Skip to main content

There are not 13 root servers

I am at the UN Internet Governance Forum, being held this week in Rio de Janeiro, Brazil. A recurring theme you can hear here is one that has vexed the technical community many times before — “Why are there 13 root servers?” This question is usually followed by questions like “Why are most of the root servers in the US?”

So let’s dispel these myths.

There are not 13 root servers.

What there are is there are many hundreds of root servers at over 130 physical locations in many different countries. There are twelve organisations responsible for the overall coordination of the management of these servers.

So where does the 13 number come from?

There is a technical design limitation that means thirteen is a practical maximum to the number of named authorities in the delegation data for the root zone. These named authorities are listed alphabetically, from a.root-servers.net through m.root-servers.net. Each has associated with it an IP address (and shortly some will have more than one as IPv6 is further rolled out).

But when we think of servers, we probably think of physical machines that sit on a desk, or perhaps lined up in racks in a specialised computing facility. By any measure, there are not 13 servers as there is not a correlation between the number of named authorities, and the number of servers.

The majority of named authorities are spread across multiple cities, often multiple countries. The “I” root, for example, is located in 25 different countries. But ignoring the physical diversity, even those authorities that are just in one physical location — the reality is they are comprised of networks of multiple servers that handle the millions of DNS queries the root servers receive every hour.

Another thing you may hear is that some of these root servers are just copies, whilst others are the “real” name servers. The reality is that every single root server is a copy, and none of them are more special than the others. In fact, the true master server from which the copies are made is not one of the public root servers.

So next time you hear there are 13 root servers, or that they are mostly in the US, just remember this map, courtesy of Patrik Fältström:

Map of Root Servers

Comments

    Domain Name System
    Internationalized Domain Name ,IDN,"IDNs are domain names that include characters used in the local representation of languages that are not written with the twenty-six letters of the basic Latin alphabet ""a-z"". An IDN can contain Latin letters with diacritical marks, as required by many European languages, or may consist of characters from non-Latin scripts such as Arabic or Chinese. Many languages also use other types of digits than the European ""0-9"". The basic Latin alphabet together with the European-Arabic digits are, for the purpose of domain names, termed ""ASCII characters"" (ASCII = American Standard Code for Information Interchange). These are also included in the broader range of ""Unicode characters"" that provides the basis for IDNs. The ""hostname rule"" requires that all domain names of the type under consideration here are stored in the DNS using only the ASCII characters listed above, with the one further addition of the hyphen ""-"". The Unicode form of an IDN therefore requires special encoding before it is entered into the DNS. The following terminology is used when distinguishing between these forms: A domain name consists of a series of ""labels"" (separated by ""dots""). The ASCII form of an IDN label is termed an ""A-label"". All operations defined in the DNS protocol use A-labels exclusively. The Unicode form, which a user expects to be displayed, is termed a ""U-label"". The difference may be illustrated with the Hindi word for ""test"" — परीका — appearing here as a U-label would (in the Devanagari script). A special form of ""ASCII compatible encoding"" (abbreviated ACE) is applied to this to produce the corresponding A-label: xn--11b5bs1di. A domain name that only includes ASCII letters, digits, and hyphens is termed an ""LDH label"". Although the definitions of A-labels and LDH-labels overlap, a name consisting exclusively of LDH labels, such as""icann.org"" is not an IDN."