Signaling for International Roaming SMS Billing by qingyunliuliu

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									 Signaling for International Roaming SMS Billing


                                           Ver 0.3

                                      10 August 2006




Revision History
0.1       2006-05-15   Initial version
0.2       2006-08-03   Expand and update
0.3       2006-08-10   Change MT Return Result OPC/CgPA
                                                                                                                         Page 2 of 19




Contents
1.      Introduction ................................................................................................................. 3

2.      Existing Signaling ....................................................................................................... 4

     2.1.    Point Code Routing ............................................................................................. 4
        2.1.1.    Subscriber Registration ............................................................................... 5
        2.1.2.    Mobile-Originated SMS.............................................................................. 5
        2.1.3.    Mobile-Terminated SMS ............................................................................ 5
        2.1.4.    SMS Notification ........................................................................................ 6
        2.1.5.    Other Roaming Signaling ........................................................................... 6

     2.2.    Global Title Routing ........................................................................................... 7
        2.2.1.   General Roaming Signaling ........................................................................ 7
        2.2.2.   Subscriber Registration and SMS Notification ........................................... 8

3.      Proposed Solution ....................................................................................................... 9

     3.1.    Point Code Routing ............................................................................................. 9
        3.1.1.    Subscriber Registration ............................................................................. 10
        3.1.2.    Mobile-Originated SMS............................................................................ 10
        3.1.3.    Mobile-Terminated SMS .......................................................................... 12
        3.1.4.    SMS Notification ...................................................................................... 13
        3.1.5.    Other Roaming Signaling ......................................................................... 13
        3.1.6.    Signaling Management ............................................................................. 14

     3.2.    Global Title Translation .................................................................................... 14
        3.2.1.   Subscriber Registration and SMS Notification ......................................... 14
        3.2.2.   Mobile-Originated SMS............................................................................ 14
        3.2.3.   Mobile-Terminated SMS .......................................................................... 15
        3.2.4.   Other Roaming Signaling ......................................................................... 15
        3.2.5.   One-way Global Title ............................................................................... 16

     3.3.      Discussion ......................................................................................................... 16

4.      Glossary .................................................................................................................... 17

5.      Appendix – MAP Layer Identifier ............................................................................ 18
                                                                                         Page 3 of 19




1. Introduction
    The Voice and SMS Working Group (VSWG) of the CDG IRT is working to address the
    issues involved with International Short Message Service (SMS) Roaming Billing.

    Of particular interest has been the need to ensure that the home operator is able to charge
    its subscribers at a rate which accurately reflects the different intercarrier wholesale rates
    that may be charged by the operator’s individual roaming partners.

    There are several broad options possible and/or available for delivery of the necessary
    information (identification of the serving operator) to the home operator. Based on
    expressed operator preference (and the fact that some other options are already available),
    the VSWG has focused on the use of the existing internetwork ANSI-41 signaling to
    carry the necessary information to the home operator’s Message Center (MC, aka SMSC).
    The billing record generated by the MC is used for subscriber billing.

    Given this general approach, there are a number of parameters within the relevant
    signaling messages that could be used to carry the necessary information. At the June
    2006 IRT, operators expressed their preference for the use of a transport-layer identifier
    (e.g. point code, Calling Party Address) to specify the serving network. This document
    describes this approach in further detail, including modifications to accommodate
    different signaling methods (point code routing and Global Title Translation). When
    point code routing is used, there are two locations for the serving network identifier, and
    operator feedback on the preferred approach is invited. An appendix describes an
    alternative approach using ANSI-41 parameters to identify the serving network.
                                                                                                Page 4 of 19




2. Existing Signaling
     Most CDMA operators today connect to their international roaming partners via a
     Roaming Service Provider (RSP). The RSP can represent all remote network elements as
     a single identity. This arrangement greatly simplifies the configuration requirements in
     the operator’s network, however in the process the identity of the serving network can be
     masked from the home operator for SMS.

