dynamicsoft Inc. Proprietary VON Developers Conference 1/19/00 C O N N E C T I N G T H E W O R L D W I T H A P P L I C A T I O N S MGC to MGC Communications: Leveraging the Value of SIP Jonathan Rosenberg Chief Scientist

dynamicsoft Inc. Proprietary VON Developers Conference 1/19/00 C O N N E C T I N G T H E W O R L D W I T H A P P L I C A T I O N S Overview Requirements for MGC to MGC Communications SIP As A Solution SIP Extensions Required Standards Update

dynamicsoft Inc. Proprietary VON Developers Conference 1/19/00 C O N N E C T I N G T H E W O R L D W I T H A P P L I C A T I O N S What Is MGC To MGC Communications? Supports Scalable, Transparent, Multi-provider Phone-to-phone Service Through SS7 Terminations MGC Is a Single Component of the Solution Non-decomposed gateways can also be used Functions Required NPA-NXX routing Services Inter-device signaling Billing and settlements OAM&P

dynamicsoft Inc. Proprietary VON Developers Conference 1/19/00 C O N N E C T I N G T H E W O R L D W I T H A P P L I C A T I O N S Inter-MGC Architecture MGC MG Proxy Subscriber Database SG SS7 T1/3 SCTP Megaco SIP Proxy Location Server Proxy Location Server Location Server Location Server MGC Complex MGC Complex MGC Location Server Proxy SQL TRIP

dynamicsoft Inc. Proprietary VON Developers Conference 1/19/00 C O N N E C T I N G T H E W O R L D W I T H A P P L I C A T I O N S TRIP For NPA-NXX Routing Telephony Routing Over IP Being specified in IPTEL working group in the IETF Formerly known as GLP Used to exchange routing information between service providers TRIP Supports Numerous Models Bilateral agreements Centralized settlements provider Wholesaler service

dynamicsoft Inc. Proprietary VON Developers Conference 1/19/00 C O N N E C T I N G T H E W O R L D W I T H A P P L I C A T I O N S TRIP For NPA-NXX Routing continued TRIP Is Based on Scalable IP Routing Technology Uses BGP4 as a basis Supports aggregation, multiple providers Uses proven algorithms TRIP Provides Routing Tables for SIP Servers and Gatekeepers Access mechanisms include OSP LDAP

dynamicsoft Inc. Proprietary VON Developers Conference 1/19/00 C O N N E C T I N G T H E W O R L D W I T H A P P L I C A T I O N S Enabling Services Subscriber Database Is a Critical Component Providing User identification Current location Features enabled Feature parameters Authorization information

dynamicsoft Inc. Proprietary VON Developers Conference 1/19/00 C O N N E C T I N G T H E W O R L D W I T H A P P L I C A T I O N S Enabling Services continued Proxies Provide an Execution Environment to Manage features for parties in the call Access subscriber database for feature information Interface to other service provider networks Level of State Dependent on Features That Need to Be Executed Pre-call services enable proxy to drop out after call completes Mid-call services require proxies to be involved in a call signaling

dynamicsoft Inc. Proprietary VON Developers Conference 1/19/00 C O N N E C T I N G T H E W O R L D W I T H A P P L I C A T I O N S Requirements For Call Signaling Traditional Call Signaling Needed Call setup, tear down Capabilities exchange Feature invocation Service Transparency Want phone-to-phone service to work identically to non-IP Requirement: ISUP transport

dynamicsoft Inc. Proprietary VON Developers Conference 1/19/00 C O N N E C T I N G T H E W O R L D W I T H A P P L I C A T I O N S Three Solutions For Call Signaling Call States Derived from ISUP, ISUP Extended to Convey IP Media Information (BICC) Call States Derived From IP Signaling, ISUP Information Mapped to IP Signaling Call States Derived from IP Signaling, ISUP Messages Carried as Opaque Payloads

dynamicsoft Inc. Proprietary VON Developers Conference 1/19/00 C O N N E C T I N G T H E W O R L D W I T H A P P L I C A T I O N S SIP As A Solution For Third Approach MIME MIME = Multipurpose Internet Mail Extensions Allows arbitrary content to be carried in Also used for HTTP SIP Uses MIME SIP can carry arbitrary payloads Simple to define an ISUP MIME type Map each ISUP message type to SIP method, encapsulate ISUP message in SIP body

