# Patent

## Title
Methods, systems, and computer program products for routing and processing ENUM queries

## Abstract

The subject matter described herein includes methods, systems, and computer program products for routing ENUM queries to an ENUM database. According to one aspect, the subject matter described herein includes a method for routing ENUM queries to an ENUM database. The method includes receiving an ENUM query including a subscriber identifier. An ENUM database is identified among a plurality of non-identically provisioned ENUM databases based on the subscriber identifier. The ENUM query is routed to the identified ENUM database.

## Background
RELATED APPLICATIONS
This application claims the benefit of U.S. Provisional Patent Application Ser. No. 60/832,084 filed Jul. 20, 2006; the disclosure of which is incorporated herein by reference in its entirety.


TECHNICAL FIELD
The subject matter described herein relates to ENUM queries. More specifically, the subject matter relates to methods, systems, and computer program products for routing and processing ENUM queries.
BACKGROUND
E.164 number mapping (ENUM) refers to the translation of E.164-formatted telephone numbers into uniform resource indicators (URIs) resolvable by a domain name system (DNS) server into Internet protocol (IP) addresses. ENUM has been extensively deployed worldwide in order to provide integration between IP networks, such as the Internet, and the public switched telephone network (PSTN). In one proposal, as described in RFC 2916, the telephone number format used in ENUM translation is the E.164 number format. According to ITU-T standards, an E.164 telephone number may include up to 15 digits and include a leading + symbol indicating that the number is globally unique. For example, a valid E.164 telephone number may include +420-123456789. ENUM translation of an E.164 number into an IP network identifier may include formulating an ENUM query including the E.164 number and querying an ENUM database containing one or more naming authority pointer (NAPTR) records that associate individual E.164 numbers with one or more IP network identifiers. A NAPTR record is a type of DNS record that supports regular-expression-based rewriting, where each network identifier within the NAPTR record may differentiated based on a variety of parameters. Thus, a NAPTR record may contain multiple URIs associated with a single telephone number, where each URI may be differentiated based on an order, a preference, and a service. For example, the E.164 telephone number +420-123456789 may be associated with SIP URI smith@domain.org, H.323 URI smith@domain.org, and email URI smith@domain.org within a NAPTR record located in an ENUM database.
Upon receiving an ENUM query, the ENUM database may locate and return the NAPTR record associated with the telephone number included in the query. Additional translations may be required in order to select a particular network identifier from within the provided NAPTR record to first attempt to connect to. Typically, ENUM queries are processed by an ENUM database located near the query originator in order to reduce the response time for an ENUM response. Therefore, conventionally, multiple identically provisioned ENUM databases may be distributed throughout a particular geographic area such that each database is capable of responding to an ENUM query associated with any subscriber within the network.
One problem with some conventional ENUM systems is that all ENUM databases contain a complete set of ENUM data associated with all subscribers in the network. Yet as more subscribers and services are added to existing networks, including text and multimedia messaging services, voice over IP (VoIP), and other Internet multimedia subsystem (IMS) services, the volume of ENUM data stored in each of these ENUM databases increases correspondingly. As the volume of ENUM data increases, it becomes increasingly difficult to maintain all ENUM data within a single ENUM database.
In ENUM database systems where multiple identically provisioned databases serve a network, routing is simple because queries can be sent to any of the databases for translations. For example, queries may be load shared among identically provisioned ENUM databases.
In some instances, ENUM databases that serve a network may not be identically provisioned. For example, when an operator's existing ENUM database becomes maximally utilized, the operator may desire to bring a new ENUM database into service and move a portion of the subscriber data from the old ENUM database to the new ENUM database. As a result of moving the portion of the subscriber data to the new ENUM database, the new and old ENUM databases do not contain identical sets of subscribers ENUM data. Consequently, switches that formulate ENUM queries must be provisioned with location information that identifies the ENUM database that holds a particular subscriber's data. Requiring switches to be reprovisioned with ENUM database location information for each subscriber is labor intensive, especially in networks with a large number of existing switches. Such reprovisioning can be required any time the service provider desires to move subscriber ENUM data among ENUM databases. As a result, there exists a need for improved methods, systems, and computer program products for routing and processing ENUM queries.
SUMMARY
The subject matter described herein includes methods, systems, and computer program products for routing ENUM queries to an ENUM database. According to one aspect, the subject matter described herein includes a method for routing ENUM queries to an ENUM database. The method includes receiving an ENUM query including a subscriber identifier. An ENUM database is identified among a plurality of non-identically provisioned ENUM databases based on the subscriber identifier. The ENUM query is routed to the identified ENUM database.
According to another aspect, the subject matter described herein includes a flexible ENUM routing node for routing ENUM queries to an ENUM database. The flexible ENUM routing node includes a communications module for receiving an ENUM query including a subscriber identifier and an E.164-to-ENUM database identifier mapping data structure for associating one or more subscriber identifiers with one or more ENUM database identifiers. The flexible ENUM routing node further includes an ENUM database identifier function for identifying, based on the subscriber identifier and using the E.164-to-ENUM database identifier mapping data structure, an ENUM database from a plurality of non-identically provisioned ENUM databases, and for routing the ENUM query to the identified ENUM database.
The subject matter described herein may be implemented using a computer program product comprising computer executable instructions embodied in a computer readable medium. Exemplary computer readable media suitable for implementing the subject matter described herein include chip memory devices, disc memory devices, application specific integrated circuits, and programmable logic devices. In addition, a computer program product that implements a subject matter described herein may reside on a single device or computing platform or maybe distributed across multiple devices or computing platforms.



