draft-ietf-enum-e164-gstn-np-01.txt

bind-3.2.

                                    /\ 
                                     | 
                                   4.| 
                                     | 
    +----------+                +----------+     3.    +----------+ 
    |   Orig.  |                |   Donor  |<----------| Internal | 
    |  Network |--------------->|  Network |---------->|   NPDB   | 
    +----------+      1.        +----------+    2.     +----------+ 
    
                   
                 Figure 4 - Onward Routing (OR) Scheme. 
  
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5.5 Comparisons of the Four Schemes 
    
   Only the ACQ scheme does not involve the donor network when routing 
   the call to the new serving network of the dialed ported number.  
   The other three schemes involve call setup to or signaling with the 
   donor network.   
    
   Only the OR scheme requires the setup of two physical call segments, 
   one from the Originating Network to the donor network and the other 
   from the donor network to the new serving network.  The OR scheme is 
   the least efficient in terms of using the network resources.  The 
   QoR and Dropback schemes set up calls to the donor network first but 
   release the call back to the Originating Network that then initiates 
   a new call to the Current Serving Network.  For the QoR and Dropback 
   schemes, circuits are still reserved one by one between the 
   Originating Network and the donor network when the Originating 
   Network sets up the call towards the donor network.  Those circuits 
   are released one by one when the call is released from the donor 
   network back to the Originating Network.  The ACQ scheme is the most 
   efficient in terms of using the switching and transmission 
   facilities for the call. 
    
   Both the ACQ and QoR schemes involve Centralized NPDBs for the 
   Originating Network to retrieve the routing information.  
   Centralized NPDB means that the NPDB contains ported number 
   information from multiple networks.  This is in contrast to the 
   internal network-specific NPDB that is used for the Dropback and OR 
   schemes.  The internal NPDB only contains information about the 
   numbers that were ported out of the donor network.  The internal 
   NPDB can be a stand-alone database that contains information about 
   all or some ported-out numbers from the donor network.  It can also 
   reside on the donor switch and only contains information about those 
   numbers ported out of the donor switch.  In that case, no query to a 
   stand-alone internal NPDB is required.  The donor switch for a 
   particular phone number is the switch to which the number range is 
   assigned from which that phone number was originally assigned. 
    
   For example, number ranges in the North American Numbering Plan 
   (NANP) are usually assigned in the form of central office codes (CO 
   codes) comprising a six-digit prefix formatted as a NPA+NXX.  Thus a 
   switch serving +1-202-533 would typically serve [phone] 
   through [phone]. In major cities, switches usually host 
   several CO codes.  NPA stands for Numbering Plan Area that is also 
   known as the area code.  It is three-digit long and has the format 
   of NXX where N is any digit from 2 to 9 and X is any digit from 0 to 
   9.  NXX in the NPA+NXX format is known as the office code that has 
   the same format as the NPA.  When the first number out of an NPA+NXX 
   code is ported out to another switch, that NPA+NXX is called 
   "portable NPA+NXX." 
    
   Similarly, in other national E.164 numbering plans, number ranges 
   cover a contiguous range of numbers within that range.  Once a 
  
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   number within that range has ported away from the donor network, all 
   numbers in that range are considered potentially ported and should 
   be queried in the NPDB. 
    
   The ACQ scheme has two versions.  One version is for the Originating 
   Network to always query the NPDB when a call is received from the 
   caller regardless whether the dialed directory number is ported or 
   not. The other version is to check whether the dialed directory 
   number belongs to any portable number range.  If yes, an NPDB query 
   is sent. If not, no NPDB query is sent.  The former performs better 
   when there are many portable number ranges.  The latter performs 
   better when there are not too many portable number ranges at the 
   expense of checking every call to see whether NPDB query is needed.  
   The latter ACQ scheme is similar to the QoR scheme except that the 
   QoR scheme uses call setup and relies on the donor network to 
   indicate "number ported out" before launching the NPDB query. 
    
    
6. Database Queries in the NP Environment 
    
   As indicated earlier, the ACQ and QoR schemes require that a switch 
   query the NPDB for routing information.  Various standards have been 
   defined for the switch-to-NPDB interface.  Those interfaces with 
   their protocol stacks are briefly described below.  The term "NPDB" 
   is used for a stand-alone database that may support just one or some 
   or all of the interfaces mentioned below.  The NPDB query contains 
   the dialed directory number and the NPDB response contains the 
   routing number.  There are certainly other information that is sent 
   in the query and response.  The primary interest is to get the 
   routing number from the NPDB to the switch for call routing. 
    
 
6.1 U.S. and Canada 
    
   One of the following five NPDB interfaces can be used to query an 
   NPDB: 
    
   (a) Advanced Intelligent Network (AIN) using the American National 
       Standards Institute (ANSI)  version of the Intelligent Network 
       Application Part (INAP) [ANSI SS] [ANSI DB].  The INAP is 
       carried on top of the protocol stack that includes the (ANSI) 
       Message Transfer Part (MTP) Levels 1 through 3, ANSI Signaling 
       Connection Control Part (SCCP), and ANSI Transaction 
       Capabilities Application Part (TCAP).  This interface can be 
       used by the wireline or wireless switches, is specific to the NP 
       implementation in North America, and is modeled on the Public 
       Office Dialing Plan (PODP) trigger defined in the Advanced 
       Intelligent Network (AIN) 0.1 call model.  
    
   (b) Intelligent Network (IN), which is similar to the one used for 
       querying the 800 databases.  The IN protocol is carried on top 
       of the protocol stack that includes the ANSI MTP Levels 1 

  
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       through 3, ANSI SCCP, and ANSI TCAP.  This interface can be used 
       by the wireline or wireless switches. 
    
