DNS Reverse IP Automatic Multicast Tunneling (AMT) Discovery
RFC 8777

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Internet Engineering Task Force (IETF)                        J. Holland
Request for Comments: 8777                     Akamai Technologies, Inc.
Updates: 7450                                                 April 2020
Category: Standards Track                                               
ISSN: 2070-1721

      DNS Reverse IP Automatic Multicast Tunneling (AMT) Discovery

Abstract

   This document updates RFC 7450, "Automatic Multicast Tunneling" (or
   AMT), by modifying the relay discovery process.  A new DNS resource
   record named AMTRELAY is defined for publishing AMT relays for
   source-specific multicast channels.  The reverse IP DNS zone for a
   multicast sender's IP address is configured to use AMTRELAY resource
   records to advertise a set of AMT relays that can receive and forward
   multicast traffic from that sender over an AMT tunnel.  Other
   extensions and clarifications to the relay discovery process are also
   defined.

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 7841.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   https://www.rfc-editor.org/info/rfc8777.

Copyright Notice

   Copyright (c) 2020 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
   (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
     1.1.  Background
     1.2.  Terminology
       1.2.1.  Relays and Gateways
       1.2.2.  Definitions
       1.2.3.  Requirements Language
   2.  Relay Discovery Overview
     2.1.  Basic Mechanics
     2.2.  Signaling and Discovery
     2.3.  Example Deployments
       2.3.1.  Example Receiving Networks
       2.3.2.  Example Sending Networks
   3.  Relay Discovery Operation
     3.1.  Optimal Relay Selection
       3.1.1.  Overview
       3.1.2.  Preference Ordering
       3.1.3.  Connecting to Multiple Relays
     3.2.  Happy Eyeballs
       3.2.1.  Overview
       3.2.2.  Algorithm Guidelines
       3.2.3.  Connection Definition
     3.3.  Guidelines for Restarting Discovery
       3.3.1.  Overview
       3.3.2.  Updates to Restarting Events
       3.3.3.  Tunnel Stability
       3.3.4.  Traffic Health
       3.3.5.  Relay Loaded or Shutting Down
       3.3.6.  Relay Discovery Messages vs. Restarting Discovery
       3.3.7.  Independent Discovery per Traffic Source
     3.4.  DNS Configuration
     3.5.  Waiting for DNS Resolution
   4.  AMTRELAY Resource Record Definition
     4.1.  AMTRELAY RRType
     4.2.  AMTRELAY RData Format
       4.2.1.  RData Format - Precedence
       4.2.2.  RData Format - Discovery Optional (D-bit)
       4.2.3.  RData Format - Type
       4.2.4.  RData Format - Relay
     4.3.  AMTRELAY Record Presentation Format
       4.3.1.  Representation of AMTRELAY RRs
       4.3.2.  Examples
   5.  IANA Considerations
   6.  Security Considerations
     6.1.  Use of AMT
     6.2.  Record-Spoofing
     6.3.  Congestion
   7.  References
     7.1.  Normative References
     7.2.  Informative References
   Appendix A.  Unknown RRType Construction
   Acknowledgements
   Author's Address

1.  Introduction

   This document defines DNS Reverse IP AMT Discovery (DRIAD), a
   mechanism for AMT gateways to discover AMT relays that are capable of
   forwarding multicast traffic from a known source IP address.

   AMT (Automatic Multicast Tunneling) is defined in [RFC7450] and
   provides a method to transport multicast traffic over a unicast
   tunnel in order to traverse network segments that are not multicast
   capable.

   Section 4.1.5 of [RFC7450] explains that the relay selection process
   for AMT is intended to be more flexible than the particular discovery
   method described in that document.  That section further explains
   that the selection process might need to depend on the source of the
   multicast traffic in some deployments, since a relay must be able to
   receive multicast traffic from the desired source in order to forward
   it.

   Section 4.1.5 of [RFC7450] goes on to suggest DNS-based queries as a
   possible solution: DRIAD is DNS based.  This solution also addresses