WG MMUSIC Albrecht Schwarz Internet Draft Alcatel-Lucent Intended status: Standards track March 27, 2014 Expires: September 2014 SDP codepoints for gateway control draft-schwarz-sdp-for-gw-01.txt Status of this Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. This document may contain material from IETF Documents or IETF Contributions published or made publicly available before November 10, 2008. The person(s) controlling the copyright in some of this material may not have granted the IETF Trust the right to allow modifications of such material outside the IETF Standards Process. Without obtaining an adequate license from the person(s) controlling the copyright in such materials, this document may not be modified outside the IETF Standards Process, and derivative works of it may not be created outside the IETF Standards Process, except to format it for publication as an RFC or to translate it into languages other than English. 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 September 27, 2014. Schwarz Expires September 27, 2014 [Page 1] Internet-Draft SDP codepoints for gateway control March 2014 Copyright Notice Copyright (c) 2014 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Abstract SDP is used in many signalling protocols at call control level (such as SAP, SIP, BICC), bearer control level (such as RTSP, IPBCP) and gateway control level (such as H.248/MEGACO, MGCP). Scope of this RFC is related to gateway control specific SDP usage. Gateway control protocols do usually NOT define and introduce any new SDP parameters, however, gateway control protocols need specific SDP parameter values in addition to SDP usage at call or bearer control level. Such SDP codepoints are collected by this RFC with the purpose of registration with IANA. Table of Contents 1. Introduction...................................................3 1.1. Background - Gateway control protocols in scope...........3 1.2. Background - SDP usage in gateway control protocol(s).....4 1.3. Motivation - Why gateway control specific SDP?............4 1.4. Scope.....................................................5 2. Conventions used in this document..............................5 2.1. Prescriptive language.....................................5 2.2. Terminology used..........................................5 2.3. Abbreviations used........................................6 3. Decomposed gateways - usage of SDP.............................7 3.1. SDP for bearer type indication............................7 3.2. SDP for controlling the mode of operation of a gateway....7 4. SDP codepoints related to "m="-line element............7 4.1. Purpose...................................................7 4.2. Application-agnostic indications..........................7 4.3. Protocol individual indications...........................8 4.4. SDP codepoints related to "m="-line element........8 4.5. SDP codepoints related to "m="-line element.......8 5. SDP codepoints related to "a="-lines (SDP attributes)..........8 5.1. SDP attribute "ITU-T H.248 package".......................8 Schwarz Expires September 27, 2014 [Page 2] Internet-Draft SDP codepoints for gateway control March 2014 6. Security Considerations........................................8 7. IANA Considerations............................................8 7.1. SDP codepoints related to "m="-line element.......8 8. References.....................................................9 8.1. Normative References......................................9 8.2. Informative References...................................11 9. Acknowledgments...............................................11 10. CHANGE LOG...................................................12 10.1. Changes against "-00"...................................12 1. Introduction 1.1. Background - Gateway control protocols in scope Gateway control protocols are required for decomposed network elements which separating media plane and signalling plane related network functions (see e.g., [RFC7092] concerning a decomposed B2BUA with a SIP specific signalling B2BUA plus a media plane B2BUA entity). The gateway control interface between the controlling entity (known as media gateway controller MGC) and controlled entity (known as media gateway) follows a disclosed, open, standardized protocol. This RFC considers such gateway control protocols which use the SDP [RFC4566] as embeded signalling for media-related characteristics. This RFC focuses on following gateway control protocol, known as "H.248", as