  2.1.      Point Code Routing
     Many operators today use Point Code (PC) routing for signaling to and from the RSP.
     The PCs are meaningful only within a given network/country. The Roaming Service
     Provider (RSP) is assigned a point code inside each of its customer networks, and uses
     leased lines to connect back to its own premises. All roaming signaling to and from an
     operator’s roaming partners is via the single RSP point code. This arrangement is shown
     in Figure 1 below.


                                                                         Signaling flow

                        Operator 1                                       RSP PC, as viewed by Operator 1




                           RSP



           Operator 2                 Operator 3


                                     Figure 1 - Existing RSP Signaling

     The following subsections show specific scenarios relevant for SMS. In each case there
     may be one or more Signaling Transfer Points (STPs) present between the RSP and the
     indicated operator network element – these STPs do not modify the traversing message in
     any way. The Signaling Connection Control Part (SCCP) layer of the messages is
     assumed to have Called and Calling Party Addresses either containing PCs that match the
     Destination and Originating Point Codes (respectively) together with a Subsystem
     Number (SSN), or SSN only. The SCCP routing indicator indicates that routing is based
     on the MTP PC and the SSN.
                                                                                 Page 5 of 19




2.1.1. Subscriber Registration
Figure 2 below shows subscriber registration. No indication is available of the actual
serving network. The SMS_Address parameter points only to the RSP.


                     REGNOT: DPC         = HLR PC
                             OPC         = RSP PC
        HLR                  SMS_Address = RSP PC                            RSP
                     regnot:    DPC               = RSP PC
                                OPC               = HLR PC



                               Figure 2 - Subscriber Registration

2.1.2. Mobile-Originated SMS
Figure 3 below shows a mobile-originated (MO) SMS. The transport layer identifiers
received at the MC only refer to the RSP, and not to the serving operator. The MAP layer
contents likewise provide no information about the serving operator.


                     SMDPP:     DPC               = MC PC
                                OPC               = RSP PC
         MC                                                                  RSP
                     smdpp:     DPC               = RSP PC
                                OPC               = MC PC



                               Figure 3 - Mobile-Originated SMS

2.1.3. Mobile-Terminated SMS
Figure 4 below shows a mobile terminated (MT) SMS. The MC sends the SMS to the
destination PC received from the HLR in the SMS_Address parameter (the same received
by the HLR at registration time). No identification of the serving operator is available at
the MC.
                                                                              Page 6 of 19




                    SMDPP:      DPC              = RSP PC
                                OPC              = MC PC
         MC                                                              RSP
                    smdpp:      DPC              = MC PC
                                OPC              = RSP PC



                               Figure 4 - Mobile-Terminated SMS

2.1.4. SMS Notification
Figure 5 below shows a notification from the RSP to the MC (e.g. when a subscriber with
a pending message becomes available). The SMS_Address points to the RSP, and the
resulting MT-SMS will be as above in Figure 4.


                    SMSNOT: DPC         = MC PC
                            OPC         = RSP PC
         MC                 SMS_Address = RSP PC                         RSP
                    smsnot:     DPC              = RSP PC
                                OPC              = MC PC



                              Figure 5 - SMS Notification from RSP

2.1.5. Other Roaming Signaling
Figure 6 below shows a general representation of other signaling between the RSP and
the operator. All traffic is received from/directed to the single RSP PC.


                    INV/RR:     DPC              = Network Element PC
      Operator                  OPC              = RSP PC
      Network                                                            RSP
      Element
                    RR/INV:     DPC              = RSP PC
                                OPC              = Network Element PC



                                   Figure 6 - Other Signaling
                                                                                  Page 7 of 19




2.2.      Global Title Routing
   Some operators use Global Title Translation (GTT) to route calls through their network,
   and to and from the RSP. Although the use of GTT can allow the transfer of messages
   between networks without knowledge of each other’s MTP PC allocations, as used today
   for CDMA international roaming the RSP is still present as a PC that appears “inside” the
   operator’s network: GTT is used as a tool to simplify routing tables in nodes of large
   networks.

   STPs/SCCP Relay points in the operator’s network route the message, changing the MTP
   addresses accordingly.

   The following subsections highlight differences between Point Code and Global Title
   routing.

