SAM J. Buford, Panasonic Internet Draft August 30, 2006 Expires: February 28, 2007 SAM Problem Statement draft-irtf-sam-problem-statement-00.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 February 28, 2007. Copyright Notice Copyright (C) The Internet Society (2006). All Rights Reserved. Abstract We describe the generally expected behavior of a scalable and adaptive multicast architecture, leaving further details to separate documents on requirements and the SAM design space. This document is a starting point for discussions of feasibility, priority, and deployability. Buford Expires February 28, 2007 [Page 1] Internet-Draft SAM Problem Statement August 2006 Conventions used in this document In examples, "C:" and "S:" indicate lines sent by the client and server respectively. 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 [1]. Table of Contents 1. Introduction...................................................2 2. Heterogeneous Multicast Infrastructure.........................3 2.1. Varying Infrastructure by Network Region..................3 2.2. Regional Transitions......................................4 3. Quality of Service.............................................4 3.1. Native QOS, No Native Multicast...........................4 3.2. Other Combinations........................................5 4. Mobility.......................................................5 5. Security Considerations........................................6 6. Conclusions....................................................6 7. References.....................................................6 7.1. Normative References......................................6 7.2. Informative References....................................6 Author's Addresses................................................7 Intellectual Property Statement...................................7 Disclaimer of Validity............................................7 Copyright Statement...............................................8 Acknowledgment....................................................8 1. Introduction The concept of scalable adaptive multicast includes both scaling properties and adaptability properties. Scalability is intended to cover: o large group size o large numbers of small groups o rate of group membership change o admission control for QoS o use with network layer QoS mechanisms Buford Expires February 28, 2007 [Page 2] Internet-Draft SAM Problem Statement August 2006 o varying degrees of reliability o trees connect nodes over global internet Adaptability includes o use of different control mechanisms for different multicast trees depending on initial application parameters or application class o changing multicast tree structure depending on changes in application requirements, network conditions, and membership o use of different control mechanisms and tree structure in different regions of network depending on native multicast support, network characteristics, and node behavior The following sections describe some adaptation scenarios. After the base scenarios are elaborated, then scenarios for scalability and dynamic adaptation should be added. 2. Heterogeneous Multicast Infrastructure 2.1. Varying Infrastructure by Network Region Regions A, B, C are disjoint areas of the network with some type of native multicast support. Region Z is all other areas of the network with no native multicast support. Region Z may be partitioned by A, B, and/or C. A multicast connection between nodes in A, B, C, and Z is needed. In each region A, B, C, the respective native multicast mechanism is used. Multicast topology choices include: o Multicast applications see an end-to-end multicast application layer which is mapped to a native layer transparently in the regions that it is available. The overlay’s group management mechansisms hold for all nodes, and are mapped transparently to the native layer mechanisms in the appropriate regions. All nodes have addresses in the overlay. o Multicast applications see an end-to-end native multicast, where nodes in region Z connect to native regions using tunnels. The native group management mechanisms hold for all nodes. Buford Expires February 28, 2007 [Page 3] Internet-Draft SAM Problem Statement August 2006 Homogeneous sub-case: regions A, B, C may use the same native multicast protocol. 