Protocol between two SMSCs in the following deployments?

[nagesh.kumar]

Hi Experts,

Please could you clarify the following?

When an SMS is sent by User A, it reaches User A's SMSC and the SMS is transferred to User B's SMSC, which in turn
delivers to User B. What is the protocol used between SMSCs in typical GSM deployments under the following scenarios?

1. When a SMS is sent between two GSM network segments belonging to the same operator? Is it SMPP or SS7 or it can
    be any thing? What is typically used? (Here the assumption is that there are two SMSCs for both of the network segments.)

2. When a SMS is sent between two GSM network segments belonging to the "different" operators? Is it SMPP or SS7 or it can
    be any thing? What is typically used? (Here the assumption is that there are two SMSCs for both of the network segments.)
 
3. When a SMS is sent between two network segments of different technologies? Is it SMPP only or is there any other protocol that
    is typically used?

I am aware that SMPP can be used for all the above-mentioned deployments. However, I would like to get inputs on what is
the typical protocol used in most of the actual deployments?

Thanks in advance for your time.

Regards
Nagesh

[dineshonsms]

Hi Nagesh,

There is no other protocol apart from ss7 and smpp(Application protocol like cimd,EMI , etc.)  for interoperability between two smsc.

Once i had used smpp to communicate between cdma smsc and gsm smsc for same network area.



Thx

[parasa]

In GSM communication happens between SMSC and MSC (Where mobile is latched) over GSMMAP layer of SS7 protocol.

in CDMA network there are chances that SMSC communicate with other SMSC and might happen via IS41 of SS7 or protocols like SMPP/CIMD/UCP. As SMPP is widely accepted it is preffered.

GSM - GSM.
Same operator : MAP on SS7.
Different operator : MAP on SS7.

CDMA-CDMA
Same operator : IS41 on SS7.
Different operator : SMPP (TCP/IP).

GSM - CDMA
Interworking gateway. Is vendor specific.

[nagesh.kumar]

Hi Parasa Kiran,

Thanks for your reply. Please could you clarify the following doubt too in GSM context?

I assume that in case of inter-technology SMSC communication, typically SMPP is used.

Assuming an SMSC supports both SS7 and SMPP (the former is required to communicate with another operator's SMSC of same technology and the latter is required to talk to another operator's SMSC of a different technology), how does a given SMSC determine which one to use when it receives a SMS from
a mobile?

In other words, can SMSCs be configured to use SS7 for certain ranges of destination numbers
and use SMPP for another range of destination numbers?

Is the above mechanism applicable for CDMA technology too?


Thanks a lot for your time and help in clarifying the same.

Regards
Nagesh

[parasa]

SMPP and SS7 are different and are used for different functionality.

SS7 is used for terminating/receving messages from the network. So SMSC uses ss7 while interacting with the network. In case of CDMA it uses IS41 over ss7/sigtran and in case of GSM is uses MAP over ss7/sigtran.

Now usually there is separate SMSC for these networks. In CDMA it becomes bit more complex as SMSCs in CDMA network handle only local subscribers.

SMPP acts as bridge between SMSCs to exchange cross platform messages.

Some SMSCs are strong enough to handle the cross platform transactions over SS7 itself.

So the interoperability solutions depends more on operators requirement and vendor's design.

[nagesh.kumar]

Hi Parasa,

Thanks for your comments. I think I put my question in a cryptic way (Sorry for that!) and I
have elaborated my question as below. Please share your comments. I appreciate your help.

In the below call-flows, I assumed that SMSC has co-located SMS-IWMSC and SMS-GMSC
functionalities with it.

1. When User A and User B are served by the same operator and same SMSC, the call-flow would
 be as shown below.

User A ----> MSC (User A) ------> SMSC (User A) -----> MSC (User B)----> User B.

Here, SMSC (on receiving SMS from User A destined for User B) recognizes that the User B
is also served by it and hence checks with HLR to know whether User B is currently available
and forwards he SMS to MSC (User B) using MAP.

2. When User A and User B are served by different operators (and hence difference SMSCs), the
call-flow would be as shown below.

User A ----> MSC (User A) ------> SMSC (User A) ----->SMSC (User B)------> MSC (User B)----> User B.

Here, SMSC (on receiving SMS from User A destined for User B) recognizes that the User B
is NOT served by it and hence forwards to SMSC (User B) using MAP. (As per your clarification this would
be MAP). SMSC (User B) would deliver it to User B as appropriate.

