Source: https://patents.google.com/patent/US9712341B2/en
Timestamp: 2019-04-23 18:52:41+00:00

Document:
The subject matter described herein includes methods, systems and computer readable media for providing E.164 number mapping (ENUM) translation at a bearer independent call control (BICC) and/or session initiation protocol (SIP) router. One aspect of the subject matter described herein includes a system for providing ENUM translation. The system includes an ENUM database. The system also includes a signaling router for receiving a bearer independent call control (BICC) signaling message that includes a first call party identifier, for obtaining, from the ENUM database, a first SIP address associated with the first call party identifier, for generating a first SIP signaling message that includes the first SIP address, and for routing the first SIP signaling message to a destination SIP node.
This application is a continuation-in-part of U.S. patent application Ser. No. 12/689,702 filed Jan. 19, 2010, which claims the benefit of U.S. Provisional Patent Application Ser. No. 61/145,517, filed Jan. 16, 2009. This application further claims the benefit of U.S. Provisional Patent Application Ser. No. 61/318,233 filed Mar. 26, 2010. The disclosures of each of the applications referenced in this paragraph are incorporated herein by reference in their entireties.
The subject matter described herein relates to the bearer independent call control protocol. More particularly, the subject matter described herein relates to methods, systems, and computer readable media for providing ENUM translation at a BICC and/or SIP router.
The BICC protocol is a signaling protocol based on narrowband-ISDN user part (N-ISUP) that is used to support narrowband integrated services digital network (ISDN) service over a broadband backbone network. BICC supports narrowband ISDN services independently of bearer and signaling message transport technology. The BICC architecture also separates the call control function from the bearer control function.
SIP is an application-layer control protocol for creating, modifying, and terminating sessions between communicating parties. The sessions may include Internet multimedia conferences, Internet telephone calls, and multimedia distribution. Members in a session can communicate via unicast, multicast, or a mesh of unicast communications.
In order to facilitate the integration of BICC and/or SIP signaling in a given network, communications between BICC, SIP, and/or legacy nodes need to be possible. Accordingly, there exists a need for methods, systems, and computer readable media for providing ENUM translation at a BICC and/or SIP router.
According to another aspect, the subject matter described herein includes a method for providing ENUM translation. The method occurs at a signaling router. The method includes receiving a first bearer independent call control (BICC) signaling message that includes a first call party identifier. The method also includes obtaining, from an ENUM database, a first SIP address associated with the first call party identifier. The method further includes generating a first SIP signaling message that includes the first SIP address and routing the first SIP signaling message to a destination SIP node.
The subject matter described herein can be implemented in software in combination with hardware and/or firmware. For example, the subject matter described herein can be implemented in software executed by a processor. In one exemplary implementation, the subject matter described herein may be implemented using a computer readable medium having stored thereon computer executable instructions that when executed by the processor of a computer control the computer to perform steps. Exemplary computer readable media suitable for implementing the subject matter described herein include non-transitory devices, such as disk memory devices, chip memory devices, programmable logic devices, and application specific integrated circuits. In addition, a computer readable medium that implements the subject matter described herein may be located on a single device or computing platform or may be distributed across multiple devices or computing platforms.
As used herein, the term “ENUM translation” refers to translating or mapping between non-SIP identifiers (e.g., E.164 formatted telephone numbers and telephone numbers formatted by other standards) and SIP identifiers (e.g., universal resource identifiers (URIs) and Internet protocol (IP) addresses).
FIG. 5 is a flow chart illustrating exemplary steps for performing ENUM translation according to an embodiment of the subject matter described herein.
FIG. 1 is a diagram of a communications network 100. Communications network 100 may include a signaling router (SR) 108, BICC-capable signaling points (SPs) 102A-B, SIP or IMS nodes, such as an IMS call signaling control function (CSCF) 104, and 3rd generation partnership project (3GPP) long term evolution (LTE) nodes, such as a mobility management entity (MME) 106.
SPs 102A-B may be any nodes capable of communicating using BICC signaling messages. Exemplary SPs 102 may include SS7 signaling points (SPs), media gateway controllers (MGCs), mobile switching centers (MSCs), Class 5 end offices, softswitches, tandem switches, packet switches, time division multiplexed (TDM) switches, session border control nodes, gateway nodes, service control points (SCPs), application servers, voice mail servers, interactive voice response (IVR) servers, and the like. SPs 102A-B may be associated with point codes. For example, each SP 102 may be identified by a unique point code and a destination point code (DPC) may be used in addressing BICC signaling messages for delivery to a given destination BICC node.
