Overview
Big picture​
Secure cross-cluster connections with identity-aware network policy, and federate services for cross-cluster service discovery.
Utilize Calico Cloud to establish cross-cluster connectivity.
Value​
At some point in your Kubernetes journey, you may have applications that need to access services and workloads running in another cluster.
By default, pods can only communicate with pods within the same cluster. Additionally, services and network policy only select pods from within the same cluster. Calico Cloud can help overcome these barriers by forming a cluster mesh the following features:
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Federated endpoint identity
Allow a local Kubernetes cluster to include the workload endpoints (pods) and host endpoints of a remote cluster in the calculation of local network policies applied on each node of the local cluster.
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Federated services
Enable a local Kubernetes Service to populate with Endpoints selected from both local cluster and remote cluster Services.
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Multi-cluster networking
Establish an overlay network between clusters to provide cross-cluster connectivity with Calico Cloud.
Concepts​
Pod IP routability​
Calico Cloud cluster mesh is implemented at Kubernetes at the network layer, based on pod IPs.
Taking advantage of federated workload endpoint identity and federated services requires that pod IPs are routable between clusters. This is because identity-aware network policy requires source and destination pod IPs to be preserved to establish pod identity. Additionally, the Endpoint IPs of pods selected by a federated Service must be routable in order for that Service to be of value.
You can utilize Calico Cloud multi-cluster networking to establish pod IP routability between clusters via overlay. Alternatively, you can manually set up pod IP routability between clusters without encapsulation (e.g. VPC routing, BGP routing).
Federated endpoint identity​
Federated endpoint identity in a cluster mesh allows a local Kubernetes cluster to include the workload endpoints (pods) and host endpoints of a remote cluster in the calculation of the local policies for each node, e.g. Cluster A network policy allows its application pods to talk to database pods in Cluster B.
This feature does not federate network policies; policies from a remote cluster are not applied to the endpoints on the local cluster, and the policy from the local cluster is rendered only locally and applied to the local endpoints.
Federated services​
Federated services in a cluster mesh works with federated endpoint identity, providing cross-cluster service discovery for a local cluster. If you have an existing service discovery mechanism, this feature is optional.
Federated services use the Tigera Federated Services Controller to federate all Kubernetes endpoints (workload and host endpoints) across all of the clusters. The Federated Services Controller accesses service and endpoints data in the remote clusters directly through the Kubernetes API.