An Active Node Architecture for Proactive Services

We propose an active node architecture that supports proactive services able to take into account adaptability to varying conditions and exible supervision by the application or the user. Proactive services are software modules that can be deployed in the network at chosen nodes. Each service processes ows of packets forwarded by a node. A packet lter recognizes some packets according to the information in the packet header and passes them to the right proactive service. Intercepting packets can be activated and disabled dynamically, so that there is no overhead for forwarding packets that do not require active processing. Association of a proactive service with the packet lter is also dynamic. Services are adaptable with respect to the environment of the active node by means of monitors, which gather information from probes and notify services about the current state of the active node, links, or other network resources. We have prototyped the active node for proactive services on Linux. Each proactive service runs as a user space process. We have modi ed the Net lter module in the Linux kernel so that it delivers matching packets directly to the right user process without passing by a multiplexer daemon. Measures of packet forwarding show that deviating packets to the user space for processing incurs a slight overhead, however it only concerns data ows that require speci c processing by proactive services.