standardized within the ITU-T H.248.x-series of Recommendations [ITU-T H.248.x]. The core protocol is defined by H.248.1 [ITU-T H.248.1], which actually originates in the IETF, known as MEGACO (media gateway control): IETF history: o Closed working group "MEGACO" (since technology was transferred to ITU-T); o IETF MEGACO protocol versions: see [RFC2885], [RFC3015], [RFC3525]; o Transfer IETF to ITU-T: "Reclassification of RFC 3525 to Historic", [RFC5125]. Schwarz Expires September 27, 2014 [Page 3] Internet-Draft SDP codepoints for gateway control March 2014 1.2. Background - SDP usage in gateway control protocol(s) Gateway control protocol H.248 supports two message encoding modes: binary and text. Gateway deployments in IP network environments use primarily H.248 text encoding mode in order to benefit from SDP usage at call control signalling level. For instance, the SIP level SDP information is mapped by the H.248 MGC entity to SDP information as used in H.248 gateway control signaling. Following list indicates typical areas in H.248 gateway control: o SDP in H.248: clause 7.1.8 "Local and Remote Descriptors" and particularily clause 7.1.8.1.1.2 "Summary - ITU-T H.248 usage of SDP" in [ITU-T H.248.1]; o Wildcarding in SDP: "H.248 SDP parameter identification and wildcarding" [ITU-T H.248.39]; o SDP versioning: "SDP RFC and capabilities packages", [ITU-T H.248.49]; o SDP profiling: the allowed SDP elements and codespace could be limited by H.248 profile specifications, see "ITU-T H.248 profile definition template" in Appendix III/[ITU-T H.248.1] (profile template clauses 6.15 and 6.16 are related to SDP); o SDP offer/answer models: "Usage of the revised SDP offer / answer model with H.248", [ITU-T H.248.80]; o SDP mapping between call control and H.248: "SDP Interworking between Call/Session Control Protocols (SIP/SDP, RTSP/SDP; etc.) and the Gateway Control Protocol (H.248/SDP)" [ETSI 183046]. o SDP for mode control in border gateways: see Annex G "Illustration of BGF modes of operation" and particularily Annex G.2 "BGF modes driven by particular SDP lines" [ETSI 183068]. 1.3. Motivation - Why gateway control specific SDP? Gateway control protocol (GCP) specific SDP codepoints are primarily required in two areas: 1. SDP for bearer type indication 2. SDP for controlling the mode of operation of a gateway Schwarz Expires September 27, 2014 [Page 4] Internet-Draft SDP codepoints for gateway control March 2014 Clause 3 provides detailed background and [ETSI 183068], Annex G indicates a bunch of illustrative examples in the area of IP-to-IP gateways (also known as border gateways). 1.4. Scope Collection of SDP codepoints, which are specific to gateway control protocols, with the purpose of registration with IANA. The focus is (but not limited to) on SDP codepoints related to the SDP "m=" line. 2. Conventions used in this document 2.1. Prescriptive language The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC-2119 [RFC2119]. 2.2. Terminology used APPLICATION: This term, when used in the context of "application-agnostic" or "application-aware", refers to the IP application protocol on top of a "L4 transport protocol" (e.g., "TCP", "UDP") with or without a "transport security protocol" (e.g., "TLS", "DTLS"). NOTE - The notion of application includes (if present) also the associated protocol layer of "application level framing protocol" (e.g., "RTP"). BORDER GATEWAY: A H.248 packet-to-packet (media) gateway, such as an IP-to-IP gateway, with scope on two-party communication services. NOTE: not to be confused with border gateway entities in the native IP router space, such as a border router with support of border gateway protocols (such as BGP, e.g. [RFC1163]). CODEPOINT: The combination of a "signalling parameter" plus assigned "value" in protocol engineering. The "value" represents a codepoint (or code position) in the code space. X-AGNOSTIC / X-AWARE: Schwarz Expires September 27, 2014 [Page 5] Internet-Draft SDP codepoints for gateway control March 2014 Placeholder 'X' denotes a protocol layer, a protocol stack or an abtracted model such as "application", "media", "transport", etc. This term indicates whether the controlled entity (here: H.248 MG) becomes aware or not about information concerning 'X'. 