Measuring Network Performance

This wiki page contains the tutorial of measuring network performance.


Artur Minakhmetov, Telecom Paris : artur.minakhmetov[at]
Michael Sherman, Rutgers University : msherman[at]

Last Updated: 26 June 2019


Cosmos test-bed provides a set of different network interfaces with different speed and rates. In this tutorial we will show how to measure the network performance.


This tutorial is based on topology and settings described in the optical network tutorial.

This example includes a server srv4-lg1 with connected to it tengigabitethernet 1/34 and joined with twentyFiveGigE 1/¼ on vlan 124. Binding tengigabitethernet 1/32 with twentyFiveGigE 1/¼ is performed the same way as in the optical network tutorial.

The server srv4-lg1 has an IP address assigned to it on eno1 interface.

For simplicity, the Calient Switch S320 connects tengigabitethernet 1/34 with tengigabitethernet 1/32/1 through direct optical connection: 5.7.4←→5.7.6


Measurements are preformed through a command line tool iperf. Examples and descriptions of its operation could be found here.

  • Set srv1-lg1 as a server:
native@srv1-lg1:~$ iperf -s   
Server listening on TCP port 5001
TCP window size: 85.3 KByte (default)
  • Set srv4-lg1 as a client with sending traffic to srv1-lg1:
native@srv4-lg1:~$ iperf -c   
Client connecting to, TCP port 5001
TCP window size: 85.0 KByte (default)
[  3] local port 35486 connected with port 5001
[ ID] Interval       Transfer     Bandwidth
[  3]  0.0-10.0 sec  11.0 GBytes  9.42 Gbits/sec
  • This measurement shows that the it's possible to have 9.42 Gbits/sec of bandwidth.
  • Previous measurement creates a TCP connection. In order to test UDP traffic, a bitrate of UDP traffic has to be specified through and option -b. UDP traffic is specified through an option -u. Results of UDP traffic test are below :

Server side:

native@srv1-lg1:~$ iperf -s -u
Server listening on UDP port 5001
Receiving 1470 byte datagrams
UDP buffer size:  208 KByte (default)

Client side:

native@srv4-lg1:~$ iperf -c -u -b 9gbps
Client connecting to, UDP port 5001
Sending 1470 byte datagrams, IPG target: 1.31 us (kalman adjust)
UDP buffer size:  208 KByte (default)
[  3] local port 33737 connected with port 5001
[ ID] Interval       Transfer     Bandwidth
[  3]  0.0-10.0 sec  9.77 GBytes  8.39 Gbits/sec
[  3] Sent 7134255 datagrams
[  3] Server Report:
[  3]  0.0-10.0 sec  9.30 GBytes  7.99 Gbits/sec   0.000 ms 342498/7134255 (0%)
  • UDP traffic measurements show possible bandwidth of 7.99 Gbits/sec. This result could be ameliorated through specific settings potentially.


In this tutorial we showed how it's possible to measure network performance and verify 10Gbit possibilities of optical transceivers achieving 9.42 Gbits/sec for TCP traffic and 7.99 Gbits/sec for UDP traffic.

Last modified 3 months ago Last modified on May 11, 2020, 12:47:54 AM
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