Abstract: A method of operating a cluster of machines includes receiving a request for a disruption, determining a subset of machines of the cluster affected by the requested disruption, and determining a set of jobs having corresponding tasks on the affected machines. The method also includes computing a drain time for a drain that drains the tasks of the jobs from the affected machines, and scheduling on a drain calendar stored in non-transitory memory a drain interval for the drain. The drain interval has a start time and an end time. A maintenance system that includes a scheduler may execute such a method to maintain a cluster of machines.

Abstract: A method for tracing packets in a communications network directed to tracing a stream of anonymous packets received at a given target host, in order to identify their source, in response, for example, to a Denial-of-Service (“DoS”) attack on the target host. Advantageously, the tracing is performed without reliance on knowledge or cooperation from intervening Internet Service Providers (ISPs) along the path. The method is performed by applying a “burst load” (i.e., a brief but heavy load of transmitted packets) to various elements (i.e., links or routers) in the network and measuring the change in the rate with which the stream of packets arrive at the target. If the rate is substantially altered upon introduction of the burst load, then it may be deduced that the given element is most likely on the path from the source host of the DoS attack to the target host.

Abstract: A method and apparatus for analyzing the perimeter security of communications networks. More particularly, information is identified which defines a particular communications network, e.g., an intranet, and identifying the connected hosts thereto. Utilizing such information, a determination is made with respect to identifying the routes that define the network. Utilizing the routing information, the connectivity of the hosts within the network, e.g., an intranet, is probed to ascertain the integrity of the network and thereby identifying potential security risks across the perimeter defense of the network.

Abstract: A method for tracing packets in a communications network directed to tracing a stream of anonymous packets received at a given target host, in order to identify their source, in response, for example, to a Denial-of-Service (“DoS”) attack on the target host. Advantageously, the tracing is performed without reliance on knowledge or cooperation from intervening Internet Service Providers (ISPs) along the path. The method is performed by applying a “burst load” (i.e., a brief but heavy load of transmitted packets) to various elements (i.e., links or routers) in the network and measuring the change in the rate with which the stream of packets arrive at the target. If the rate is substantially altered upon introduction of the burst load, then it may be deduced that the given element is most likely on the path from the source host of the DoS attack to the target host.