BRIEF DESCRIPTION OF THE DRAWINGS
The subject matter described herein will now be explained with reference to the accompanying drawings of which:
FIG. 1 is a network diagram of an exemplary system for routing ENUM queries to an ENUM database including a range-based E.164-to-ENUM database identifier mapping data structure according to an embodiment of the subject matter described herein;
FIG. 2 is a network diagram of an exemplary system for routing ENUM queries to an ENUM database including a combination range-based and exception-based E.164-to-ENUM database identifier mapping data structure according to an embodiment of the subject matter described herein;
FIG. 3 is a flow chart of an exemplary process for routing ENUM queries to an ENUM database according to an embodiment of the subject matter described herein;
FIG. 4 is a block diagram of an exemplary internal architecture of a flexible ENUM routing node for routing ENUM queries to an ENUM database according to an embodiment of the subject matter described herein; and
FIG. 5 is a network diagram of an exemplary system for routing ENUM queries to an ENUM database.



DETAILED DESCRIPTION
The subject matter described herein includes methods, systems, and computer program products for routing and processing ENUM queries. FIG. 1 is a network diagram of an exemplary system for routing ENUM queries to an ENUM database. In FIG. 1, the system includes a range-based E.164-to-ENUM database identifier mapping data structure. Referring to FIG. 1, network 100 may include a signaling point (SP) 102, a flexible ENUM routing node 104, and ENUM databases 106, 108 and 110. SP 102 may be connected to flexible ENUM routing node 104 via a communications link, such as a signaling system number 7 (SS7) communications link, an IP communications link, or an SS7-over-IP communications link, for communicating signaling messages, such as ENUM query and response messages, with flexible ENUM routing node 104. Similarly, flexible ENUM routing node 104 may be connected to ENUM databases 106-110 via one or more suitable communications links for sending and receiving ENUM query messages and ENUM response messages with ENUM databases 106-110.
SP 102 may be any suitable network element for generating and/or transmitting ENUM queries within network 100 according to the subject matter described herein. For example, SP 102 may include be a mobile switching center (MSC), a media gateway controller (MGC), a session initiation protocol (SIP) proxy server, an H.323 gatekeeper, an IP multimedia subsystem (IMS) node, or other suitable node for generating ENUM queries.
ENUM data may be distributed across ENUM databases 106-110, where, in one example, each ENUM database 106-110 may contain a subset of the ENUM data associated with subscribers within network 100. For example, ENUM database 106 may contain ENUM data associated with a first set of subscribers, ENUM database 108 may contain ENUM data associated with a second set of subscribers, and ENUM database 110 may contain ENUM data associated with a third set of subscribers. Therefore, collectively, ENUM databases 106-110 contain a complete set of ENUM data associated with subscribers in network 100. In another example, ENUM databases 106-110 may include some overlapping data.
Within network 100, ENUM databases 106-110 may be identified by one or more network identifiers. In the embodiment illustrated in FIG. 1, ENUM databases 106-110 may be identified by network identifiers including a uniform resource indicator and a combination of an IP address and a port number. For example, ENUM database 106 may be identified within network 100 by ENUM1@translate.net and 100.98.10.0/port x, where port x indicates any suitable port value selected from all available ports and conforming to conventional port numbering rules so as not to conflict with other services operating on ENUM database 106. ENUM databases 108 and 110 may be similarly identified by URIs ENUM2@translate.net and ENUMn@tranlsate.net and IP addresses/port numbers 100.98.10.1/port x and 100.98.10.2/port x, respectively. It is appreciated that in addition to the network identifiers described above, other identifiers may be used for identifying ENUM databases 106-110 within network 100 without departing from the scope of the subject matter described herein.
In FIG. 1, ENUM queries including a subscriber identifier, such as an E.164 number, may be generated by SP 102 and transmitted to flexible ENUM routing node 104. ENUM queries may be received by flexible ENUM routing node 104 and a lookup may be performed to determine the appropriate ENUM database from among ENUM databases 106-110 to process the query. For example, flexible ENUM routing node 104 may include E.164-to-ENUM database identifier mapping data structure 112 for associating ranges of E.164 telephone numbers with ENUM database URIs and IP address/port combinations. Referring to table 112, E.164 numbers 1-234-234-2000 through 1-234-234-2999 are associated with ENUM1@translate.net and 100.98.10.0/port x, and E.164 numbers 1-234-234-3000 through 1-234-234-3999 are associated with ENUM2@translate.net and 100.98.10.1/port x. A lookup may be performed using table 112 based on a received E.164 address by locating a row in table 112 where the searched number may be located between the values of the E.164 numbers located in the first and second columns. In addition to the data structure illustrated in FIG. 1, it is appreciated that E.164-to-ENUM database identifier mapping data structure 112 may include other data structures, including a database, a flat file, a list, an array, and a binary tree, without departing from the scope of the subject matter described herein. Table 112 may be located in computer readable medium, such as random access memory (RAM), or any other suitable means according to the subject matter described herein.