   2.2.1. General Roaming Signaling
   Figure 7 below shows a generic ANSI-41 message pair (which could be SMS or other
   roaming signaling). The MTP layer addresses are modified en route by intervening STPs
   which also perform Global Title Translation. At the SCCP layer, the routing indicator
   indicates routing is based on the global title address, and the called and calling party
   addresses contain Global Titles for the message endpoints. As per IS-807, the Global
   Titles are in E.212 format. In some cases the Global Title will be the relevant mobile’s
   IMSI, in other cases an identifier assigned directly to a network element. The RSP may
   be physically located in a different country to the operator, however as with the point
   code routing arrangement it is assigned a local point code. For this reason the Global
   Title for the RSP uses the same Mobile Country Code as the operator.

       INV/RR:   DPC       = Nwk Element PC         INV/RR:    DPC     = STP PC
                 OPC       = STP PC                            OPC     = RSP PC
                 CdPA      = Nwk Element GT                    CdPA    = Nwk Element GT
                 CgPA      = RSP GT                            CgPA    = RSP GT



          Operator                            STP
          Network                                                              RSP
          Element



       RR/INV:   DPC       = STP PC                 RR/INV:    DPC     = RSP PC
                 OPC       = Nwk Element PC                    OPC     = STP PC
                 CdPA      = RSP GT                            CdPA    = RSP GT
                 CgPA      = Nwk Element GT                    CgPA    = Nwk Element GT

                                     Figure 7- GTT signaling
                                                                            Page 8 of 19




2.2.2. Subscriber Registration and SMS Notification
Subscriber registration and SMS Notification use the same signaling techniques as
described in §2.2.1 above. The MAP layer SMS_Address parameter contains the RSP GT
address instead of a point code, so that mobile-terminated SMS can be addressed using
GTT.
                                                                                             Page 9 of 19




3. Proposed Solution
     As stated above, the approach preferred by operators is for the RSP to modify an address
     parameter in a transport layer (MTP and/or SCCP) to identify the serving network. The
     message will appear to the home operator to be coming from (or going to) a different
     location for each serving operator, rather than just to the single RSP location as today.

     Many MCs today include the far end transport layer information in their billing record. If
     this information is set to a value that is specific to the serving operator, a home operator
     can potentially implement a per-serve charging scheme with no modifications to their
     MCs. This was the primary reason for the operator preference for this approach (see the
     meeting minutes for more detail).

     The differences between the existing point code and GT routing schemes necessitate
     different approaches to incorporate serving network information for operators who use
     these schemes.

  3.1.      Point Code Routing
     For operators using point code routing, the proposed approach is to replace the single
     RSP point code with a PC that is specific to the serving operator. The set of roaming
     partner PCs would be unique to each home operator (for example, SMS traffic for
     Operator 1’s subscribers roaming in Operator 2’s network may appear to Operator 1 to
     use point code A (a point code assigned to the RSP for this purpose by Operator 1), while
     SMS traffic for Operator 3’s subscribers roaming in Operator 2’s network appears to
     Operator 3 to use point code B). This arrangement is illustrated in Figure 8 below.


                                                                      Non-SMS signaling

                         Operator 1                                   SMS signaling – arrow points
                                                                      from Serve to Home, e.g. MO-
                                                                      SMS SMDPP
                                                                      RSP PC, as viewed by Operator
                                                                      1, for non-[Home SMS] traffic
                                                                      RSP PC, as viewed by Operator
                                                                      3, for Home SMS traffic served
                            RSP                                       by Operator 2.
                                                                      (Different to  )


           Operator 2                 Operator 3


                               Figure 8 - Serve-specific Point Codes for SMS

     The following subsections show the changes to specific scenarios. Note that Point Codes
     can be carried in both the MTP and SCCP layers, leading to some options regarding
                                                                                 Page 10 of 19



where to place the serve-specific value. Except where noted, the SCCP point codes are
assumed to either be absent, or the same as their MTP counterparts.

