PALS W. Cheng Internet-Draft China Mobile Intended status: Informational J. Dong Expires: May 21, 2020 Huawei Technologies November 18, 2019 Efficient Layer 2 Multicast with Point-to-Point Pseudowires draft-cheng-pals-p2p-pw-multicast-01 Abstract Multicast services such as Evolved Multimedia Broadcast/Multicast Service (eMBMS) become more and more popular in mobile networks. In mobile transport network, it is important for the operators to provide efficient transport of multicast services with existing network devices. This document describes a mechanism of using point- to-point Pseudowires (PW) [RFC3985] to achieve efficient layer 2 multicast transportation in mobile transport networks.The document gives a multicast method by utilizing a Point-to-Point (P2P) path between nodes in a packet transport network , according to the destination IP address. With it, the PTN nodes can replicate and forward the service message, which are received from the multicast server, to the plurality of multicast clients corresponding to the destination IP address. Status of This Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at https://datatracker.ietf.org/drafts/current/. 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." This Internet-Draft will expire on May 21, 2020. Copyright Notice Copyright (c) 2019 IETF Trust and the persons identified as the document authors. All rights reserved. Cheng & Dong Expires May 21, 2020 [Page 1] Internet-DraftEfficient Layer 2 Multicast with Point-to-PoiNovember 2019 This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (https://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. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1.1. Conventions used in this document . . . . . . . . . . . . 3 1.1.1. Terminology . . . . . . . . . . . . . . . . . . . . . 3 1.1.2. Requirements Language . . . . . . . . . . . . . . . . 4 2. Efficient Multicast with P2P PWs . . . . . . . . . . . . . . 4 3. Protection Mechanism . . . . . . . . . . . . . . . . . . . . 4 4. OAM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5 6. Security Considerations . . . . . . . . . . . . . . . . . . . 5 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 5 8. Normative References . . . . . . . . . . . . . . . . . . . . 5 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 6 1. Introduction Multicast services such as evolved Multimedia Broadcast/Multicast Service (eMBMS) become more and more popular in mobile networks. In mobile transport network, it is important for the operators to provide efficient transport of multicast services with existing network devices. Cheng & Dong Expires May 21, 2020 [Page 2] Internet-DraftEfficient Layer 2 Multicast with Point-to-PoiNovember 2019 ---------------- ///// multicast \\\\\ // source \\ | | | Layer 3 Multicast Network | | | \\ // \\\\\ ///// +--+--+ +--+--+ | R-1 +-----+ R-2 | +--+--+ +--+--+ L2 | | +--+--+ +--+--+ Multicast | R-3 +-----+-R-4 | *---+-+ +-+---* Network / | | \ / | | \ +-----+ +--+--+ +--+--+ +-----+ | R-5 +--+ R-6 | | R-7 +--+ R-8 | +---+-+ +-+-+-+ +-+-+-+ +-+---+ / | | | | | | \ / | | | | | | \ Clients Clients Clients Clients Figure 1. L2 Multicast Topology PTN network comprise at least one root node and at least one leaf node, the multicast source server is connected to the root node, and the multicast clients are connected to the leaf node.Figure 1 shows a typical topology of mobile transport network, which is composed of the layer 3 network at the core and the layer 2 network at the aggregation and edge. R-1 and R-2 connect to the upstream layer 3 network, in which the multicast source locates. This document focuses on the efficient multicast service transportation in the layer 2 segment of the network using point-to- point (P2P) Pseudowires (PW) [RFC3985]. 