--- title: Project Calico Documentation description: Home layout: docwithnav canonical_url: 'https://docs.projectcalico.org/v3.5/introduction/' ---

Calico is a new approach to virtual networking and network security for containers, VMs, and bare metal services, that provides a rich set of security enforcement capabilities running on top of a highly scalable and efficient virtual network fabric. Calico includes pre-integration with Kubernetes and Mesos (as a CNI network plugin), Docker (as a libnetwork plugin) and OpenStack (as a Neutron plugin). Calico supports a broad range of deployment options including on premise or public cloud (AWS, GCE, etc) providing the same rich set of features across all.

Calico's network policy enforcement ensures that the only packets that flow to/from a workload are the ones the developer or operater expects. This is achieved by mapping high-level developer/operator intent to fully distributed ACLs running on every host. You can think of Calico as providing every workload with a fully automated virtual firewall to protect the workload and to protect the rest of your application should that workload become compromised. Calico automatically maps any network policy concepts from the orchetration envirnoment into Calico network policy. (For example, Calico was selected as the reference implementation of network policy for Kubernetes.) Calico network policy can also be specified using the Calico command line tools and APIs, either in place of or augmenting the policy concepts provided by the orchestration system.

Calico's highly scalable network fabric is built using the same principles as the internet - the most highly scaled network in existence. In contrast to most virtual networking solutions, Calico provides a flat IP network that can typically be run without any encapsulation (no overlays). The ability to run without an overlay provides exceptional throughput characteristics, and for large scale service operators makes diagnosing network connectivity issues a breeze. In addition Calico's network fabric also includes the ability to route packets using a stateless IP-in-IP overlay for any scenarios where an overlay network might be preferred.

Calico's network policy enforcement can also be combined with other virtual networking solutions. For example, the Canal project adds Calico policy enforcement to Flannel virtual networking. This exciting project brings rich network policy to Flannel users, and brings more network connectivity options to Calico users.