Overview

You wish to know how SMSC processes the SRI-SM request for Concatenated SMS. For instance, does it send only 1 SRI-SM Request  for concatenated SMS, regardless of the number of SMS parts? 

Solution

SRI-SM for concatenated messages could depend on the routing path and how the message is being handled.

• For messages handled via the AMS, if MMS (More messages to send) is enabled, RTR will keep the result of the previous SRI-SM in memory for a definitive time and based on that will either re-use the SRI-Response information or perform another SRI. It also depends on the TCAP dialog as detailed below.
  
  The following describes the behavior of RTR for managing SRI-SMs for concatenated messages when MMS (More messages to send) = TRUE, and there are more than 1 message in the AMS for the same recipient:
  
  
  • RTR normally stores and keeps the SRI-Response for 3 seconds (after which the previous sorted result shall be cleared and there will be another SRI-SM Request sent out for the same recipient when attempting delivery from the AMS).
  • However under specific conditions, the storage of the SRI-response can be extended by another 3 seconds.
  • If the TCAP dialog is open with the MSC (TCAP Continue scenario) and MTFSM Ack is received then the stored SRI-SM response is extended for another 3 seconds.
    
    So, the timing of the AO, followed by timing of SRI/MT, could affect the behavior of the SRI-Sm for concatenated messages

• It is not mandatory to have MMS flag for concatenated messages, however in such cases, there are a few observations:
  
  
  • If the MMS flag is not set, the Lithium will not maintain a TCAP session with the B-MSC as each segment will be handled separately. Separate TCAP dialog for each segment, but this depends on the originating SMSC on how it wants to handle long messages - Single TCAP or multiple.
    
    So, it is possible that if there are multiple traffic nodes, each segment could arrive a different router and hence handled independently. Though very less, there could be some timing issues at times (delays on the radio/transmission side) and this could have an impact such that segments could arrive out of order. However most handsets can do the assembly of the message in the correct sequence.
    
    
  • In case AMS is used, and if there are more than 1 messages queued in the AMS for the same recipient, AMS will automatically use the MMS flag while delivering messages to the B-Party MSC/VLR.
    
    Application Originated messages could be using SAR to identify segmented messages.