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'Moon 81' ** Downref: Normative reference to an Informational RFC: RFC 1591 ** Obsolete normative reference: RFC 2434 (Obsoleted by RFC 5226) ** Obsolete normative reference: RFC 2535 (Obsoleted by RFC 4033, RFC 4034, RFC 4035) ** Obsolete normative reference: RFC 2671 (Obsoleted by RFC 6891) ** Obsolete normative reference: RFC 2672 (Obsoleted by RFC 6672) ** Obsolete normative reference: RFC 2673 (Obsoleted by RFC 6891) -- No information found for draft-ietf-dnsind-tsig- - is the name correct? -- Possible downref: Normative reference to a draft: ref. 'RFC XXX3' -- Possible downref: Non-RFC (?) normative reference: ref. 'US-ASCII' Summary: 10 errors (**), 0 flaws (~~), 5 warnings (==), 12 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 1 INTERNET-DRAFT Donald E. Eastlake 3rd 2 Eric Brunner (Nokia) 3 Bill Manning (ISI) 4 Expires: June 2000 December 1999 5 draft-ietf-dnsind-iana-dns-04.txt 7 Domain Name System (DNS) IANA Considerations 8 ------ ---- ------ ----- ---- -------------- 10 Status of This Document 12 Distribution of this draft , which 13 is intended to become a Best Current Practice, is unlimited. Comments 14 should be sent to the DNS Working Group mailing list 15 or to the authors. 17 This document is an Internet-Draft and is in full conformance with 18 all provisions of Section 10 of RFC2026. Internet-Drafts are working 19 documents of the Internet Engineering Task Force (IETF), its areas, 20 and its working groups. Note that other groups may also distribute 21 working documents as Internet-Drafts. 23 Internet-Drafts are draft documents valid for a maximum of six 24 months. Internet-Drafts may be updated, replaced, or obsoleted by 25 other documents at any time. It is not appropriate to use Internet- 26 Drafts as reference material or to cite them other than as a 27 ``working draft'' or ``work in progress.'' 29 The list of current Internet-Drafts can be accessed at 30 http://www.ietf.org/ietf/1id-abstracts.txt 32 The list of Internet-Draft Shadow Directories can be accessed at 33 http://www.ietf.org/shadow.html. 35 Abstract 37 Internet Assigned Number Authority (IANA) parameter assignment 38 considerations are given for the allocation of Domain Name System 39 (DNS) classes, RR types, operation codes, error codes, etc. 41 Table of Contents 43 Status of This Document....................................1 45 Abstract...................................................2 46 Table of Contents..........................................2 48 1. Introduction............................................3 49 2. DNS Query/Response Headers..............................3 50 2.1 One Spare Bit?.........................................4 51 2.2 Opcode Assignment......................................4 52 2.3 RCODE Assignment.......................................5 53 3. DNS Resource Records....................................5 54 3.1 RR TYPE IANA Considerations............................7 55 3.1.1 Special Note on the OPT RR...........................8 56 3.2 RR CLASS IANA Considerations...........................8 57 3.3 RR NAME Considerations.................................9 58 4. Security Considerations................................10 60 References................................................11 61 Authors Addresses.........................................12 62 Expiration and File Name..................................12 64 1. Introduction 66 The Domain Name System (DNS) provides replicated distributed secure 67 hierarchical databases which hierarchically store "resource records" 68 (RRs) by CLASS under domain names. 70 This data is structured into CLASSes and zones which can be 71 independently maintained. See [RFC 1034, 1035, 2136, 2181, 2535] 72 familiarity with which is assumed. 74 This document covers, either directly or by reference, general IANA 75 parameter assignment considerations applying across DNS query and 76 response headers and all RRs. There may be additional IANA 77 considerations that apply to only a particular RR type or 78 query/response opcode. See the specific RFC defining that RR type or 79 query/response opcode for such considerations if they have been 80 defined. 82 IANA currently maintains a web page of DNS parameters at 83 . 85 "IETF Standards Action", "IETF Consensus", "Specification Required", 86 and "Private Use" are as defined in [RFC 2434]. 