3.1.1. Subscriber Registration
Figure 9 below shows the subscriber registering. The regular RSP PC is used at the MTP
layer, but inside the ANSI-41 message the SMS_Address parameter (which will be used
for subsequent MT-SMS attempts) is set to the new point code used by the RSP for SMS
roaming between this serving operator and this home operator. Note that some HLRs may
store SMS_Address against the MSCID, rather than against the subscriber. In this case
another RSP feature may be required to provide a per-serve MSCID in the message.

No modifications in the operator’s signaling network are required to support this solution.
If differentiated billing for MT-SMS is not required, this modification is not necessary.


                     REGNOT: DPC         = HLR PC
                             OPC         = RSP PC
        HLR                  SMS_Address = RSP new PC for serve                RSP
                     regnot:     DPC              = RSP PC
                                 OPC              = HLR PC



                     Figure 9 - Registration with serve-specific SMS_Address

3.1.2. Mobile-Originated SMS
For MO-SMS, the RSP may choose to either modify the MTP Originating Point Code
(OPC), or the PC in the SCCP Calling Party Address (CgPA), leaving the OPC as the
(generic) RSP PC. SCCP modification may represent a simpler task for the RSPs. For the
home operator, there should be little difference between the two.

Figure 10 below shows a mobile-originated SMS with the modifications applied at the
MTP layer. When sending the SMDPP to the home operator’s MC (indirect SMS routing
is assumed here), the RSP sets the MTP Originating Point Code (OPC) to the per-serve
value. The MC responds to the same point code. The SCCP Calling Party Address is
assumed to contain the MC SSN, and the same serve-specific PC.

The home operator must configure its network elements to route the set of serve-specific
point codes to the RSP. Modifications to STP Gateway Screening rules may also be
necessary to allow incoming traffic from the new OPCs. The RSP accepts the incoming
smdpp addressed to the new PC.
                                                                                        Page 11 of 19




                      SMDPP:     DPC              = MC PC
                                 OPC              = RSP new PC for serve
         MC                                                                           RSP
                      smdpp:     DPC              = RSP new PC for serve
                                 OPC              = MC PC



              Figure 10 - MO-SMS from serve-specific point code – MTP modifications

As an alternative, the RSP could modify the SCCP CgPA PC, while leaving the OPC
untouched. This may represent a simpler development effort for the RSP than the MTP
modification discussed above. The resulting messaging is shown in Figure 11 below:

                      SMDPP:     DPC         = MC PC
                                 OPC         = RSP PC
                                 CdPA        = MC PC/SSN
                                 CgPA        = RSP new PC for serve + SSN

         MC                                                                           RSP
                      smdpp:     DPC         = RSP new PC for serve
                                 OPC         = MC PC
                                 CdPA        = RSP new PC for serve + SSN
                                 CgPA        = (MC PC)/SSN

              Figure 11 - MO-SMS from serve-specific point code - SCCP modification

The Return Result addressing is identical to the MTP modification case. Although it
would be convenient if the Return Result were to use the RSP (generic) PC at the MTP
layer (thereby avoiding the need for STP routing tables to include the serve-specific PCs),
this is unlikely to be the case for real-world MCs. The reason is that the internal primitive
used to pass the received message from the SCCP layer up to the application can only
carry a single point code. If, as here, both MTP and SCCP carry a (different) PC, only
that from SCCP will be preserved. When the application sends the return message, it will
be directed to the PC seen by the application. Both SCCP and MTP will use this PC for
their respective destination address parameters. This arrangement is shown in Figure 12
below:
                                                                                                Page 12 of 19



                                               Home Operator MC


                                                       Appln
                      N-UNITDATA Indication                       N-UNITDATA Request
Calling Address = RSP new PC for serve + SSN                      Calling Address = MC PC/SSN (or blank)
                     Called Address = MC PC                       Called Address = RSP new PC for serve + SSN
                                   User Data                      User Data

                                                   SCCP
                  MTP-TRANSFER Indication                         MTP-TRANSFER Request
                          OPC = RSP PC                            OPC = MC PC
                           DPC = MC PC                            DPC = RSP new PC for serve
                              User Data                           User Data
                                                       MTP


                                          SMDPP
                                               smdpp


                                Figure 12 - Internal Primitives for MO-SMS

For the home operator, the SCCP modification approach may mean that no STP gateway
screening changes are required (unless gateway screening / access mediation is used that
checks the SCCP CgPA). Although the use of different MTP and SCCP PCs may be
somewhat unusual, there should be no problem transporting these messages through the
operator’s network, as the SCCP layer is not examined by STPs.

