MULTIMOB Group J. C. Zuniga INTERNET-DRAFT (InterDigital Communications, LLC) Intended Status: Standards Track L. M. Contreras Expires: April 26, 2012 (Telefonica I+D) C. J. Bernardos (Universidad Carlos III de Madrid) S. Jeon Y. Kim (Soongsil University) October 24, 2011 Multicast Mobility Routing Optimizations for Proxy Mobile IPv6 Abstract The MULTIMOB group has specified a base solution to support IP multicasting in a PMIPv6 domain [RFC6224]. In this document, some enhancements are proposed to the base solution. These enhancements include the use of a multicast tree mobility anchor as the topological anchor point for multicast traffic, as well as a direct routing option where the MAG can provide access to multicast content in the local network. These enhancements provide benefits such as reducing multicast traffic replication and supporting different PMIPv6 deployments scenarios. Status of this Memo This Internet-Draft is submitted to IETF in full conformance with the provisions of BCP 78 and 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/1id-abstracts.html Zuniga, et al. Expires April 26, 2012 [Page 1] INTERNET DRAFT Multicast Mobility Routing Optimizations October, 2011 The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html Copyright and License Notice Copyright (c) 2011 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. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Zuniga, et al. Expires April 26, 2012 [Page 2] INTERNET DRAFT Multicast Mobility Routing Optimizations October, 2011 Table of Contents 1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 2 Conventions and Terminology . . . . . . . . . . . . . . . . . . 4 3 Solution . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 3.1 Architecture . . . . . . . . . . . . . . . . . . . . . . . 6 3.2 Deployment Scenarios . . . . . . . . . . . . . . . . . . . 7 3.2.1 PMIPv6 domain with ratio 1:1 . . . . . . . . . . . . . 8 3.2.2 PMIPv6 domain with ratio N:1 . . . . . . . . . . . . . 8 3.2.3 PMIPv6 domain with ratio 1:N . . . . . . . . . . . . . 10 3.2.4 PMIPv6 domain with H-LMA . . . . . . . . . . . . . . . 11 3.3 Multicast Establishment . . . . . . . . . . . . . . . . . . 13 3.4 Multicast Mobility . . . . . . . . . . . . . . . . . . . . 14 3.5 PMIPv6 enhancements . . . . . . . . . . . . . . . . . . . . 15 3.5.1 New Binding Update List in MAG . . . . . . . . . . . . 15 3.5.2 Policy Profile Information with Multicast Parameters . 16 3.5.3 MAG to MTMA attach requirements . . . . . . . . . . . . 16 3.5.4. Data structure stored by MTMA . . . . . . . . . . . . . 16 3.6 Advantages . . . . . . . . . . . . . . . . . . . . . . . . 16 4 Direct routing . . . . . . . . . . . . . . . . . . . . . . . . 20 4.1 MAG as MLD proxy . . . . . . . . . . . . . . . . . . . . . . 21 4.1.1 Local subscription when the MAG implements MLD proxy functionality . . . . . . . . . . . . . . . . . . . . . 21 4.1.1.1 Local subscription architecture . . . . . . . . . . 21 4.1.1.2 Handover procedure for local routing . . . . . . . . 22 4.1.2 Remote subscription when the MAG implements MLD proxy functionality . . . . . . . . . . . . . . . . . . . . . 23 4.2 MAG as multicast router . . . . . . . . . . . . . . . . . . 24 4.2.1 Local subscription when the MAG implements a multicast routing protocol . . . . . . . . . . . . . . . . . . . . 24 4.2.2 Remote subscription when the MAG implements a multicast routing protocol . . . . . . . . . . . . . . . 24 5 Dynamic selection of local versus remote multicast subscription . . . . . . . . . . . . . . . . . . . . . . . . . . 24 5.1 Any source multicast scenario . . . . . . . . . . . . . . . 25 5.2 Source specific multicast scenario . . . . . . . . . . . . . 25 6 Security Considerations . . . . . . . . . . . . . . . . . . . . 26 7 IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 26 8 Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 26 9 References . . . . . . . . . . . . . . . . . . . . . . . . . . 26 9.1 Normative References . . . . . . . . . . . . . . . . . . . 26 9.2 Informative References . . . . . . . . . . . . . . . . . . 27 Author's Addresses . . . . . . . . . . . . . . . . . . . . . . . . 28 Zuniga, et al. Expires April 26, 2012 [Page 3] INTERNET DRAFT Multicast Mobility Routing Optimizations October, 2011 1 Introduction Proxy Mobile IPv6 [RFC5213] is a network-based approach to solving the IP mobility problem. In a Proxy Mobile IPv6 (PMIPv6) domain, the Mobile Access Gateway (MAG) behaves as a proxy mobility agent in the network and does the mobility management on behalf of the Mobile Node (MN). The Local Mobility Anchor (LMA) is the home agent for the MN and the topological anchor point. PMIPv6 was originally designed for unicast traffic. The Internet Group Management Protocol (IGMPv3) [RFC3376] is used by IPv4 hosts to report their IP multicast group memberships to neighboring multicast routers. Multicast Listener Discovery (MLDv2) [RFC3810] is used in a similar way by IPv6 routers to discover the presence of IPv6 multicast hosts. Also, the IGMP/MLD proxy [RFC4605] allows an intermediate (edge) node to appear as a multicast router to downstream hosts, and as a host to upstream multicast routers. IGMP and MLD related protocols were not originally designed to address IP mobility of multicast listeners (i.e. IGMP and MLD protocols were originally designed for fixed networks). The MULTIMOB group has specified a base solution to support IP multicast listener mobility in a PMIPv6 domain [RFC6224], which describes deployment options without modifying mobility and multicast protocol standards. The PMIPv6 allows a MAG to establish a multiple of PMIPv6 tunnels with LMAs. Hence, when IP multicasting is applied into PMIPv6, it leads to redundant traffic at a MAG called "Tunnel Convergence problem". To address this issue, two enhancements are proposed in this document; multicast anchor and direct routing. The former uses a multicast tree mobility anchor (MTMA) as the topological anchor point for delivering multicast traffic, while the latter uses direct routing, allowing a MAG to connect directly to a multicast router for simple access to local content. Both schemes have no impact on the MN to support multicast listener mobility. The MTMA architecture and solution are described in section 3. Section 4 describes the direct routing solution and the enhancements details. Section 5 describes the details about the selection at the MAG between direct routing (e.g. for local access) and MTMA (e.g. for remote access). 