iperf: add page (#2059)

pages/common/iperf.md

@@ -0,0 +1,15 @@
+# iperf
+
+> Measure network bandwidth between computers.
+
+- Run on server:
+
+`iperf -s`
+
+- Run on client:
+
+`iperf -c {{server_address}}`
+
+- Run on client with 5 parallel threads:
+
+`iperf -c {{server_address}} -P {{5}}`