Inter-process communication within OpenStack is facilitated via message queueing services. Today, three messaging service backends are supported: RabbitMQ Qpid ZeroMQ Both RabbitMQ and Qpid are Advanced Message Queuing Protocol (AMQP) frameworks which provide message queues for peer-to-peer communication. Queue implementations are typically deployed as centralized or decentralized pool of queue servers. ZeroMQ differs by communicating directly using TCP sockets between peers. Message queues effectively facilitate command and control functions across OpenStack deployments. Once access to the queue is permitted no further authorization checks are performed. Services accessible via the queue do validate the contexts and tokens within the actual message payload. However, awareness of the token's expiration value should be noted as these tokens are potentially replayable and may provide authorization for other services within the infrastructure. OpenStack does not support message-level confidence (i.e., message signing). Because of this, the message transport itself must be secured and authentication to the queue server must be performed. For HA configurations, queue to queue authentication and encryption should to be performed as well. With ZeroMQ messaging, IPC sockets are used on individual machines. These sockets may be vulnerable to attack for local message injection and snooping unless secured by an operator.