2 Conventions and Terminology 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]. Zuniga, et al. Expires April 26, 2012 [Page 4] INTERNET DRAFT Multicast Mobility Routing Optimizations October, 2011 This document uses the terminology defined in [RFC5213], [RFC3775], and [RFC3810]. Specifically, the definition of PMIPv6 domain is reused from [RFC5213] and reproduced here for completeness. - Proxy Mobile IPv6 Domain (PMIPv6-Domain): Proxy Mobile IPv6 domain refers to the network where the mobility management of a mobile node is handled using the Proxy Mobile IPv6 protocol as defined in [RFC5213]. The Proxy Mobile IPv6 domain includes local mobility anchors and mobile access gateways between which security associations can be set up and authorization for sending Proxy Binding Updates on behalf of the mobile nodes can be ensured. In this draft we refine such definition from the point of view of the kind of traffic served to the MN in the following way: - PMIPv6 unicast domain: PMIPv6 unicast domain refers to the network covered by one LMA for unicast service in such a way that an MN using that service is not aware of mobility as it moves from one MAG to another associated to that LMA regarding its unicast traffic. - PMIPv6 multicast domain: PMIPv6 multicast domain refers to the network covered by one network element named MTMA (defined below) for multicast service in such a way that an MN using that service is not aware of mobility as it moves from one MAG to another. - Direct routing: it uses native multicast infrastructure for retrieving multicast data. For the operator having its own local content, this technique also includes the case that content source is directly connected to a MAG. This means that a PMIPv6 domain can have several PMIPv6 unicast domains and PMIPv6 multicast domains. Additionally, some other definitions are introduced, as follows. - MTMA or multicast tree mobility anchor: an entity working as topological anchor point for multicast traffic exclusively. - H-LMA or Hybrid-LMA: an entity dedicated to both unicast and multicast services, that is, it is able to work as both LMA and MTMA simultaneously. 3 Solution A PMIPv6 domain may handle data from both unicast and multicast sources. This document addresses optimizations to the base solution Zuniga, et al. Expires April 26, 2012 [Page 5] INTERNET DRAFT Multicast Mobility Routing Optimizations October, 2011 specified for multicast support in PMIPv6 domains [RFC6224] by firstly introducing a complementary network entity, named multicast tree mobility anchor (MTMA), and defining the architecture and protocol flows derived from it; and secondly by defining a direct routing option where a MAG can directly receive packets from a multicast router. An MTMA can be used to serve as the mobility anchor for multicast traffic. The MTMA connects to the MAG as described in [RFC6224] and it can reuse native PMIPv6 features such as tunnel establishment and security [RFC5213], heartbeat [RFC5847], etc. Unicast traffic will go normally to the LMAs in the PMIPv6 domain. This section describes how the MTMA works in scenarios of MN attachment and multicast mobility. We first concentrate on the case of both LMA and MTMA defining a unique PMIPv6 domain, and then different deployment scenarios are presented. 3.1 Architecture Figure 1 shows an example of a PMIPv6 domain supporting multicast mobility. LMA1 is dedicated to unicast traffic, and MTMA1 is dedicated to multicast traffic. The tree mobility anchor MTMA1 can be considered to be a form of upstream multicast router with tunnel interfaces allowing remote subscription for the MNs. Note that there can be multiple LMAs for unicast traffic (not shown in Figure 1) in a given PMIPv6 domain. Similarly, more than one MTMA can be deployed by the operator (not shown in Figure 1). Also in this architecture, all MAGs that are connected to the MTMA must support the MLD proxy [RFC4605] function. Specifically in Figure 1, each of the MAG1-MTMA1 and MAG2-MTMA1 tunnel interfaces defines an MLD proxy domain. The MNs are considered to be on the downstream interface of the MLD proxy (in the MAG), and MTMA1 is considered to be on the upstream interface (of the MAG) as per [RFC4605]. Note that MAG could also be an IGMP proxy. For brevity this document will refer primarily to MLD proxy, but all references to "MLD proxy" should be understood to also include "IGMP/MLD proxy" functionality. As shown in Figure 1, MAG1 may connect to both unicast (LMAs) and multicast (MTMAs) entities. Thus, a given MN may simultaneously receive both unicast and multicast traffic. In Figure 1, MN1 and MN2 receive unicast traffic, multicast traffic, or both, whereas MN3 receives multicast traffic only, despite of that, this draft considers that every MN demanding multicast-only services is previously registered in a PMIPv6 unicast domain to get a unicast IP address. This registration can be required also for several purposes Zuniga, et al. Expires April 26, 2012 [Page 6] INTERNET DRAFT Multicast Mobility Routing Optimizations October, 2011 such as remote management, billing, etc. +--------------+ |Content Source| +--------------+ | | *** *** *** *** *** *** *** *** * ** ** ** * * ** ** ** * * * * * * Unicast Traffic * * Multicast Traffic * * * * * * ** ** ** * * ** ** ** * *** *** *** *** *** *** *** *** | | | | | | +-----+ +------+ Unicast | LMA1| | MTMA1| Multicast Anchor +-----+ +------+ Anchor \ // || \ // || \ // || \ // || \ // || \ // || \ // || \ // || \ // || +-----+ +-----+ | MAG1| | MAG2| MLD Proxy +-----+ +-----+ | | | | | | {MN1} {MN2} {MN3} Figure 1. Architecture of Multicast Tree Mobility Anchor (MTMA) 3.2 Deployment Scenarios From the network architecture point of view, there are several options when considering the multicast tree mobility anchor (MTMA) approach. These options can be distinguished in terms of the number of LMAs and MTMAs present in a PMIPv6 domain and the service relationship that a set of MNs gets from them, in the form of a "LMA : MTMA" ratio. According to that, it is possible to differentiate the following approaches: Zuniga, et al. Expires April 26, 2012 [Page 7] INTERNET DRAFT Multicast Mobility Routing Optimizations October, 2011 - A set of MNs is served in a PMIPv6 domain by two entities, one MTMA for multicast service, and one LMA for unicast, in such a way that the ratio is 1:1 (one common PMIPv6 unicast and multicast domain). - A set of MNs is served in a PMIPv6 domain by several entities, one MTMA for multicast service, while the others (LMAs) for unicast, in such a way that the ratio is N:1 (N PMIPv6 unicast domains coexist with a unique multicast domain). - A set of MNs is served in a PMIPv6 domain by several entities, one LMA for unicast, while the others (MTMAs) are devoted to multicast service, in such a way that the ratio is 1:N (one single PMIPv6 unicast domain coexists with multiple multicast domains). Scenarios with an N:M ratio are considered to be a combination of the previous ones. 3.2.1 PMIPv6 domain with ratio 1:1 This approach basically refers to the architecture presented in figure 1. Within this approach, a common set of MNs is served by a couple of entities, one LMA for unicast and one MTMA for multicast. All the MNs of the set are served by these two elements as they move in the PMIPv6 domain. 3.2.2 PMIPv6 domain with ratio N:1 This approach basically refers to the situation where a common set of MNs is served by a unique MTMA for multicast service, but simultaneously there are subsets from that group of MNs which are served by distinct LMAs for unicast service as they move in the PMIPv6 domain. Each particular MN association with the LMAs (unicast) and MTMA (multicast) remains always the same as it moves in the PMIPv6 domain. Figure 2 shows the scenario here described. Zuniga, et al. Expires April 26, 2012 [Page 8] INTERNET DRAFT Multicast Mobility Routing Optimizations October, 2011 +----------------+ +----------------+ |Content Source A| |Content Source B| +----------------+ +----------------+ | | | | *** *** *** *** *** *** *** *** *** *** *** * ** ** ** ** ** ** ** ** ** ** * * * * Fixed Internet * * (Unicast & Multicast Traffic) * * ** ** ** ** ** ** ** ** ** ** * *** *** *** *** *** *** *** *** *** *** *** | | | | | | | | | +-------+ +-----------------+ +-------+ | LMA1 | | MTMA2 | | LMA3 | +-------+ +-----------------+ +-------+ || \ oo oo oo oo // || || \ oo oo oo oo // || || \ oo oo oo oo // || || \ oo oo oo oo // || || \oo oo oo oo // || || \ oo oo oo// || || oo\ oo oo // || || oo \ oo oo //oo || || oo \ oo oo // oo || || oo \ oo oo // oo || +------+ +--------+ +--------+ +--------+ | MAG1 | | MAG2 | | MAG3 | | MAG4 | +------+ +--------+ +--------+ +--------+ | | | | | | | | | | | | | | | | {MN10} {MN11} {MN20} {MN21} {MN30} {MN31} {MN40} {MN41} Figure 2. PMIPv6 domain with ratio N:1 The figure 2 proposes an architecture where there are two entities acting as LMAs, LMA1 and LMA3, while there is another one, named MTMA2, working as multicast tree mobility anchor. LMA1 and LMA3 constitute two distinct unicast domains, whereas MTMA2 forms a single multicast domain. The tunnels among MAGs and LMAs represented by lines ("||") indicate a tunnel transporting unicast traffic, while the tunnels among MAGs and MTMA2 depicted with circles ("o") show a tunnel transporting multicast traffic. In the figure it can be observed that all the MNs are served by MTMA2 for the incoming multicast traffic from sources A or B. However, Zuniga, et al. Expires April 26, 2012 [Page 9] INTERNET DRAFT Multicast Mobility Routing Optimizations October, 2011 there are different subsets regarding unicast traffic which maintain distinct associations within the PMIPv6 domain. For instance, the subset formed by MN10, MN11, MN20 and MN21 is served by LMA1 for unicast, and the rest of MNs are being served by LMA3. For the scenario described above, the association between each MN and the corresponding LMA and MTMA is permanently maintained. 3.2.3 PMIPv6 domain with ratio 1:N This approach is related to a scenario where a common group of MNs is served by a unique LMA for unicast service, but simultaneously there are subsets from that group of MNs which are served by distinct MTMAs for multicast service as they move in the PMIPv6 domain. Each particular MN association with the LMA and MTMAs (unicast and multicast respectively) remains always the same as it moves in the PMIPv6 domain. Figure 3 shows the scenario here described. The figure 3 proposes an architecture where the LMA2 is the unique LMA for a certain group of MNs, while there are two others entities, MTMA1 and MTMA3, acting as MTMAs for different subsets of MNs of the same group. MTMA1 and MTMA3 constitute two distinct multicast domains, whereas LMA2 forms a single unicast domain. Each MTMA could be devoted to carry on a different content (for instance, MTMA1 for source A and MTMA3 for source B) or not. Looking at the picture, the subset formed by MN10, MN11, MN20 and MN21 is served