CSCF 104 represents a node capable of communicating using SIP signaling messages. Other exemplary SIP nodes may include SIP proxy servers, SIP application servers, MMEs, MSCs, and the like. MME 106 represents an LTE node capable of communicating using SIP and Diameter signaling messages. Other exemplary LTE nodes may include home subscriber servers (HSSs) and/or authentication, authorization, and accounting (AAA) server, a Bearer Binding and Event Reporting Function (BBERF), a policy charging enforcement function (PCEF), a policy charging and rules function (PCRF), a subscriber profile repository (SPR), a serving gateway (SGW), a packet data network (PDN) gateway, a Diameter signaling router (DSR), and the like. LTE nodes and/or SIP nodes may use one or more uniform resource identifiers (URIs) for identification and/or addressing purposes. For example, URIs may be IP addresses, email addresses, URLs, or other identifiers.
SR 108 may be any suitable entity for routing and/or relaying signaling messages, e.g., SIP, BICC, Diameter, and signaling system number 7 (SS7) messages. For example, SR 108 may be a BICC-capable router that can provide a centralized routing function, among other things, for BICC-capable call control elements (e.g., BICC-capable SPs) in a network. In another example, SR 108 may be a SIP router for routing and/or relaying SIP messages. In yet another example, SR 108 may be a signaling routing or relaying node that includes one or more interworking functions. The interworking functions may allow SR 108 to communicate with various nodes in communications network 100. For example, SR 108 may include an IMS-interworking unit (I-IWU) 114. I-IWU 114 may be adapted to translate BICC messages to equivalent SIP messages and vice-versa thereby generally facilitating signaling communications between BICC and SIP signaling points.
SR 108 may include or have access to various databases, such as a state information database (SIDB) 112, a routing database (RDB) 110, and an ENUM database 116. SIDB 112 may be any suitable entity (e.g., a storage device, memory, or non-transitory computer readable medium) for storing or maintaining state information. For example, call instance codes (CICs) may be associated with BICC sessions or call legs. SIP call identifiers (CIDs) may be associated with SIP sessions or call legs. SIDB 112 may store associations between CICs and CIDs relating to the same session or communication. SIDB 112 may also store source and/or destination node addresses associated with sessions. Additional state information may also be maintained related to the call or signaling session. For example, the additional state information may include available CICs at each SP 102A-B, congestion states for each node (e.g., SP 102B or CSCF 104) associated with SR 108, and relative traffic load of each node associated with SR 108.
RDB 110 may be any suitable entity for storing or maintaining routing information. For example, information stored at RDB 110 may be used by a routing module to perform routing for BICC signaling messages and/or other signaling messages. In one embodiment, RDB 110 may include a central routing table and a status table among other things.
A routing table may contain information about how to process given signaling messages. For example, the routing table may contain three fields: a subscriber identifier field which contains a subscriber or device identifier, such as a called party number (CdPN), calling party number (CgPN) or a portion thereof, a primary node field which contains a destination point code (DPC), universal resource identifier (URI), or other information that identifies a primary node which handles calls for that number, and a secondary node field which contains a DPC, URI, or other information that identifies a primary node which handles calls for that number if the primary node cannot (e.g., if is down or congested). A status table may contain information on whether a given DPC (i.e., SP) is available to handle signaling messages and whether any associated CICs are available. SR 108 may use these databases and other maintained information to determine how signaling traffic should be routed and/or load balanced among nodes in network 100.
ENUM database 116 may be any suitable entity for storing or maintaining ENUM translation information. ENUM database 116 may also include functionality for performing ENUM translation transactions or dips. For example, ENUM database 116 may be used for translating a telephone number into a URI (e.g., an IP address) that can be used in SIP or Internet communications. In another example, ENUM translation information may be used for translating a URI or an IP address into a telephone number for use in BICC or SS7 communications. In some embodiments, ENUM database 116 may be associated with a stand-alone node or computing platform (e.g., an ENUM server). In other embodiments, ENUM database 116 may be integrated with or co-located at SR 108.
