How do those Dynamic DNS servers work for dial in accounts?

[Robert Chalmers]

I've come across organisations that provide Dynamic IP/DNS services for users who are not online a lot. Somehow they recognise the caller through a link with somesoftware, and assign them an IP, which gives them full duplex internet access. www.24Link.com is one that comes to mind, or I think dynadns . not sure of its name, but anyway. I'm curious to know how such a thing works, and if it's possible to set something like that up. If one had a crew in the field, it might be a very handy thing.

Sorry if this is one of theose areas I should know about ..

Thanks for any ideas anyone has on the subject

cheers
Robert