2.3. Abbreviations used B2BUA Back-to-Back User Agent DTLS Datagram Transport Layer Security GCP Gateway Control Protocol IPBCP (ITU-T) IP Bearer Control Protocol ITU-T International Telecommunication Union Telecommunication Standardization Sector IWF Interworking Function MEGACO Media Gateway Control MG (H.248) Media Gateway MG (H.248) Media Gateway Controller RTSP Real-Time Streaming Protocol SAP Session Announcement Protocol SCTP Stream Control Transmission Protocol SDP Session Description Protocol SIP Session Initiation Protocol TCP Transmission Control Protocol TLS Transport Layer Security UA User Agent UDP User Datagram Protocol Schwarz Expires September 27, 2014 [Page 6] Internet-Draft SDP codepoints for gateway control March 2014 3. Decomposed gateways - usage of SDP Gateway control protocol (GCP) specific SDP codepoints are primarily required in two areas: 3.1. SDP for bearer type indication The bearer connection endpoint at media gateway level needs to be specified concerning the required bearer protocol or protocol stack segment respectively. This relates essentially to the SDP "m="line element. However, media gateways require in addition so called "agnostic" type of SDP codepoints, which is in contrast to the so called application-aware, transport protocol type aware, etc SDP codepoints used by communication endpoints (such as a SIP UA located in an IP host entity). 3.2. SDP for controlling the mode of operation of a gateway A media gateway (MG) is typically interconnecting internally multiple bearer connection endpoints. A plethora of interworking functions (IWF) may be supported in the media plane by the MG. The type of IWF is known as mode of operation, and typically controlled via SDP. The semantic is actually the result of the SDP information of ALL involved bearer connection endpoints (in H.248: terminations / stream endpoints) and/or BOTH traffic directions (if applicable). 4. SDP codepoints related to "m="-line element 4.1. Purpose The SDP "m=" line element allows the indication of a) a single protocol (layer) or b) a protocol stack (i.e., multiple, consecutive protocol layers). The protocol stack based value is inherently ambiguous in case of the requirement in indicating a particular protocol layer out of the stack. This is a well-known issue of this element. 4.2. Application-agnostic indications Application-agnostic, - or X-agnostic in general -, indications are typically realized by using character "-" instead of a concrete value in SDP fields (see [ITU-T H.248.39]). Such an SDP value is basically out of scope of IANA registration. Schwarz Expires September 27, 2014 [Page 7] Internet-Draft SDP codepoints for gateway control March 2014 4.3. Protocol individual indications FIXTHIS - This is related to the indication of single protocol layer related endpoints in stream endpoint interlinkage configurations, see [ITU-T H.248.92]. 4.4. SDP codepoints related to "m="-line element None specific from H.248 perspective. 4.5. SDP codepoints related to "m="-line element See [ITU-T H.Supp.IANA]. Editor's note: this is still work in progress. 5. SDP codepoints related to "a="-lines (SDP attributes) 5.1. SDP attribute "ITU-T H.248 package" ITU-T Recommendation [ITU-T H.248.15] defines an ITU-T specific extension for SDP. The SDP attribute "a=h248item:" allows for the carriage of general ITU-T H.248 properties in the local and remote descriptor in the textual ITU-T H.248 protocol encoding mode. 6. Security Considerations This RFC is related to the registration of protocol codepoints, thus outside any security aspects. 7. IANA Considerations 7.1. SDP codepoints related to "m="-line element This document updates the "Session Description Protocol (SDP) Parameters" registry as specified in Section 8.2.2 of [RFC4566]. Specifically, it adds the values in Table 1 to the table for the SDP "proto" field registry. +-------+----------------------+-------------------------+ | Type | SDP Name | Reference | +-------+----------------------+-------------------------+ | proto | "TLS" | [ITU-T H.248.90] | +-------+----------------------+-------------------------+ | proto | "TCP/TLS" | [ITU-T H.248.90] | +-------+----------------------+-------------------------+ | proto | "SCTP/TLS" | [ITU-T H.248.90] | Schwarz Expires September 27, 2014 [Page 8] Internet-Draft SDP codepoints for gateway control March 2014 +-------+----------------------+-------------------------+ | proto | "DTLS" | [ITU-T H.248.DTLS] | +-------+----------------------+-------------------------+ | proto | "UDP/DTLS" | [ITU-T H.248.DTLS] | +-------+----------------------+-------------------------+ | proto | "DCCP/DTLS" | [ITU-T H.248.DTLS] | +-------+----------------------+-------------------------+ | proto | "SCTP" | [ITU-T H.248.SCTP] Note1| +-------+----------------------+-------------------------+ | proto | "SCTP/DTLS" | [ITU-T H.248.SCTP] Note1| +-------+----------------------+-------------------------+ | proto | "DTLS/SCTP" | [ITU-T H.248.SCTP] Note1| +-------+----------------------+-------------------------+ Table 1: SDP "proto" field values Note 1 - Table entry may be deleted again dependent on progress of IETF draft "draft-ietf-mmusic-sctp-sdp" (http://tools.ietf.org/wg/mmusic/draft-ietf-mmusic-sctp-sdp/). 