Calico represents a new approach to virtual networking, based on the same scalable IP networking principles as the Internet.

First established in enterprise data centers, virtual networking provides the logical fabric that enables workloads in virtual machines to communicate securely, ultimately over a shared physical fabric. Initially this was achieved by using VLANs; as that approach quickly hit well-known scalability limits, other techniques such as VXLAN, GRE-based tunnels and SDN controlled flows were taken. All of these approaches introduced greater complexity and ultimately hit scalability and performance limits inherent in extending an enterprise-class layer 2 network over large numbers of servers and wide area links.

A new approach is required. One that recognizes that the vast majority of today’s workloads are based on IP, and that leverages everything we already know about how to build high-performance, large-scale networks.

Enter Project Calico. With Calico, we went back to the drawing board and redesigned how virtual networks should be built, based on an intimate understanding of the requirements of modern workloads and virtualization environments.

Calico integrates seamlessly with the cloud orchestration system (such as OpenStack) to enable secure IP communication between virtual machines or containers. As VMs or containers are created or destroyed, their IP addresses are advertised to the rest of the network and they are able to send/receive data over IP just as they would with the native networking implementation – but with higher security, scalability and performance.

To get started on OpenStack follow the instructions here. To get started on Docker follow the instructions here.

Technical documentation is here. For information about contributing to Calico itself, see the section titled 'Contributing' below.

There are two options for getting support for Calico. You can simply get in contact and ask any question you like – there is an active group of users and developers who will usually try their best to help you or point you in the right direction. Or you can work with one of the commercial vendors and system integrators who provide installation, integration, customization and support services for Calico.

Currently, we are aware of the following vendors who provide commercial support services:

• Metaswitch Networks.

Please contact us if you are a vendor providing commercial support services and wish to be added to this list.

Project Calico was founded by Metaswitch Networks, who also contributed the original implementation to open source and are responsible for the ongoing management of the project. However, it is open to any members of the community – individuals or organizations – to get involved and contribute code.

Please contact us if you are interested in getting involved and contributing to the project.

Thanks for thinking about contributing to Project Calico! The success of an open source project is entirely down to the efforts of its contributors, so we do genuinely want to thank you for even thinking of contributing.

Before you do so, you should check out our contributing guidelines in the CONTRIBUTING.md file, to make sure it's as easy as possible for us to accept your contribution.

It's great that you're interested! In additional to being able to install Calico from packages, you can install the source directly. If you want to work on the code, we recommend installing the source directly in a Python virtual environment. In your virtual environment, switch to the directory containing the code and type:

pip install -e .

This will install the code and all its dependencies, except for Neutron or Docker dependencies. This is all you need to work on Felix. If you want to work on our OpenStack plugin, you'll also need to install Neutron: doing that is outside the scope of this article. If you want to work on Docker integration please see the calico-docker repo.

To run the unit tests, you'll also need to type:

pip install nose mock

Then, still at the root of the calico directory, run:

nosetests

If you only want to hack on one or two components you may not want to install the dependencies for the others. To do that, you can set the $CALICODEPS environment variable before installing the code. Set the variable to a comma-separated list of the names of the components you want to install the dependencies for.

For example, if you want to work on Felix, you will want to set it to felix. With that set, you can then run pip install -e ., which will install the subset of the dependencies needed for those components.