DDNS is a term used for the updating in real time

Dynamic DNS or DDNS is a term used for the updating in real time of Internet Domain Name System (DNS) name servers to keep up to date the active DNS configuration of their configured hostnames, addresses and other information.The term is used in two contexts which, while what they do in technical terms is similar, have very different purposes and user populations.

The technically expert people who maintain the Internet, and those who are associated with domains, use networked devices, such as routers and computer systems using the Internet Protocol Suite, to keep DNS server information up to date for the proper functioning of the Internet, and uninterrupted access to devices and services whose numeric IP address may change. This process is dynamic DNS updating. The Secure DNS Update protocol discussed in RFC 2136 may be used.

Non-expert users of the Internet who connect to it via an Internet Service Provider (ISP) will be allocated a numeric IP address by the ISP; the address may either be stable ("static"), or may change from one session on the Internet to the next ("dynamic"). If it is necessary to be able to access the computer from another location, a numeric address is inconvenient to remember; an address which changes unpredictably makes connection impossible. For example, a user may need access to their home or office computer while travelling; if and only if its address is known it can be set up to be accessed over a VPN, or by a remote control program such as VNC server.

This could be accomplished with a name server, but setting one up is a complex task for the non-expert. Instead there are a number of providers, free of charge or for payment, of what is called a Dynamic DNS service. The DDNS provider allocates a static hostname to the user; whenever the user is allocated a new IP address this is communicated to the DDNS provider by proprietary software running on a computer at that address; the provider distributes the association between the hostname and the address to the Internet's DNS servers so that they may resolve DNS queries.

The ultimate result is that the traveller may communicate with the home system at, say myname.ddnsservice.org instead of an unknown set of four varying numbers; the host name is resolved to the current address of the home computer with a DNS query invisible to the user. The communication between the user's computer and the DDNS provider is not standardised, varying from one provider to another.

December 29, 2011

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