dynamicsoft Inc. Proprietary VON Developers Conference 1/19/00 C O N N E C T I N G T H E W O R L D W I T H A P P L I C A T I O N S SIP As A Solution For Third Approach continued Multipart SIP messages already carry a body (usually SDP) With ISUP, SIP must carry two bodies MIME Multipart allows multiple bodies Messages That Dont Map Many ISUP message type dont map to SIP Mid-call messages: SUS, RES, INR, INF Solution: SIP INFO method

dynamicsoft Inc. Proprietary VON Developers Conference 1/19/00 C O N N E C T I N G T H E W O R L D W I T H A P P L I C A T I O N S INFO Method Semantics of INFO Method Used for established calls Has no SIP call state semantics Presents information FYI, purpose depends on body type Usage for ISUP Mid-call ISUP messages placed into body of INFO Decapsulated at far side

dynamicsoft Inc. Proprietary VON Developers Conference 1/19/00 C O N N E C T I N G T H E W O R L D W I T H A P P L I C A T I O N S ISUP Flavors Problem Many National Variants of ISUP How Is This Handled in VoIP? Several Approaches Agree on a single version of ISUP for the Internet Ingress and egress gateways support several and negotiate a common one ISUP translation at intermediate proxies

dynamicsoft Inc. Proprietary VON Developers Conference 1/19/00 C O N N E C T I N G T H E W O R L D W I T H A P P L I C A T I O N S SIP As A Solution SIP Helps Solve All Three MIME provides labeling and negotiation capabilities Approach I: Universal ISUP Simple to support in SIP Content labeled with the agreed variant

dynamicsoft Inc. Proprietary VON Developers Conference 1/19/00 C O N N E C T I N G T H E W O R L D W I T H A P P L I C A T I O N S SIP As A Solution continued Approach II: Negotiation Ingress gateway picks its favorite, sends it in a request If egress gateway doesnt support it, it returns a 415 Media Unsupported Error response contains an Accept header, listing allowed MIME types (i.e., ISUP flavors) supported Ingress gateway tries again, picking a flavor that is supported Approach III: Translation Proxies can look at MIME type in ingress request Based on the next hop, translate ISUP and attach new body End-to-end authentication fails

dynamicsoft Inc. Proprietary VON Developers Conference 1/19/00 C O N N E C T I N G T H E W O R L D W I T H A P P L I C A T I O N S Non-ISUP Termination Problem In a Multi-provider Network, It Is Not Clear Where the Call Will Terminate On another ISUP gateway On an analog gateway On a PC terminal On a standalone PC phone On an IP PBX Will Not Know Ahead of Call Setup To Include ISUP or Not?

dynamicsoft Inc. Proprietary VON Developers Conference 1/19/00 C O N N E C T I N G T H E W O R L D W I T H A P P L I C A T I O N S Non-ISUP Termination Problem continued Solution I First check where the call terminates SIP has an OPTIONS message for querying remote participant about capability OPTIONS response contains the list of supported MIME types Can determine if ISUP is supported Solution II Always send ISUP If gateway doesnt understand the body, it discards it

dynamicsoft Inc. Proprietary VON Developers Conference 1/19/00 C O N N E C T I N G T H E W O R L D W I T H A P P L I C A T I O N S Standardization Status International Softswitch Consortium Developed Concept Initially called SIP+ Single provider only Now called SIP for Telephony, (SIP-T) or SIP Best Current Practice for Telephony (SIP-BCP-T) IETF SIP Working Group Has Now Adopted It As a Work Item

dynamicsoft Inc. Proprietary VON Developers Conference 1/19/00 C O N N E C T I N G T H E W O R L D W I T H A P P L I C A T I O N S Standardization Status continued Several Outputs From IETF INFO Method extension ISUP to SIP message conversions MIME payload type for ISUP Umbrella specification All Four Outputs Will Be Proposed Standard RFCs Priority of Focus Ensure SIP-T works for general SIP operation; multi-provider, security, etc.

dynamicsoft Inc. Proprietary VON Developers Conference 1/19/00 C O N N E C T I N G T H E W O R L D W I T H A P P L I C A T I O N S Conclusions MGC to MGC Communications Require Several Components Signaling That Supports Transparent ISUP Operation Is Important SIP Is A Good Basis For Such A Solution MIME support makes carrying ISUP easy MIME negotiation helps ISUP national variant problem Extensions underway in IETF and ISC

dynamicsoft Inc. Proprietary VON Developers Conference 1/19/00 C O N N E C T I N G T H E W O R L D W I T H A P P L I C A T I O N S Information Resource Jonathan Rosenberg