Secure dynamic anycasting for 'best' server selection using active networks
The networking community has tackled the resource-finding problem using several methods. The knowledge of the name or property of the resource enables one to find it over the network. Many techniques were proposed and investigated for a single instance of the resource. The Internet has experienced dramatic growth in the use and provision of services such as ftp, gopher, archie and World-Wide-Web. The heavy demands being placed on servers inspire replication (mirroring) of servers. This replication results in client intending to contact the 'best' server among many content-equivalent servers. The solutions that were used for the `best' server selection include multicast and broadcast communication to send request to all servers and choose the best one from all the replies. These solutions require the client to be powerful enough to handle all the replies, which may be overwhelming leading to client's machine getting hung. The other solution uses the name servers to provide a different unicast address for one member of a group of servers at different locations. The inherent disadvantage in this method is that the user is unable to choose the best server. The idea of application layer anycasting allows the user to select the best server according to the user's selection criteria. The main disadvantage of this scheme is that the client that does the selection may not be powerful to handle responses from all the content-equivalent servers. In this paper the idea of application layer anycasting has been extended by allowing the active routers to locate the best server. Active networks, unlike the traditional networks are not just passive carrier of bits but instead provides the capability for the user to inject customized programs into the networks that may modify, store or redirect the user data flowing through the network. Anycasting is done in the application level as it provides better end-to-end control, and there is no support in the network level. The choice of `best' server is done based on the first response from the servers. The active routers do the filtering of responses from laggards and the client gets the response only from the best server, thus the client machine is not overwhelmed by responses. The client deals with the vital issue of security with respect to Active networks by the use of various encryption schemes. Since the `best' server chosen is not always the best forever, a TTL value is associated with each of the best server found, and the best one is reselected after its expiry. The performance of the proposed scheme is compared with the networks without active networks and is found to provide better response time for requests. Further, the proposed scheme avoids the overloading of a server, jockeying, and reduces the overhead of the client in selecting the best server. The overhead on the routers in active networks is insignificant compared to the advantages accrued due to it. (C) 2001 Elsevier Science B.V. All rights reserved.
dynamic anycasting active networks multicasting unicasting best server active router