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

bind-3.2.

   URL     Universal Resource Locator 
   U.S.    United States 
    
    
4. Types of Number Portability 
    
   As there are several types of E.164 numbers (telephone numbers, or 
   just TN) in the GSTN, there are correspondingly several types of 
   E.164 NP in the GSTN.  First there are so-call non-geographic E.164 
   numbers, commonly used for service-specific applications such as 
   freephone (800 or 0800).  Portability of these numbers is called 
   non-geographic number portability (NGNP).  NGNP, for example, was 
   deployed in the U.S. in 1986-92. 
    
   Geographic number portability, which includes traditional fixed or 
   wireline numbers as well as mobile numbers which are allocated out 
   of geographic number range prefixes, is called NP or GNP or in the 
   U.S. local number portability (LNP). 
    
   Number portability allows the telephony subscribers in the Global 
   Switched Telephone Network (GSTN) to keep their phone numbers when 
   they change their service providers or subscribed services, or when 
   they move to a new location.   
    
   The ability to change the service provider while keeping the same 
   phone number is called service provider portability (SPNP) also 
   known as "operator portability." 
    
   The ability to change the subscriber苨 fixed service location while 
   keeping the same phone number is called location portability. 
    
   The ability to change the subscribed services (e.g., from the plain 
   old telephone service to Integrated Services Digital Network (ISDN) 
   services) while keeping the same phone number is called service 
  
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Number Portability in the GSTN: An Overview           February 9, 2000 
 
 
   portability.  Another aspect of service portability is to allow the 
   subscribers to enjoy the subscribed services in the same way when 
   they roam outside their home networks as is supported by the 
   cellular/wireless networks. 
    
   In addition, mobile number portability (MNP) refers to specific NP 
   implementation in mobile networks either as part of a broader NP 
   implementation in the GSTN or on a stand-alone basis.  Where 
   interoperation of LNP and MNP is supported, service portability 
   between fixed and mobile service types is possible. 
    
   At present, SPNP has been the primary form of NP deployed due to its 
   relevance in enabling local service competition. 
    
   Also in use in the GSTN are the terms interim NP (INP) or Interim 
   LNP (ILNP) and true NP.  Interim NP usually refers to the use of 
   remote call forwarding-like measures to forward calls to ported 
   numbers through the donor network to the new service network.  These 
   are considered interim relative to true NP, which seeks to remove 
   the donor network or old service provider from the call or signaling 
   path altogether.  Often the distinction between interim and true NP 
   is a national regulatory matter relative to the 
   technical/operational requirements imposed on NP in that country. 
    
   Implementations of true NP in certain countries (e.g. U.S., Canada, 
   Spain, Belgium, Denmark) may pose specific requirements for IP 
   telephony implementations as a result of regulatory and industry 
   requirements for providing call routing and signaling independent of 
   the donor network or last previous serving network. 
    
    
5. Service Provider Number Portability Schemes 
    
   Four schemes can be used to support service provider portability and 
   are briefly described below.  But first, some further terms are 
   introduced. 
    
   The donor network is the network that first assigned a telephone 
   number (e.g., TN [phone]) to a subscriber, out of a number 
   range administratively (e.g., +1 202-533) assigned to it.  The 
   current service provider (new SP) or new serving network is the 
   network that currently serves the ported number. The old serving 
   network (or old SP) is the network that previously served the ported 
   number before the number was ported to the new serving network. 
   Since a TN can port a number of times, the old SP is not necessarily 
   the same as the donor network, except for the first time the TN 
   ports away, or if the TN ports back into the donor network and away 
   again.  While the new SP and old SP roles are transitory as a TN 
   ports around, the donor network is always the same for any 
   particular TN based on the service provider to whom the subtending 
   number range was administratively assigned.  See the discussion 
   below on number pooling, as this enhancement to NP further 

  
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Number Portability in the GSTN: An Overview           February 9, 2000 
 
 
   bifurcates the role of donor network into two (the number range or 
   code holder network, and the block holder network). 
    
   To simplify the illustration, all the transit networks are ignored, 
   the originating or donor network is the one that performs the 
   database queries or call redirection, and the dialed directory 
   number (TN) has been ported out of the donor network before.  
    
   It is assumed that the old serving network, the new serving network 
   and the donor network are different networks so as to show which 
   networks are involved in call handling and routing and database 
   queries in each of four schemes.  Please note that the port of the 
   number (process of moving it from one network to another) happened 
   prior to the call setup and is not included in the call steps.  
   Information carried in the signaling messages to support each of the 
   four schemes is not discussed to simplify the explanation. 
    
