SPEERMINT Working Group D. Malas, Ed. Internet-Draft CableLabs Intended status: Informational D. Meyer, Ed. Expires: May 2009 November 7, 2008 SPEERMINT Terminology draft-ietf-speermint-terminology-17.txt Status of this Memo By submitting this Internet-Draft, each author represents that any applicable patent or other IPR claims of which he or she is aware have been or will be disclosed, and any of which he or she becomes aware will be disclosed, in accordance with Section 6 of BCP 79. 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 This Internet-Draft will expire on May 7, 2009. Abstract This document defines the terminology that is to be used in describing Session PEERing for Multimedia INTerconnect (SPEERMINT). Table of Contents 1. Introduction...................................................2 2. SPEERMINT Context..............................................3 3. General Definitions............................................3 3.1. Signaling Path Border Element.............................3 3.2. Data Path Border Element..................................4 3.3. Session Establishment Data................................4 3.4. Call Routing..............................................5 3.5. PSTN......................................................5 Malas & Meyer Expires May 7, 2009 [Page 1] Internet-Draft SPEERMINT Terminology November 2008 3.6. IP Path...................................................5 3.7. Peer Network..............................................5 3.8. Service Provider..........................................5 3.9. SIP Service Provider......................................5 4. Peering........................................................6 4.1. Layer 3 Peering...........................................6 4.2. Layer 5 Peering...........................................6 4.2.1. Direct Peering.......................................6 4.2.2. Indirect Peering.....................................6 4.2.3. On-demand Peering....................................7 4.2.4. Static Peering.......................................7 4.3. Functions.................................................7 4.3.1. Signaling Function...................................7 4.3.2. Media Function.......................................7 4.3.3. Look-Up Function.....................................7 4.3.4. Location Routing Function............................8 5. Federations....................................................8 6. Acknowledgments................................................9 7. Security Considerations........................................9 8. IANA Considerations............................................9 9. Informative References.........................................9 Author's Addresses...............................................11 Intellectual Property Statement..................................11 Disclaimer of Validity...........................................11 Copyright Statement..............................................12 Acknowledgment...................................................12 1. Introduction The term "Voice over IP Peering" (VoIP Peering) has historically been used to describe a wide variety of practices pertaining to the interconnection of service provider networks and to the delivery of Session Initiation Protocol (SIP [2]) call termination over those interconnections. The discussion of these interconnections has at times been confused by the fact that the term "peering" is used in various contexts to describe interconnection at different levels in a protocol stack. Session Peering for Multimedia Interconnect focuses on how to identify and route real-time sessions (such as VoIP calls) at the session layer, and it does not (necessarily) cover the exchange of packet routing data or media sessions. In particular, "layer 5 network" is used here to refer to the interconnection between SIP servers, as opposed to interconnection at the IP layer ("layer 3"). The term "peering" will be used throughout the remainder of the document for the purpose of indicating a layer 5 interconnection. This document introduces standard terminology for use in characterizing real-time session peering. Note however, that while Malas & Meyer Expires May 7, 2009 [Page 2] Internet-Draft SPEERMINT Terminology November 2008 this document is primarily targeted at the VoIP peering case, the terminology described here is applicable to those cases in which service providers peer using SIP signaling (defined as SIP Service Providers, See Section 3.9) for non-voice or quasi-real-time communications like instant messaging. The remainder of this document is organized as follows: Section 2 provides the general context for the Session PEERing for Multimedia INTerconnect Working Group (SPEERMINT). Section 3 provides the general definitions for real-time SIP based communication, with initial focus on the VoIP peering case, and Section 4 defines the terminology describing the various forms of peering. Finally, Section 5 introduces the concept of federations. 