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quick pass with some doc cleanup and reformatting to fix various issues

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docs/architecture.md
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* CORE Daemon
* Manages emulation sessions
* Builds the emulated networks using kernel virtualization for nodes and some form of bridging and packet manipulation for virtual networks
* Nodes and networks come together via interfaces installed on nodes
* Builds the emulated networks using Linux namespaces for nodes and
some form of bridging and packet manipulation for virtual networks
* Nodes and networks come together via interfaces installed on nodes
* Controlled via the CORE GUI
* Written in python and can be scripted, given direct control of scenarios
* CORE GUI
* GUI and daemon communicate using a custom, asynchronous, sockets-based API, known as the CORE API
* GUI and daemon communicate using a custom, asynchronous, sockets-based
API, known as the CORE API
* Drag and drop creation for nodes and network interfaces
* Can launch terminals for emulated nodes in running scenarios
* Can save/open scenario files to recreate previous sessions
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![](static/core-architecture.jpg)
## Sessions
CORE can create and run multiple sessions at once, below is a high level
overview of the states a session will go between.
![](static/core-workflow.jpg)
## How Does it Work?
A CORE node is a lightweight virtual machine. The CORE framework runs on Linux. CORE uses Linux network namespace virtualization to build virtual nodes, and ties them together with virtual networks using Linux Ethernet bridging.
The CORE framework runs on Linux and uses Linux namespacing for creating
node containers. These nodes are linked together using Linux bridging and
virtual interfaces. CORE sessions are a set of nodes and links operating
together for a specific purpose.
### Linux
Linux network namespaces (also known as netns) is the primary virtualization technique used by CORE. Most recent Linux distributions have namespaces-enabled kernels out of the box. A namespace is created using the ```clone()``` system call. Each namespace has its own process environment and private network stack. Network namespaces share the same filesystem in CORE.
Linux network namespaces (also known as netns) is the primary virtualization
technique used by CORE. Most recent Linux distributions have
namespaces-enabled kernels out of the box. Each namespace has its own process
environment and private network stack. Network namespaces share the same
filesystem in CORE.
CORE combines these namespaces with Linux Ethernet bridging to form networks. Link characteristics are applied using Linux Netem queuing disciplines. Ebtables is Ethernet frame filtering on Linux bridges. Wireless networks are emulated by controlling which interfaces can send and receive with ebtables rules.
CORE combines these namespaces with Linux Ethernet bridging to form networks.
Link characteristics are applied using Linux Netem queuing disciplines.
Ebtables is Ethernet frame filtering on Linux bridges. Wireless networks are
emulated by controlling which interfaces can send and receive with ebtables
rules.
## Prior Work
The Tcl/Tk CORE GUI was originally derived from the open source [IMUNES](http://imunes.net) project from the University of Zagreb as a custom project within Boeing Research and Technology's Network Technology research group in 2004. Since then they have developed the CORE framework to use Linux virtualization, have developed a Python framework, and made numerous user- and kernel-space developments, such as support for wireless networks, IPsec, distribute emulation, simulation integration, and more. The IMUNES project also consists of userspace and kernel components.
The Tcl/Tk CORE GUI was originally derived from the open source
[IMUNES](http://imunes.net) project from the University of Zagreb as a custom
project within Boeing Research and Technology's Network Technology research
group in 2004. Since then they have developed the CORE framework to use Linux
virtualization, have developed a Python framework, and made numerous user and
kernel-space developments, such as support for wireless networks, IPsec,
distribute emulation, simulation integration, and more. The IMUNES project
also consists of userspace and kernel components.
## Open Source Project and Resources
CORE has been released by Boeing to the open source community under the BSD license. If you find CORE useful for your work, please contribute back to the project. Contributions can be as simple as reporting a bug, dropping a line of encouragement or technical suggestions to the mailing lists, or can also include submitting patches or maintaining aspects of the tool. For contributing to CORE, please visit [CORE GitHub](https://github.com/coreemu/core).
CORE has been released by Boeing to the open source community under the BSD
license. If you find CORE useful for your work, please contribute back to the
project. Contributions can be as simple as reporting a bug, dropping a line of
encouragement or technical suggestions to the mailing lists, or can also
include submitting patches or maintaining aspects of the tool.