*:ref:`Linux` CORE uses Linux network namespace virtualization to build virtual nodes, and ties them together with virtual networks using Linux Ethernet bridging.
*:ref:`FreeBSD` CORE uses jails with a network stack virtualization kernel option to build virtual nodes, and ties them together with virtual networks using BSD's Netgraph system.
.._Linux:
Linux
-----
Linux network namespaces (also known as netns, LXC, or `Linux containers
<http://lxc.sourceforge.net/>`_) is the primary virtualization
technique used by CORE. LXC has been part of the mainline Linux kernel since
2.6.24. Recent Linux distributions such as Fedora and Ubuntu have
namespaces-enabled kernels out of the box, so the kernel does not need to be
patched or recompiled.
A namespace is created using the ``clone()`` system call. Similar
to the BSD jails, each namespace has its own process environment and private
network stack. Network namespaces share the same filesystem in CORE.
..index::
single: Linux; bridging
single: Linux; networking
single: ebtables
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.
.._FreeBSD:
FreeBSD
-------
..index::
single: FreeBSD; Network stack virtualization
single: FreeBSD; jails
single: FreeBSD; vimages
FreeBSD jails provide an isolated process space, a virtual environment for
running programs. Starting with FreeBSD 8.0, a new `vimage` kernel option
extends BSD jails so that each jail can have its own virtual network stack --
its own networking variables such as addresses, interfaces, routes, counters,
protocol state, socket information, etc. The existing networking algorithms and
*`CORE supplemental website <http://code.google.com/p/coreemu/>`_ - supplemental Google Code page with a quickstart guide, wiki, bug tracker, and screenshots.
..index::
single: wiki
single: CORE; wiki
The `CORE wiki <http://code.google.com/p/coreemu/wiki/Home>`_ is a good place to check for the latest documentation and tips.
Goals
-----
These are the Goals of the CORE project; they are similar to what we consider to be the :ref:`key features <Introduction>`.
#. Ease of use - In a few clicks the user should have a running network.
#. Efficiency and scalability - A node is more lightweight than a full virtual machine. Tens of nodes should be possible on a standard laptop computer.
#. Networking - CORE is focused on emulating networks and offers various ways to connect the running emulation with real or simulated networks.
#. Hackable - The source code is available and easy to understand and modify.
Non-Goals
---------
This is a list of Non-Goals, specific things that people may be interested in but are not areas that we will pursue.
#. Reinventing the wheel - Where possible, CORE reuses existing open source components such as virtualization, Netgraph, netem, bridging, Quagga, etc.
#. 1,000,000 nodes - While the goal of CORE is to provide efficient, scalable network emulation, there is no set goal of N number of nodes. There are realistic limits on what a machine can handle as its resources are divided amongst virtual nodes. We will continue to make things more efficient and let the user determine the right number of nodes based on available hardware and the activities each node is performing.
#. Solves every problem - CORE is about emulating networking layers 3-7 using virtual network stacks in the Linux or FreeBSD operating systems.
#. Hardware-specific - CORE itself is not an instantiation of hardware, a testbed, or a specific laboratory setup; it should run on commodity laptop and desktop PCs, in addition to high-end server hardware.
