Internet Engineering Task Force SIP WG Internet Draft G. Camarillo Ericsson A. Monrad Ericsson draft-ietf-mmusic-reservation-flows-00.txt October 14, 2002 Expires: April 2003 Mapping of Media Streams to Resource Reservation Flows 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 To view the list Internet-Draft Shadow Directories, see http://www.ietf.org/shadow.html. Abstract This document defines an extension to the SDP grouping framework. It allows requesting that a group of media streams is mapped into a single resource reservation flow. G. Camarillo et. al. [Page 1] Internet Draft SIP October 14, 2002 Table of Contents 1 Introduction ........................................ 3 1.1 Terminology ......................................... 3 2 SRF Semantics ....................................... 3 3 Examples ............................................ 4 4 IANA Considerations ................................. 4 5 Security Considerations ............................. 5 6 Authors' Addresses .................................. 5 7 Normative References ................................ 5 8 Informative References .............................. 5 G. Camarillo et. al. [Page 2] Internet Draft SIP October 14, 2002 1 Introduction Resource reservation protocols assign network resources to particular flows of IP packets. When a router receives an IP packet, it applies a filter in order to map the packet to the flow it belongs. The router provides the IP packet with the Quality of Service (QoS) corresponding to its flow. Routers typically use the source and the destination IP addresses and port numbers to filter packets. Multimedia sessions typically contain multiple media streams (e.g., an audio stream and a video stream). In order to provide QoS for a multimedia session it is necessary to map all the media streams to resource reservation flows. This mapping can be performed in different ways. Two possible ways are to map all the media streams to a single resource reservation flow and to map every single media stream to a different resource reservation flow. Some applications require that the former type of mapping is performed while other applications require the latter. It is even possible that a mixture of both mappings is required for a particular media session. For instance, a multimedia session with three media streams might require that two of them are mapped into a single reservation flow while the third media stream uses a second reservation flow. This document defines the SDP [1] syntax needed to express how media streams need to be mapped into reservation flows. For this purpose, we use the SDP grouping framework [2] and define a new "semantics" attribute called SRF (Single Reservation Flow). 1.1 Terminology In this document, the key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" are to be interpreted as described in RFC 2119 [3] and indicate requirement levels for compliant SIP implementations. 2 SRF Semantics We define a new "semantics" attribute within the SDP grouping framework [2]: SRF (Single Reservation Flow). Media lines grouped using SRF semantics SHOULD be mapped into the same resource reservation flow. Media lines that do not belong to a particular SRF group SHOULD NOT be mapped into the reservation flow used for that SRF group. Note that an SRF group MAY consist of a single media line. In that case, following the definition above, that media line will be mapped into one reservation flow. That reservation flow will carry traffic G. Camarillo et. al. [Page 3] Internet Draft SIP October 14, 2002 from that media line, and from no other media lines. 3 Examples For this example, we have chosen to use SIP [4] to transport SDP sessions and RSVP [5] to establish reservation flows. However, other protocols or mechanisms could be used instead without affecting the SDP syntax. A user agent receives a SIP INVITE with the SDP below: v=0 o=Laura 289083124 289083124 IN IP4 one.example.com t=0 0 c=IN IP4 192.0.0.1 a=group:SRF 1 2 m=audio 30000 RTP/AVP 0 a=mid:1 m=video 30002 RTP/AVP 31 a=mid:2 This user agent uses RSVP to perform resource reservation. Since both media streams are part of a SRF group, the user agent will establish a single RSVP session. An RSVP session is defined by the triple: (DestAddress, ProtocolId[, DstPort]). Table 1 shows the parameters used to establish the RSVP session. Session Number DestAddress ProtocolId DstPort ________________________________________________ 1 192.0.0.1 UDP any Table 1: Parameters needed to establish the RSVP session If the same user agent received an SDP session description with the same media streams but without the group line, it would be free to map the two media streams into two different RSVP sessions. 4 IANA Considerations IANA needs to register the following new "semantics" attribute for the SDP grouping framework [2]: G. Camarillo et. al. [Page 4] Internet Draft SIP October 14, 2002 Semantics Token Reference ------------------- ----- --------- Single Reservation flow SRF [RFCxxxx] It should be registered in the SDP parameters registry (http://www.iana.org/assignments/sdp-parameters) under Semantics for the "group" SDP Attribute. 5 Security Considerations An attacker adding group lines using the SRF semantics to an SDP session description could force a user agent to establish a larger or a smaller number of resource reservation flows than needed. This could consume extra resources in the end-point or degrade the quality of service for a particular session. It is thus RECOMMENDED that some kind of integrity protection is applied to SDP session descriptions. 6 Authors' Addresses Gonzalo Camarillo Ericsson Advanced Signalling Research Lab. FIN-02420 Jorvas Finland electronic mail: Gonzalo.Camarillo@ericsson.com Atle Monrad Ericsson N-4898 Grimstad Norway electronic mail: atle.monrad@ericsson.com 7 Normative References [1] M. Handley and V. Jacobson, "SDP: session description protocol," RFC 2327, Internet Engineering Task Force, Apr. 1998. [2] G. Camarillo, J. Holler, G. Eriksson, and H. Schulzrinne, "Grouping of m lines in SDP," Internet Draft, Internet Engineering Task Force, Feb. 2002. Work in progress. [3] S. Bradner, "Key words for use in RFCs to indicate requirement levels," RFC 2119, Internet Engineering Task Force, Mar. 1997. 8 Informative References G. Camarillo et. al. [Page 5] Internet Draft SIP October 14, 2002 [4] J. Rosenberg, H. Schulzrinne, et al. , "SIP: Session initiation protocol," Internet Draft, Internet Engineering Task Force, Feb. 2002. Work in progress. [5] R. Braden, L. Zhang, S. Berson, S. Herzog, and S. Jamin, "Resource ReSerVation protocol (RSVP) -- version 1 functional specification," RFC 2205, Internet Engineering Task Force, Sept. 1997. Full Copyright Statement Copyright (c) The Internet Society (2002). All Rights Reserved. This document and translations of it may be copied and furnished to others, and derivative works that comment on or otherwise explain it or assist in its implementation may be prepared, copied, published and distributed, in whole or in part, without restriction of any kind, provided that the above copyright notice and this paragraph are included on all such copies and derivative works. However, this document itself may not be modified in any way, such as by removing the copyright notice or references to the Internet Society or other Internet organizations, except as needed for the purpose of developing Internet standards in which case the procedures for copyrights defined in the Internet Standards process must be followed, or as required to translate it into languages other than English. The limited permissions granted above are perpetual and will not be revoked by the Internet Society or its successors or assigns. This document and the information contained herein is provided on an "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK FORCE DISCLAIMS 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. G. Camarillo et. al. [Page 6]