Internet Engineering Task Force SIGTRAN WG Internet Draft G. Sidebottom, J. Yoakum draft-sidebottom-ips7-00.txt Nortel Networks June 18, 1999 Expires: January 2000 Open Architecture for IP/SS7 Interworking STATUS OF THIS MEMO This document is an Internet-Draft and is in full conformance with all provisions of Section 10 of RFC2026. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet-Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. ABSTRACT This memo defines an open architecture for interworking of Internet and PSTN Signaling System 7 control networks, including services, supporting protocols and internal Signaling Gateway functions. 1 Introduction This memo defines an open architecture for IP/SS7 interworking, identifying services that would be provided by an IP/SS7 (IPS7) Signaling Gateway (SG), the supporting protocols needed - some of which are being addressed through the SIGTRAN Working Group - and supporting internal SG functions, which are not subject to standardization. This memo is being submitted in hopes of providing direction for future protocol work in IETF. Sidebottom [Page 1] Internet Draft IPS7 June 18, 1998 2. IP-to-SS7 (IPS7) Basic Services The following sections identify a set of services that should be provided by the SG and other IPS7 supporting systems in order to provide high performance, high availability interworking of IP and SS7 networks and applications. 2.1 Networking Control Services The following are services dealing with network control to support transport of messages between IPS7 systems. - Transport Path Availability Management (TPAM) Management of IP transport paths between SGs and IP telephony elements to support high availability of services. transport paths between SGs and IP telephony elements - IP Node Maintenance (IPNM) Capability to coordinate availability and failure recovery of the SGs and associated IP telephony elements such as MGCs in addition to the transport elements. - SS7 Network Management (SSNM) Capability of extending SS7 MTP signaling network management principles to MGCs and other IP telephony elements to enable seamless end-to-end management. 2.2 Call Control Services The following are services provided for interworking of call control signaling between SS7 and IP applications. - ISUP Tunneling (ITUN) Signaling gateway (SG) functionality and signaling gateway-media gateway controller (MGC) protocol to support the encapsulation and transfer of ISUP messages between SGs and MGCs - Call Control Gateway Function (CCGF) Provides gateway functionality between different call control protocols used in the IP and PSTN domains. Sidebottom [Page 2] Internet Draft IPS7 June 18, 1998 2.2 Intelligent Network Services The following are services provided in support of Intelligent Network or equivalent services being provided across both IP and PSTN domains. - SCCP/TCAP Tunneling (STUN) SG functionality and SG-IP telephony element protocol to support the encapsulation and transfer of SCCP/TCAP messages between SGs and MGCs or other IP telephony elements - Service Control Gateway Function (SCGF) Provides Intelligent Network (IN) services level gateway functionality between the IP and PSTN domains - TCAP Transactions over IP (TCIP) Protocol supporting the transport of TCAP transactions directly over IP between MGCs and IP telephony elements 3. Supporting Protocols There are a number of protocols now being defined, and more that will need to be defined in order to support IPS7 interworking, including both transport and functional protocols. 3.1 SIGTRAN Activities - Signaling Common Transport Protocol (SCTP) An IP transport protocol to support the reliable, ordered delivery of PSTN signaling payloads and supporting protocols. Currently an activity in the SIGTRAN Working Group. This protocol should support functions such as: - Reliable Transport of Signaling Protocols (RTSP) Compensation for IP network limitations (e.g., packet loss, device failure) sufficient to meet SS7 performance requirements - Signaling Traffic Load Distribution (STLD) Distribution of signaling traffic across multiple transport paths, i.e., MGC to PSTN and between IP telephony elements Sidebottom [Page 3] Internet Draft IPS7 June 18, 1998 In addition to SCTP, there need to be a set of adaptation protocols that support mapping of SS7 signaling to the common transport mechanism over IP: - SS7 Link Adaptation Protocol Adaptation protocol to enable use of IP transport between SGs that emulates an SS7 link between SS7 entities. - Signaling Gateway Associated Signaling Adaptation protocol supporting the transport of F-link based SS7 signaling received at an Media Gateway (MG) to an MGC for further processing Signaling Gateway Direct Signaling Adaptation protocol supporting transport of SS7 A/B-link based SS7 signaling from an SS7 Signal Transfer Point through the SG terminating on the MGC for call processing. 3.2 PINT Activities PINT protocol work (and the new PIN activity) has resulted in definition of protocol that would support an SCGF function attaching PSTN and IP networks. The PINT activity has resulted in definition of the PINT Profile for SIP and SDP. 3.3 Independent Activities The following protocols are not being addressed by IETF Working Groups: - Signaling Secure Association Protocol IP network application protocol enabling registration, authentication and accounting for entities involved in signaling transport. - Overload Control (OVLC) Protocol between an MGC or other IP telephony element and an SG supporting the SG control of the offered call or transaction load to a node in the IP domain from the PSTN Sidebottom [Page 4] Internet Draft IPS7 June 18, 1998 4. SG Internal Functions The protocols above need to be supported within the SG by a set of internal functions that would not be standardized. The following list of functions is provided as a means of structuring further discussion or investigation of IPS7 protocol requirements. - IP Quality of Service Function (IPQF) SG functionality enabling utilization of IP QoS mechanisms in signaling - IP Secure Association Function (IPSF) IP network level and/or transaction level function enabling secure communication between trusted entities involved - Signaling Gateway Screening Function (SGSF) SG support of an SS7 gateway screening function - Signaling Gateway Mediation Function (SGMF) SG support of an 'application firewall' function operating at the ISUP/TCAP level - Signaling Protocol Conversion Function A stateless function at the application layer that maps or translates signaling messages across the SG to converge the number and variations of the protocols supported at IP entities 6 Acknowledgements 7 Bibliography [1] , work in progress. [2] , work in progress. [3] , work in progress Sidebottom [Page 5] Internet Draft IPS7 June 18, 1998 8 Author's Contact Information Greg Sidebottom Nortel Networks 3685 Richmond Rd, Nepean, Ontario Canada K2H5B7 gregside@nortelnetworks.com This document expires January 2000. Sidebottom [Page 6]