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Tutorial 1 - Wired Network

Overview

This tutorial will cover some use cases when using a wired 2 node scenario in CORE.

Files

Below is the list of files used for this tutorial.

  • 2 node wired scenario
    • scenario.xml
    • scenario.py
  • 2 node wired scenario, with n1 running the "Chat App Server" service
    • scenario_service.xml
    • scenario_service.py

Running this Tutorial

This section covers interactions that can be carried out for this scenario.

Our scenario has the following nodes and addresses:

  • n1 - 10.0.0.20
  • n2 - 10.0.0.21

All usages below assume a clean scenario start.

Using Ping

Using the command line utility ping can be a good way to verify connectivity between nodes in CORE.

  • Make sure the CORE daemon is running a terminal, if not already 
    sudop core-daemon
  • In another terminal run the GUI 
    core-gui
  • In the GUI menu bar select File->Open..., then navigate to and select scenario.xml

  • You can now click on the Start Session button to run the scenario

  • Open a terminal on n1 by double clicking it in the GUI
  • Run the following in n1 terminal 
    ping -c 3 10.0.0.21
  • You should see the following output 
    PING 10.0.0.21 (10.0.0.21) 56(84) bytes of data.
64 bytes from 10.0.0.21: icmp_seq=1 ttl=64 time=0.085 ms
64 bytes from 10.0.0.21: icmp_seq=2 ttl=64 time=0.079 ms
64 bytes from 10.0.0.21: icmp_seq=3 ttl=64 time=0.072 ms

--- 10.0.0.21 ping statistics ---
3 packets transmitted, 3 received, 0% packet loss, time 1999ms
rtt min/avg/max/mdev = 0.072/0.078/0.085/0.011 ms

Using Tcpdump

Using tcpdump can be very beneficial for examining a network. You can verify traffic being sent/received among many other uses.

  • Make sure the CORE daemon is running a terminal, if not already 
    sudop core-daemon
  • In another terminal run the GUI 
    core-gui
  • In the GUI menu bar select File->Open..., then navigate to and select scenario.xml

  • You can now click on the Start Session button to run the scenario

  • Open a terminal on n1 by double clicking it in the GUI
  • Open a terminal on n2 by double clicking it in the GUI
  • Run the following in n2 terminal 
    tcpdump -lenni eth0
  • Run the following in n1 terminal 
    ping -c 1 10.0.0.21
  • You should see the following in n2 terminal 
    tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on eth0, link-type EN10MB (Ethernet), capture size 262144 bytes
10:23:04.685292 00:00:00:aa:00:00 > 00:00:00:aa:00:01, ethertype IPv4 (0x0800), length 98: 10.0.0.20 > 10.0.0.21: ICMP echo request, id 67, seq 1, length 64
10:23:04.685329 00:00:00:aa:00:01 > 00:00:00:aa:00:00, ethertype IPv4 (0x0800), length 98: 10.0.0.21 > 10.0.0.20: ICMP echo reply, id 67, seq 1, length 64

Editing a Link

You can edit links between nodes in CORE to modify loss, delay, bandwidth, and more. This can be beneficial for understanding how software will behave in adverse conditions.

  • Make sure the CORE daemon is running a terminal, if not already 
    sudop core-daemon
  • In another terminal run the GUI 
    core-gui
  • In the GUI menu bar select File->Open..., then navigate to and select scenario.xml

  • You can now click on the Start Session button to run the scenario

  • Right click the link between n1 and n2
  • Select Configure

  • Update the loss to 25

  • Open a terminal on n1 by double clicking it in the GUI
  • Run the following in n1 terminal 
    ping -c 10 10.0.0.21
  • You should see something similar for the summary output, reflecting the change in loss 
    --- 10.0.0.21 ping statistics ---
10 packets transmitted, 6 received, 40% packet loss, time 9000ms
rtt min/avg/max/mdev = 0.077/0.093/0.108/0.016 ms
  • Remember that the loss above is compounded, since a ping and the loss applied occurs in both directions

Running Software

We will now leverage the installed Chat App software to stand up a server and client within the nodes of our scenario.

  • Make sure the CORE daemon is running a terminal, if not already 
    sudop core-daemon
  • In another terminal run the GUI 
    core-gui
  • In the GUI menu bar select File->Open..., then navigate to and select scenario.xml

  • You can now click on the Start Session button to run the scenario

  • Open a terminal on n1 by double clicking it in the GUI
  • Run the following in n1 terminal 
    export PATH=$PATH:/usr/local/bin
chatapp-server
  • Open a terminal on n2 by double clicking it in the GUI
  • Run the following in n2 terminal 
    export PATH=$PATH:/usr/local/bin
chatapp-client -a 10.0.0.20
  • You will see the following output in n1 terminal 
    chat server listening on: :9001
[server] 10.0.0.21:44362 joining
  • Type the following in n2 terminal and hit enter 
    hello world
  • You will see the following output in n1 terminal 
    chat server listening on: :9001
[server] 10.0.0.21:44362 joining
[10.0.0.21:44362] hello world

Tailing a Log

In this case we are using the service based scenario. This will automatically start and run the Chat App Server on n1 and log to a file. This case will demonstrate using tail -f to observe the output of running software.

  • Make sure the CORE daemon is running a terminal, if not already 
    sudop core-daemon
  • In another terminal run the GUI 
    core-gui
  • In the GUI menu bar select File->Open..., then navigate to and select scenario_service.xml

  • You can now click on the Start Session button to run the scenario

  • Open a terminal on n1 by double clicking it in the GUI
  • Run the following in n1 terminal 
    tail -f chatapp.log
  • Open a terminal on n2 by double clicking it in the GUI
  • Run the following in n2 terminal 
    export PATH=$PATH:/usr/local/bin
chatapp-client -a 10.0.0.20
  • You will see the following output in n1 terminal 
    chat server listening on: :9001
[server] 10.0.0.21:44362 joining
  • Type the following in n2 terminal and hit enter 
    hello world
  • You will see the following output in n1 terminal 
    chat server listening on: :9001
[server] 10.0.0.21:44362 joining
[10.0.0.21:44362] hello world

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