Re: I-D Action: New draft - draft-bellis-enum-send-n-00

Paul Kyzivat said:
> This would be good *if* we could be assured that there would be enough 
> public ENUM entries to define the endpoint of all dial strings.

No. If there aren't any end-point records in the relevant tree, then it
doesn't matter whether send-n gives you the right answer or not.

Suppose that a particular numbering plan has numbers of the form:
    123456x
    123457xx
If it was fully populated with end-user records, then:
    at the 5 node, there would be a record send-n/2-3
    at the 6 node, there would be a record send-n/1-1
    at the 7 node, there would be a record send-n/2-2
Now suppose that the only public ENUM entry in this tree is for 1234568.
It doesn't matter whether the entry at the 5 node says send-n/2-2 or
send-n/2-3. If it says the former, then after dialling 1234579, the device
will look for records and get none back even though the wrong number of
digits have been dialled. But even if it waited for the next digit, that
wouldn't help.

In the converse case where the only records are for 123457xx, the entry at
the 5 node might say send-n/3-3. This is slightly more problematic if the
user dials 1234560, but *only* if you're using the ENUM database to
determine when to stop accepting digits. In this situation, you need to
ensure that the send-n records are correct or be prepared to timeout
dialling.

Ray, it might be worth adding something on this point of using the data to
determine when a number is complete even though there are no records in
the tree.

> I guess each device must at least know how to get to the country level. 
> After that, there ought to at least be one of these entries for the 
> country code. For each country there ought to be either a fixed length 
> or a range. If a range, then there ought to be an entry for each string 
> of length equal to the minimum of the range, which narrows it down.

True. However, in reality a device might have received more than the
minimum number of digits before querying. So you need to fill in the gaps
as well.

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