In the example illustrated in FIG. 1, ENUM query 114 may be received by flexible ENUM routing node 104, where ENUM query 114 includes the address 1.4.3.2.4.3.2.4.3.2.1.e164.arpa corresponding to E.164 telephone number 1-234-234-2341. It is appreciated that in other embodiments, ENUM query 114 may be addressed to flexible ENUM routing node 104 or may be addressed to one of ENUM databases 106-110. Therefore, flexible ENUM routing node 104 may be configured to receive ENUM queries addressed to it directly, or may intercept ENUM queries addressed to one of ENUM databases 106-110.
Upon receiving ENUM query 114, flexible ENUM routing node 104 may perform a lookup in E.164-to-ENUM database identifier mapping data structure 112 as described above to locate a URI or an IP address/port number associated with one of ENUM databases 106-110. In this example, a lookup performed may result in determining that 1-234-234-2341 is within the range indicated by the first row of table 112, and therefore, network address information corresponding to ENUM database 106 is returned. For example, flexible ENUM routing node 104 may locate URI ENUM1@translate.net and IP address/port number 100.98.10.0/port x and modify ENUM query 118 to include the determined ENUM database address.
In one embodiment, flexible ENUM routing node 104 may modify ENUM query 114 to include the ENUM database address determined in the lookup and route the query to the determined ENUM database, as indicated by modified ENUM query 116 illustrated in FIG. 1. Modified ENUM query 116 may be delivered to ENUM database 106 for processing. In another embodiment, flexible ENUM routing node 104 may forward unmodified ENUM query 114 to one of ENUM databases 106-110 identified in the lookup in table 112. It is appreciated that an intermediate DNS query may be generated by flexible ENUM routing node 104 to obtain an IP address and port number for modifying and delivering ENUM query 114 to ENUM database 106 as described above if, for example, a URI is returned as the result of a lookup in E.164-to-ENUM database identifier mapping data structure.
Upon receiving modified ENUM query 116, ENUM database 106 may locate a NAPTR record associated with the subscriber identifier included in query 114 and generate ENUM response 118. ENUM response 118 may be sent directly to SP 102 in one embodiment or, alternately, may be routed to SP 102 via flexible ENUM routing node 104.
FIG. 2 is a network diagram of an exemplary system for routing ENUM queries to an ENUM database. In FIG. 2, the system includes a range-based data structure and an exception-based data structure for identifying an ENUM database. In contrast to the embodiment shown in FIG. 1, ENUM routing table 112 shown in FIG. 2 includes an exception-based data structure in addition to a range-based data structure. As used herein, a range-based data structure is a data structure in which entries are indexed by ranges of subscriber identifiers. For example, each entry in range based data structure 200 illustrated in FIG. 2 is indexed by a range of E.164 numbers. As used herein, an exception-based data structure is a data structure whose entries are indexed by individual subscriber identifiers that are exceptions to the ranges by which the entries in the range-based data structure are indexed. An exception may be a subscriber that is within one of the ranges in the range-based data structure but specifies a different ENUM server or an entry that is outside of all the ranges in the range-based data structure. For example, the entry in exception-based data structure 201 indexed by the individual E.164 number 1234-234-3342 is within the range corresponding to the second entry in range data structure 200. However, the entry in exception data structure 201 returns the ENUM server ENUM 1 while the range-based entry in data structure 202 returns the ENUM server ENUM 2. It may be desirable to provision an individual number that is an exception to a range of numbers, for example, when moving subscriber identifiers among ENUM databases for load balancing purposes or when new databases are brought into service. Because such numbers can be reallocated among the databases and the routing information needs only to be changed at flexible routing node 104, efficiency is achieved over implementations where each individual query originator, such as SP 102 needs to be modified with the new ENUM database information. Another example of an exception-based entry may occur when a subscriber is ported-in to a service provider's network. When the subscriber is ported in and maintains the same E.164 number, the subscriber's ENUM translation information may be assigned to one of the new service provider's ENUM databases, even though the E.164 number of the subscriber is outside of all the ranges of subscriber identifiers corresponding to the service provider's ENUM databases.
