Anycast Distributed Service Model And Distributed Tunnel Broker System

This paper studies distributed service model based on anycast. It also designs andimplements a distributed tunnel broker system with this service model.The TCP/IP-based Internet supports three communication paradigms: unicast,multicast and anycast. Anycast features one-to-one-of-many communicationcapability, and it is very useful for deploying distributed services. However, currentlyanycast is utilized in the way that only one anycast address is used to provide serviceson all the server nodes, in which case routing system or server node failure will easilylead to service blackhole. This paper proves the necessity of simultaneously utilizingmultiple anycast addresses and discusses the principles for determining the number ofanycast addresses to use. It also provides an algorithm to get the best way of utilizinga fixed set of anycast addresses and analyzes its time complexity. To meet the needsof deploying large scale distributed services, this paper designs several easy-to-getand reasonably-well schemes of utilizing multiple anycast addresses. It also discussesbackup system design for anycast-based distributed services.IPv6 is the next generation IP. In the transition from IPv4 to IPv6 there will bemany IPv6 nodes separated by IPv4 routers. Tunnel broker could provide virtual dial-up services to connect the separated IPv6 nodes to large IPv6 networks, which makesit extremely helpful for IPv6 deployment. However, traditional tunnel brokers allprovide centralized services that are not optimized when many users are scattered inlarge areas, and they could not serve IPv6 nodes behind NAT gateways because theyuse IPv6/IPv4 tunneling. This paper designs a distributed tunnel broker system basedon anycast, which is able to provide optimized service to all the scattered users evenwhen some server nodes are down. It also adopts a new IPv6/UDPv4 tunnelingscheme that makes it able to serve IPv6 nodes behind NAT gateways.This paper also finishes a prototype implementation of the distributed tunnelbroker system, which has been providing test service.