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RFC 7450

Automatic Multicast Tunneling

Pages: 82
Proposed Standard
Updated by:  8777
Part 1 of 4 – Pages 1 to 6
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Top   ToC   RFC7450 - Page 1
Internet Engineering Task Force (IETF)                     G. Bumgardner
Request for Comments: 7450                                 February 2015
Category: Standards Track
ISSN: 2070-1721


                     Automatic Multicast Tunneling

Abstract

This document describes Automatic Multicast Tunneling (AMT), a protocol for delivering multicast traffic from sources in a multicast-enabled network to receivers that lack multicast connectivity to the source network. The protocol uses UDP encapsulation and unicast replication to provide this functionality. The AMT protocol is specifically designed to support rapid deployment by requiring minimal changes to existing network infrastructure. Status of This Memo This is an Internet Standards Track document. This document is a product of the Internet Engineering Task Force (IETF). It represents the consensus of the IETF community. It has received public review and has been approved for publication by the Internet Engineering Steering Group (IESG). Further information on Internet Standards is available in Section 2 of RFC 5741. Information about the current status of this document, any errata, and how to provide feedback on it may be obtained at http://www.rfc-editor.org/info/rfc7450. Copyright Notice Copyright (c) 2015 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.
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Table of Contents

1. Introduction ....................................................3 2. Applicability ...................................................3 3. Terminology .....................................................4 3.1. Requirements Notation ......................................4 3.2. Definitions ................................................4 3.3. Abbreviations ..............................................5 4. Protocol Overview ...............................................6 4.1. General Architecture .......................................6 4.1.1. Relationship to IGMP and MLD Protocols ..............6 4.1.2. Gateways ............................................7 4.1.3. Relays .............................................10 4.1.4. Deployment .........................................13 4.1.5. Discovery ..........................................14 4.2. General Operation .........................................15 4.2.1. Message Sequences ..................................15 4.2.2. Tunneling ..........................................26 5. Protocol Description ...........................................31 5.1. Protocol Messages .........................................31 5.1.1. Relay Discovery ....................................31 5.1.2. Relay Advertisement ................................32 5.1.3. Request ............................................34 5.1.4. Membership Query ...................................35 5.1.5. Membership Update ..................................39 5.1.6. Multicast Data .....................................41 5.1.7. Teardown ...........................................43 5.2. Gateway Operation .........................................45 5.2.1. IP/IGMP/MLD Protocol Requirements ..................45 5.2.2. Pseudo-Interface Configuration .....................47 5.2.3. Gateway Service ....................................48 5.3. Relay Operation ...........................................61 5.3.1. IP/IGMP/MLD Protocol Requirements ..................61 5.3.2. Startup ............................................61 5.3.3. Running ............................................62 5.3.4. Shutdown ...........................................73 5.3.5. Response MAC Generation ............................73 5.3.6. Private Secret Generation ..........................74 6. Security Considerations ........................................74 6.1. Relays ....................................................74 6.2. Gateways ..................................................76 6.3. Encapsulated IP Packets ...................................76 7. IANA Considerations ............................................77 7.1. IPv4 and IPv6 Anycast Prefix Allocation ...................77 7.1.1. IPv4 ...............................................77 7.1.2. IPv6 ...............................................78 7.2. UDP Port Number ...........................................78
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   8. References .....................................................78
      8.1. Normative References ......................................78
      8.2. Informative References ....................................79
   Acknowledgments ...................................................81
   Contributors ......................................................82
   Author's Address ..................................................82

1. Introduction

The advantages and benefits provided by multicast technologies are well known. There are a number of application areas that are ideal candidates for the use of multicast, including media broadcasting, video conferencing, collaboration, real-time data feeds, data replication, and software updates. Unfortunately, many of these applications lack multicast connectivity to networks that carry traffic generated by multicast sources. The reasons for the lack of connectivity vary but are primarily the result of service provider policies and network limitations. Automatic Multicast Tunneling (AMT) is a protocol that uses UDP-based encapsulation to overcome the aforementioned lack of multicast connectivity. AMT enables sites, hosts, or applications that do not have native multicast access to a network with multicast connectivity to a source, to request and receive Source-Specific Multicast (SSM) [RFC4607] and Any-Source Multicast (ASM) [RFC1112] traffic from a network that does provide multicast connectivity to that source.