2. SPEERMINT Context SPEERMINT provides a peering framework which leverages the building blocks of existing IETF defined protocols such as SIP [2] and ENUM [4]. While the SPEERMINT working group describes the use of these protocols in peering, it does not redefine how these protocols use input or output variables necessary for creating Session Establishment Data (SED) or the methods in which this data will be used during the peering process. See Section 3.3 for additional detail on SED and its principal variables such as telephone numbers of E.164 numbers [5] and Uniform Resource Identifiers (URI) [3]. For example, while the SPEERMINT working group is not limited to the use of telephone numbers, an E.164 number may be used as a key in an E.164 to URI mapping using ENUM. This mapping involves looking up Naming Authority Pointer (NAPTR) records in the DNS and results in a SIP URI. The process for deriving this information has already been defined in [4], but is used as a building block for SPEERMINT SED, on which the subsequent call routing is based. Note that the call routing step does not depend on the presence of an E.164 number. Indeed, the URI resulting from an ENUM query may no longer even contain numbers of any type. In particular, the SIP URI can be advertised in various other ways, such as on a web page. Finally, note that the term "call" is being used here in the most general sense, i.e., call routing and session routing are used interchangeably. 3. General Definitions 3.1. Signaling Path Border Element A signaling path border element (SBE) is located on the administrative border of a domain through which inter-domain session layer messages will flow. It typically provides signaling functions Malas & Meyer Expires May 7, 2009 [Page 3] Internet-Draft SPEERMINT Terminology November 2008 such as protocol inter-working (for example, H.323 to SIP), identity and topology hiding, and Session Admission Control for a domain. 3.2. Data Path Border Element A data path border element (DBE) is located on the administrative border of a domain through which flows the media associated with an inter-domain session. It typically provides media-related functions such as deep packet inspection and modification, media relay, and firewall traversal support. The DBE may be controlled by the SBE. 3.3. Session Establishment Data Session Establishment Data, or SED, is the data used to route a call to the next hop associated with the called domain's ingress point. A domain's ingress point might for example be the location derived from various types of DNS records (NAPTR, SRV, and A record) [1] that resulted from the resolution of the SIP URI. More specifically, the SED is the set of parameters that the outgoing SBEs need to complete the call, and may include: . A destination SIP URI . A SIP proxy or ingress SBE to send the INVITE to, including o Fully Qualified Domain Name (FQDN) o Port o Transport Protocol (UDP [9], TCP [10], and TLS [11]) . Security Parameters, including o TLS certificate to use o TLS certificate to expect o TLS certificate verification setting . Optional resource control parameters such as o Limits on the total number of call initiations to a peer o Limits on SIP transactions per second Malas & Meyer Expires May 7, 2009 [Page 4] Internet-Draft SPEERMINT Terminology November 2008 3.4. Call Routing Call routing is the set of processes and rules used to route a call and any subsequent mid-dialog SIP requests to their proper (SIP) destination. More generally, call routing can be thought of as the set of processes and rules, which are used to route a real-time session to its termination point. 3.5. PSTN The term "PSTN" refers to the Public Switched Telephone Network. In particular, the PSTN refers to the collection of interconnected circuit-switched voice-oriented public telephone networks, both commercial and government-owned. In general, PSTN terminals are addressed using E.164 numbers; various dial-plans (such as emergency services dial-plans), however, some applications may not directly use E.164 numbers. 3.6. IP Path For purposes of this document, an IP path is defined to be a sequence of zero or more IP router hops. 3.7. Peer Network This document defines a peer network as the set of SIP user agents (UAs) (customers) that are associated with a single administrative domain and can be reached via some IP path. Note that such a peer network may also contain end-users who are located on the PSTN (and hence may also be interconnected with the PSTN), as long as they are also reachable via some IP path. 3.8. Service Provider A Service Provider (SP) is defined to be an entity that provides layer 3 (IP) transport of SIP signaling and media packets. Example services may include, but are not limited too, Ethernet Private Line (EPL), Frame Relay, and IP VPN. An example of this may be an Internet Service Provider (ISP). 3.9. SIP Service Provider A SIP Service Provider (SSP) is an entity that provides session services utilizing SIP signaling to its customers. In the event that the SSP is also a function of the SP, it may also provide media streams to its customers. Such an SSP may additionally be peered with other SSPs. An SSP may also interconnect with the PSTN. An SSP may also be referred to as an Internet Telephony Service Provider (ITSP). While the terms ITSP and SSP are frequently used Malas & Meyer Expires May 7, 2009 [Page 5] Internet-Draft SPEERMINT Terminology November 2008 interchangeably, this document and other subsequent SIP peering related documents should use the term SSP. SSP more accurately depicts the use of SIP as the underlying layer 5 signaling protocol. 