88 2. DNS Query/Response Headers 90 The header for DNS queries and responses contains field/bits in the 91 following diagram taken from [RFC 2136, 2535]: 93 1 1 1 1 1 1 94 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 95 +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ 96 | ID | 97 +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ 98 |QR| Opcode |AA|TC|RD|RA| Z|AD|CD| RCODE | 99 +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ 100 | QDCOUNT/ZOCOUNT | 101 +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ 102 | ANCOUNT/PRCOUNT | 103 +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ 104 | NSCOUNT/UPCOUNT | 105 +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ 106 | ARCOUNT | 107 +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ 109 The ID field identifies the query and is echoed in the response so 110 they can be matched. 112 The QR bit indicates whether the header is for a query or a response. 114 The AA, TC, RD, RA, AD, and CD bits are each theoretically meaningful 115 only in queries or only in responses, depending on the bit. However, 116 many DNS implementations copy the query header as the initial value 117 of the response header without clearing bits. Thus any attempt to 118 use a "query" bit with a different meaning in a response or to define 119 a query meaning for a "response" bit is dangerous given existing 120 implementation. Such meanings may only be assigned by an IETF 121 Standards Action. 123 The unsigned fields query count (QDCOUNT), answer count (ANCOUNT), 124 authority count (NSCOUNT), and additional information count (ARCOUNT) 125 express the number of records in each section for all opcodes except 126 Update. These fields have the same structure and data type for 127 Update but are instead the counts for the zone (ZOCOUNT), 128 prerequisite (PRCOUNT), update (UPCOUNT), and additional information 129 (ARCOUNT) sections. 131 2.1 One Spare Bit? 133 There have been ancient DNS implementations for which the Z bit being 134 on in a query meant that only a response from the primary server for 135 a zone is acceptable. It is believed that current DNS 136 implementations ignore this bit. 138 Assigning a meaning to the Z bit requires an IETF Standards Action. 140 2.2 Opcode Assignment 142 New OpCode assignments require an IETF Standards Action. 144 Currently DNS OpCodes are assigned as follows: 146 OpCode Name Reference 148 0 Query [RFC 1035] 149 1 IQuery (Inverse Query) [RFC 1035] 150 2 Status [RFC 1035] 151 3 available for assignment 152 4 Notify [RFC 1996] 153 5 Update [RFC 2136] 154 6-15 available for assignment 156 2.3 RCODE Assignment 158 It would appear from the DNS header above that only four bits of 159 RCODE, or response/error code are available. However, RCODEs can 160 appear not only at the top level of a DNS response but also inside 161 TSIG RRs [RFC XXX3] and OPT RRs [RFC 2671]. The OPT RR provides an 162 eight bit extension resulting in a 12 bit RCODE field and the TSIG RR 163 has a 16 bit RCODE field. 165 RCODE Name Description Reference 166 Decimal 167 Hexadecimal 168 0 NoError No Error [RFC 1035] 169 1 FormErr Format Error [RFC 1035] 170 2 ServFail Server Failure [RFC 1035] 171 3 NXDomain Non-Existent Domain [RFC 1035] 172 4 NotImp Not Implemented [RFC 1035] 173 5 Refused Query Refused [RFC 1035] 174 6 YXDomain Name Exists when it should not [RFC 2136] 175 7 YXRRSet RR Set Exists when it should not [RFC 2136] 176 8 NXRRSet RR Set that should exist does not [RFC 2136] 177 9 NotAuth Server Not Authoritative for zone [RFC 2136] 178 10 NotZone Name not contained in zone [RFC 2136] 179 11-15 available for assignment 180 16 BADSIG Signature Failure [RFC XXX3] 181 17 BADKEY Key not recognized [RFC XXX3] 182 18 BADTIME Signature out of time window [RFC XXX3] 183 19-3840 available for assignment 184 0x0013-0x0F00 185 3841-4095 Private Use 186 0x0F01-0x0FFF 187 4096-65535 available for assignment 188 0x1000-0xFFFF 190 Since it is important that RCODEs be understood for interoperability, 191 assignment of new RCODE listed above as "available for assignment" 192 requires an IETF Consensus. 