1.1. Conventions used in this document 1.1.1. Terminology The terminology is defined as [RFC3985] . Cheng & Dong Expires May 21, 2020 [Page 3] Internet-DraftEfficient Layer 2 Multicast with Point-to-PoiNovember 2019 1.1.2. Requirements Language The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all capitals, as shown here. 2. Efficient Multicast with P2P PWs This section describes the mechanism of efficient layer 2 multicast transportation with point-to-point PWs. In the layer 2 multicast segment, nodes which connect to the L3 network are called Root nodes, and nodes which connect to the multicast clients are called Leaf nodes. For each multicast service, between the Root nodes and the Leaf nodes, 1-hop P2P PWs are provisioned between the adjacent nodes. The multicast tree from the Root nodes to the Leaf nodes is the concatenation of P2P PWs provisioned by NMS or central controller. Multicast traffic is carried by the P2P PWs. On each PW hop, the PW label is popped, and the forwarding is performed according to the layer 2 multicast forwarding table of the node. The layer 2 multicast forwarding entries can be either statically provisioned by NMS or central controller, or dynamically generated via IGMP snooping [RFC4541]. For multicast traffic received on a specific P2P PW, the outbound PWs and ACs are determined by the corresponding L2 multicast forwarding table. For packets to be forwarded to next P2P PW, the PW label is pushed according to the forwarding table. With this mechanism, on each P2P PW in the network, at most one copy of the multicast traffic is delivered. On the Leaf nodes, IGMP snooping [RFC4541] is used to optimize the layer 2 multicast forwarding to the clients, so that only the clients which express interests to the multicast service would receive the corresponding multicast traffic. 3. Protection Mechanism For layer 2 multicast service, 1+1 protection is provided. The working and protection multicast trees are provisioned seperately by NMS or central controller, and multicast service is carried on both the working mutlicast tree and the protection multicast tree simultaneously. In network topology of Figure 1, the Root node of the working PW is R-1, while the Root node of the protection PW is R-2. Each Leaf node has a working PW from its working upstream, and a protection PW from the protection upstream. According to the Cheng & Dong Expires May 21, 2020 [Page 4] Internet-DraftEfficient Layer 2 Multicast with Point-to-PoiNovember 2019 result of OAM detection mechanism, the Leaf nodes choose to receive multicast traffic from either the working or protection PW. 4. OAM PW OAM mechanisms as defined in [RFC5085] [RFC6428] are deployed on each P2P PW, including both the working PWs and protection PWs. When failure occurs on a working PW, the node which detects the failure SHOULD send AIS message as defined in [RFC6427] to notify its downstream nodes of the failure. This AIS message is propagated along the multicast tree to the downstream Leaf nodes. Then the Leaf nodes which are impacted by the failure can switchover to receive the multicast service traffic from the protection PWs 5. IANA Considerations This document makes no request of IANA. Note to RFC Editor: this section may be removed on publication as an RFC. 6. Security Considerations This document describes a layer 2 multicst mechansim with point-to- point PWs and NMS or controller provisioned multicast tree. The security condierations as specified in [RFC3985] apply to this document. 7. Acknowledgements The authors would like to thank Jun Wu, Kai Liu and Yongjian Hu for the review and comments. 8. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, . [RFC3985] Bryant, S., Ed. and P. Pate, Ed., "Pseudo Wire Emulation Edge-to-Edge (PWE3) Architecture", RFC 3985, DOI 10.17487/RFC3985, March 2005, . Cheng & Dong Expires May 21, 2020 [Page 5] Internet-DraftEfficient Layer 2 Multicast with Point-to-PoiNovember 2019 [RFC4541] Christensen, M., Kimball, K., and F. Solensky, "Considerations for Internet Group Management Protocol (IGMP) and Multicast Listener Discovery (MLD) Snooping Switches", RFC 4541, DOI 10.17487/RFC4541, May 2006, . [RFC5085] Nadeau, T., Ed. and C. Pignataro, Ed., "Pseudowire Virtual Circuit Connectivity Verification (VCCV): A Control Channel for Pseudowires", RFC 5085, DOI 10.17487/RFC5085, December 2007, . [RFC6427] Swallow, G., Ed., Fulignoli, A., Ed., Vigoureux, M., Ed., Boutros, S., and D. Ward, "MPLS Fault Management Operations, Administration, and Maintenance (OAM)", RFC 6427, DOI 10.17487/RFC6427, November 2011, . [RFC6428] Allan, D., Ed., Swallow, G., Ed., and J. Drake, Ed., "Proactive Connectivity Verification, Continuity Check, and Remote Defect Indication for the MPLS Transport Profile", RFC 6428, DOI 10.17487/RFC6428, November 2011, . [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017, . Authors' Addresses Weiqiang Cheng China Mobile Beijing China Email: chengweiqiang@chinamobile.com Jie Dong Huawei Technologies China Email: jie.dong@huawei.com Cheng & Dong Expires May 21, 2020 [Page 6]