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Goals Coarse ("unbalanced") distribution of load across nodes, to allow infrastructure to scale to increased numbers of queries and to accommodate transient query peaks Mitigation of non-distributed denial of service attacks by localizing damage to single anycast nodes Constraint of distributed denial of service attacks or flash crowds to local regions around anycast nodes (perhaps restricting query traffic to local peering links, rather than paid transit circuits) Triangulation of traffic sources, in the case of attack (or query) traffic which incorporates spoofed source addresses Improvement of query response time, by reducing the network RTT between client and server with the provision of a local Anycast Node Reduction of a list of servers to a single, distributed address. For example, a large number of authoritative nameservers for a zone may be deployed using a small set of anycast service addresses; this approach can increase the accessibility of zone data in the DNS without increasing the size of a referral response from a parent nameserver. |