2. Applicability

This document describes a protocol that may be used to deliver multicast traffic from a multicast-enabled network to sites that lack multicast connectivity to the source network. This document does not describe any methods for sourcing multicast traffic from isolated sites, as this topic is out of scope. AMT is not intended to be used as a substitute for native multicast, especially in conditions or environments requiring high traffic flow. AMT uses unicast replication to reach multiple receivers, and the bandwidth cost for this replication will be higher than that required if the receivers were reachable via native multicast. AMT is designed to be deployed at the border of networks possessing native multicast capabilities where access and provisioning can be managed by the AMT service provider.
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3. Terminology

3.1. Requirements Notation

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 [RFC2119].

3.2. Definitions

This document adopts the following definitions for use in describing the protocol: Downstream: A downstream interface or connection that faces away from the multicast distribution root or towards multicast receivers. Upstream: An upstream interface or connection that faces a multicast distribution root or source. Non-Broadcast Multi-Access (NBMA): An NBMA network or interface is one to which multiple network nodes (hosts or routers) are attached, but where packets are transmitted directly from one node to another node over a virtual circuit or physical link. NBMA networks do not support multicast or broadcast traffic -- a node that sources multicast traffic must replicate the multicast packets for separate transmission to each node that has requested the multicast traffic. Multicast Receiver: An entity that requests and receives multicast traffic. A receiver may be a router, host, application, or application component. The method by which a receiver transmits group membership requests and receives multicast traffic varies according to receiver type. Group Membership Database: A group membership database describes the current multicast subscription state (also referred to as "reception state") for an interface or system. See Section 3 of [RFC3376] for a detailed definition. Reception State: The multicast subscription state of a pseudo-interface, virtual interface, or physical network interface. Often synonymous with group membership database.
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   Subscription:
      A group or state entry in a group membership database or reception
      state table.  The presence of a subscription entry indicates
      membership in an IP multicast group.

   Group Membership Protocol:
      The term "group membership protocol" is used as a generic
      reference to the Internet Group Management Protocol (IGMP)
      [RFC1112] [RFC2236] [RFC3376] or the Multicast Listener Discovery
      protocol [RFC2710] [RFC3810].

   Multicast Protocol:
      The term "multicast protocol" is used as a generic reference to
      multicast routing protocols used to join or leave multicast
      distribution trees, such as Protocol Independent Multicast -
      Sparse Mode (PIM-SM) [RFC4601].

   Network Address Translation (NAT):
      Network Address Translation is the process of modifying the source
      IP address and port numbers carried by an IP packet while
      transiting a network node (see [RFC2663]).  Intervening NAT
      devices may change the source address and port carried by messages
      sent from an AMT gateway to an AMT relay, possibly producing
      changes in protocol state and behavior.

   Anycast:
      A network addressing and routing method in which packets from a
      single sender are routed to the topologically nearest node in a
      group of potential receivers all identified by the same
      destination address.  See [RFC4786].

3.3. Abbreviations

AMT - Automatic Multicast Tunneling protocol. ASM - Any-Source Multicast. DoS - Denial-of-Service (attack) and DDoS for distributed DoS. IGMP - Internet Group Management Protocol (v1, v2, and v3). IP - Internet Protocol (v4 and v6). MAC - Message Authentication Code (or Cookie). MLD - Multicast Listener Discovery protocol (v1 and v2). NAT - Network Address Translation (or translation node).
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      NBMA - Non-Broadcast Multi-Access (network, interface, or mode).

      PIM - Protocol Independent Multicast.

      SSM - Source-Specific Multicast.



(page 6 continued on part 2)

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