| Popis: |
Managing complex networks while ensuring that certain high level goals such as security are met is a complicated process. This is evidenced by the recent Internet outages caused by operators misconfiguring BGP routers. Clearly, there is a growing need to separate the high level goals/policies from the low level mechanisms that implement the various services. We propose a declarative framework for specifying and enforcing high level policies in networks. The declarative framework offers flexibility in terms of specifying the higher level goals rather than focusing on the lower level mechanisms employed in the implementation, and robustness in terms of recovering from failure. One of the key building blocks of our framework is to allow applications to expose their semantics, thereby allowing the underlying network to exploit the semantics and provide better-than-best-effort service where possible. Our framework employs semantic web languages such as OWL and RDF to formally express application and network specifications, and thereby leverages the inherent reasoning and conflict resolution capabilities of these languages. Once the applications and networks are formally specified in our framework, operators can write adaptation policies to jointly adapt the application and network layers in response to changing network conditions. We demonstrate our approach by applying it to a variety of diverse problems in network configuration and management. Our experiments with video over wireless show that the joint adaptation provides higher performance compared to no adaptation as well as application/network layer alone adaptation. Furthermore, the adaptation policies are easy to express in our framework and can be dynamically changed at run time. We also show how our framework can be used to automatically configure BGP routers. High level organizational routing policies can be captured in our framework through appropriate ontological specifications. These specifications which can then be checked for correctness are automatically compiled into appropriate low level BGP configurations by our framework and installed on the routers. Furthermore, the logical basis of our specifications enables reasoning, and routers can engage in an argumentation with their neighbors to diagnose and recover from routing misconfigurations through policy controlled reconfigurations. In cases where the argumentation protocol does not converge or the reconfiguration needed is not permitted by policy, the network administrator is alerted along with a log of the argumentation protocol executed so far, helping in isolating the location and cause of failure. |