by MTMA1 for multicast. The rest of MNs are being served by MTMA3 also for multicast. Finally, all of them are served by LMA2 for unicast. For the scenario described above, the association between each MN and the corresponding LMA and MTMA is permanently maintained. Zuniga, et al. Expires April 26, 2012 [Page 10] INTERNET DRAFT Multicast Mobility Routing Optimizations October, 2011 +----------------+ +----------------+ |Content Source A| |Content Source B| +----------------+ +----------------+ | | | | *** *** *** *** *** *** *** *** *** *** *** * ** ** ** ** ** ** ** ** ** ** * * * * Fixed Internet * * (Unicast & Multicast Traffic) * * ** ** ** ** ** ** ** ** ** ** * *** *** *** *** *** *** *** *** *** *** *** | | | | | | | | | +-------+ +-----------------+ +-------+ | MTMA1 | | LMA2 | | MTMA3 | +-------+ +-----------------+ +-------+ oo oo // || || \ oo oo oo oo // || || \ oo oo oo oo // || || \ oo oo oo oo // || || \ oo oo oo oo// || || \ oo oo oo oo || || \oo oo oo //oo || || \ oo oo // oo || || oo\ oo oo // oo || || oo \ oo oo // oo || || oo \ oo +------+ +--------+ +--------+ +--------+ | MAG1 | | MAG2 | | MAG3 | | MAG4 | +------+ +--------+ +--------+ +--------+ | | | | | | | | | | | | | | | | {MN10} {MN11} {MN20} {MN21} {MN30} {MN31} {MN40} {MN41} Figure 3. PMIPv6 domain with ratio 1:N 3.2.4 PMIPv6 domain with H-LMA The H-LMA is defined as an entity which simultaneously transports unicast and multicast service, that is, it simultaneously works as LMA and MTMA. In the context of the MTMA solution, an H-LMA can play the role of MTMA for an entire group of MNs in a PMIPv6 domain, while acting simultaneously as LMA for a subset of them. The figure 4 adapts the PMIPv6 domain with ratio N:1 scenario of figure 2 to the case where MTMA2 is an H-LMA, which serves multicast traffic to all the MNs in the picture, and simultaneously, it is able to serve unicast traffic to the subset formed by MN30, MN40 and MN41. Zuniga, et al. Expires April 26, 2012 [Page 11] INTERNET DRAFT Multicast Mobility Routing Optimizations October, 2011 +----------------+ +----------------+ |Content Source A| |Content Source B| +----------------+ +----------------+ | | | | *** *** *** *** *** *** *** *** *** *** *** * ** ** ** ** ** ** ** ** ** ** * * * * Fixed Internet * * (Unicast & Multicast Traffic) * * ** ** ** ** ** ** ** ** ** ** * *** *** *** *** *** *** *** *** *** *** *** | | | | | | | | | +------+ +-----------------+ +------+ | LMA1 | | H-LMA | | LMA3 | +------+ +-----------------+ +------+ || \ oo db db oo // || || \ oo db db oo // || || \ oo db db oo // || || \ oo db db oo // || || \oo db db oo // || || \ db db oo// || || oo\ db db // || || oo \ db db //oo || || oo \ db db // oo || || oo \ db db // oo || +------+ +--------+ +--------+ +--------+ | MAG1 | | MAG2 | | MAG3 | | MAG4 | +------+ +--------+ +--------+ +--------+ | | | | | | | | | | | | | | | | {MN10} {MN11} {MN20} {MN21} {MN30} {MN31} {MN40} {MN41} Figure 4. PMIPv6 domain with H-LMA Figure 4 presents a PMIPv6 network where there are two pure unicast LMAs, LMA1 and LMA3, and a hybrid LMA, labeled as H-LMA in the figure. The H-LMA is an MTMA from the perspective of MAG1 and MAG4. The tunnels among MAGs and LMAs represented by lines ("||") indicate a tunnel transporting exclusively unicast traffic, the tunnels depicted with circles ("o") show a tunnel transporting exclusively multicast traffic, and the tunnels with mixed lines and circles ("db") describe a tunnel transporting both types of traffic simultaneously. All of the MNs in the figure receive the multicast traffic from H-LMA Zuniga, et al. Expires April 26, 2012 [Page 12] INTERNET DRAFT Multicast Mobility Routing Optimizations October, 2011 (one single multicast domain), but it is possible to distinguish three subsets from the unicast service perspective (that is, three unicast domains). The first subset is the one formed by MN10, MN11 and MN 20, which receives unicast traffic from LMA1. A second subset is the one formed by MN21 and MN30, which receives unicast traffic from H-LMA. And finally, a third subset is built on MN31, MN40 and MN41, which receives unicast traffic from LMA3. For the scenario described above, the association between each MN and the corresponding LMA and H-LMA is permanently maintained. 3.3 Multicast Establishment Figure 5 shows the procedure when MN1 attaches to MAG1, and establishes associations with LMA (unicast) and MTMA (multicast). MN1 MAG1 LMA MTMA | (MLD Proxy) (Unicast) (Multicast) MN attaches to MAG1 | | | | | | | |------Rtr Sol----- ->| | | | |--PBU -- >| | | | | | | |<-- PBA --| | | | | | | |=Unicast= | | | | Tunnel | | |<-----Rtr Adv ------ | | | | | | | |< ------ Unicast Traffic------ >| | | | | | | |==Multicast Tunnel ==| | | | | |<--MLD Query --------| | | | | | | MN requires | | | multicast services | | | | | | | |---MLD Report (G) -->| | | | | | | | |---- Aggregated ---> | | | MLD Report (G) | | | | | | | | | |< --------- Multicast Traffic ----------- >| | | | | Figure 5. MN Attachment and Multicast Service Establishment Zuniga, et al. Expires April 26, 2012 [Page 13] INTERNET DRAFT Multicast Mobility Routing Optimizations October, 2011 In Figure 5, MAG1 first establishes the PMIPv6 tunnel with LMA for unicast traffic as defined in [RFC5213] after being triggered by the Router Solicitation message from MN1. Unicast traffic will then flow between MN1 and LMA. For multicast traffic, a multicast tunnel may have been pre- configured between MAG1 and MTMA. Or the multicast tunnel may be dynamically established when the first MN appears at the MAG. MN1 sends the MLD report message (when required by its upper layer applications) as defined in [RFC3810] in response to an MLD Query from MAG1. MAG1 acting as a MLD Proxy as defined in [RFC4605] will then send an Aggregated MLD Report to the multicast anchor, MTMA (assuming that this is a new multicast group which MAG1 had not previously subscribed to). Multicast traffic will then flow from MTMA towards MN1. 