Final answer:
To authenticate communication between cluster nodes, a 'shared secret' or 'cluster secret' is used as an authentication attribute to secure communication and prevent unauthorized access.
Step-by-step explanation:
The attribute used to authenticate communication between cluster nodes is commonly referred to as a 'shared secret' or 'cluster secret'. This is a key or token that is shared amongst all the nodes in a cluster to ensure that communication between them is secure. The shared secret is used in various authentication mechanisms, such as challenge-response or certificate-based authentication, to verify the identity of a node before allowing communication. This process helps to prevent unauthorized access and ensures that the data being transferred is from a trusted source within the cluster.