3. When User A and User B are served by different operators and of different technologies (and hence difference SMSCs), the call-flow would be as shown below.

User A ----> MSC (User A) ------> SMSC (User A) ----->SMSC (User B)------> MSC (User B)----> User B.

Here, SMSC (on receiving SMS from User A destined for User B) recognizes that the User B
is NOT served by it and hence forwards to SMSC (User B) using SMPP. (Since this inter-technology SMS transfer between two SMSCs, it would be SMPP). SMSC (User B) would deliver it to User B as appropriate.


Now following are the clarications I would request:

1. How does SMSC (User A) know whether it shall query HLR (Scenaro 1), forward to another SMSC using MAP (Scenario 2) and forward to another SMSC using SMPP (Scenario 3)?
    Is it based on some configuration at SMSC that for some range of numbers - use HLR, another range  use MAP, another range of numbers - use SMPP etc.

2. In Scenario 2, what is the exact MAP message is it MAP_MO_ForwardShortMessage or MAP_MT_ForwardShortMessage ()?

Thanks a lot in advance for clarifying these.

Regards
Nagesh

[parasa]

2. When User A and User B are served by different operators (and hence difference SMSCs), the
call-flow would be as shown below.

User A ----> MSC (User A) ------> SMSC (User A) ----->SMSC (User B)------> MSC (User B)----> User B.

Here, SMSC (on receiving SMS from User A destined for User B) recognizes that the User B
is NOT served by it and hence forwards to SMSC (User B) using MAP. (As per your clarification this would
be MAP). SMSC (User B) would deliver it to User B as appropriate.

  ---- Wrong.

Check the following ::
GSM
User A ----> MSC (User A) ------> SMSC (User A) ---(SRI, FSM)-->MSC (User B)----> User B.

CDMA Local numbers
User A ----> MSC (User A) ------> SMSC (User A) -----(SMSReq, SMDPP) ----->MSC (User B)----> User B.

CDMA other Operators or GSM - CDMA
User A ----> MSC (User A) ------> SMSC (User A) ---(Number analysis)(SMPP)-->SMSC (User B)------> MSC (User B)----> User B.

    Is it based on some configuration at SMSC that for some range of numbers - use HLR, another range  use MAP, another range of numbers - use SMPP etc.

-- When u are sending message to HLR it has to be via MAP.
Yes the routing of messages across SMSC happens on the basis of number analysis.

2. In Scenario 2, what is the exact MAP message is it MAP_MO_ForwardShortMessage or MAP_MT_ForwardShortMessage ()?

---- For Mobile orginated message it would be MAP_MO_ForwardShortMessage , for termination on mobile it is MAP_MT_ForwardShortMessage

Regards

[nagesh.kumar]

Hi Parasa,

Thanks for the clarification. Please bear with me and allow me to ask one last question on this topic.

Are you mentioning that in GSM Network (when User A and User B are supported by two different
network operators), SMSC of User A (which is in originating network) will query HLR of User B (which
is in a different network) and forward to Visited MSC (which is in a different network) directly? Do
operators allow their HLRs to be queried by other network's SMSCs?

How does SMSC (User A) know the HLR address of User B to perform SRI, in such a case? Would this be
configured at SMSC (User A)? (This might multiple ranges as well as the associated HLRs to be configured).

My understading may be wrong, I just wanted to double check.

Thanks once again.

Regards
Nagesh

[parasa]

yes in GSM the orginator's SMSC (Home network SMSC) queries the HLR of the destination subscriber. And the SRI is routed using a routing strategy widely known as GT routing.

By the way may I know where are you working ? Thats a personal question though but wanted to know as a similar set of question were asked to me earlier too..

[nagesh.kumar]

Hi Parasa,

Thanks for the clarification. Sorry for being sticky on this issue:

Do SMSCs never need to communicate with each other in GSM domain? This would imply that a foreign
operator's SMSC might end up storing SMSs for a subscriber, when he is not reachable.

Thanks once again.

Regards
Nagesh

PS> I have sent a personal mail to you regarding my details. Thanks.

[parasa]

Do SMSCs never need to communicate with each other in GSM domain? This would imply that a foreign
operator's SMSC might end up storing SMSs for a subscriber, when he is not reachable.

Thats the advantage the operator wants to give to his subscribers.

--Parasa Kiran

[nagesh.kumar]

OK. Got it. Thanks.

Regards
Nagesh