3.4 Multicast Mobility Figure 6 illustrates the mobility scenario for multicast traffic. Specifically, MN2 with ongoing multicast subscription moves from MAG1 to MAG2. Note that, for simplicity, in this scenario we only consider the tunnel of MAG2 with MTMA (for multicast traffic) and we assume that MN2 does not receive unicast traffic. Of course, if it was desired to support unicast traffic, this is served by a tunnel between MAG2 and LMA to transfer unicast traffic. According to baseline solution signaling method described in [RFC6224], after MN2 mobility, MAG2 acting in its role of MLD proxy will send an MLD Query to the newly observed MN on its downlink. Assuming that the subsequent MLD Report from MN2 requests membership of a new multicast group (from MAG2's point of view), this will then result in an Aggregated MLD Report being sent to MTMA from MAG2. This message will be sent through a pre-established (or dynamically established) multicast tunnel between MAG2 and MTMA. When MN2 detaches, MAG1 may keep the multicast tunnel with the multicast MTMA if there are still other MNs using the multicast tunnel. Even if there are no MNs currently on the multicast tunnel, MAG1 may decide to keep the multicast tunnel for potential future use. As discussed above, existing MLD (and Proxy MLD) signaling will handle a large part of the multicast mobility management for the MN. Zuniga, et al. Expires April 26, 2012 [Page 14] INTERNET DRAFT Multicast Mobility Routing Optimizations October, 2011 MN2 MAG1 MAG2 LMA MTMA | (MLD Proxy) (MLD Proxy) (Unicast)(Multicast) | | | | | MN Attached | | | | To MAG1 | | | | | | | | | | |========= Multicast Tunnel ======= | | | | | | MN Detaches | | | | From MAG1 | | | | | | | | | | | | | | MN Attaches | | | | To MAG2 | | | | | | | | | | | |==Multicast Tunnel === | | | | | | |---------Rtr Sol------ >| | | | | |--- PBU --->| | | | | | | | | |<-- PBA ----| | |<-----Rtr Adv --------- | | | | | | | | | | | | | |<---------MLD Query---- | | | | | | | | |---MLD Report (G) ----> | | | | | | | | | | |---- Aggregated -----> | | | | MLD Report (G) | | | | | | |< --------- Multicast Traffic ---------------- >| | | | | | | | | | | Figure 6. Multicast Mobility Signaling 3.5 PMIPv6 enhancements This section describes the enhancements to the Proxy Mobile IPv6 [RFC5213] protocol required to support the MTMA architecture. 3.5.1 New Binding Update List in MAG The Binding Update List in the MAG must be updated to be able to Zuniga, et al. Expires April 26, 2012 [Page 15] INTERNET DRAFT Multicast Mobility Routing Optimizations October, 2011 handle the fact that more than one entity (i.e. LMA and MTMA) may be serving the mobile node. 3.5.2 Policy Profile Information with Multicast Parameters A given mobile node's policy profile information must be updated to be able to store the IPv6 addresses of both the LMA and MTMA. 3.5.3 MAG to MTMA attach requirements The MAG procedures must be updated to be able to handle simultaneous attach for a given mobile node to both the LMA and MTMA. For example, packets coming from a given mobile node must be screened to determine if it should be sent to the LMA or to the MTMA. 3.5.4. Data structure stored by MTMA The MTMA does not directly interact with the MNs attached to any of the MAGs. The MTMA only manages the multicast groups subscribed per MAG on behalf of the MNs attached to it. Having this in mind, the relevant information to be stored in the MTMA should be the tunnel interface identifier (tunnel-if-id) of the bi-directional tunnel for multicast between the MTMA and every MAG (as stated in [RFC5213] for the unicast case), the IP addresses of the multicast group delivered per tunnel to each of the MAGs, and the IP addresses of the sources injecting the multicast traffic per tunnel to the multicast domain defined by the MTMA. 3.6 Advantages An advantage of the proposed MTMA architecture is that it allows a PMIPv6 domain to closely follow a simple multicast tree topology for Proxy MLD forwarding (cf., sections 1.1 and 1.2 of [RFC4605]). In contrast, the combined unicast/multicast LMA as proposed in [RFC6224] will be a more complex set of trees. Another advantage of the proposed dedicated multicast solution is that it allows a gradual network upgrade of a PMIPv6 domain to support multicast functionality. This is because the operator does not have to upgrade all the LMAs in the network to support multicast functionality. Only certain nodes (MTMAs), dedicated to multicast support, will have to be upgraded to support the new multicast functionality. Also, multiple deployment scenarios are supported as required by the operator for expected traffic distributions. Zuniga, et al. Expires April 26, 2012 [Page 16] INTERNET DRAFT Multicast Mobility Routing Optimizations October, 2011 A final advantage is that a specific multicast elements minimize the replication of multicast packets (the Tunnel Convergence problem), in certain scenarios, compared to [RFC6224]. Figures 7 and 8 illustrate this point visually. For this simple scenario, it can be observed that the multicast MTMA topology (Figure 7) generates 6 packets for one input multicast packet. In comparison, the combined unicast/multicast LMA topology (Figure 8) generates 8 packets for one input multicast packet. In general, it can be seen that the extra multiplication of packets in the combined unicast/multicast LMA topology will be proportional to the number of LMAs, and the number of MNs (in a given MAG) associated to different LMAs, for a given multicast group. The packet multiplication problem aggravates as more MNs associated to different LMAs receive the same multicast traffic when attached to the same