194 3. DNS Resource Records 196 All RRs have the same top level format shown in the figure below 197 taken from [RFC 1035]: 199 1 1 1 1 1 1 200 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 201 +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ 202 | | 203 / / 204 / NAME / 205 | | 206 +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ 207 | TYPE | 208 +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ 209 | CLASS | 210 +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ 211 | TTL | 212 | | 213 +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ 214 | RDLENGTH | 215 +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--| 216 / RDATA / 217 / / 218 +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ 220 NAME is an owner name, i.e., the name of the node to which this 221 resource record pertains. NAMEs are specific to a CLASS as described 222 in section 3.2. NAMEs consist of an ordered sequence of one or more 223 labels each of which has a label type [RFC 1035, 2671]. 225 TYPE is a two octet unsigned integer containing one of the RR TYPE 226 codes. See section 3.1. 228 CLASS is a two octet unsigned integer containing one of the RR CLASS 229 codes. See section 3.2. 231 TTL is a four octet (32 bit) bit unsigned integer that specifies the 232 number of seconds that the resource record may be cached before the 233 source of the information should again be consulted. Zero is 234 interpreted to mean that the RR can only be used for the transaction 235 in progress. 237 RDLENGTH is an unsigned 16 bit integer that specifies the length in 238 octets of the RDATA field. 240 RDATA is a variable length string of octets that constitutes the 241 resource. The format of this information varies according to the 242 TYPE and in some cases the CLASS of the resource record. 244 3.1 RR TYPE IANA Considerations 246 There are three subcategories of RR TYPE numbers: data TYPEs, QTYPEs, 247 and MetaTYPEs. 249 Data TYPEs are the primary means of storing data. QTYPES can only be 250 used in queries. Meta-TYPEs designate transient data associated with 251 an particular DNS message and in some cases can also be used in 252 queries. Thus far, data TYPEs have been assigned from 1 upwards plus 253 the block from 100 through 103 while Q and Meta Types have been 254 assigned from 255 downwards (except for the OPT Meta-RR which is 255 assigned TYPE 41). There have been DNS implementations which made 256 caching decisions based on the top bit of the bottom byte of the RR 257 TYPE. 259 There are currently two Meta-TYPEs: TSIG [RFC XXX3] and OPT [RFC 260 2671]. 262 There are currently five QTYPEs: * (all), MAILA, MAILB, AXFR, and 263 IXFR. 265 Considerations for the allocation of new RR TYPEs are as follows: 267 Decimal 268 Hexadecimal 270 0 271 0x0000 - TYPE zero is used as a special indicator for the SIG RR [RFC 272 2535] and in other circumstances and must never be allocated 273 for ordinary use. 275 1 - 127 276 0x0001 - 0x007F - remaining TYPEs in this range are assigned for data 277 TYPEs only by IETF Consensus. 279 128 - 255 280 0x0080 - 0x00FF - remaining TYPEs in this rage are assigned for Q and 281 Meta TYPEs only by IETF Consensus. 283 256 - 32767 284 0x0100 - 0x7FFF - assigned for data, Q, or Meta TYPE use by IETF 285 Consensus. 287 32768 - 65279 288 0x8000 - 0xFEFF - Specification Required. 290 65280 - 65535 291 0xFF00 - 0xFFFF - Private Use. 293 3.1.1 Special Note on the OPT RR 295 The OPT (OPTion) RR, number 41, is specified in [RFC 2671]. Its 296 primary purpose is to extend the effective field size of various DNS 297 fields including RCODE, label type, OpCode, flag bits, and RDATA 298 size. In particular, for resolvers and servers that recognize it, it 299 extends the RCODE field from 4 to 12 bits. 301 3.2 RR CLASS IANA Considerations 303 DNS CLASSes have been little used but constitute another dimension of 304 the DNS distributed database. In particular, there is no necessary 305 relationship between the name space or roots servers for one CLASS 306 and those for another CLASS. The same name can have completely 307 different meanings in different CLASSes although the label types are 308 the same and the null label is usable only as root in every CLASS. 309 However, as global networking and DNS have evolved, the IN, or 310 Internet, CLASS has dominated DNS use. 312 There are two subcategories of DNS CLASSes: normal data containing 313 classes and QCLASSes that are only meaningful in queries or updates. 315 The current data class assignments and considerations for future 316 assignments are as follows: 318 Decimal 319 Hexadecimal 321 0 322 0x0000 - assignment requires an IETF Standards Action. 324 1 325 0x0001 - Internet (IN). 327 2 328 0x0002 - available for assignment by IETF Consensus as a data CLASS. 330 3 331 0x0003 - Chaos (CH) [Moon 81]. 333 4 334 0x0004 - Hesiod (HS) [Dyer 87]. 