In one embodiment, ENUM database 116 may include an ENUM table 118. ENUM table 118 may store or maintain associations between phone numbers or device identifiers (e.g., E.164 formatted telephone numbers, mobile subscriber integrated services digital network numbers (MSISDNs), or international mobile subscriber identities (IMSIs)) and SIP identifiers (e.g., universal resource identifiers (URIs), Internet protocol (IP) addresses, domain name system (DNS) addresses, or an email addresses). For example, ENUM database 116 may receive an ENUM query message from SR 108. The ENUM query message may include CdPN or MSISDN information. ENUM database 116 may query, using the CdPN or MSISDN information, ENUM table 118 for determining an associated SIP URI. If a match is found (e.g., if ENUM table 118 includes an entry with the same MSISDN as the ENUM query message), an associated SIP URI may be determined and sent back to SR 108 in an ENUM answer message. If a match is not found, ENUM database 116 may not respond or may send a response indicating that an associated SIP URI was not found.
Referring to the example illustrated in FIG. 1, a call indication (e.g., dialed digits) originating from a calling party may reach SP 102A in communications network 100. In response, a BICC call setup signaling message (e.g., an ISDN User Part (ISUP) initial address message (IAM)) may be generated by SP 102A. The BICC message may include a call party number or identifier, such as CdPN information (e.g., “9193457015”) or CgPN information. An exemplary call party number may be an E.164 formatted MSISDN or a telephone number that is formatted according to a different standard.
In step 1, the BICC call setup signaling message may be sent from SP 102A to SR 108. The BICC call setup signaling message may be received at SR 108 and the CdPN information may be examined. SR 108 may generate an ENUM query message that includes the CdPN information or a variation thereof. For example, generating an ENUM query message may include formatting or changing CdPN information, e.g., such that the CdPN information is formatted similar to a DNS address. For instance, a CdPN of “9193457015” may be reformatted as “5.1.0.7.5.4.3.9.1.9.E164.arpa” in the ENUM query message. In this example, CdPN information is reversed and each digit is separated by a period. Additionally, after the last digit of the CdPN and its corresponding period, a format type identifier (e.g., “E164”), a period, and a generic domain identifier (e.g., “arpa”) may be added.
In step 2, the ENUM query message may be sent to an external ENUM database 116. ENUM database 116 may be integrated with and/or co-located at an ENUM server. In an alternate implementation, ENUM database 116 may be a component of SR 108. ENUM database 116 and/or server may process the ENUM query message. For example, ENUM database 116 may use the CdPN information to identify a relevant entry in ENUM table 118 that contains associated SIP identifiers. If a relevant entry is found, ENUM database 116 and/or server may generate an ENUM answer message that includes one or more SIP identifiers (e.g., URIs) associated with the CdPN information.
In step 3, the ENUM answer message including URI information may be sent from ENUM database 116 to SR 108. SR 108 may receive the ENUM answer message and examine and/or extract the URI information. SR 108 may generate a SIP signaling message (e.g., a SIP INVITE message) associated with the BICC call setup signaling message. The SIP signaling message may include the URI information, or a portion thereof, provided in the ENUM answer message. For example, I-IWU 114 at SR 108 may generate the SIP INVITE message that includes the received URI information as a destination address and a URI associated with SR 108 as the origination address.
SR 108 may maintain state information associated with the BICC-SIP translation (e.g., at SIDB 112). The state information may include a mapping of the CdPN information to the URI information, e.g., as determined from the ENUM dip. The state information may be use during the routing or processing of subsequent BICC and SIP messages associated with the communication and/or session.
In step 4, the SIP signaling message including the URI information may be sent to CSCF 104. CSCF 104 may receive the SIP signaling message and forwards the message to a destination.
In step 5, a SIP signaling message (e.g., a SIP 200 OK message) may be sent from CSCF 104 to SR 108. The SIP signaling message may be for indicating that the SIP signaling message has been successfully sent (e.g., that the call party has been reached). SR 108 (e.g., using I-IWU 114 and SIDB 112) may generate a BICC signaling message associated with the SIP signaling message. The BICC signaling message may include CdPN information associated with the URI information in the SIP signaling message. For example, I-IWU 114 at SR 108 may generate a BICC ISUP answer call message (ACM). The BICC ACM may include the CdPN information and CgPN information associated with the caller. The BICC ACM may be for indicating that the call party has been reached.
In step 6, the BICC call setup signaling message may be sent from SR 108 to SP 102A. SP 102A may receive the message. The caller may receive indication that a call party has been reached (e.g., via ringing).
FIG. 2 is a diagram of communications network 100 according to another embodiment of the subject matter described herein. Except as disclosed herein, communications network 100 is essentially the same as described in related to FIG. 1. In this embodiment, ENUM database 116 may be integrated with or co-located at SR 108. As such, querying ENUM database 116 and/or ENUM table 118 may involve fewer signaling messages being sent via communications network 100.
