[asterisk-biz] Mobile extensions from Asterisk - HLR registration?

[Trixter aka Bret McDanel]

On Wed, 2009-05-20 at 11:00 -0400, John Todd wrote:
> I've posed this question in person to people with some frequency over  
> the last few years, and the answer has always been "No, I don't know  
> of such a service." but I'll try on the list and see what I get.
> 
> I think it would be a great asset to the Asterisk community to have a  
> service provider (let's call them "SP-A") who is a mobile carrier who  
> offered the following method: if I register a SIP entity with their  
> servers, they would then register with the HLR of my mobile carrier  
> ("SP-B") and act as if I was roaming into a mobile network operated  
> by  SP-A. 

so similar to truphone.com except that you have to get the number from
them (or port in) and they become your carrier, when you have GSM
service you use that, when you have SIP it goes that way, and they even
do a hot handoff of a live call or something.  I havent used them just
heard about them.

truphone may bring some "bad blood" into the discussion since it uses
freeswitch.org and there are some on this list that get livid when that
is mentioned, but they have been doing this for several years now on a
freeswitch platform.

As for registering the roaming stuff, that becomes more difficult, you
have to have SS7 connectivity with a SS7 stack with the MAP extensions.
You also have to have a roaming agreement and honestly there is no
incentive for the mobile carriers to allow this, so its a hard sell.  It
also screws up their fraud detection algorithms in that you have
multiple phones registered on the same account, sure they could change
this, but why change it to allow competition? Its easier to do it the
other way around, which is what truphone does.

truphone is geared more towards a mobile phone, use sip when its
available otherwise use the GSM network, and not "give priority to a sip
registered device otherwise failover to the mobile phone".  


> This would, I believe, quickly make Asterisk a roaming-capable  
> solution for mobile devices.

except that without realtime routing updates it can get into a confused
state.  What if your expire time is 3600 seconds, which seems common for
many devices, although NAT can lower that to 20 seconds if the device
does keepalives in a way that works.  


you could also make it 'roaming' by giving out 1 number that goes to
your asterisk box that then concurrently rings your sip device and your
mobile and whomever answers first gets the call.  The trick is that your
outbound caller id would be wrong if you did not first call your
asterisk box to place the call, although GSM uses a modified Q.931 stack
which might allow a clever person a way around this.


>  I have faith that Asterisk  
> developers and administrators would descend upon this type of service  
> like locusts.


do you have faith in the mobile carriers to allow this?  To interconnect
their SS7 networks when they dont have to?  To modify their fraud
detection algorithms to not freak out and lock the account when there
are 2 registered devices?  




> Potential problems: what if my mobile phone is registered with SP-A or  
> some other provider already?  Who gets the messages?  How do HLRs  
> manage multi-registration conflicts?
> 
generally they say "ut oh this cant happen so it must be a cloned phone"
and a trigger is fired off to lock the account.  Many HLR
implementations also do not allow for multiple registrations by
different devices since in theory that should never happen.  How
companies like tmobile that does a sip handoff deal with it is to do it
in the routing part and not in the HLR part, so that when a call is
placed to your number they see that you are registered via SIP and give
that priority, failing over to the actual mobile.

-- 
Trixter http://www.0xdecafbad.com     Bret McDanel
pgp key: http://pgp.mit.edu:11371/pks/lookup?op=get&search=0x8AE5C721