 10.10.10.1:60001)
o Use linux realtime scheduler and packet level timestamps for improved latency accuracy
o Suggest PTP on client and server to synch clocks to microsecond
o Suggest a quality reference for the PTP grandmaster such as a GPS disciplined oscillator from companies like Spectracom


2.0.6 change set (rjmcmahon@rjmcmahon.com) March 2014
-----------------------------------------------------
o Increase the shared memory for report headers reducing mutex contention.  Needed to increase performance.  Minor code change that should be platform/os independent