Referring to the example illustrated in FIG. 2, a call indication (e.g., dialed digits) originating from a calling party may reach SP 102A in communications network 100. In response, a BICC call setup signaling message (e.g., BICC ISUP IAM) may be generated by SP 102A. The BICC message may include a call party number or identifier, such as CdPN information stored in a CdPN parameter. An exemplary call party number may be an E.164 formatted MSISDN or a telephone number that is formatted according to a different standard.
In step 1, the BICC call setup signaling message may be sent from SP 102A to SR 108. The BICC call setup signaling message may be received at SR 108 and the CdPN information may be examined. Using the CdPN information, SR 108 may query ENUM database 116 and/or ENUM table 118. For example, a call party number may be used to identify an entry in ENUM table 118 that includes associated SIP URIs and/or IP addresses.
SR 108 may generate a SIP signaling message (e.g., a SIP INVITE message) associated with the BICC call setup signaling message. The SIP signaling message may include the information determined from the ENUM dip, e.g., a SIP URI or IP address. For example, I-IWU 114 at SR 108 may generate an SIP INVITE message that includes URI information retrieved from ENUM database 116.
In step 2, the SIP signaling message including the URI information may be sent to CSCF 104. CSCF 104 may receive the SIP signaling message and forwards the message to a destination.
In step 3, a SIP signaling message (e.g., a SIP 200 OK message) may be sent from CSCF 104 to SR 108. The SIP signaling message may be for indicating that the SIP signaling message has been successfully sent. SR 108 (e.g., using I-IWU 114 and SIDB 112) may generate a BICC signaling message associated with the SIP signaling message. The BICC signaling message may include CdPN information associated with the URI information in the SIP signaling message. For example, I-IWU 114 at SR 108 may generate a BICC ISUP ACM. The BICC ACM may include the CdPN information and CgPN information associated with the caller. The BICC ACM may be for indicating that the call party has been reached.
In step 4, the BICC call setup signaling message may be sent from SR 108 to SP 102A. SP 102A may receive the message. The caller may receive indication that a call party has been reached (e.g., via ringing).
FIG. 3 is a diagram illustrating exemplary ENUM query information according to an embodiment of the subject matter described herein. Referring to FIG. 3, an ENUM query message 300 may include various sections or portions for storing ENUM related information. ENUM related information may include parameters, flags, identifiers, resource records (e.g., name authority pointer (NAPTR) records), and other information for performing an ENUM translation transaction or ENUM dip.
In this embodiment, ENUM query message 300 may include a header section, a question section, an authority section, and an additional section. The header section of ENUM query message 300 may include a transaction identification parameter (id), a query/response parameter (qr), an operation code parameter (opcode), an authoritative answer parameter (aa), a truncated parameter (tc), a recursive desired parameter (rd), a recursive available parameter (ra), an authenticated data parameter (ad), a checking disabled parameter (cd), and/or return code parameter (rcode). An id may include a value used to identify associated responses and answer messages (e.g., both may have the same ID value). A qr may include a value (e.g., ‘0’=query and ‘1’=response) for indicating whether a message is a query or a response. An opcode may include a value or other information for indicating a particular type of ENUM message. For example, as depicted in FIG. 3, ENUM query message 300 includes a qr of “0” and an opcode of “QUERY” in the header section.
An aa may include a value (e.g., ‘0’=not authoritative and ‘1’=authoritative) for indicating whether a responding name server (e.g., ENUM database 116) is an authority for the domain name (e.g., the formatted CdPN information) in the question section. A tr may include a value (e.g., ‘0’=not truncated and ‘1’=truncated) for indicating whether a message is truncated. A rd may include a value (e.g., ‘0’=recursive not desired and ‘1’=recursive desired) for indicating whether a name server is to pursue the query recursively (e.g., in searching a data structure for entries). An ra may include a value (e.g., ‘0’=recursive query support not available and ‘1’=recursive query support available) for indicating whether a name server is capable of pursuing a query recursively. An ad may include a value (e.g., ‘0’=not authenticated and ‘1’=authenticated) for indicating whether all data in the message has been authenticated (e.g., by a name server using local security policies). A cd may include a value (e.g., ‘0’=checking is disabled and ‘1’=checking is enabled) for indicating whether a name server can avoid performing signature validation. An rcode may include a value or other information for indicating the outcome of a particular message.