In the scenario illustrated in FIG. 2, flexible ENUM routing node 104 may receive ENUM query 202 including 2.4.3.3.4.3.2.4.3.2.1.e164.arpa corresponding to E.164 number 1-234-234-3342. Upon receiving ENUM query 202, flexible ENUM routing node 104 may first perform a lookup in exception-based data structure 201 for an entry matching 1-234-234-3342. In this example, exception-based data structure 201 includes one entry matching queried address 1-234-234-3342. Accordingly, no further searching need be performed and network address information corresponding to ENUM database 106 may be returned for routing query 202 to ENUM database 106.
Alternately, if a lookup performed in exception-based data structure 201 fails to locate a match, a lookup may be performed in range-based data structure 200 in a manner like that described above with respect to FIG. 1. For example, if ENUM query 202 had included telephone number 1-234-234-2000, then a lookup performed in exception-based data structure 201 would fail to locate a match, and an entry located in the first row of the range data structure would be returned including ENUM1@translate.net and/or 100.98.10.0/port x. After determining the ENUM database identifier associated with the subscriber identifier extracted from ENUM query 202, flexible ENUM routing node 104 may modify and/or forward the ENUM query to ENUM database 106.
FIG. 3 is a flow chart of an exemplary process for distributing and accessing ENUM data located in multiple ENUM databases according to an embodiment of the subject matter described herein. In block 300, an ENUM query including a subscriber identifier is received. For example, as described above, signaling point 102 may generate ENUM query 114 including an E.164 telephone number and transmit the ENUM query to, or the ENUM query may be intercepted by, flexible ENUM routing node 104.
In block 302, an ENUM database is identified among a plurality of non-identically provisioned ENUM databases based on the subscriber identifier. For example, as illustrated in FIGS. 1 and 2, network 100 may include multiple ENUM databases 106, 108, and 110 containing ENUM data associated with a first set of subscribers, a second set of subscribers, and a third set of subscribers, respectively. The ENUM data stored in databases 106, 108, and 110 may be non-overlapping or partially overlapping. The determination of an ENUM database identifier associated with the E.164 number included in a received ENUM query may be made by searching an E.164-to-ENUM database identifier mapping data structure associating one or more E.164 numbers with one or more ENUM database identifiers.
As described above, E.164-to-ENUM database identifier mapping data structure may include a range-based data structure, a combination of exception-based and range-based data structures, or any other suitable data structure indexed by E.164 numbers. Such a data structure may be implemented using any suitable construct, such as a table, a flat file, a list, an array, a tree, or a trie. As stated above, in FIGS. 1 and 2, E.164-to-ENUM database identifier mapping data structures 112, 200, and 201 include a range-based table and a combination exception-based and range-based table, respectively. Because the E.164-to-ENUM database identifier mapping data structure may be indexed by individual E.164 numbers or by ranges of E.164 numbers, ENUM databases may be added or removed dynamically and ENUM data may be redistributed across ENUM databases so as to provide for more efficient usage of ENUM database storage resources. Moreover, by segmenting ENUM data and storing it across multiple ENUM databases, ENUM service providers may more easily scale with increases in ENUM data volume.
In block 304, the ENUM query is routed to the identified ENUM database. For example, based on ENUM database identifier 100.98.10.0/port x, flexible ENUM routing node 104 may route a received ENUM query to ENUM database 106. According to one embodiment, routing the ENUM query to the appropriate ENUM database may include modifying the ENUM query to include the ENUM database identifier determined in block 302. For example, flexible ENUM routing node 104 may generate modified ENUM query 116 including IP address 100.98.10.0 and port x for delivery to ENUM database 106. It is appreciated that in addition to the exemplary network components shown in FIGS. 1 and 2, additional network components (not shown) may be located between flexible ENUM routing node 104 and one or more of ENUM databases 106-110, where additional network components (not shown) may route ENUM queries to ENUM databases 106-110 according to conventional methods.
FIG. 4 is a block diagram of an exemplary internal architecture of a flexible ENUM routing node 104 according to an embodiment of the subject matter described herein. Referring to FIG. 4, exemplary flexible ENUM routing node 104 may include communication module 400 and flexible ENUM processing modules 402 and 404 connected via a bus 406. As illustrated in FIG. 4, it is appreciated that one or more ENUM processing modules may be included in flexible ENUM routing node 104.
