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Re: questions

  • To: Max Tulyev < >
  • From: Jim Reid < >
  • Date: Tue, 25 Nov 2003 09:53:57 +0000

>>>>> "Max" == Max Tulyev maxtul@localhost writes:

    >> You seem very confused. ENUM is a protocol for mapping E.164
    >> telephone numbers into domain names. That's all. The domain
    >> names resulting from that mapping can be looked up in the
    >> DNS. The answers from the DNS should (but don't have to be) a
    >> set of NAPTR records which describe how to contact that user in
    >> a variety of ways. These needn't necessarily be for
    >> telephony-like services such as the details of someone's chosen
    >> SIP server or IP address of their VoIP phone. NAPTR records
    >> could provide someone's email address or details of their web
    >> server or...

    Max> And can I use other type of records than NAPTR? For example,
    Max> TXT record to provide extra infromation about me, my name,
    Max> company, physical address, etc? 

Of course. The DNS does not place any restriction on which resource
record types may or may not exist for some name.

    Max> So when I do call to ENUM-enabled application, it looks up my
    Max> extra data and gives it to my peer with my phone number?

Probably not. Though in theory the application could do that if it has
prior knowledge that these other record types exist and contain that
sort of information. An ENUM-aware application will expect to process
NAPTR records, so it's unlikely to lookup other types of records for
an ENUM name. Or make sense of any TXT record (say) if such a thing
existed. How could the application know that this TXT record encoded a
postal address? Even harder would be determining what that postal
address was for or to do anything sensible with it.

So adding other record types to ENUM zones is possible. But it's not
likely to be useful. First of all, applications are very unlikely to
look up these additional records (or know they exist). Secondly the
information in those records could be so generic and and ad hoc -- eg
TXT records -- that it would be almost impossible to extract any
worthwhile meaning for them. Maybe your TXT records provide your name
and address while mine give my PGP and SSH keys?

By suggesting TXT records you help me make this comparison. I use RCS
on the zone files I manage. Each zone gets a TXT record containing the
RCS version string, a good DNS administrator practice. However, apart
from occasional troubleshooting by myself, nothing looks up these TXT
records. They're not needed for routine DNS operation and nothing
knows these TXT records exist or needs to look for them. Well I
suppose everyone on this list knows about these TXT records now... :-)

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