The objective of this task force is to identify a baseline set of features that should be common to all IP-NNI implementations for voice service. The Task Force may also identify gaps or ambiguities in existing standards and request that those gaps be addressed by the responsible Standards Development Organization [SDO]. The task group will produce one or more specifications that define a common set of implementation rules for SIP Service Providers [SSP] who desire to interconnect with another SSP for voice initially. Ultimately, there will be a need for specifications that cover other types of real time multimedia traffic, but that will not be explicitly considered by this Task Force. However, any specifications that the Task Force produces will not preclude or inhibit other forms of media. The specifications will define which standards and options must be supported. They will provide SSP’s with a precise description of the IP-NNI in the areas where the standards leave multiple options, or where the existing specifications are ambiguous. In addition, these specifications will increase requirements [i.e. MAY, SHOULD, MUST] where operational experience indicates that such enhancements are necessary to support full interoperability.
Specific objectives of the Task Force are:
- Define a reference architecture that sets forth the common functional entities necessary for SIP Service Provider [SSP] to SIP Service Provider Interconnection. This reference architecture will be from the perspective of the interconnection points between carriers and will not deal with implementation details inside the networks on either side of the IP-NNI.
- Specify the exact specifications (including IETF RFCs, 3GPP, and other existing standards) associated with these protocols that must or should be supported by each element of the reference architecture. Where required, the options that MUST or SHOULD be supported within a given standard will also be specified.
- Specify customary methods for negotiating protocols, protocol extensions, and exchanging capability information between SSP’s. Specify consensus methods of formulating SIP protocol messages where multiple options exist in standards.
- Specify the exact presentations of Fully Qualified Domain Names in “From:” and “To:” fields including use of TEL URI format, including PAI.
- Define the architecture and requirements for a shared “Thin” registry of NNI interconnection data.
- Specify a mechanism for determination of the terminating carrier of record irrespective of what the shared registry is and the method and format of the data retrieved from the terminating carrier.
- For IP originated Calls, specify the preferred header [SHOULD] for Calling Name data [CNAM], and specify how that data is presented to the terminating proxy including format, syntax and processing of such data. Note: The expectation is that the signaling of CNAM would not survive interworking to SS7.
- Define mandated support for underlying transport [e.g. UDP, TCP, SCTP].
- Specify an audio codec selection strategy that minimizes the need for transcoding and a transcoding strategy that balances the workload between originating and terminating carrier.
- Define strategies for DTMF and Fax support.
- Specify call loop detection and avoidance methods.
- Define common Quality of Service objectives including network overload and congestion notification and processing mechanisms.
- Investigate issues surrounding known interoperability problems (e.g. PRACK [RFC 3262], early media, ptime, etc.).
Areas that should be considreed by the Task Force are:
- Role of IPv6 to IPv4 interworking among SSPs.
- Define how unknown headers [e.g. x Headers] should be handled at the IP-NNI.
- Role of DNSSEC in an all SIP/IP interconnection environment.
- Assess the level of consensus for a practical method of carrier authentication and for providing adequate security for SIP signaling.
- Consider if the Audio Codec selection strategy would also apply to Video Codec to promote interoperability in multimedia multi stream sessions.
- Handling of re-invites as calls gets transferred from endpoint to endpoint and media suspension and restart for calls on hold or muted.
- Achieve consensus on a registry approach to support routing of E.164 number-address named SIP sessions including:
- Structure of interconnection data.
- The manner in which the data is used within the reference architecture.
- Anticipated responses to queries based on the defined interconnection data.
The Task Force may also consider sharing:
- Technical views on Caller-ID /name authentication and verification consistent with the overall NNI architecture and assess the level of industry consensus for:
- Common dustry psition on IETF STIR work.
- Who manages the Public Key infrastructure.
- Technical views on the architecture and protocol objectives for Enhanced Calling Name delivery and display including calling party reputation data on called party User Agents.
Areas that are explicitly beyond the scope of the Task Group are:
- Any discussion of the US Communication Act of 1934, As Amended.
- Any terms and conditions of Interconnection between service providers that are properly the role of a business negotiation.
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