It is further appreciated that the components and/or the functionality of flexible ENUM routing node 104 may be implemented in a standalone network element, may be incorporated into an existing network element, or may be distributed across multiple network elements. For example, flexible ENUM routing according to the subject matter described herein may be provided by a signaling gateway node, a network router, an SS7-IP router, an IP router, a SIP server, an IMS node such as a CSCF, a softswitch, an application server, or any other communications network element.
Communication module 400 may include an SS7 or IP stack 408 and a distribution module 410. Stack 408 may be configured to send and receive messages, such as ENUM query and response messages, via a communications network. For example, stack 408 may be connected to an SS7 or IP network and configured to receive ENUM query 405 and send modified ENUM query 409. Distribution module 410 may receive messages from stack 408 and distribute them among ENUM processing modules 402. For example, distribution module 410 may receive ENUM query 405 from stack 408 and send the query to ENUM processing module 402 for processing. In one implementation, ENUM processing modules 402 and 404 may be identically provisioned. As a result, distributions module 410 may load share queries between ENUM processing modules 402 and 404.
ENUM processing module 402 may include an ENUM database identifier function 412, an E.164-to-ENUM database mapping data structure 414, and a routing function 416. ENUM database identifier function 412 may receive ENUM query messages from distribution function 410 via internal communications bus 406 and may extract an E.164 subscriber identifier used to query E.164-to-ENUM database identifier mapping data structure 414. Data structure 414 may be provisioned as a range-based data structure (see FIG. 1), as a combination of range-based and exception-based data structures (see FIG. 2), or as any other suitable data structure for providing access to ENUM database location information. If a matching entry in mapping data structure 414 is located, ENUM database identifier function 412 may modify ENUM query 405 to include the address of the determined ENUM database. The modified ENUM query may then be passed to routing function 416 for delivery to the appropriate ENUM database via stack 408 on communications module 400. For example, routing function 416 may determine on which outbound communication link, socket, SCTP association or other suitable connection the modified query is to be transmitted. ENUM query processing module 404 may be identically provisioned to module 404. However, a description of the corresponding components will not be repeated herein.
In the examples described above, flexible routing node 104 routes ENUM queries to ENUM databases. In alternate implementation, flexible routing node 104 may terminate ENUM queries, store state information relating to ENUM transactions, originate new ENUM queries, process responses, pair responses with queries using stored state information, and forward ENUM responses to query originators. Such an implementation is illustrated in FIG. 5. In FIG. 5, flexible routing node 104 receives an ENUM query from signaling point 102. The ENUM query may be addressed to flexible routing node 104. Flexible routing node 104 identifies the ENUM database to which the query should be routed using any of the methods described above. Rather than routing the original query to the database, flexible routing node 104 sends a new ENUM query to the ENUM database, which in this example is ENUM database 106. Flexible routing node 104 also stores state information indicating that the ENUM query that it sent to database 106 corresponds to a receipt received ENUM query from node 102. This information may be stored on the processing module 402 or 404 to which the original ENUM query was routed. In addition, distribution function 410 may store information that identifies the processing module that processes a particular ENUM query.
When ENUM database 106 responds to the ENUM query from routing node 104, the ENUM response is received by communication interface 400 illustrated in FIG. 4. Distribution function 410 forwards the response to the processing module that originated the ENUM query. That processing module pairs the ENUM response data with the original query, formulates a new response, and routes the response to the query originator, which in this example is SP 102. Accordingly, a flexible ENUM routing node according to the subject matter described herein may have a stateful implementation. Such an implementation, simplifies processing by query originators because the query originators simply forward ENUM queries to flexible routing node 104 and flexible routing node 104 handles the processing with the ENUM databases to obtain the ENUM translation information.
It will be understood that various details of the subject matter described herein may be changed without departing from the scope of the subject matter described herein. Furthermore, the foregoing description is for the purpose of illustration only, and not for the purpose of limitation, as the subject matter described herein is defined by the claims as set forth hereinafter.

