Internet-Draft DS Multicast Router Extension July 2001 INTERNET-DRAFT R. Bless Expires: January 2002 K. Wehrle Universitaet Karlsruhe (TH) Document: draft-bless-diffserv-mcast-routerext-00.txt July 2001 A Router Extension to Support Multicast in Differentiated Services Networks 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 draft proposes an extension to the multicast routing table in routers in order to achieve better support for using multicast within Differentiated Services (DS) networks. Only one additional DS codepoint for each virtual interface in the multicast routing table is required to open up a variety of different uses, e.g., to solve resource provisioning problems or to support heterogeneous DiffServ multicast groups. Bless & Wehrle Expires: January 2002 [Page 1] Internet-Draft DS Multicast Router Extension July 2001 1 Introduction Basically, Differentiated Services mechanisms are also applicable to multicast traffic. This means that usually all replicates of an incoming multicast packet get the same DS codepoint [1]. However, that would not always be desirable, because provisioning of network resources is much more difficult (see [3] and sec.5 of [2]) if joins are happening uncontrolled. The proposed solution would allow to assign a different DS codepoint to any branch of the multicast delivery tree, thus allowing different forwarding treatment within a multicast group. This can be useful to prevent resource over- utilization or to allow multicast groups with heterogeneous quality- of-service delivery. 2 Description of the proposed extension Each router should provide entries to store a DS codepoint value within each multicast routing table entry per outgoing virtual interface (cf. Figure 1). A virtual interface means in this context, that it is either a multicast tunnel or a real physical network interface. So there may be several configured tunnels over one physical interface present. The multicast routing table entry contains usually information about the multicast group address (destination address), source address and (virtual) outgoing interfaces where packets should be copied to during packet forwarding. Multicast Other List Destination Fields of Address virtual Inter- DS interfaces face ID Entry +--------------------------------+ +-------------------+ | X | .... | *-------------------->| C | DSCP | |--------------------------------| +-------------------+ | Y | .... | *-----------+ | D | DSCP | |--------------------------------| | +-------------------+ | ... | .... | ... | | . . . . | +-------------------+ . ... . .... . ... . +-------->| B | DSCP | +--------------------------------+ +-------------------+ | ... | .... | ... | | D | DSCP | +--------------------------------+ +-------------------+ | ... | ... | . . . . . . Figure 1: Multicast routing table with additional fields for DSCP values Bless & Wehrle Expires: January 2002 [Page 2] Internet-Draft DS Multicast Router Extension July 2001 Setting and use of the codepoint should be controlled by management mechanisms allowing to either use the original codepoint of the incoming packet or to use the stored codepoint in the multicast routing table. Therefore, the used management protocol must be capable of transporting the codepoint value for a specific multicast group and interface to a certain router. Alternatively, the value could also be distributed by an enhanced multicast routing protocol. Actual use of the codepoint entry should be encoded together with the codepoint entry, e.g., in the remaining 2 bits of the entry if a whole byte is used to store the DSCP value (however, the specific implementation technique is out of scope of this document). Possible actions for setting the codepoint of outgoing multicast packets are: . Copy original codepoint of incoming packet . Use configured codepoint from multicast routing table entry . Use configured codepoint from multicast routing table entry only if original incoming codepoint is different from a set of pre- configured codepoints (e.g., DSCP 0). 3 Security Considerations Basically, service degradation or theft of resources will be possible if an attacker is able to set codepoint entries in multicast routing tables. This should be avoided by using only secure router administration and configuration mechanisms which are widely known and in use. Therefore router management should generally be protected against unauthorized use, thus preventing such attacks. 4 References [1] F. Baker, D. Black, S. Blake, and K. Nichols. Definition of the Differentiated Services Field (DS Field) in the IPv4 and IPv6 Headers. RFC 2474, Dec. 1998. [2] S. Blake, D. Black, M. Carlson, E. Davies, Z. Wang, and W. Weiss. An Architecture for Differentiated Services. RFC 2475, Dec. 1998. [3] R. Bless, K. Wehrle: "Group Communication in Differentiated Services Networks", Internet QoS for the Global Computing 2001 (IQ 2001), Workshop at CCGRID 2001 (IEEE International Symposium on Cluster Computing and the Grid), 15.-18. May 2001, Brisbane, Australia, IEEE Press, ISBN 0-7695-1010-8, pp. 618-625 Bless & Wehrle Expires: January 2002 [Page 3] Internet-Draft DS Multicast Router Extension July 2001 5 Authors' addresses Comments and questions related to this draft can be addressed to one of the authors listed below. Roland Bless Institute of Telematics Universitaet Karlsruhe (TH) Zirkel 2 D-76128 Karlsruhe Germany Tel.: +49 721 608 6413 bless@tm.uka.de Klaus Wehrle Institute of Telematics Universitaet Karlsruhe (TH) Zirkel 2 D-76128 Karlsruhe Germany Tel.: +49 721 608 6414 wehrle@tm.uka.de Bless & Wehrle Expires: January 2002 [Page 4]