Domain names - implementation and specification
RFC 1035

Network Working Group                                     P. Mockapetris
Request for Comments: 1035                                           ISI
                                                           November 1987
Obsoletes: RFCs 882, 883, 973

            DOMAIN NAMES - IMPLEMENTATION AND SPECIFICATION

1. STATUS OF THIS MEMO

This RFC describes the details of the domain system and protocol, and
assumes that the reader is familiar with the concepts discussed in a
companion RFC, "Domain Names - Concepts and Facilities" [RFC-1034].

The domain system is a mixture of functions and data types which are an
official protocol and functions and data types which are still
experimental.  Since the domain system is intentionally extensible, new
data types and experimental behavior should always be expected in parts
of the system beyond the official protocol.  The official protocol parts
include standard queries, responses and the Internet class RR data
formats (e.g., host addresses).  Since the previous RFC set, several
definitions have changed, so some previous definitions are obsolete.

Experimental or obsolete features are clearly marked in these RFCs, and
such information should be used with caution.

The reader is especially cautioned not to depend on the values which
appear in examples to be current or complete, since their purpose is
primarily pedagogical.  Distribution of this memo is unlimited.

                           Table of Contents

  1. STATUS OF THIS MEMO                                              1
  2. INTRODUCTION                                                     3
      2.1. Overview                                                   3
      2.2. Common configurations                                      4
      2.3. Conventions                                                7
          2.3.1. Preferred name syntax                                7
          2.3.2. Data Transmission Order                              8
          2.3.3. Character Case                                       9
          2.3.4. Size limits                                         10
  3. DOMAIN NAME SPACE AND RR DEFINITIONS                            10
      3.1. Name space definitions                                    10
      3.2. RR definitions                                            11
          3.2.1. Format                                              11
          3.2.2. TYPE values                                         12
          3.2.3. QTYPE values                                        12
          3.2.4. CLASS values                                        13

Mockapetris                                                     [Page 1]
RFC 1035        Domain Implementation and Specification    November 1987

          3.2.5. QCLASS values                                       13
      3.3. Standard RRs                                              13
          3.3.1. CNAME RDATA format                                  14
          3.3.2. HINFO RDATA format                                  14
          3.3.3. MB RDATA format (EXPERIMENTAL)                      14
          3.3.4. MD RDATA format (Obsolete)                          15
          3.3.5. MF RDATA format (Obsolete)                          15
          3.3.6. MG RDATA format (EXPERIMENTAL)                      16
          3.3.7. MINFO RDATA format (EXPERIMENTAL)                   16
          3.3.8. MR RDATA format (EXPERIMENTAL)                      17
          3.3.9. MX RDATA format                                     17
          3.3.10. NULL RDATA format (EXPERIMENTAL)                   17
          3.3.11. NS RDATA format                                    18
          3.3.12. PTR RDATA format                                   18
          3.3.13. SOA RDATA format                                   19
          3.3.14. TXT RDATA format                                   20
      3.4. ARPA Internet specific RRs                                20
          3.4.1. A RDATA format                                      20
          3.4.2. WKS RDATA format                                    21
      3.5. IN-ADDR.ARPA domain                                       22
      3.6. Defining new types, classes, and special namespaces       24
  4. MESSAGES                                                        25
      4.1. Format                                                    25
          4.1.1. Header section format                               26
          4.1.2. Question section format                             28
          4.1.3. Resource record format                              29
          4.1.4. Message compression                                 30
      4.2. Transport                                                 32
          4.2.1. UDP usage                                           32
          4.2.2. TCP usage                                           32