2.2. Regional Transitions A node in a new region D joins the multicast tree. Region D has native support. What is the minimum number of nodes in a region needed for native support to be used in that part of the tree? 3. Quality of Service 3.1. Native QOS, No Native Multicast Each endpoint in the multicast tree specifies QOS constraints such as bandwidth, delay, and jitter for a given source. Multicast join includes admission control step for the selected QOS mechanism. This means that the join decision combines both multicast tree considerations (eg., best metrics) and an admission control decision. Paths to different endpoints from a given source might have different QOS constraints. A given multicast tree may mix QOS delivery and best effort delivery to different receivers. Available IP QOS mechanisms include Intserv, Diffserv, and MPLS. Assume all regions of network have interoperable native QOS mechanism. Assume all receivers have homogenous capabilities. The topology of the overlay is not assumed to be isomorphic to available QOS paths. The overlay must be sophisticated enough to determine what paths are available and arrange its tree construction and routing behaviour accordingly. In order to enforce QOS, a measurement mechanism is needed. The scalability of the measurement, feedback and policing mechanism is an important issue. RTP is such a measurement and feedback protocol for UDP. A source might adapt its bit rate and quality depending on feedback from receivers. There might be graceful degradation mechanisms such as multi-description coding over different multicast paths. This behavior is application dependent. Buford Expires February 28, 2007 [Page 4] Internet-Draft SAM Problem Statement August 2006 3.2. Other Combinations Heterogeneous QOS refers to either 1) portions of the network where no QOS mechanism exists at native level, or 2) receivers which have heterogeneous capabilities. These combinations need further elaboration. o Native QOS with Regional Native Multicast o Heterogeneous QOS, No Native Multicast o Heterogeneous QOS, Regional Native Multicast 4. Mobility A mobile node’s home IP address is associated with its overlay address (if this is an overlay) or group multicast address. As the node moves to another network, multicast messages are routed to it via the home agent. In addition to increased latency, node mobility can impact robustness of multicast delivery due to loss of connectivity during mobility transitions. Some link layer solutions may mitigate or eliminate connectivity loss, but may require sending packets to both old and new care-of addresses during the transition. If the node uses its care-of address in the overlay or multicast tree, then any mobility transition will be disruptive, causing a leave-join sequence. Forwarding of packets can be through the home agent. If the source address is the care-of address, these might be rejected by nodes expecting packets only from overlay-registered addresses. In general, mobile node transitions to another network lead to lost packets during the transition, and downstream nodes in the tree will also be disconnected. Possibile solutions are bi-casting the packets to both old and new mobile addresses, or buffering packets at the home agent. If the overlay is aware that the node is mobile, then it could construct a mesh rather than tree to connect to. The mesh might provide redundant paths to the mobile node’s children in the tree. There can be different scenarios depending on whether all nodes in multicast tree are mobile or a subset of nodes. Buford Expires February 28, 2007 [Page 5] Internet-Draft SAM Problem Statement August 2006 5. Security Considerations [RESC2006] surveys the security issues specific to overlay networks which include: o Correctness of routing due to malicious nodes acting individually or collectively o Node impersonation due to lack of secure routing and identity o Fairness enforcement since each node acts autonomously, it can chose to limit its resource contribution to the operation of the overlay o Denial of service (DOS) o Using overlays for launching DDoS attacks [ROSS2006] SAM will not solve the overlay security problems, but should work with overlays that provide security mechanisms. 6. Conclusions Using this discussion with the separately developed SAM Design Space, we will be able to enumerate those ares of the problem space for which solutions exist and those which are open problems. This will suggest the steps by which the SAM Framework is designed. 7. References 7.1. Normative References [1] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. 7.2. Informative References [MUR2006] E. Muramoto, Y. Imai, N. Kawaguchi. Requirements for Scalable Adaptive Multicast Framework in Non-GIG Networks. June 2007. Internet Draft draft-muramoto-irtf-sam-generic- require-00.txt, work in progress. [RESC2006] E. Rescorla. Introduction to Distributed Hash Tables. IETF-65 Technical Plenary, March 2006. www3.ietf.org/proceedings/06mar/slides/plenaryt-2.pdf Buford Expires February 28, 2007 [Page 6] Internet-Draft SAM Problem Statement August 2006 [ROSS2006] K. Ross. Exploiting P2P Systems for DDOS Attacks. IETF 65 P2PRG CORE Subgroup. www.cs.uml.edu/~buford/irtf- p2prg/ietf65/ietf65-irtf-p2prg-core-ddos.pdf Author's Addresses John Buford Panasonic Princeton Laboratory rd 2 Research Way, 3 Floor Princeton, NJ 08540, USA Email: buford@research.panasonic.com 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 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. Buford Expires February 28, 2007 [Page 7] Internet-Draft SAM Problem Statement August 2006 Copyright Statement Copyright (C) The Internet Society (2006). 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. Buford Expires February 28, 2007 [Page 8]