ENUM query message 300 may also include parameters, such as a question section counter parameter (qdcount), an answer section counter parameter (ancount), an authority section counter parameter (nscount), and an additional section counter parameter (arcount), for indicating number of entries, e.g., resource records or other data structures, in particular message sections. For example, a qdcount may include a value for indicating the number of resource records in the question section of ENUM query message 300. An ancount may include a value for indicating the number of resource records in the answer section of ENUM query message 300. An nscount may include a value for indicating the number of resource records in the authority section of ENUM query message 300. An arcount may indicate the number of resource records in the additional section of ENUM query message 300.
As stated above, ENUM query message 300 may include a question section for storing questions. For example, a question section may include call party information used for querying ENUM database 116 to find an associated SIP identifier. ENUM query message 300 may include an answer section for storing answers to questions. For example, an answer section may include a list of SIP identifiers associated with a particular question. ENUM query message 300 may include an authority section for storing name server information. For example, an authority section may include a list of name servers that provided answers. ENUM query message 300 may include an additional section for storing additional information. For example, an additional section may include additional information (e.g., glue records to break circular dependency created by delegating name servers).
While ENUM query message 300 may include an answer section, authority section, and an additional section, it will be appreciated that typical ENUM query messages 300 may contain little, if any, relevant information in these sections. Instead, ENUM answer messages may use such sections for providing relevant ENUM translation information. For example, after an ENUM database 116 has been queried, ENUM answer messages may include resource records in an answer section that contains SIP identifiers associated with call party information in the question section of ENUM query message 300.
FIG. 4 a diagram illustrating exemplary ENUM answer information according to an embodiment of the subject matter described herein. Except as described herein, exemplary ENUM answer message 400 may include essentially the same parameters, counters, and sections as described in reference to ENUM query message 300. In this embodiment, ENUM answer message 400 may be associated with ENUM query message 300, e.g., as determined by each message having the id value of “41555” in their header sections.
ENUM answer message 400 may include parameters, counters, and/or sections that are different and/or additional to related ENUM query message 300. For example, as illustrated in FIG. 4, ENUM answer message 400 may include one or more resource records in its answer section. Each resource record in the answer section of ENUM answer message 400 may include a SIP identifier (e.g., a SIP URI) that is associated with a resource record in the question section of ENUM answer message 400 or a related message (e.g., ENUM query message 300. Further, ENUM answer message 400 may include one or more resource records providing information associated with ENUM database 116 in an authority section. For example, as illustrated in FIG. 4, a resource record in the authority section of ENUM answer message 400 may include a DNS address for ENUM database 116 and geographical location information.
FIG. 5 is a flow chart illustrating exemplary steps for performing ENUM translation according to an embodiment of the subject matter described herein. In this embodiment, one or more exemplary steps described herein may be performed at or performed by a SR 108. In some embodiments, SR 108 may include functionality (e.g., I-IWU 114) for communicating between various protocols, e.g., BICC signaling messages and SIP signaling messages.
In FIG. 5, in step 500, a first BICC signaling message that includes a first call party identifier may be received. For example, as illustrated in FIG. 1, a BICC ISUP IAM may be received at SR 108. The BICC ISUP IAM may include a CdPN parameter with an E.164 formatted telephone number as its value. In other examples, a call party identifier may be a dialed number or other information in a different format, such as an E.212 formatted IMSI value.
In step 502, a first SIP identifier associated with the first call party identifier may be obtained from an ENUM database. For example, as illustrated in FIG. 1, SR 108 may generate an ENUM query message that includes call party information (e.g., a DNS-formatted telephone number). SR 108 may send the ENUM query message to an external ENUM database 116. ENUM database 116 may process the ENUM query message and send an ENUM answer message that includes one or more SIP identifiers to SR 108.
In step 504, a first SIP signaling message that includes the first SIP identifier may be generated. For example, as illustrated in FIG. 1, SR 108 and/or I-IWU 114 may generate a SIP INVITE message that includes a SIP identifier from an ENUM dip.
In step 506, the first SIP signaling message may be routed to a destination SIP node. For example, as illustrated in FIG. 1, a SIP INVITE message may be sent to CSCF 104. CSCF 104 may receive the SIP INVITE message and attempt to reach the called party.
