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CORE - Distributed Emulation
- Table of Contents {:toc}
Overview
A large emulation scenario can be deployed on multiple emulation servers and controlled by a single GUI. The GUI, representing the entire topology, can be run on one of the emulation servers or on a separate machine.
Each machine that will act as an emulation server would ideally have the same version of CORE installed. It is not important to have the GUI component but the CORE Python daemon core-daemon needs to be installed.
NOTE: The server that the GUI connects with is referred to as the master server.
Configuring Listen Address
First we need to configure the core-daemon on all servers to listen on an interface over the network. The simplest way would be updating the core configuration file to listen on all interfaces. Alternatively, configure it to listen to the specific interface you desire by supplying the correct address.
The listenaddr configuration should be set to the address of the interface that should receive CORE API control commands from the other servers; setting listenaddr = 0.0.0.0 causes the Python daemon to listen on all interfaces. CORE uses TCP port 4038 by default to communicate from the controlling machine (with GUI) to the emulation servers. Make sure that firewall rules are configured as necessary to allow this traffic.
# open configuration file
vi /etc/core/core.conf
# within core.conf
[core-daemon]
listenaddr = 0.0.0.0
Enabling Remote SSH Shells
Update GUI Terminal Program
Edit -> Preferences... -> Terminal program:
Currently recommend setting this to xterm -e as the default gnome-terminal will not work.
May need to install xterm if, not already installed.
sudo apt install xterm
Setup SSH
In order to easily open shells on the emulation servers, the servers should be running an SSH server, and public key login should be enabled. This is accomplished by generating an SSH key for your user on all servers being used for distributed emulation, if you do not already have one. Then copying your master server public key to the authorized_keys file on all other servers that will be used to help drive the distributed emulation. When double-clicking on a node during runtime, instead of opening a local shell, the GUI will attempt to SSH to the emulation server to run an interactive shell.
You need to have the same user defined on each server, since the user used for these remote shells is the same user that is running the CORE GUI.
# install openssh-server
sudo apt install openssh-server
# generate ssh if needed
ssh-keygen -o -t rsa -b 4096
# copy public key to authorized_keys file
ssh-copy-id user@server
# or
scp ~/.ssh/id_rsa.pub username@server:~/.ssh/authorized_keys
Add Emulation Servers in GUI
Within the core-gui navigate to menu option:
Session -> Emulation servers...
Within the dialog box presented, add or modify an existing server if present to use the name, address, and port for the a server you plan to use.
Server configurations are loaded and written to in a configuration file for the GUI.
~/.core/servers.conf
# name address port
server2 192.168.0.2 4038
Assigning Nodes
The user needs to assign nodes to emulation servers in the scenario. Making no assignment means the node will be emulated on the master server In the configuration window of every node, a drop-down box located between the Node name and the Image button will select the name of the emulation server. By default, this menu shows (none), indicating that the node will be emulated locally on the master. When entering Execute mode, the CORE GUI will deploy the node on its assigned emulation server.
Another way to assign emulation servers is to select one or more nodes using the select tool (shift-click to select multiple), and right-click one of the nodes and choose Assign to....
The CORE emulation servers dialog box may also be used to assign nodes to servers. The assigned server name appears in parenthesis next to the node name. To assign all nodes to one of the servers, click on the server name and then the all nodes button. Servers that have assigned nodes are shown in blue in the server list. Another option is to first select a subset of nodes, then open the CORE emulation servers box and use the selected nodes button.
IMPORTANT: Leave the nodes unassigned if they are to be run on the master server. Do not explicitly assign the nodes to the master server.
GUI Visualization
If there is a link between two nodes residing on different servers, the GUI will draw the link with a dashed line.
Concerns and Limitations
Wireless nodes, i.e. those connected to a WLAN node, can be assigned to different emulation servers and participate in the same wireless network only if an EMANE model is used for the WLAN. The basic range model does not work across multiple servers due to the Linux bridging and ebtables rules that are used.
NOTE: The basic range wireless model does not support distributed emulation, but EMANE does.
When nodes are linked across servers core-daemons will automatically create necessary tunnels between the nodes when executed. Care should be taken to arrange the topology such that the number of tunnels is minimized. The tunnels carry data between servers to connect nodes as specified in the topology. These tunnels are created using GRE tunneling, similar to the Tunnel Tool.
EMANE Configuration and Issues
EMANE needs to have controlnet configured in core.conf in order to startup correctly. The names before the addresses need to match the servers configured in ~/.core/servers.conf previously.
controlnet = core1:172.16.1.0/24 core2:172.16.2.0/24 core3:172.16.3.0/24 core4:172.16.4.0/24 core5:172.16.5.0/24
EMANE appears to require location events for nodes to be sync'ed across all EMANE instances for nodes to find each other. Using an EMANE eel file for your scenario can help clear this up, which might be desired anyway.
You can also move nodes within the GUI to help trigger location events from CORE when the core.conf settings below is used. Assuming the nodes did not find each other by default and you are not using an eel file.
emane_event_generate = True
Distributed Checklist
- Install the same version of the CORE daemon on all servers.
- Set listenaddr configuration in all of the server's core.conf files, then start (or restart) the daemon.
- Installed and configure public-key SSH access on all servers (if you want to use double-click shells or Widgets.)
- Assign nodes to desired servers, empty for master server
- Press the Start button to launch the distributed emulation.