## Claims

1. A method for routing E.164 number mapping (ENUM) queries to an ENUM database, the method comprising:
receiving an ENUM query including a subscriber identifier;
identifying an ENUM database among a plurality of non-identically provisioned ENUM databases belonging to the same service provider's network based on the subscriber identifier, wherein each of the ENUM databases contains ENUM data associated with subscribers belonging to the same service provider's network and wherein at least some of the ENUM databases contain ENUM data for different subscribers belonging to the same service provider's network, wherein receiving an ENUM query includes receiving an ENUM query including an E.164 telephone number and wherein identifying an ENUM database includes searching a range-based data structure using the subscriber identifier; and
routing the ENUM query to the identified ENUM database.

2. The method of claim 1 wherein receiving an ENUM query includes receiving an ENUM query generated by one of a service switching point (SSP), a mobile switching center (MSC), a media gateway controller (MGC), a session initiation protocol (SIP) proxy server, an H.323 gatekeeper, and an IP multimedia subsystem (IMS) node.

3. The method of claim 1 wherein receiving an ENUM query includes receiving an ENUM query at a flexible ENUM routing node where the query is addressed to the flexible ENUM routing node.

4. The method of claim 1 wherein receiving an ENUM query includes intercepting an ENUM query addressed to an ENUM database.

5. The method of claim 1 wherein identifying an ENUM database includes searching an exception-based data structure and, in response to failing to identify an ENUM database corresponding to the subscriber identifier in the exception-based data structure, searching the range-based data structure.

6. The method of claim 1 wherein identifying an ENUM database includes determining at least one of a uniform resource indicator (URI), an IP address, and a port number associated with the identified ENUM database.

7. The method of claim 1 wherein identifying an ENUM database includes determining a uniform resource indicator (URI) associated with the identified ENUM database.

8. The method of claim 1 wherein routing an ENUM query includes modifying the ENUM query to include the address of the identified ENUM database.

