Who plays RBT ?

[ssc]

When customer from network A dials a number of Network B than I suppose the RBT (ringback tone )is played by network B? right or wrong?

can there be any cases or parameters in SS7 connection which specify that the ringing tone is to be played by netwok A itself ?

[filius]

There is not one lone parameter in any protocol I know to accommodate this.

You can however, use an scp and inap/camel to get the rbt played from an eip/srf.

[bu4man]

Originally Posted by ssc

When customer from network A dials a number of Network B than I suppose the RBT (ringback tone )is played by network B? right or wrong?

can there be any cases or parameters in SS7 connection which specify that the ringing tone is to be played by netwok A itself ?

This is part of ISUP protocol. Switch A send ISUP IAM messages with Circuit Identity Code inside it. This CIC is a reference number of voice channel. Once swich B answers with ACM (Address Complete Message), it starts playing RBT into voice channel with allocated CIC.

[ssc]

Originally Posted by bu4man

This is part of ISUP protocol. Switch A send ISUP IAM messages with Circuit Identity Code inside it. This CIC is a reference number of voice channel. Once swich B answers with ACM (Address Complete Message), it starts playing RBT into voice channel with allocated CIC.

Thanks
and what about the case when some announcemment has to be played?
like If call goes from Network A to Network B but the user in Network B is powered off than how is it decided that from which the network the announcent telling that user powerd-off will be played

I am asking this, as I have seem variable behaviour, like there are some cases when you hear the announcemet from network A that user is off and in some cases from network B

[bu4man]

Originally Posted by ssc

Thanks
and what about the case when some announcemment has to be played?
like If call goes from Network A to Network B but the user in Network B is powered off than how is it decided that from which the network the announcent telling that user powerd-off will be played

When user is powered off - then "Not reachable" announcement is played by B-network. Call always "goes" to network B, where GMSC tries to find subscriber (route call to MSC, where subscriber was registered last time). If subscriber doesn't answer on paging request, then remote switch plays announcement and disconnects call.
If you heard A-network announcement, then, I suppose, subscriber was registered in network A (e.g. national roaming enabled, Number portability, etc). Otherwise, don't know how this might happens - I'm not guru of GSM yet

[ssc]

thanks
that was very helpful, you already seem to be a guru I wonder what can be more than that
one more thing,
what happend in case when call orginates and terminates within the same GSM network

it the sunscriber is powered off than who plays the announcement? t he priginating MSC or the terminating MSC ?

I think that in that case the announcement is just played by originating MSC, as when MSC will querey HLR and find that number is not registered than there is no need to carry the call to terminating MSC
what you think?

[bu4man]

Originally Posted by ssc

what happend in case when call orginates and terminates within the same GSM network
if the subscriber is powered off than who plays the announcement? the originating MSC or the terminating MSC ?
I think that in that case the announcement is just played by originating MSC, as when MSC will querey HLR and find that number is not registered than there is no need to carry the call to terminating MSC
what you think?

As far as I remember, in classical GSM network, all MT calls are processed by GMSC. Switch A sends ISUP IAM to GMSC in it's own network and then GMSC tries to find where B-number is.
If subscriber already marked as unreachable in HLR (IMSI detached), then GMSC will play announcement.
In some modern networks all MSCs have GMSC functionality. So MSC A can get subscriber's state from HLR (using MAP sendRoutingInfo request) and then either play announcement (in case of IMSI detached) or route call to MSC B (using MSRN which will be received in sendRoutingInfo response). In second case, MSC B will try to find subscriber in all cells using paging request. And if it's not answering on paging, then nothing to do - announcement will be played by MSC B. After this announcement MSC B will update HLR that IMSI isn't reachable anymore.

[ssc]

thanks, what you said makes sense and is understandable
we can safely say that If a CIC has been allocatted between MSCA and MSCB than any announcements will be played by MSCB, if there has not no CIC allocation than announcement playing will be done by MSC A