Understanding IP Anycast

In this paper we present the first detailed analysis of IP anycast as used in the anycasting of the root-servers. The main results of our study are: The anycasting of an IP prefix does not have any unfavorable interactions with the routing system. Hence, IP anycast offers very good affinity2 - this alleviates concerns regarding running connection oriented services on top of anycast. IP Anycast, by itself, does not offer proximity in terms of metrics such as latency. IP Anycast's backwards compatibility derives from the fact that it is transparent to existing routing protocols, but this transparency also implies that in many cases inter-domain routing, which was designed with unicast path-selection in mind, chooses anycast locations which are not close to the source. We also present deployment schemes 1the problems include scalability by the number of anycast groups, difficulty of deployment etc.; these have restricted the use of IP anycast to critical infrastructure services 2tendency of subsequent packets of a connection to be delivered to the same target that might allow anycast to achieve good latency based proximit