The generation of a billing record is presumably a function of the application, rather than
the signaling transport layers. The point code included in the billing record should
therefore be the one carried in SCCP, which will give the desired effect of identifying the
serving network.

3.1.3. Mobile-Terminated SMS
Figure 13 below shows a MT-SMS. The serve-specific point code is received from the
HLR in the SMSRequest Return Result message, and used as the Destination Point Code
(DPC) by the MC. Serve-specific billing for roaming MT-SMS, if desired, is achieved by
an assumed inclusion of the DPC in the MC’s billing record. The RSP responds with the
serve-specific PC in the OPC/CgPA of the Return Result, in case the MC uses this value
to populate its billing record.

The alternative SCCP modification is shown in Figure 14.
                                                                                       Page 13 of 19




                      SMDPP:     DPC              = RSP new PC for serve
                                 OPC              = MC PC
         MC                                                                          RSP
                      smdpp:     DPC              = MC PC
                                 OPC              = RSP new PC for serve



                Figure 13 - MT-SMS to serve-specific point code, MTP modification

                      SMDPP:     DPC         = RSP new PC for serve
                                 OPC         = MC PC
                                 CdPA        = RSP new PC for serve + SSN
                                 CgPA        = (MC PC)/SSN

         MC                                                                          RSP
                      smdpp:     DPC         = MC PC
                                 OPC         = RSP PC
                                 CdPA        = MC PC/SSN
                                 CgPA        = RSP new PC for serve + SSN

                Figure 14 - MT-SMS to serve-specific point code, SCCP modification

3.1.4. SMS Notification
Figure 15 below shows an SMS Notification from the RSP. The key parameter is the
(MAP-layer) SMS_Address, which will be used as the DPC in the resulting MT-SMS.
The normal RSP PC is used at the MTP layer of the SMSNOT message itself.


                      SMSNOT: DPC         = MC PC
                              OPC         = RSP PC
         MC                   SMS_Address = RSP new PC for serve                     RSP
                      smsnot:    DPC              = RSP PC
                                 OPC              = MC PC



                   Figure 15 - SMS Notification with serve-specific SMS_Address

3.1.5. Other Roaming Signaling
Other roaming traffic to/from the operator (including SMS traffic where the operator is
the serving operator) uses the standard RSP PC assigned for that operator (i.e. no change
to existing arrangement).
                                                                                   Page 14 of 19




   3.1.6. Signaling Management
   The RSP should manage the compete set of serve-specific PCs, and issue TFP/TFA
   messages concerning these point codes as appropriate to the operator’s network elements.

3.2.      Global Title Translation
   For operators using Global Title (GT) routing to signal to/from the RSP, a serve-specific
   Global Title is used instead of a Point Code. The MC must include the SCCP
   Called/Calling Party Address Global Title in its billing record to enable MT/MO serve-
   specific billing, respectively.

   The following subsections discuss changes for individual scenarios.

   3.2.1. Subscriber Registration and SMS Notification
   Both subscriber registration and SMS Notification require no changes to the transport
   layer arrangements shown in Figure 7 above. At the ANSI-41 layer, the SMS_Address
   parameter is changed to contain a serve-specific Global Title.

   While it may be possible to build this (E.212) GT using the serving operator’s true
   Mobile Country Code (MCC) and Mobile Network Code (MNC), this may impact
   translation tables if current or future deployments use GT without the RSP. Instead, the
   recommended approach is to assign a set of addresses from the home operator’s own
   MCC-MNC range, which will be used to route the message to the RSP’s local presence in
   the operator’s network.