4. Peering While the precise definition of the term "peering" is the subject of considerable debate, peering in general refers to the negotiation of reciprocal interconnection arrangements, settlement-free or otherwise, between operationally independent service providers. This document distinguishes two types of peering, Layer 3 Peering and Layer 5 peering, which are described below. 4.1. Layer 3 Peering Layer 3 peering refers to interconnection of two service providers' networks for the purposes of exchanging IP packets which destined for one (or both) of the peer's networks. Layer 3 peering is generally agnostic to the IP payload, and is frequently achieved using a routing protocol such as Border Gateway Protocol (BGP) [6] to exchange the required routing information. An alternate, perhaps more operational definition of layer 3 peering is that two peers exchange only customer routes, and hence any traffic between peers terminates on the peer's network or the peer's customer's network. 4.2. Layer 5 Peering Layer 5 (Session) peering refers to interconnection of two SSPs for the purposes of routing real-time (or quasi-real time) call signaling between their respective customers using SIP methods. Such peering may be direct or indirect (see Section 4.2.1 and Section 4.2.2 below). Note that media streams associated with this signaling (if any) are not constrained to follow the same set of IP paths. 4.2.1. Direct Peering Direct peering describes those cases in which two SSPs peer without using an intervening layer 5 network. 4.2.2. Indirect Peering Indirect, or transit, peering refers to the establishment of either a signaling and media path or signaling path alone via one (or more) layer 5 transit network(s). In this case it is generally required that a trust relationship is established between the originating SSP Malas & Meyer Expires May 7, 2009 [Page 6] Internet-Draft SPEERMINT Terminology November 2008 and the transit SSP on one side; and, between the transit SSP and the termination SSP on the other side. 4.2.3. On-demand Peering SSPs are said to peer on-demand when they are able to exchange SIP traffic without any pre-association prior to the origination of a real-time transaction (like a SIP message) between the domains. Any information that needs to be exchanged between domains in support of peering can be learned through a dynamic protocol mechanism. On- demand peering can occur as direct or indirect. 4.2.4. Static Peering SSPs are said to peer statically when pre-association between providers is required for the initiation of any real-time transactions (like a SIP message). Static peering can occur as direct or indirect. An example of static peering is a federation. Each of the peers within the federation must first agree on a common set of rules and guidelines for peering, thus pre-associating with each other prior to initiating session requests. 4.3. Functions The following are terms associated with the functions required for peering. 4.3.1. Signaling Function The Signaling Function (SF) performs routing of SIP requests for establishing and maintaining calls, and to assist in the discovery or exchange of parameters to be used by the Media Function (MF). The SF is a capability of SIP processing elements such as a SIP proxy, SBE, and user agent. 4.3.2. Media Function The Media Function (MF) performs media related functions such as media transcoding and media security implementation between two SSPs. The MF is a capability of SIP session associated media end-points such as a DBE and user agent. 4.3.3. Look-Up Function The Look-Up Function (LUF) provides a mechanism for determining for a given request the target domain to which the request should be routed. An example of the LUF is an ENUM [4] look-up or a SIP INVITE request to a SIP proxy providing redirect responses for peers. Malas & Meyer Expires May 7, 2009 [Page 7] Internet-Draft SPEERMINT Terminology November 2008 In some cases, some entity (usually a 3rd party or federation) provides peering assistance to the originating SSP by providing this function. The assisting entity may provide information relating to direct (Section 4.2.1) or indirect (Section 4.2.2) peering as necessary. 4.3.4. Location Routing Function The Location Routing Function (LRF) determines for the target domain of a given request the location of the SF in that domain and optionally develops other SED required to route the request to that domain. An example of the LRF may be applied to either example in Section 4.3.3. Once the ENUM response or SIP 302 redirect is received with the destination's SIP URI, the LRF must derive the destination peer's SF from the FQDN in the domain portion of the URI. In some cases, some entity (usually a 3rd party or federation) provides peering assistance to the originating SSP by providing this function. The assisting entity may provide information relating to direct (Section 4.2.1) or indirect (Section 4.2.2) peering as necessary. 