US Patent 9112919 Secure network address translation (NAT) port block allocation

A node is configured to receive, from a second node, a request to establish a session; perform, in response to the request, a network address translation (NAT) operation to establish the session, the NAT operation causing a first port block to be allocated to the session, the first port block including a first set of ports via which traffic, associated with the session, is transported; determine that the set of ports are no longer available for the session; determine whether a quantity of times that the first port block has been allocated to the session is greater than a threshold; and retain the first port block, for the session, when the quantity of times that the first port block has been allocated to the session is not greater than the threshold.