Skip to main content

Enough addresses?

I moved to Brussels to work from our office here at the start of August. One of the things I’d normally do when moving is working out which ISP to buy a service from. I haven’t done that yet because ‘Internet’ access is bundled along with the rent, water and electricity charges for my apartment.

What is delivered is very fast access with an RFC 1918 address. That’s an address from a range that’s been set aside for use on private networks, like the one shared by all the apartments in my building. Private addresses are widely used, and most home networks use them with a NAT to share a unique, public IPv4 address.

NAT isn’t perfect and some services don’t work well behind one, but on the whole it works reasonably well and most people don’t notice it. But because I want to do what so many people do – and have several computers share one connection – I have had to place my own NAT behind the apartment building’s NAT. And now some of the things that worked when I used a single NAT in my old place don’t work in my new place.

Some of the VoIP software I use doesn’t work in the new apartment and nor does FTP. These aren’t insurmountable problems and there are workarounds but it is a little awkward.

I suppose my landlord could ask the ISP for enough addresses to assign one to each apartment in the building. And there is nothing stopping the ISP from assigning the addresses on his request. But in a few years from now there might not be enough addresses available. Less than one fifth of the IPv4 address space remains in IANA’s free pool, waiting to be allocated. The Internet is growing fast and the free pool is shrinking.

Soon the options for new home networks might only be double NAT or IPv6. I’m not sure which will win out because I’m using double NAT and it works reasonably well for most applications. The building’s ISP has IPv6 addresses but they don’t seem to be announcing them to other ISPs yet. Maybe they will. Maybe my apartment building will get IPv6 addresses in a couple of years. And maybe double NAT is good enough.


    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"""" is not an IDN."