    
5.1 All Call Query (ACQ) 
    
   Figure 1 shows the call steps for the ACQ scheme.  Those call steps 
   are as follows: 
    
    
   +-------------+              +-----------+    Number   +-----------+ 
   | Centralized |              | New Serv. |    ported   | Old Serv. | 
   |    NPDB     |    +-------->|  Network  |<------------|  Network  | 
   +-------------+    |         +-----------+             +-----------+ 
       ^  |           | 
       |  |           | 
      1|  |         3.| 
       |  | 2.        | 
       |  |           | 
       |  v           | 
    +----------+      |         +----------+           +----------+ 
    |   Orig.  |------+         |   Donor  |           | Internal | 
    |  Network |                |  Network |           |   NPDB   | 
    +----------+                +----------+           +----------+ 
    
    
              Figure 1 - All Call Query (ACQ) Scheme. 
 
 
   (1) The Originating Network receives a call from the caller and 
       sends a query to a centrally administered Number Portability 
       Database (NPDB), a copy of which is usually resident on a 
       network element within its network or through a third party 
       provider. 
   (2) The NPDB returns the routing number associated with the dialed 
       directory number.  The routing number is discussed later in 
       Section 7. 
   (3) The Originating Network uses the routing number to route the 
       call to the new serving network. 
  
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Number Portability in the GSTN: An Overview           February 9, 2000 
 
 
 
5.2 Query on Release (QoR) 
 
  Figure 2 shows the call steps for the QoR scheme.  Those call steps 
  are as follows: 
    
   (1) The Originating Network receives a call from the caller and 
       routes the call to the donor network. 
   (2) The donor network releases the call and indicates that the 
       dialed directory number has been ported out of that switch. 
   (3) The Originating Network sends a query to its copy of the 
       centrally administered NPDB. 
   (4) The NPDB returns the routing number associated with the dialed 
       directory number.   
   (5) The Originating Network uses the routing number to route the 
       call to the new serving network. 
    
    
   +-------------+              +-----------+    Number   +-----------+ 
   | Centralized |              | New Serv. |    ported   | Old Serv. | 
   |    NPDB     |              |  Network  |<------------|  Network  | 
   +-------------+              +-----------+             +-----------+ 
       ^  |                          ^ 
       |  | 4.                       | 
     3.|  |              5.          | 
       |  |   +----------------------+ 
       |  |   | 
       |  v   | 
    +----------+      2.        +----------+           +----------+ 
    |   Orig.  |<---------------|   Donor  |           | Internal | 
    |  Network |--------------->|  Network |           |   NPDB   | 
    +----------+      1.        +----------+           +----------+ 
    
                   
                Figure 2 - Query on Release (QoR) Scheme. 
    
    
5.3 Call Dropback 
    
  Figure 3 shows the call steps for the Dropback scheme.  This scheme 
  is also known as "Return to Pivot (RTP)."  Those call steps are as 
  follows: 
    
   (1) The Originating Network receives a call from the caller and 
       routes the call to the donor network. 
   (2) The donor network detects that the dialed directory number has 
       been ported out of the donor switch and checks with an internal 
       network-specific NPDB.  
   (3) The internal NPDB returns the routing number associated with the 
       dialed directory number. 
   (4) The donor network releases the call by providing the routing 
       number. 

  
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   (5) The Originating Network uses the routing number to route the 
       call to the new serving network. 
    
   +-------------+              +-----------+    Number   +-----------+ 
   | Centralized |              | New Serv. |    porting  | Old Serv. | 
   |    NPDB     |              |  Network  |<------------|  Network  | 
   +-------------+              +-----------+             +-----------+ 
                                    /\ 
                                     | 
                           5.        | 
            +------------------------+ 
            | 
            | 
    +----------+       4.       +----------+     3.    +----------+ 
    |   Orig.  |<---------------|   Donor  |<----------| Internal | 
    |  Network |--------------->|  Network |---------->|   NPDB   | 
    +----------+      1.        +----------+    2.     +----------+ 
    
                   
                      Figure 3 - Dropback Scheme. 
    
    
5.4 Onward Routing (OR) 
    
  Figure 4 shows the call steps for the OR scheme.  This scheme is also 
  called Remote Call Forwarding.  Those call steps are as follows: 
    
   (1) The Originating Network receives a call from the caller and 
       routes the call to the donor network. 
   (2) The donor network detects that the dialed directory number has 
       been ported out of the donor switch and checks with an internal 
       network-specific NPDB.  
   (3) The internal NPDB returns the routing number associated with the 
       dialed directory number. 
   (4) The donor network uses the routing number to route the call to 
       the new serving network. 
 
    
   +-------------+              +-----------+    Number   +-----------+ 
   | Centralized |              | New Serv. |    porting  | Old Serv. | 
   |    NPDB     |              |  Network  |<------------|  Network  | 
   +-------------+              +-----------+             +-----------+