James points out that there are 80 million fax terminals, none of which have alpha keyboards but only have numeric keyboards. The address must handle the telephone number case, and that it was argued that at least we should handle telephone number addressing and maybe subaddressing. The phone system considers the location of the switches and gateways as private information. Keith says that putting the relay name in the address has had a lot of problems in mail relays. In a perfect world, what goes in the address, you put the address of the recipient fax machine.
Many providers consider the actual position of the secrets.
Phone number is a universal address space that is shared by everyone, but you're allowed to specify a service provider. Keith proposed a possibility that there be two possibilities, one of which is a provider-less address, and one of which specifies a provider. This syntax is compatible with the URL syntax for absolute and relative addressing, rather than another syntax which wouldn't be URL-compatible. There were a number of suggestions for looking up other standards that might provide an extended syntax for telephone numbers. At least in the room, lots of people think a fax URL is useful.