Internet Engineering Task Force SIP WG Internet Draft G. Camarillo Ericsson A. Monrad Ericsson draft-camarillo-mmusic-separate-streams-00.txt May 22, 2002 Expires: December 2002 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 to request that different media streams are mapped into different resource reservation flows. G. Camarillo et. al. [Page 1] Internet Draft SIP May 22, 2002 Table of Contents 1 Introduction ........................................ 3 1.1 Terminology ......................................... 3 2 KIS Semantics ....................................... 3 3 Example ............................................. 3 4 IANA Considerations ................................. 4 5 Security Considerations ............................. 4 6 Authors' Addresses .................................. 4 7 Normative References ................................ 5 8 Informative References .............................. 5 G. Camarillo et. al. [Page 2] Internet Draft SIP May 22, 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 and provide it with the Quality of Service (QoS) corresponding to that 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 possibilities 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 latter type of mapping is performed (i.e., a single media stream is mapped to a single resource reservation flow). This document defines the syntax needed to express that need in SDP [1]. For this purpose, we make use of the SDP grouping framework [2] and define a new "semantics" attribute called KIS (Keep It Separate). 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 KIS Semantics We define a new "semantics" attribute within the SDP grouping framework [2]: KIS (Keep It Separate). Media lines grouped using KIS semantics SHOULD NOT be mapped into the same resource reservation flow. A different resource reservation flow SHOULD be used (or established) for each media line of the KIS group. 3 Example A user agent receives a SIP [4] 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 G. Camarillo et. al. [Page 3] Internet Draft SIP May 22, 2002 a=group:KIS 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 [5] to perform resource reservation. Since both media streams are part of a KIS group, the user agent will establish two different RSVP sessions; one for the audio stream and one for the video stream. An RSVP session is defined by the triple: (DestAddress, ProtocolId[, DstPort]). Table 1 shows the parameters used to establish both RSVP sessions. Session Number DestAddress ProtocolId DstPort ________________________________________________ 1 192.0.0.1 UDP 30000 2 192.0.0.1 UDP 30002 Table 1: Parameters needed to establish both RSVP sessions 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 both media streams into the same RSVP session. 4 IANA Considerations IANA needs to register the following new "semantics" attribute for the SDP grouping framework [2]: KIS: Keep It Separate 5 Security Considerations An attacker adding group lines using the KIS semantics to an SDP session description could force a user agent to establish a larger number of resource reservation flows than needed. It is thus RECOMMENDED that some kind of integrity protection is applied to SDP session descriptions. 6 Authors' Addresses G. Camarillo et. al. [Page 4] Internet Draft SIP May 22, 2002 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 [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, Ed., 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. 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