Boian, Ivan,

In response to your last two questions...

·         If [this switching function isn't supported], is there a simple way 
it could be added? - Yes, I think there are several possible ways.

o   I think the best way is to use ENUM.  For any all-numeric SIP URI, sprout 
does an ENUM lookup (a DNS NAPTR query) and applies the resulting regular 
expression.  You could build an ENUM server and configure it to return the 
corresponding alphanumeric SIP URI for each PSTN SIP URI.  Our ENUM support is 
described in more detail at 
https://github.com/Metaswitch/clearwater-docs/wiki/ENUM.  I would suggest first 
testing this out using bind or dnsmasq and static configuration - while we're 
pretty sure ENUM will work, we haven't tested it and this should be a low-cost 
way of doing so.  Once you're confident ENUM works, you could then move to 
using a DNS server such as PowerDNS, for which you can write custom back-ends 
(http://doc.powerdns.com/html/backends-detail.html) - this would mean that you 
could pull the mapping data from Homestead or your HSS on demand, rather than 
requiring static configuration files.

o   If ENUM doesn't work, you could configure call diversion (using the basic 
MMTEL AS function built into sprout) from the PSTN URI to the alphanumeric URI. 
 This is easy but has a few drawbacks:

§  sprout will send "181 Call being forwarded" notifications, which the caller 
will see

§  sprout will add "History-Info" headers, which the called party will see

§  you won't be able to use the call diversion service on the PSTN URI for 
anything else, although you will still be able to use it on the alphanumeric URI

§  you end up mastering your data in two places.

o   If neither of the approaches above work for you, you could write a simple 
application server.  There are two possible approaches here.

§  You could write a stateless proxy that just modifies the headers you need.  
You would insert this at the beginning of the IFCs for the PSTN URI.  If you 
did this, you'd need to keep the PSTN and alphanumeric URIs' IFCs in sync, as 
all processing would actually be done in the context of the PSTN URI's IFCs.

§  You could write a stateful proxy that actually redirects the call.  This 
would restart IFC processing, so only the first application server in the PSTN 
URI's IFCs would be hit and then, after the redirect, all the application 
servers in the alphanumeric URI's IFCs be hit.

o   (It could also be implemented in sprout itself, as a separate lookup, but I 
can't see any real benefits to this over the ENUM approach.)

·         Is Rf interface will be be supported in near future on I/S-CSCF? - 
Sprout doesn't currently support the RF interface, but we're planning to add 
this function.  We don't have a firm timescale yet as we're still working 
through the details of what's required, but we're aiming to have a better view 
on this in the next month or so.

Please let me know what you think about the possible approaches (in particular 
ENUM), and let me know if you have any questions.

Thanks,

Matt

From: Matt Williams
Sent: 07 June 2013 14:35
To: [email protected]
Subject: RE: [Clearwater] URI switching

Boian, (and Ivan,)

It's good to hear from you.

I can answer your first two questions, but I'll need to have a think and ask 
around about the latter two.

·         Is this HSS config with 2 URIs supported? - Not in the 
currently-released code, but we're working on it.  We're aiming to have 
multiple PSTN URIs working in the next few weeks, and then have alphanumeric 
URIs too not long after.

·         Is this switching function supported? - No.  (In answer to your 
follow-on question, there are solutions to this, but I'm checking which will be 
simplest and work best.)

I'll aim to get back to you on Monday about the remaining two questions.

Thanks,

Matt

From: [email protected] 
[mailto:[email protected]] On Behalf Of Boian 
Jordanov
Sent: 06 June 2013 22:18
To: [email protected]
Subject: [Clearwater] URI switching

Hi there,

I'm from a European mobile operator, and we are looking at Clearwater as a 
serious replacement for our current IMS core.  We're currently using some 
function in that core which isn't in the 3GPP IMS specs and I'm wondering if it 
is supported in Clearwater.

In our HSS, a subscriber with a certain service has 2 SIP URIs configured (with 
implicit registration).  One contains their PSTN ID, the other is an 
alphanumeric one internal to our service.  If both these URIs are present, when 
the S-CSCF receives an INVITE for that subscriber addressed to the PSTN URI, it 
removes the PSTN URI and replaces it with the internal one before passing the 
INVITE to any app servers.

So:
Is this HSS config with 2 URIs supported?
Is this switching function supported?
If not, is there a simple way it could be added?
And Last but not least. Is Rf interface will be supported in near feature on 
I/S-CSCF ?

Thanks,


Best Regards,
Boian Jordanov
Head of Voice Engineering


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