DNS was initially deployed on four physical root servers, running on PDP-10 mainframe computers, in the mid-1980s.
Three different organizations ran these four servers:
• SRI International managed one DNS root server using JEEVES.
• Information Sciences Institute managed two DNS servers using JEEVES.
• The Ballistic Research Laboratory of the U.S. Army managed one server using Bind.
JEEVES was the first DNS server developed; Bind was developed quickly afterward. Bind is still available as an open-source application. In the early 2000s, management of the root domain was transferred to the Internet Assigned Numbers Authority (IANA), and the number of root servers expanded to 13, as shown in Table 16-3.
Table 16-3 Root Server Operators
Note
The j root was initially operated by a company called Network Solutions. Verisign acquired
Network Solutions in 2000, taking on responsibility for the j root in addition to the a root.
Since the 2000s, the DNS ecosystem has expanded to meet the seemingly ever-expanding Internet, but there are still only 13 root servers. How do these 13 servers support the millions of DNS queries sent to root servers daily?
Root servers are no longer single servers; each root server address represents a service, with thousands of servers supporting each service. Figure 16-6 shows a map of the root server instances in Singapore.
Figure 16-6 Root Server Sites Around Singapore
In Figure 16-6, there are
• Three sites with instances of A.
• One site with an instance of B.
• One site with an instance of C.
• Two sites with instances of D.
• Four sites with instances of E.
• Three sites with instances of F.
• One site with an instance of I.
• Three sites with instances of J.
• One site with an instance of L.
• One site with an instance of M.
Not every zone runs a site in every city, but the zones are represented worldwide. Each site also might have more than one instance; one of the f sites in Singapore has two instances.
Each instance is physically located in a different facility, with different power sources, connections to the Internet, etc.
DNS’s root zone is a highly distributed and resilient system, which is good because it is one of the principal foundations of the global Internet.
TLD Servers
A background in how domain names are distributed and managed is required to understand who operates TLD servers.
IANA does not manage individual domain names. If you want a domain name, do not look on IANA’s website. Instead:
• IANA allocates the management of a TLD to an organization.
• TLD owners allocate management of the domain names within the TLD to one or more registrars.
• Registrars sell individual domain names to hosting companies and domain name management companies, who then resell individual domain names to users.
This complex chain of interactions allows for each organization to control their part of the DNS system independently of the others, with the following implications:
• IANA has no control over how domain names are assigned and managed beyond some basic rules required to acquire a
TLD.
• Each TLD owner manages how domains are registered while
not directly controlling the assignment of individual domain names.
• Resellers, like hosting companies and domain name management companies, offer registration services for many different TLDs.
TLD servers are operated and managed by TLD owners.