When planning a nameserver deployment, one of the decisions in architecture is whether to go with a unicast or anycast deployment.
In a unicast architecture, each nameserver correlates (logically) to a single-server POP on a single IP address. I say logically because that Point-of-Presence (POP) may be a group of servers, behind load balancers or other traffic-shaping devices. Also, it is possible that the POP will be multi-homed and thus answer on multiple IP addresses, including multiple IPv4 addresses and IPv6. Take a look at the diagram:
Figure 12-1: unicast nameserver scenarios, each POP has its own IP
Contrast this with an anycast constellation, where nodes in multiple POPs across geographically diverse locations correlate to the same IP address.Take a look at this diagram:
Figure 12-2: Anycast nameserver deployment, multiple POPs respond to the...