Static Name-to-Address Policy

The simplest method for a policy to select replica addresses is to always return the first $n$ addresses from the list. This method does not differ from what a typical DNS server does. Basically, it returns all the site addresses it knows. The fact that it may ignore an exceeding number of addresses (as it only returns a certain number of them, even if the list of addresses is very long) does not change anything - it still gives the same response each time it is queried (see Figure 4.1).

Figure 4.1: The static policy always returns the same addresses

The reason for including this straightforward address selection method is very simple. The main purpose of the redirector is to support domains containing replicated services. However, these domains may also contain machines that host non-replicated services for which the static name-to-address mapping is good enough. Making the redirector capable of servicing such machines as well increases its flexibility. We will also see later in this chapter that this policy also serves as a fallback if more advanced policies fail to return a list of replicas.