   3.2.2. Mobile-Originated SMS
   Figure 16 below shows a roamer-originated SMS sent from the RSP to the home
   operator’s MC. At the MTP layer there is no change from the existing arrangements,
   while at the SCCP layer the RSP has used a serve-specific E.212 address in the Calling
   Party Address.

   If the MC includes the received CgPA in its billing record, then the desired outcome of
   serve-specific billing can be achieved.

   For the return result, the MC uses the received CgPA to build the outgoing CdPA. GT
   translations must be in place for the new serve-specific values to route to the RSP.
   Depending on the way the range of serve-specific addresses have been chosen, and the
   internal data configuration in the STPs, this may entail little or no changes to the STP
   translation tables.

   Any gateway screening or access mediation that checks the CgPA Global Title against a
   whitelist must be updated to allow the new values.
                                                                                     Page 15 of 19




 SMDPP:    DPC      = MC PC                 SMDPP:       DPC         = STP PC
           OPC      = STP PC                             OPC         = RSP PC
           CdPA     = MC GT/IMSI                         CdPA        = MC GT/IMSI
           CgPA     = RSP serve-specific GT              CgPA        = RSP serve-specific GT



                                        STP
       MC                                                                    RSP



 smdpp:    DPC      = STP PC                smdpp:       DPC         = RSP PC
           OPC      = MC PC                              OPC         = STP PC
           CdPA     = RSP serve-specific GT              CdPA        =RSP serve-specific GT
           CgPA     = MC GT                              CgPA        = MC GT

                      Figure 16 - MO-SMS with serve-specific Global Title

3.2.3. Mobile-Terminated SMS
Figure 17 below shows roamer-terminated SMS signaling between the home operator’s
MC and the RSP. The MC uses the serve-specific Global Title previously received (in
SMS_Address of smsreq or SMSNOT). As in §3.2.2, the operator’s GTT tables must
contain data to route the new address to the RSP. The RSP responds to the SMDPP using
the serve-specific GT, in case the MC uses this to populate its billing record.

 SMDPP:     DPC      = STP PC                SMDPP:       DPC         = RSP PC
            OPC      = MC PC                              OPC         = STP PC
            CdPA     = RSP serve-specific GT              CdPA        = RSP serve-specific GT
            CgPA     = MC GT                              CgPA        = MC GT



                                         STP
          MC                                                                 RSP



 smdpp:     DPC      = MC PC                 smdpp:       DPC         = STP PC
            OPC      = STP PC                             OPC         = RSP PC
            CdPA     = MC GT                              CdPA        = MC GT
            CgPA     = RSP serve-specific GT              CgPA        = RSP serve-specific GT

                      Figure 17 - MT-SMS with serve-specific Global Title

3.2.4. Other Roaming Signaling
There are no changes required to other roaming scenarios.
                                                                                  Page 16 of 19




   3.2.5. One-way Global Title
   Some operators may use Global Title routing only for the Invoke message, but not for the
   Return Result. This can relive some routing configuration/point code discovery burden on
   the invoking network element, and allows simple return routing when both source and
   destination nodes are within the same point code universe.

   Serve-specific information can be made available at the MC of an operator using one-
   way GT routing via a combination of the methods discussed above. MO-SMS routing
   will use the SCCP modification described in §3.1.2. Registration/Notification and MT-
   SMS will use the GT routing described in §§3.2.1 and 3.2.3 respectively.

3.3.      Discussion
   The solution described above should meet operators’ needs for serve-specific billing for
   SMS roaming. Operators using PC routing and those using GT routing require different
   solutions, both of which must be supported by the RSP.