336 5 - 127 337 0x0005 - 0x007F - available for assignment by IETF Consensus as data 338 CLASSes only. 340 128 - 253 341 0x0080 - 0x00FD - available for assignment by IETF Consensus as 342 QCLASSes only. 344 254 345 0x00FE - QCLASS None [RFC 2136]. 347 255 348 0x00FF - QCLASS Any [RFC 1035]. 350 256 - 32767 351 0x0100 - 0x7FFF - assigned by IETF Consensus. 353 32768 - 65280 354 0x8000 - 0xFEFF - assigned based on Specification Required. 356 65280 - 65534 357 0xFF00 - 0xFFFE - Private Use. 359 65535 360 0xFFFF - can only be assigned by an IETF Standards Action. 362 3.3 RR NAME Considerations 364 DNS NAMEs are sequences of labels [RFC 1035]. The last label in each 365 NAME is "ROOT" which is the zero length label. By definition, the 366 null or ROOT label can not be used for any other NAME purpose. 368 At the present time, there are two categories of label types, data 369 labels and compression labels. Compression labels are pointers to 370 data labels elsewhere within an RR or DNS message and are intended to 371 shorten the wire encoding of NAMEs. The two existing data label 372 types are frequently referred to as ASCII and Binary. ASCII labels 373 can, in fact, include any octet value including zero octets but most 374 current uses involve only [US-ASCII] For retrieval ASCII labels are 375 defined to treat upper and lower case letters the same. Binary 376 labels are bit sequences [RFC 2673]. 378 IANA considerations for label types are given in [RFC 2671]. 380 NAMEs are local to a CLASS. The Hesiod [Dyer 87] and Chaos [Moon 81] 381 CLASSes are essentially for local use. The IN or Internet CLASS is 382 thus the only DNS CLASS in global use on the Internet at this time. 384 A somewhat dated description of name allocation in the IN Class is 385 given in [RFC 1591]. Some information on reserved top level domain 386 names is in Best Current Practice 32 [RFC 2606]. 388 4. Security Considerations 390 This document addresses IANA considerations in the allocation of 391 general DNS parameters, not security. See [RFC 2535] for secure DNS 392 considerations. 394 References 396 [Dyer 87] - Dyer, S., and F. Hsu, "Hesiod", Project Athena Technical 397 Plan - Name Service, April 1987, 399 [Moon 81] - D. Moon, "Chaosnet", A.I. Memo 628, Massachusetts 400 Institute of Technology Artificial Intelligence Laboratory, June 401 1981. 403 [RFC 1034] - P. Mockapetris, "Domain Names - Concepts and 404 Facilities", STD 13, November 1987. 406 [RFC 1035] - P. Mockapetris, "Domain Names - Implementation and 407 Specifications", STD 13, November 1987. 409 [RFC 1591] - J. Postel, "Domain Name System Structure and 410 Delegation", March 1994. 412 [RFC 1996] - P. Vixie, "A Mechanism for Prompt Notification of Zone 413 Changes (DNS NOTIFY)", August 1996. 415 [RFC 2136] - P. Vixie, S. Thomson, Y. Rekhter, J. Bound, "Dynamic 416 Updates in the Domain Name System (DNS UPDATE)", 04/21/1997. 418 [RFC 2181] - Robert Elz, Randy Bush, "Clarifications to the DNS 419 Specification", July 1997. 421 [RFC 2434] - "Guidelines for Writing an IANA Considerations Section 422 in RFCs", T. Narten, H. Alvestrand, October 1998. 424 [RFC 2535] - D. Eastlake, "Domain Name System Security Extensions", 425 March 1999. 427 [RFC 2606] - D. Eastlake, A. Panitz, "Reserved Top Level DNS Names", 428 June 1999. 430 [RFC 2671] - P. Vixie, "Extension mechanisms for DNS (EDNS0)", August 431 1999. 433 [RFC 2672] - M. Crawford, " Non-Terminal DNS Name Redirection", 434 August 1999. 436 [RFC 2673] - M. Crawford, "Binary Labels in the Domain Name System", 437 August 1999. 439 [RFC XXX3] - P. Vixie, O. Gudmundsson, D. Eastlake, B. Wellington, 440 "Secret Key Transaction Signatures for DNS (TSIG)", xxx 1999 (draft- 441 ietf-dnsind-tsig-*.txt). 443 [US-ASCII] - ANSI, "USA Standard Code for Information 444 Interchange", X3.4, American National Standards Institute: New York, 445 1968. 447 Authors Addresses 449 Donald E. Eastlake 3rd 450 65 Shindegan Hill Road 451 Carmel, NY 10512 USA 453 Telephone: +1-914-276-2668 (h) 454 fax: +1-914-276-2947 (h) 455 email: dee3@torque.pothole.com 457 Eric Brunner 458 1415 Forest Avenue 459 Portland, ME 04103 USA 461 Telephone: +1 207-797-0525 462 email: brunner@world.std.com 464 Bill Manning 465 USC/ISI 466 4676 Admiralty Way, #1001 467 Marina del Rey, CA 90292 USA 469 Telephone: +1 310 822 1511 470 email: bmanning@isi.edu 472 Expiration and File Name 474 This draft expires June 2000. 476 Its file name is draft-ietf-dnsind-iana-dns-04.txt.