   (c) ANSI IS-41 [IS41] [ISNP], which is carried on top of the 
       protocol stack that includes the ANSI MTP Levels 1 through 3, 
       ANSI SCCP, and ANSI TCAP.  This interface can be used by the IS-
       41 based cellular/Personal Communication Services (PCS) wireless 
       switches (e.g., AMPS, TDMA and CDMA).  Cellular systems use 
       spectrum at 800 MHz range and PCS systems use spectrum at 1900 
       MHz range. 
    
   (d) Global System for Mobile Communication Mobile Application Part 
       (GSM MAP) [GSM], which is carried on top of the protocol stack 
       that includes the ANSI MTP Levels 1 through 3, ANSI SCCP, and 
       International Telecommunication Union - Telecommunication Sector  
       (ITU-TS) TCAP.  It can be used by the PCS1900 wireless switches 
       that are based on the GSM technologies.  GSM is a series of 
       wireless standards defined by the European Telecommunications 
       Standards Institute (ETSI). 
    
   (e) ISUP triggerless translation.  NP translations are performed 
       transparently to the switching network by the signaling network 
       (e.g. Signaling Transfer Points (STPs) or signaling gateways).  
       ISUP IAM messages are examined to determine if the CdPN field 
       has already been translated, and if not, an NPDB query is 
       performed, and the appropriate parameters in the IAM message 
       modified to reflect the results of the translation.   The 
       modified IAM message is forwarded by the signaling node on to 
       the designated DPC in a transparent manner to continue call 
       setup.  The NPDB can be integrated with the signaling node or be 
       accessed via an API locally or by a query to a remote NPDB using 
       a proprietary protocol or the schemes described above. 
    
    
   Wireline switches have the choice of using either (a), (b), or (e).  
   IS-41 based wireless switches have the choice of using (a), (b), 
   (c), or (e).  PCS1900 wireless switches have the choice of using 
   (a), (b), (d), or (e). In the United States, service provider 
   portability will be supported by both the wireline and wireless 
   systems, not only within the wireline or wireless domain but also 
   across the wireline/wireless boundary.  However, this is not true in 
   Europe where service provider portability is usually supported only 
   within the wireline or wireless domain, not across the 
   wireline/wireless boundary due to explicit use of service-specific 
   number range prefixes.  The reason is to avoid caller confusion 
   about the call charge. GSM systems in Europe are assigned 
   distinctive destination network codes, and the caller pays a higher 
   charge when calling a GSM directory number. 
    
      
6.2 Europe 
    
   One of the following three interfaces can be used to query an NPDB: 
  
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   (a) Capability Set 1 (CS1) of the ITU-TS INAP [CS1], which is 
       carried on top of the protocol stack that includes the ITU-TS 
       MTP Levels 1 through 3, ITU-TS SCCP, and ITU-TS TCAP. 
    
   (b) Capability Set 2 (CS2) of the ITU-TS INAP [CS2], which is 
       carried on top of the protocol stack that includes the ITU-TS 
       MTP Levels 1 through ITU-TS MTP Levels 1 through 3, ITU-TS SCCP, 
       and ITU-TS TCAP. 
    
   (c) ISUP triggerless translation.  NP translations are performed 
       transparently to the switching network by the signaling network 
       (e.g. STPs or signaling gateways).  ISUP IAM messages are 
       examined to determine if the CdPN field has already been 
       translated, and if not, an NPDB query is performed, and the 
       appropriate parameters in the IAM message modified to reflect 
       the results of the translation.   The modified IAM message is 
       forwarded by the signaling node on to the designated DPC in a 
       transparent manner to continue call setup. 
    
    
   Wireline switches have the choice of using either (a), (b), or (c); 
   however, all the implementations in Europe so far are based on CS1.  
   As indicated earlier that number portability in Europe does not go 
   across the wireline/wireless boundary.  The wireless switches can 
   also use (a) or (b) to query the NPDBs if those NPDBs contains 
   ported wireless directory numbers.  The term "Mobile Number 
   Portability (MNP)" is used for the support of service provider 
   portability by the GSM networks in Europe.  
    
   In most, if not all, cases in Europe, the calls to the wireless 
   directory numbers are routed to the wireless donor network first.  
   Over there, an internal NPDB is queried to determine whether the 
   dialed wireless directory number has been ported out or not.  In 
   this case, the interface to the internal NPDB is not subject to 
   standardization. 

   MNP in Europe can also be supported via MNP Signaling Relay Function 
   (MNP-SRF).  Again, an internal NPDB or a database integrated at the 
   MNP-SRF is used to modify the SCCP Called Party Address parameter in 
   the GSM MAP messages so that they can be re-directed to the wireless 
   serving network.   Call routing involving MNP will be explained in 
   Section 7.2. 
    
    
7. Call Routing in the NP Environment 
 
   This section discusses the call routing after the routing 
   information has been retrieved either through an NPDB query or an 
   internal database lookup at the donor switch, or from the Integrated 
   Services Digital Network User Part (ISUP) signaling message (e.g., 
   for the Dropback scheme).  For the ACQ, QoR and Dropback schemes, it 
   is the Originating Network that has the routing information and is 
  
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   ready to route the call.  For the OR scheme, it is the donor network 
   that has the routing information and is ready to route the call.   
    
   A number of triggering schemes may be employed that determine where 
   in the call path the NPDB query is performed.  In the U.S. an 鬘-1