8. References 8.1. Normative References [RFC2119] RFC 2119 (03/1997), "Key words for use in RFCs to Indicate Requirement Levels", BCP 14. [RFC2885] RFC 2885 (08/2000), "Megaco Protocol version 0.8". [RFC3015] RFC 3015 (11/2000), "Megaco Protocol Version 1.0". [RFC3525] RFC 3525 (06/2003), "Gateway Control Protocol Version 1". [RFC4566] RFC 4566 (07/2006), "SDP: Session Description Protocol". [RFC5125] RFC 5125 (02/2008), "Reclassification of RFC 3525 to Historic". [ITU-T H.248.x]The ITU-T H.248.x-series of Recommendations (Gateway Control Protocol). Website: http://www.itu.int/rec/T-REC-H/e Schwarz Expires September 27, 2014 [Page 9] Internet-Draft SDP codepoints for gateway control March 2014 [ITU-T H.248.1]Recommendation ITU-T H.248.1 (03/2013), "Gateway control protocol: Version 3". Free copy via: http://www.itu.int/rec/T-REC-H.248.1-201303- I/en [ITU-T H.248.15] Recommendation ITU-T H.248.15 (03/2013), "Gateway control protocol: SDP ITU-T H.248 package attribute". Free copy via: http://www.itu.int/rec/T-REC-H.248.15- 201303-I/en [ITU-T H.248.39] Recommendation ITU-T H.248.39 (##/2014), "Gateway control protocol: H.248 SDP parameter identification and wildcarding". Free copy via: http://www.itu.int/rec/T-REC-H.248.39/en NOTE: currently under revision by ITU-T. [ITU-T H.248.49] Recommendation ITU-T H.248.49 (08/2007), "Gateway control protocol: Session description protocol RFC and capabilities packages". Free copy via: http://www.itu.int/rec/T-REC-H.248.49/en [ITU-T H.248.80] Recommendation ITU-T H.248.80 (01/2014), "Usage of the revised SDP offer / answer model with H.248". Free copy via: http://www.itu.int/rec/T-REC-H.248.80/en [ITU-T H.248.90] Draft Recommendation ITU-T H.248.90 (03/2014), "Gateway control protocol: H.248 packages for control of transport security using TLS". Free copy via: ### insert URL ### [ITU-T H.248.92] Draft Recommendation ITU-T H.248.92 (03/2014), "Gateway control protocol: Stream endpoint interlinkage package". Free copy via: ### insert URL ### [ITU-T H.248.DTLS]Draft Recommendation ITU-T H.248.DTLS (03/2014), "Gateway control protocol: H.248 packages for control of transport security using DTLS". Free copy via: ### insert URL ### [ITU-T H.248.SCTP]Draft Recommendation ITU-T H.248.SCTP (03/2014), "Gateway control protocol: H.248 support for control of SCTP bearer connections". Free copy via: ### insert URL ### Schwarz Expires September 27, 2014 [Page 10] Internet-Draft SDP codepoints for gateway control March 2014 [ITU-T H.Supp.IANA] Supplement ITU-T H.SupX (xx/2014), "Gateway Control Protocol: ITU-T H.248.x-series - SDP codepoints for gateway control - Release 1". Free copy via: http://wftp3.itu.int/av-arch/avc-site/2013- 2016/1403_Gen/TD-32.zip (latest Draft) [ETSI 183046] ETSI TR 183 046 V3.3.1 (2009-08), "Telecommunications and Internet converged Services and Protocols for Advanced Networking (TISPAN); SDP Interworking between Call/Session Control Protocols (SIP/SDP, RTSP/SDP; etc.) and the Gateway Control Protocol (H.248/SDP)". [ETSI 183068] ETSI TR 183 068 V3.1.1 (2009-08), "Telecommunications and Internet converged Services and Protocols for Advanced Networking (TISPAN); Guidelines on using Ia H.248 profile for control of Border Gateway Functions (BGF); Border Gateway Guidelines". 8.2. Informative References [RFC1163] RFC 1163 (06/1990), "A Border Gateway Protocol (BGP)". [RFC7092] RFC 7092 (12/2013), "A Taxonomy of Session Initiation Protocol (SIP) Back-to-Back User Agents". 9. Acknowledgments Schwarz Expires September 27, 2014 [Page 11] Internet-Draft SDP codepoints for gateway control March 2014 Authors' Addresses Dr. Albrecht Schwarz ALCATEL-LUCENT Lorenzstrasse 10 D-70435 Stuttgart GERMANY Email: Albrecht.Schwarz@alcatel-lucent.com
Phone: Email: 10. CHANGE LOG 10.1. Changes against "-00" o Replace Draft ITU-T Recommandation work item name by "H.248.x" number (H.248.90 (TLS), H.248.92 (SEPLINK)) o Correction of clause 5: addition of ITU-T specific SDP attribute "a=h248item:" o Editorial: update of abbreviation list Schwarz Expires September 27, 2014 [Page 12]