In one embodiment, SR 108 may receive a second SIP message associated with the first SIP message. The second SIP message may include a second SIP identifier. For example, as illustrated in FIG. 1, a SIP 200 OK message may be sent from CSCF 104 to SR 108. SR 108 may determine a call party identifier associated with the SIP identifier in the SIP OK message. For example, SR 108 may use state information at SIDB 112 to determine that a second SIP identifier is associated with a second call party identifier (e.g., a MSISDN). After determining the second call party identifier, SR 108 may generate a second BICC signaling message that includes the second call party identifier and may route the second BICC signaling message towards a BICC node (e.g., SP 102A).
In one embodiment, the second SIP identifier may be associated with the same subscriber or device as the first SIP identifier and the second call party identifier may be the same as the first call party identifier. In another embodiment, the second SIP identifier may be the same as the first SIP identifier and the second call party identifier may be the same as the first call party identifier.
a signaling router for receiving a first bearer independent call control (BICC) signaling message that includes a first call party identifier and a CIC, for obtaining, from the ENUM database, a first SIP identifier associated with the first call party identifier, for querying, using the CIC, a state information database for identifying a SIP call identifier (CID) associated with the CIC, wherein the state information database maintains associations between CICs and CIDs associated with related communications; for generating a first SIP signaling message that includes the first SIP identifier and the SIP CID, wherein the CIC identifies a BICC signaling session associated with the first BICC signaling message and wherein the SIP CID identifies a SIP session associated with the BICC signaling session, wherein the signaling router is configured for receiving a second SIP message associated with the first SIP message, wherein the second SIP message includes a second SIP identifier, for determining a second call party identifier associated with the second SIP identifier, for generating a second BICC signaling message that includes the second call party identifier, and for routing the second BICC signaling message towards a BICC node.
2. The system of claim 1 wherein obtaining, from an ENUM database, a first SIP identifier associated with the first call party identifier includes sending a query message that includes call party information to the ENUM database and receiving an answer message that includes the first SIP identifier.
3. The system of claim 1 wherein the first call party identifier is an E.164 formatted telephone number, a mobile subscriber integrated services digital network number (MSISDN), or an international mobile subscriber identity (IMSI).
4. The system of claim 1 wherein the first SIP identifier is a uniform resource identifier (URI), an Internet protocol (IP) address, a domain name system (DNS) address, or an email address.
5. The system of claim 1 wherein the signaling router includes an interworking unit (IWU) for BICC-SIP interworking.
6. The system of claim 1 wherein the ENUM database is external to the signaling router.
7. The system of claim 1 wherein the ENUM database is internal to the signaling router.
8. The system of claim 1 wherein determining the second call party identifier associated with the second SIP identifier includes querying maintained state information.
9. The system of claim 1 wherein the second SIP identifier is associated with the same subscriber or device as the first SIP identifier and wherein the second call party identifier is the same as the first call party identifier.
10. The system of claim 1 wherein the second SIP identifier is the same as the first SIP identifier and wherein the second call party identifier is the same as the first call party identifier.
routing the second BICC signaling message towards a BICC node.
12. The method of claim 11 wherein obtaining, from an ENUM database, a first SIP identifier associated with the first call party identifier includes sending a query message that includes call party information to the ENUM database and receiving an answer message that includes the first SIP identifier.
13. The method of claim 11 wherein the first call party identifier is an E.164 formatted telephone number, a mobile subscriber integrated services digital network number (MSISDN), or an international mobile subscriber identity (IMSI).
14. The method of claim 11 wherein the first SIP identifier is a uniform resource identifier (URI), an Internet protocol (IP) address, a domain name system (DNS) address, or an email address.
15. The method of claim 11 wherein the signaling router includes an interworking unit (IWU) for BICC-SIP interworking.
16. The method of claim 11 wherein the ENUM database is external to the signaling router.
17. The method of claim 11 wherein the ENUM database is internal to the signaling router.
18. The method of claim 11 wherein determining the second call party identifier associated with the second SIP identifier includes querying maintained state information.
19. The method of claim 11 wherein the second SIP identifier is associated with the same subscriber or device as the first SIP identifier and wherein the second call party identifier is the same as the first call party identifier.
20. The method of claim 11 wherein the second SIP identifier is the same as the first SIP identifier and wherein the second call party identifier is the same as the first call party identifier.
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References: Application No. 06
 Application No. 200780048418
 Application No. 07839798
 Application No. 2935
 Application No. 200780048418
 Application No. 2935
 Application No. 06
 Application No. 200780048418
 Application No. 200680017480
 Application No. 200780048418
 Application No. 200780048418