DNS-Based Service Discovery
RFC 6763

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Internet Engineering Task Force (IETF)                       S. Cheshire
Request for Comments: 6763                                   M. Krochmal
Category: Standards Track                                     Apple Inc.
ISSN: 2070-1721                                            February 2013

                      DNS-Based Service Discovery

Abstract

   This document specifies how DNS resource records are named and
   structured to facilitate service discovery.  Given a type of service
   that a client is looking for, and a domain in which the client is
   looking for that service, this mechanism allows clients to discover
   a list of named instances of that desired service, using standard
   DNS queries.  This mechanism is referred to as DNS-based Service
   Discovery, or DNS-SD.

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/rfc6763.

Copyright Notice

   Copyright (c) 2013 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.

Cheshire & Krochmal          Standards Track                    [Page 1]
RFC 6763               DNS-Based Service Discovery         February 2013

Table of Contents

   1. Introduction ....................................................3
   2. Conventions and Terminology Used in This Document ...............5
   3. Design Goals ....................................................5
   4. Service Instance Enumeration (Browsing) .........................6
      4.1. Structured Service Instance Names ..........................6
      4.2. User Interface Presentation ................................9
      4.3. Internal Handling of Names .................................9
   5. Service Instance Resolution ....................................10
   6. Data Syntax for DNS-SD TXT Records .............................11
      6.1. General Format Rules for DNS TXT Records ..................11
      6.2. DNS-SD TXT Record Size ....................................12
      6.3. DNS TXT Record Format Rules for Use in DNS-SD .............13
      6.4. Rules for Keys in DNS-SD Key/Value Pairs ..................14
      6.5. Rules for Values in DNS-SD Key/Value Pairs ................16
      6.6. Example TXT Record ........................................17
      6.7. Version Tag ...............................................17
      6.8. Service Instances with Multiple TXT Records ...............18
   7. Service Names ..................................................19
      7.1. Selective Instance Enumeration (Subtypes) .................21
      7.2. Service Name Length Limits ................................23
   8. Flagship Naming ................................................25
   9. Service Type Enumeration .......................................27
   10. Populating the DNS with Information ...........................27
   11. Discovery of Browsing and Registration Domains (Domain
       Enumeration) ..................................................28
   12. DNS Additional Record Generation ..............................30
      12.1. PTR Records ..............................................30
      12.2. SRV Records ..............................................30
      12.3. TXT Records ..............................................31
      12.4. Other Record Types .......................................31
   13. Working Examples ..............................................31
      13.1. What web pages are being advertised from dns-sd.org? .....31
      13.2. What printer-configuration web pages are there? ..........31
      13.3. How do I access the web page called "Service
            Discovery"? ..............................................32
   14. IPv6 Considerations ...........................................32
   15. Security Considerations .......................................32
   16. IANA Considerations ...........................................32
   17. Acknowledgments ...............................................33