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+---
+bookToc: false
+title: "UDP/IP with iperf3"
+weight: 3
+---
+
+# UDP/IP with iperf3
+
+[iperf3 goodput measurement tool](https://github.com/esnet/iperf)
+is used for measuring the maximum attainable goodput of the VPP Host
+Stack connection across two instances of VPP running on separate DUT
+nodes. iperf3 is a popular open source tool for active measurements
+of the maximum achievable goodput on IP networks.
+
+Because iperf3 utilizes the POSIX socket interface APIs, the current
+test configuration utilizes the LD_PRELOAD mechanism in the linux
+kernel to connect iperf3 to the VPP Host Stack using the VPP
+Communications Library (VCL) LD_PRELOAD library (libvcl_ldpreload.so).
+
+In the future, a forked version of iperf3 which has been modified to
+directly use the VCL application APIs may be added to determine the
+difference in performance of 'VCL Native' applications versus utilizing
+LD_PRELOAD which inherently has more overhead and other limitations.
+
+The test configuration is as follows:
+
+           DUT1              Network               DUT2
+    [ iperf3-client -> VPP1 ]=======[ VPP2 -> iperf3-server]
+
+where,
+
+1. iperf3 server attaches to VPP2 and LISTENs on VPP2:UDP port 5201.
+2. iperf3 client attaches to VPP1 and transmits one or more streams
+   of packets to VPP2:UDP port 5201.
+3. iperf3 client transmits a uni-directional stream as fast as the
+   VPP Host Stack allows to the iperf3 server for the test duration.
+4. At the end of the test the iperf3 client emits the goodput
+   measurements for all streams and the sum of all streams.
+
+Test cases include 1 and 10 Streams with a 20 second test duration
+with the VPP Host Stack using the UDP transport layer..
+
+Note: iperf3 is single threaded, so it is expected that the 10 stream
+test shows little or no performance improvement due to
+multi-thread/multi-core execution.