MAG. Hence, the MTMA architecture significantly decreases the network capacity requirements in this scenario. (Note that in Figure 7, it is assumed that MN1 and MN2 are associated with MAG1-LMA1, and MN3 is associated with MAG2-MTMA2 for multicast traffic. In Figure 8, it is assumed that MN1 is associated with MAG1-LMA1, MN2 is associated with MAG1-LMA2, and MN3 is associated with MAG2-LMA2 for multicast traffic. In both Figures 7 and 8, it is assumed that the packets are transmitted point to point on the last hop wireless link.) Additional results can be found in [ERCIM], where both solutions are compared by simulation under realistic traffic conditions. It can be shown that, for multicast traffic, the number of channels that a node (LMA in the base solution, MTMA in the proposed multicast architecture) has to serve does not decrease linearly with the reduction of the number of MNs associated to that node. The key factor is the set of channels subscribed by the MNs. In fact, as the number of MNs increases in the PMIPv6 domain, we have less advantage for having several nodes serving multicast, as each of them will probably manage all the multicast channels (or at least the popular ones) anyway. Zuniga, et al. Expires April 26, 2012 [Page 17] INTERNET DRAFT Multicast Mobility Routing Optimizations October, 2011 +--------------+ |Content Source| +--------------+ | | +---+ Packet destined | 1 | for Multicast group "G" +---+ | *** *** *** *** *** *** *** *** * ** ** ** * * ** ** ** * * * * * * Unicast Traffic * * Multicast Traffic * * * * * * ** ** ** * * ** ** ** * *** *** *** *** *** *** *** *** | | | +---+ | | 2 | | +---+ | | +-----+ +------+ Unicast | LMA1| | MTMA2| Multicast Anchor +-----+ +------+ Anchor \ //|| \ // || \ // || \ // || \ +---+ +---+ \ | 3 | | 4 | \ +---+ +---+ \ // || \ // || \ // || \ // || +-----+ +-----+ | MAG1| | MAG2| MLD Proxy +-----+ +-----+ | | | +---+ +---+ +---+ | 5 | | 6 | | 7 | +---+ +---+ +---+ | | | All MNs in same | | | multicast group "G" {MN1} {MN2} {MN3} Figure 7. Packet Flow in the MTMA architecture Zuniga, et al. Expires April 26, 2012 [Page 18] INTERNET DRAFT Multicast Mobility Routing Optimizations October, 2011 +--------------+ |Content Source| +--------------+ | | +---+ Packet destined | 1 | for Multicast group "G" +---+ | *** *** *** *** *** *** *** *** *** * ** ** ** ** ** ** ** ** * * * * Fixed Internet * * (Unicast & Multicast Traffic) * * ** ** ** ** ** ** ** ** * *** *** *** *** *** *** *** *** | | +---+ +---+ | 2 | | 3 | +---+ +---+ | | +-----+ +------+ | LMA1| | LMA2 | Combined +-----+ +------+ Unicast/Multicast \ // || Anchor \ // || \ // || \ // || +---+ +---+ +---+ | 4 | | 5 | | 6 | +---+ +---+ +---+ \ // || \ // || \ // || \ // || +-----+ +-----+ | MAG1| | MAG2| MLD Proxy +-----+ +-----+ | | | +---+ +---+ +---+ | 7 | | 8 | | 9 | +---+ +---+ +---+ | | | All MNs in same | | | multicast group "G" {MN1} {MN2} {MN3} Figure 8. Packet Flow in a Combined Unicast/Multicast LMA Zuniga, et al. Expires April 26, 2012 [Page 19] INTERNET DRAFT Multicast Mobility Routing Optimizations October, 2011 4 Direct routing Direct routing uses native multicast infrastructure, allowing a MAG to connect a multicast router directly. A MAG can act as a MLD proxy or multicast router for redirecting multicast packets. The key idea of direct routing is to provide optimal routing for local content. As a consequence, it does not give the LMA processing burden for channel management and data delivery of locally available content. Direct routing is simple and easy to deploy. When thinking on the MAG reception of the multicast flow being forwarded to the attached MNs, two models for the MAG subscription to the multicast flow (on behalf of the MNs) can be considered: - Local subscription, which refers to the situation where the multicast channel is forwarded to the MAG by a multicast router within the PMIPv6 domain - Remote subscription, which refers to the situation where the multicast channel is forwarded to the MAG through the tunnel interface from the home network In the architecture described in [RFC6224], if MLD proxy is installed on a MAG, all MAGs that participate in the multicast traffic distribution in a PMIPv6 domain are considered to act as MLD proxies. An important consequence derived from such characterization is that every MLD proxy instance defined in the MAG has a unique upstream interface, and thus, an MLD proxy instance cannot dynamically choose among local or remote multicast subscription. For instance, one possible scenario pushing for local source deployment, and consequently local subscription, could be the one where there is an extremely high number of multicast channels, all of them with active subscriptions in all the MAGs along the PMIPv6 domain, resulting in the MTMA replicating the totally of the multicast flows to all the MAGs (leading to the known as "avalanche problem"). Once a decision is taken (at configuration time) about what kind of subscription, either local or remote, is applicable for a certain instance regarding all the multicast channels for all the attached MNs, this cannot be changed without resetting and reconfiguring the whole MLD instance. In order to have such kind of flexibility, the MAG needs to act as a multicast router, that is, it must implement some multicast routing protocol able to choose between local or remote subscription, for one or all the subscribed multicast channels, by using some routing criteria leveraged by the network routing information or by the network management systems. The most commonly deployed multicast Zuniga, et al. Expires April 26, 2012 [Page 20] INTERNET DRAFT Multicast Mobility Routing Optimizations October, 2011 routing protocol nowadays is PIM. So it is possible to distinguish among two situations depending on the MAG functionality. The following sub-sections describe the applying constraints. 