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The TCP/IP Guide  9  TCP/IP Application Layer Protocols, Services and Applications (OSI Layers 5, 6 and 7)       9  Name Systems and TCP/IP Name Registration and Name Resolution            9  TCP/IP Name Systems: Host Tables and Domain Name System (DNS)                 9  TCP/IP Domain Name System (DNS)                      9  DNS Name Servers and Name Resolution

DNS Name Server Enhancements: DNS Notify, Incremental Zone Transfers, and DNS Update (Dynamic DNS) 1 DNS Resolver Functions and General Operation

In the preceding three sections, I have described the Domain Name System's name space, authority and registration mechanism, and name servers. These elements can all be considered part of the infrastructure of DNS; they are the parts of the system that must be established first to enable it to be used. Once we have these components in place, we can actually get down to the business at hand: name resolution. This is accomplished using a specific set of procedures carried out by DNS clients called resolvers.

In this section I describe DNS name resolvers and the process of name resolution itself. I begin with an overview of the functions performed by DNS resolvers and how they work in general terms. I then describe the two fundamental methods of name resolution used in DNS: iterative and recursive resolution. I discuss the way that resolvers improve efficiency through local resolution and caching. I describe the steps in the actual name resolution algorithm. I then cover two special cases of name resolution: reverse name resolution using the special IN-ADDR.ARPA domain, and the way that DNS provides mail support using Mail Exchange resource records.

DNS Name Server Enhancements: DNS Notify, Incremental Zone Transfers, and DNS Update (Dynamic DNS) 1 DNS Resolver Functions and General Operation