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# CORE Architecture
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* Table of Contents
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{:toc}
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## Main Components
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* core-daemon
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* Manages emulated sessions of nodes and links for a given network
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* Nodes are created using Linux namespaces
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* Links are created using Linux bridges and virtual ethernet peers
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* Packets sent over links are manipulated using traffic control
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* Controlled via the CORE GUI
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* Provides both a custom TLV API and gRPC API
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* Python program that leverages a small C binary for node creation
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* core-gui
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* GUI and daemon communicate over the custom TLV API
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* Drag and drop creation for nodes and links
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* Can launch terminals for emulated nodes in running sessions
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* Can save/open scenario files to recreate previous sessions
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* TCL/TK program
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* coresendmsg
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* Command line utility for sending TLV API messages to the core-daemon
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* vcmd
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* Command line utility for sending shell commands to nodes
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2018-07-31 20:57:30 +01:00
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2020-04-13 19:51:12 +01:00
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2018-07-31 20:57:30 +01:00
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## Sessions
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CORE can create and run multiple emulated sessions at once, below is an
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overview of the states a session will transition between during typical
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GUI interactions.
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2020-04-09 22:34:52 +01:00
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2018-07-31 20:57:30 +01:00
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## How Does it Work?
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The CORE framework runs on Linux and uses Linux namespacing for creating
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node containers. These nodes are linked together using Linux bridging and
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virtual interfaces. CORE sessions are a set of nodes and links operating
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together for a specific purpose.
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### Linux
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Linux network namespaces (also known as netns) is the primary
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technique used by CORE. Most recent Linux distributions have
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namespaces-enabled kernels out of the box. Each namespace has its own process
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environment and private network stack. Network namespaces share the same
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filesystem in CORE.
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CORE combines these namespaces with Linux Ethernet bridging to form networks.
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Link characteristics are applied using Linux Netem queuing disciplines.
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Nftables provides Ethernet frame filtering on Linux bridges. Wireless networks are
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emulated by controlling which interfaces can send and receive with nftables
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rules.
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## Prior Work
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The Tcl/Tk CORE GUI was originally derived from the open source
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[IMUNES](http://imunes.net) project from the University of Zagreb as a custom
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project within Boeing Research and Technology's Network Technology research
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group in 2004. Since then they have developed the CORE framework to use Linux
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namespacing, have developed a Python framework, and made numerous user and
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kernel-space developments, such as support for wireless networks, IPsec,
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distribute emulation, simulation integration, and more. The IMUNES project
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also consists of userspace and kernel components.
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## Open Source Project and Resources
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2020-04-09 22:34:52 +01:00
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CORE has been released by Boeing to the open source community under the BSD
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license. If you find CORE useful for your work, please contribute back to the
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project. Contributions can be as simple as reporting a bug, dropping a line of
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encouragement or technical suggestions to the mailing lists, or can also
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include submitting patches or maintaining aspects of the tool.
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