4.1 MAG as MLD proxy In case of the MAG only incorporates MLD proxy functionality, for every one of the MLD proxy instances invoked in the MAG it is necessary to define at configuration time the upstream interface from where the multicast traffic will be received. This decision actually requires to define whether the multicast subscription by an MLD proxy instance for all the multicast channels will be local (if the upstream interface points to a multicast router internal to the PMIPv6 domain) or remote (in case of the upstream interface is the bi-directional tunnel towards the LMA, for the architecture in [RFC6224], or the MTMA, for the multicast listener optimization described in this document). 4.1.1 Local subscription when the MAG implements MLD proxy functionality If the MAG has MLD proxy functionality only, once this MLD proxy instance is configured to obtain the multicast traffic locally, the system behavior when operating with local subscription remains static. 4.1.1.1 Local subscription architecture Figure 9 shows the proposed local routing architecture using native multicasting infrastructure [I-D.deng-multimob-pmip6-requirement]. To forward IGMP/MLD signaling and multicast packets, a MLD proxy function defined in [RFC4605], SHOULD be placed on a MAG. This solution is much simpler than the base solution and easy to deploy because multicasting functions are totally separated from mobility anchor by using a native multicasting infrastructure. Zuniga, et al. Expires April 26, 2012 [Page 21] INTERNET DRAFT Multicast Mobility Routing Optimizations October, 2011 Multicast Tree : : || - PMIPv6 Tunnel +----------+ +----------+ | - Multicast Data Path | LMA | | MR | +----------+ +----------+ ||\ /| || \ / | || \ / | || \ / | || \/ | || / \ | || / \ | || / \ | +----------+ +----------+ | P-MAG | | N-MAG | |(M-Proxy) | |(M-Proxy) | +----------+ +----------+ : : +------+ +------+ | MN | -----> | MN | +------+ +------+ Figure 9. Direct routing solution for PMIPv6 Multicasting 4.1.1.2 Handover procedure for local routing Figure 10 shows the handover operation in local routing architecture. When an MN hands off to the next MAG (N-MAG) from the previous MAG (P-MAG), the N-MAG detects the newly arrived MN and transmits an MLD query message to the MN. After receiving the MLD query message, the MN sends an MLD report message that includes the multicast group information. The N-MAG then sends an aggregated MLD report message to the MR. When the N-MAG receives the multicast packets from the MR, it then simply forwards them without tunnel encapsulation. The N-MAG updates the MN's location information to the LMA by exchanging PBU/PBA signaling messages. Zuniga, et al. Expires April 26, 2012 [Page 22] INTERNET DRAFT Multicast Mobility Routing Optimizations October, 2011 MN P-MAG N-MAG LMA MR Tree | | | | | | | | | | | | |<----------|<-- Multicast Data--------------|<-------| | | . | | | | | | . | | | | | | . | | | | Link->| Handover | | | | Disconnected Detection | | | | | | | | | | | | | | | | | | MN Attachment | | | | | | | | | | | | | | | |------ Rtr. Sol. ----->| | | | | | | | | | |<----- MLD Query ------| | | | | | | | | | |------ MLD Report ---->| | | | | | | Aggregated | | | | |--- MLD Report ---->| | | | | | | | | | | | | | |<----------------------|<-- Multicast Data--|<-------| | | | | | | | | | | | | | | | Proxy | | | | | |--Binding->| | | | | | Update | | | | | | | | | | | | Proxy | | | | | |<-Binding--| | | | | | Ack. | | | | | | | | | Figure 10. Handover procedure in direct routing architecture 4.1.2 Remote subscription when the MAG implements MLD proxy functionality If the MAG has only MLD proxy functionality, the system behavior when operating with remote subscription is as described in chapter 3. Once the MLD proxy instance is configured to obtain the multicast traffic remotely, this remains static. Zuniga, et al. Expires April 26, 2012 [Page 23] INTERNET DRAFT Multicast Mobility Routing Optimizations October, 2011 4.2 MAG as multicast router If the MAG behaves as a multicast router, the MAG then implements a multicast routing protocol. This allows the MAG to make decisions about from where to receive the traffic of any multicast channel, based in routing information and/or network management criteria. The selected incoming interface for receiving multicast traffic will be then the one matching such criteria, and it could drive to either a local or remote subscription. Some situations are introduced in the next section. 4.2.1 Local subscription when the MAG implements a multicast routing protocol If the MAG is a multicast router, the system behavior when operating with local subscription is as before, but extending the role of the MAG to be a multicast router, and running a multicast routing protocol among the MAG and local multicast router serving the multicast traffic. Once the MAG decides to obtain the multicast traffic locally based in routing information and/or network management criteria, this can be dynamically changed if such criteria change. 4.2.2 Remote subscription when the MAG implements a multicast routing protocol If the MAG is a multicast router, the system behavior when operating with remote subscription is as described in chapter 3, considering that a multicast routing protocol is running among the MAG and the MTMA on the tunnel interface. Once the MAG decides to obtain the multicast traffic remotely based in routing information and/or network management criteria, this can be dynamically changed if such criteria change. 