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Diacritic (sign)

Sign (accent, cedilla, apostrophe, etc.) on a letter, or a phonetic sign, used to change its value. For domain names with diacritic signs you can read our page dedicated to IDNs.


Diacritic sign

See: Diacritic.


Distributed Denial of Service (dDoS)

Attacks are an elaborate form of DoS that involve thousands of computers generally as part of a botnet or robot network: a network of zombie computers that the attacker commandeers from their unwitting owners by spreading malware from one machine to another.



Domain Name System (or Service):

Distributed database used to register Internet resources (computer, router, etc.) as a domain name (e.g. and to allocate them an IP address.

This address is returned to the browser in response to a connection request by the domain name.

See: Illustrated diagram "DNS, Domains and Zones tree structure" — PDF (54 kb) or GIF (20 kb)


DNS or name server (NS)

Server used to host the software and data required to map IP addresses and domain names for the computers under its authority and Internet resources.  A DNS server has two main functions:

— translating into an IP address the name of the servers within its scope of authority

— if none corresponds, forwarding the request to a DNS server with authority

There are three categories of DNS servers: primary, secondary and recursive.



Domain Name System Security Extensions

Extension of the secure DNS protocol whose function is to guarantee the identity of the root domain (e.g. .fr) and the integrity of DNS records in order to prevent any malicious insertion or modification of erroneous DNS data.

Read our dedicated page to DNSSEC



Refers to a set of resources or services available via the Internet or within a local network with a common root name (e.g. "") based on a tree structure.


Domain name

Proper or generic name or a combination of words used to uniquely identify, but easily remember a resource such as a website or server. Each domain name corresponds to the IP address of the server hosting the resource. This correspondence is ensured by Domain Name Servers (DNS). Used by all the services (web, email, etc.), a domain name consists of a sequence of characters (A through Z, 0 through 9 and the hyphen) and a suffix, the TLD. The latter is either generic (".net.", ".com", ".org") or geographic (".fr", ".re", ".it", ".ch").