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Unit of information transport over IP networks. Whatever its size, the information is segmented into packets, each being enveloped (or encapsulated) in a "header", indicating in particular the address of the sender and recipient and control information about the integrity of the data carried.



Public Key Infrastructure

Set of hardware, software and procedures that can be used to create, manage and distribute digital certificates attesting to the formal identity of the bearer, whether it is a computer resource or an individual.



Numerical identifier defined by the TCP protocol enabling a computer to establish and manage, on a single IP address, multiple simultaneous connections with remote computers. Mail and FTP download servers use this feature by specifying port 25 or 21 after the domain name of the resource contacted.




Primary server

One of the three specific roles allocated to a DNS server

A server is said to be primary for a zone when it obtains the information for the zone in a configuration file. The file in question is written by an administrator.

The primary server has 'authority' for the zone.



Convention specifying the technical rules and specifications to be respected in the telecommunications sector to ensure interoperability between systems. Numerous protocols have become standardised (i.e. have obtained national or international recognition).

The value of a protocol is that it defines methods for exchanging information, independent of the hardware used to do so. Once the protocol has been defined, each terminal, client or server develops the protocol regardless of the other computers using it.


Provider (Internet service)

A provider may offer several types of Internet-related services such as access to the Internet, the registration of domain names, the hosting of domain names on its servers, the management of email addresses, the allocation of server space to host web pages, etc.

Providers do not all offer all of the services listed above.

In addition, the services may be purchased separately from each other or be a "package" offer.

Note: an Internet service provider is not necessarily an ISP or a registrar!