5 Dynamic selection of local versus remote multicast subscription As mentioned above, the MAG as multicast router provides some flexibility for choosing local versus remote multicast subscription. Considering PIM as the multicast routing protocol running on the MAG, it is possible to find out two situations where such dynamic selection can occur, according to the PIM flavor on place. For all the scenarios below we consider a certain multicast flow being injected by two different sources, one local to the PMIPv6 domain and one remote through the home network, by using an MTMA. Zuniga, et al. Expires April 26, 2012 [Page 24] INTERNET DRAFT Multicast Mobility Routing Optimizations October, 2011 5.1 Any source multicast scenario This situation applies for both PIM-SM and BIDIR PIM variants. In this case, once the MAG receives the MLD report from the MN requesting the multicast channel in the form (*,G), the MAG could decide what multicast flow subscribes to (the local or the remote one). The subscription can be statically pre-configured or dynamically configured based on some rule. For instance, static configuration can be made per MN (user), such as "multicast traffic from user X should always go through the home (i.e., via the tunnel with the MTMA/LMA- as-per-RFC6224), while traffic from user Y should go via local subscription". Also, configuration profiles can also be more complex and include considerations on types of traffic or IP flows, such as "traffic of type A from user X should always go through the home, traffic of type B from user X should be subscribed locally" using routing information and/or network management criteria. Similarly, routing information can be received dynamically, for example, at user's registration time PBU/PBA signaling can be used to carry the profile information similar to what is described in [draft- gundavelli-netext-pmipv6-sipto-option]. Also, routing information can be exchanged dynamically when the multicast group subscription is made. When focusing on PIM-SM, another scenario is possible. PIM-SM allows for switching from a multicast shared-tree to a source-specific tree to optimize the path for traffic delivery. The location of the rendezvous point and the multicast source can be either in the PMIPv6 domain or the home network, so the optimization could be from local subscription to remote subscription or vice versa. The possibility of switching to a source-based tree, and the time for doing is implementation-dependent, and it could be triggered immediately (after reception of the first multicast packet) or last to some time, or even not switching never. 5.2 Source specific multicast scenario This situation applies for PIM-SSM. Then, in a source-specific multicast scenario [RFC4607], the MAG would send the PIM request to the corresponding interface based on the multicast source address indicated on the (S,G) subscription requested by the MN in the MLD Report, using the routing information. Zuniga, et al. Expires April 26, 2012 [Page 25] INTERNET DRAFT Multicast Mobility Routing Optimizations October, 2011 6 Security Considerations This draft discusses the operations of existing protocols without modifications. It does not introduce new security threats beyond the current security considerations of PMIPv6 [RFC5213], MLD [RFC3810], IGMP [RFC3376] and IGMP/MLD Proxying [RFC4605]. 7 IANA Considerations This document makes no request of IANA. 8 Contributors The following people have considerably contributed to this draft: Akbar Rahman InterDigital Communications, LLC Email: Akbar.Rahman@InterDigital.com Ignacio Soto Universidad Politecnica de Madrid Email: isoto@dit.upm.es 9 References 9.1 Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC5213] Gundavelli, S., Leung, K., Devarapalli, V., Chowdhury, K., and B. Patil, "Proxy Mobile IPv6", RFC 5213, August 2008. [RFC3775] Johnson, D., Perkins, C., and J. Arkko, "Mobility Support in Ipv6", RFC 3775, June 2004. [RFC3810] Vida, R. and L.Costa, "Multicast Listener Discovery Version 2 (MLDv2) for IPv6", RFC 3810, June 2004. [RFC3376] Cain, B., Deering, S., Kouvelas, I., Fenner, B., and A. Thyagarajan, "Internet Group Management Protocol, Version 3", RFC 3376, October 2002. [RFC4605] Fenner, B., He, H., Haberman, B., and H. Sandick, Zuniga, et al. Expires April 26, 2012 [Page 26] INTERNET DRAFT Multicast Mobility Routing Optimizations October, 2011 "Internet Group Management Protocol (IGMP)/ Multicast Listener Discovery (MLD)-Based Multicast Forwarding ("IGMP/MLD Proxying")", RFC 4605, August 2006. [RFC5847] Devarapalli, V., Koodli, R., Lim, H., Kant, N., Krishnan, S., Laganier, J., "Heartbeat Mechanism for Proxy Mobile IPv6", RFC 5847, June 2010. [RFC4601] Fenner, B., Handley, M., Holbrook, H., and I. Kouvelas, "Protocol Independent Multicast - Sparse Mode (PIM-SM): Protocol Specification (Revised)", RFC 4601, August 2006. [RFC4607] Holbrook, H., and B. Cain, "Source-Specific Multicast for IP", RFC 4607, August 2006. 9.2 Informative References [RFC6224] Schmidt, T.C., Waehlisch, M., and S.Krishnan, "Base Deployment for Multicast Listener Support in PMIPv6 Domains", RFC 6224, April 2011. [ERCIM] L.M. Contreras, C.J. Bernardos, I. Soto, "On the efficiency of a dedicated LMA for multicast traffic distribution in PMIPv6 domains", 5th ERCIM Workshop in eMobility, Vilanova i la Geltru, Spain, June 2011. [I-D.deng-multimob-pmip6-requirement] H. Deng, T. Schmidt, P. Seite, and P. Yang, "Multicast Support Requirements for Proxy Mobile IPv6", draft-deng-multimob-pmip6-requirement- 02.txt (work in progress), July 2009. Zuniga, et al. Expires April 26, 2012 [Page 27] INTERNET DRAFT Multicast Mobility Routing Optimizations October, 2011 Author's Addresses Juan Carlos Zuniga InterDigital Communications, LLC EMail: JuanCarlos.Zuniga@InterDigital.com Luis M. Contreras Telefonica I+D EMail: lmcm@tid.es Carlos J. Bernardos Universidad Carlos III de Madrid EMail: cjbc@it.uc3m.es Seil Jeon Soongsil University Email: sijeon@dcn.ssu.ac.kr Younghan Kim Soongsil University Email: yhkim@dcn.ssu.ac.kr Zuniga, et al. Expires April 26, 2012 [Page 28]