   Two options are shown for PC routing. The SCCP modification approach is preferred on
   the assumption that this is easier for the RSPs to implement (and may also require fewer
   Gateway Screening changes on the part of the home operator). The requirements on the
   MC billing record should be the same for either option.
                                                       Page 17 of 19




4. Glossary
    CDG       CDMA Development Group
    CdPA      Called Party Address
    CgPA      Calling Party Address
    DPC       Destination Point Code
    GT        Global Title
    GTT       Global Title Translation
    HLR       Home Location Register
    IMSI      International Mobile Station Identity
    IRT       International Roaming Team
    MAP       Mobile Application Part
    MC        Message Center (aka SMSC)
    MCC       Mobile Country Code
    MNC       Mobile Network Code
    MO        Mobile-Originated
    MSC       Mobile Switching Center
    MSCID     Mobile Switching Center Identification
    MT        Mobile-Terminated
    MTP       Message Transfer Part
    OPC       Originating Point Code
    PC        Point Code
    RSP       Roaming Service Provider
    SCCP      Signaling Connection Control Part
    SMDPP     SMS Delivery Point to Point
    SMS       Short Message Service
    SMS_OA    SMS_OriginatingAddress
    SMSC      Short Message Service Center (aka MC)
    SMSNOT    SMS Notification
    SMSREQ    SMS Request
    SSN       Sub-System Number
    TFA       Transfer Allowed
    TFP       Transfer Prohibited
    VSWG      Voice & SMS Working Group
                                                                                     Page 18 of 19




5. Appendix – MAP Layer Identifier
    At the June 2006 IRT meeting, VSWG participants decided on the transport layer
    modification approach discussed in the main body of this document. However, for some
    operators a MAP-layer modification may be better suited. See the meeting minutes for
    discussion of the relative merits of a MAP- and a transport-layer solution. An operator
    desiring a MAP-based solution as described below would need to approach their RSP on
    an individual basis.

    In this approach, the RSP adds a parameter to the SMSDeliveryPointToPoint Invoke (for
    MO-SMS) or Return Result (for MT-SMS) to indicate the serving system. While
    “cleaner” from a system impact point of view, this approach may require more
    modification to the MC, depending on which ANSI-41 parameters are normally included
    in the MC billing record.

    There are a number of parameters that may conceivably be used to store the serving
    system identifier. Ideally, the chosen parameter would have the following characteristics:
          Defined in ANSI-41 for inclusion in the SMSDeliveryPointToPoint operation
           (invoke and/or return Result as appropriate for MO/MT SMS billing)
          Not populated/examined by existing implementations
          Allow for sufficient values to cover all CDMA networks
          Included in MC billing records
          Intuitively relate somehow to the serving system

    The parameters described below meet many but not all of these criteria.

    For the Invoke, custom values of the SMS_OriginatingAddress (SMS_OA) are used to
    identify the serving network. Information available at the time of writing indicates that
    while some operators may populate this parameter, no-one is examining it when received
    at the MC. Whether it is included on MC billing records is unknown. The exact format of
    the identifier is largely unimportant, and is left for future specification if required. An
    MSCID-like value or MCC-MNC would seem to be logical candidates.

    For the Return Result, ANSI-41 Rev E (following IS-725) allows the presence of the
    MSCID parameter in the message. Although intended for OTASP usage, the MC could
    be modified to include this value in the billing record (no further MC action on this
    parameter is required). A single MSCID per serving operator would be defined and
    advised by the RSP.

    The serve-specific values chosen are assumed to be common for all home operators using
    this solution. This is in contrast to the transport-layer solution in the main body of the
    document, in which a full set of per-serving roaming partner values is maintained by the
    RSP for each participating home operator.

    Figure 18 and Figure 19 below show the changes to the SMDPP/smdpp operation for
    MO- and MT-SMS. PC routing is assumed in the diagram, but the MAP layer changes
                                                                                   Page 19 of 19



apply equally to GT routing. All other operations are unchanged from the existing
arrangement.


                     SMDPP:   DPC           = MC PC
                              OPC           = RSP PC
         MC          SMS_OriginatingAddress = Serve-specific value               RSP
                     smdpp:      DPC              = RSP PC
                                 OPC              = MC PC



                  Figure 18 - MO-SMS with serve-specific MAP-layer identifier



                     SMDPP:      DPC              = RSP PC
                                 OPC              = MC PC
         MC                                                                      RSP
                     smdpp:      DPC              = MC PC
                                 OPC              = RSP PC
                                 MSCID            = Serve-specific value


                   Figure 19 - MT-SMS with serve-specific MAP-layer identifier

								
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