9. A method for processing an E.164 number mapping (ENUM) query, the method comprising:
receiving an ENUM query including a subscriber identifier;
utilizing the subscriber identifier to identify an ENUM database among a plurality of non-identically provisioned ENUM databases belonging to the same service provider's network, wherein each of the ENUM databases contains ENUM data associated with subscribers belonging to the same service provider's network and wherein at least some of the ENUM databases contain ENUM data for different subscribers belonging to the same service provider's network, wherein receiving an ENUM query including a subscriber identifier includes receiving an ENUM query that includes an E.164 telephone number and wherein utilizing the subscriber identifier to identify an ENUM database includes searching a range-based data structure utilizing the subscriber identifier; and
terminating the ENUM query, generating and forwarding a new ENUM query to the identified ENUM database.

10. The method of claim 9 comprising storing state information for an ENUM transaction associated with the ENUM queries.

11. The method of claim 10 comprising:
receiving an ENUM response;
associating the ENUM response with the ENUM transaction using the stored state information;
terminating the ENUM response, generating a new ENUM response, and forwarding the new ENUM response to an originator of the received ENUM query.

12. A flexible ENUM routing node for routing ENUM queries to an ENUM database, the node comprising:
a communications module for receiving an ENUM query including a subscriber identifier;
an E.164-to-ENUM database identifier mapping data structure for associating one or more subscriber identifiers with one or more ENUM database identifiers; and
an ENUM database identifier function for identifying, based on the subscriber identifier and using the E.164-to-ENUM database identifier mapping data structure, an ENUM database from a plurality of non-identically provisioned ENUM databases belonging to the same service provider's network, wherein each of the ENUM databases contains ENUM data associated with subscribers belonging to the same service provider's network and wherein at least some of the ENUM databases contain ENUM data for different subscribers belonging to the same service provider's network, wherein the E.164-to-ENUM database identifier mapping data structure includes a range-based data structure.

13. The flexible ENUM routing node of claim 12 wherein the communications module is configured to receive an ENUM query generated by one of a service switching point (SSP), a mobile switching center (MSC), a media gateway controller (MGC), a session initiation protocol (SIP) proxy server, an H.323 gatekeeper, and an IP multimedia subsystem (IMS) node.

14. The flexible ENUM routing node of claim 12 wherein the communications module is configured to receive an ENUM query addressed to the flexible ENUM routing node.

15. The flexible ENUM routing node of claim 12 wherein the communications module is configured to intercept an ENUM query addressed to one of the ENUM databases.

16. The flexible ENUM routing node of claim 12 wherein the E.164-to-ENUM database identifier mapping data structure includes an exception-based and the range-based data structure and wherein the ENUM database identifier function is adapted to search the exception-based data structure for an entry matching the subscriber identifier, and, in response to failing to locate a matching entry in the exception-based data structure, to search the range-based data structure for an entry matching the subscriber identifier.

17. The flexible ENUM routing node of claim 12 wherein the ENUM database identifier function is configured to determine at least one of a uniform resource indicator (URI), an IP address, and a port number associated with the identified ENUM database.

18. The flexible ENUM routing node of claim 12 wherein the ENUM database identifier function is configured to determine a uniform resource indicator (URI) associated with the identified ENUM database and to perform a domain name system (DNS) query to resolve the URI into an Internet protocol (IP) address.

19. The flexible ENUM routing node of claim 12 wherein the ENUM database identifier function is configured to modify the ENUM query to include an address of the identified ENUM database.

20. A non-transitory computer program product comprising computer executable instructions embodied in a computer readable medium for performing steps comprising:
receiving an ENUM query including a subscriber identifier;
identifying an ENUM database among a plurality of non-identically provisioned ENUM databases belonging to the same service provider's network based on the subscriber identifier, wherein each of the ENUM databases contains ENUM data associated with subscribers belonging to the same service provider's network and wherein at least some of the ENUM databases contain ENUM data for different subscribers belonging to the same service provider's network, wherein receiving an ENUM query including a subscriber identifier includes receiving an ENUM query that includes an E.164 telephone number and wherein identifying an ENUM database includes searching a range-based data structure utilizing the subscriber identifier; and
routing the ENUM query to the identified ENUM database.