Discussion List for Freenum/ITAD Subscriber Number (ISN) Project

[John Todd <>]

On Nov 21, 2010, at 5:39 PM, Ross Lindsay wrote:

> Hi all,
> Am I missing something or can you not route different calls (XXXX*YYYY) 
> where the XXXX differs to a different destination than others? Ex: Route 
> 1111*1111 to extension 1111 on Server A, but send 1112*1111 to extension 
> 123 on server A?
> Let me know if I need to clarify. 
> Thanks!
> Ross Lindsay


I see there's been some discussion on this while I was away for dinner.  :-)

The answer is: YES!  And not in the ways that the other folks here have 
identified, though using the protocol level stuff with SIP would also work.  
The more scalable way (the DNS way) is baked into the ISN dialing methods, 
but almost nobody uses it because it's over on the "sophisticated" end of the 
spectrum that most organizations don't require.

It is possible for each SUBSCRIBER number to have their own SIP NAPTR 
records.  That means you can make each subscriber number go wherever you want 
- you could have this:

1112*1111 maps to 
sip:
1113*1111 maps to 
sip:
1114*1111 maps to 
sip:

So, how does one go about this?  Well, there is some pain involved.  The pain 
is that you'll have to give up the easy life of letting the freenum.org 
servers carry a wildcard for all your subscriber numbers that does the same 
thing.  Almost everyone (though not quite _everyone_) simply puts a regular 
expression string in the freenum.org servers for their ITAD that says (in 
meta-speak): "Re-write all my ISN queries in the freenum.org domain under my 
ITAD so that the subscriber portion is slapped into the front of a plain old 
SIP URI that points to <subscribernumber>@mydomain.net"

For instance, when someone looks up the NAPTRs for 1234*256, they get this:

empty-zot:~ jtodd$ dig +short NAPTR 4.3.2.1.256.freenum.org.
100 10 "u" "E2U+iax2" "!^\\+*([^\\*]*)!iax2:@204.91.156.10/\\1!" .
100 10 "u" "E2U+web:http:" "!^.*$!http://www.loligo.com/!"; .
100 10 "u" "E2U+sip" 
"!^\\+*([^\\*]*)!sip:\\!"
 .
empty-zot:~ jtodd$ 

So, their server takes the SIP regular expression from that list, applies 
regexp magic on it, and ends up with:

 
sip:

as the final answer.  Presto, they attempt a connection on that SIP URI 
through the regular SIP methods.  The ITAD 256 has a wildcard that does this 
for EVERY lookup in *.256.freenum.org.  This is the lazy and normal way to 
have entries in the Freenum database/DNS zone, because most organizations 
only have one external SIP server (or at least, they only have one policy 
that applies to all users even if they have multiple priorities and weights 
in the list of NAPTR records they hand back.)

What YOU want to do is delegate your ITAD (1340) to your own nameservers and 
split up the subscriber portion so that each subscriber has their OWN record 
instead of using the wildcard method.  This can be done via the FAAST web 
interface by selecting "DNS -> Delegated" and then specifying your two 
nameservers.  You would then create a zone called "1340.freenum.org" on YOUR 
nameservers, and populate it with a lot of records like this:


2.1.1.1  IN NAPTR 100 10 "u" "E2U+sip" 
"!^\\+*([^\\*]*)!sip:!"
 
3.1.1.1  IN NAPTR 100 10 "u" "E2U+sip" 
"!^\\+*([^\\*]*)!sip:!"
 
4.1.1.1  IN NAPTR 100 10 "u" "E2U+sip" 
"!^\\+*([^\\*]*)!sip:!"
 

These say "take a ISN-style number and... well... er, ignore everything and 
just use this URI I give back to you."

This method allows for darn near infinite scaling down to each individual 
subscriber, and subscriber number space can be delegated on number boundaries 
even further, if your organization needs that kind of administrative control 
and segmentation.  We require delegating the zone to your nameservers if you 
aren't using the wildcard method, since the Freenum project doesn't have the 
tools to do true DNS administration, plus this is not something we really 
want to put ourselves in the business of managing.  If you know enough about 
the DNS, then you'd probably want to do this yourself anyway.

Good luck!  I'm happy to answer more questions on this if it isn't clear.

JT


---
John Todd - Advocate - 

ISN: 2203*256       tel: +1-301-561-1020