5. Federations A federation is a group of SSPs which agree to exchange calls with each other via SIP, and who agree on a set of administrative rules for such calls (settlement, abuse-handling, ...) and the specific rules for the technical details of the peering. The following provides examples of rules the peers of a federation may agree to and enforce upon all participants: . Common domain for all federation peers (e.g. bob@peer1.federation.example.com) . Codec rule (e.g. all peers must use the ITU-T G.711 codec [15]) . Authentication preference (e.g. all peers must use TLS when requesting to establish sessions with other peers) . Transport protocol (e.g. all peers must use TCP) . SIP address resolution mechanisms (e.g. all peers must use ENUM for resolving TNs to SIP URIs) Finally, note that an SSP can be a member of o No federation (e.g., the SSP has only bilateral peering agreements) Malas & Meyer Expires May 7, 2009 [Page 8] Internet-Draft SPEERMINT Terminology November 2008 o A single federation o Multiple federations and an SSP can have any combination of bi-lateral and multi- lateral (i.e., federated) peers. 6. Acknowledgments Many of the definitions were gleaned from detailed discussions on the SPEERMINT, ENUM, and SIPPING mailing lists. Scott Brim, Mike Hammer, Eli Katz, Gaurav Kulshreshtha, Otmar Lendl, Jason Livingood, Alexander Mayrhofer, Jean-Francois Mule, Jonathan Rosenberg, David Schwartz, Richard Shockey, Henry Sinnreich, Richard Stastny, Hannes Tschofenig, Dan Wing, John Elwell, and Adam Uzelac all made valuable contributions to early versions of this document. Patrik Faltstrom also made many insightful comments to early versions of this draft. 7. Security Considerations This document introduces no new security considerations. However, it is important to note that session peering, as described in this document, has a wide variety of security issues that should be considered in documents addressing both protocol and use case analysis. 8. IANA Considerations This document has no IANA actions. 9. Informative References [1] Gulbrandsen, A., Vixie, P., and L. Esibov, "A DNS RR for specifying the location of services (DNS SRV)", RFC 2782, February 2000. [2] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, A., Peterson, J., Sparks, R., Handley, M., and E. Schooler, "SIP: Session Initiation Protocol", RFC 3261, June 2002. [3] Mealling, M., "Dynamic Delegation Discovery System (DDDS) Part Four: The Uniform Resource Identifiers (URI)", RFC 3404, October 2002. [4] Faltstrom, P. and M. Mealling, "The E.164 to Uniform Resource Identifiers (URI) Dynamic Delegation Discovery System (DDDS) Application (ENUM)", RFC 3761, April 2004. Malas & Meyer Expires May 7, 2009 [Page 9] Internet-Draft SPEERMINT Terminology November 2008 [5] International Telecommunications Union, "The International Public Telecommunication Numbering Plan", ITU-T Recommendation E.164, 02 2005. [6] Rekhter, Y., Li, T., and S. Hares, "A Border Gateway Protocol 4 (BGP-4)", RFC 4271, January 2006. [7] Schulzrinne, H., Casner, S., Frederick, R., and V. Jacobson, "RTP: A Transport Protocol for Real-Time Applications", RFC 3550, July 2003. [8] Friedman, T., Caceres, R., and A. Clark, "RTP Control Protocol Extended Reports (RTCP XR)", RFC 3611, November 2003. [9] Narten, T. and H. Alvestrand, "Guidelines for Writing an IANA Considerations Section in RFCs", BCP 26, RFC 2434, October 1998. [10] Dierks, T. and E. Rescorla, "The TLS Protocol Version 1.1", RFC 4346, April 2006. [11] Postel, J., "User Datagram Protocol", STD 6, RFC 768, August 1980. [12] Postel, J., "DoD Standard Transmission Control Protocol", RFC 761, January 1980. [13] Plummer, David C., "An Ethernet Address Resolution Protocol", RFC 826, November 1982. [14] Babiarz, J., Chan, K., and F. Baker, "Configuration Guidelines for DiffServ Service Classes", RFC 4594, August 2006. [15] ITU Recommendation G.711 (11/88) - Pulse code modulation (PCM) of voice frequencies. Malas & Meyer Expires May 7, 2009 [Page 10] Internet-Draft SPEERMINT Terminology November 2008 Author's Addresses Daryl Malas CableLabs 858 Coal Creek Circle Louisville, CO 80027 USA Email: d.malas@cablelabs.com David Meyer Email: dmm@1-4-5.net Intellectual Property Statement The IETF takes no position regarding the validity or scope of any Intellectual Property Rights or other rights that might be claimed to pertain to the implementation or use of the technology described in this document or the extent to which any license under such rights might or might not be available; nor does it represent that it has made any independent effort to identify any such rights. Information on the procedures with respect to rights in RFC documents can be found in BCP 78 and BCP 79. Copies of IPR disclosures made to the IETF Secretariat and any assurances of licenses to be made available, or the result of an attempt made to obtain a general license or permission for the use of such proprietary rights by implementers or users of this specification can be obtained from the IETF on-line IPR repository at http://www.ietf.org/ipr. The IETF invites any interested party to bring to its attention any copyrights, patents or patent applications, or other proprietary rights that may cover technology that may be required to implement this standard. Please address the information to the IETF at ietf-ipr@ietf.org. Disclaimer of Validity This document and the information contained herein are provided on an "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. Malas & Meyer Expires May 7, 2009 [Page 11] Internet-Draft SPEERMINT Terminology November 2008 Copyright Statement Copyright (C) The IETF Trust (2008). This document is subject to the rights, licenses and restrictions contained in BCP 78, and except as set forth therein, the authors retain all their rights. Acknowledgment Funding for the RFC Editor function is currently provided by the Internet Society. Malas & Meyer Expires May 7, 2009 [Page 12]