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Checking nits according to https://www.ietf.org/id-info/checklist : ---------------------------------------------------------------------------- ** The abstract seems to contain references ([RFC4291]), which it shouldn't. Please replace those with straight textual mentions of the documents in question. Miscellaneous warnings: ---------------------------------------------------------------------------- == The copyright year in the IETF Trust and authors Copyright Line does not match the current year == The document doesn't use any RFC 2119 keywords, yet seems to have RFC 2119 boilerplate text. -- The document date (April 21, 2009) is 4777 days in the past. Is this intentional? Checking references for intended status: Informational ---------------------------------------------------------------------------- == Unused Reference: 'RFC3493' is defined on line 477, but no explicit reference was found in the text == Unused Reference: 'RFC4038' is defined on line 481, but no explicit reference was found in the text == Unused Reference: 'RFC5156' is defined on line 485, but no explicit reference was found in the text -- Obsolete informational reference (is this intentional?): RFC 5156 (Obsoleted by RFC 6890) Summary: 2 errors (**), 0 flaws (~~), 5 warnings (==), 2 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Internet Engineering Task Force S. Kawamura 3 Internet-Draft NEC BIGLOBE, Ltd. 4 Intended status: Informational M. Kawashima 5 Expires: October 23, 2009 NEC AccessTechnica, Ltd. 6 April 21, 2009 8 A Recommendation for IPv6 Address Text Representation 9 draft-kawamura-ipv6-text-representation-01 11 Status of this Memo 13 This Internet-Draft is submitted to IETF in full conformance with the 14 provisions of BCP 78 and BCP 79. 16 Internet-Drafts are working documents of the Internet Engineering 17 Task Force (IETF), its areas, and its working groups. Note that 18 other groups may also distribute working documents as Internet- 19 Drafts. 21 Internet-Drafts are draft documents valid for a maximum of six months 22 and may be updated, replaced, or obsoleted by other documents at any 23 time. It is inappropriate to use Internet-Drafts as reference 24 material or to cite them other than as "work in progress." 26 The list of current Internet-Drafts can be accessed at 27 http://www.ietf.org/ietf/1id-abstracts.txt. 29 The list of Internet-Draft Shadow Directories can be accessed at 30 http://www.ietf.org/shadow.html. 32 This Internet-Draft will expire on October 23, 2009. 34 Copyright Notice 36 Copyright (c) 2009 IETF Trust and the persons identified as the 37 document authors. All rights reserved. 39 This document is subject to BCP 78 and the IETF Trust's Legal 40 Provisions Relating to IETF Documents in effect on the date of 41 publication of this document (http://trustee.ietf.org/license-info). 42 Please review these documents carefully, as they describe your rights 43 and restrictions with respect to this document. 45 Abstract 47 As IPv6 network grows, there will be more engineers and also non- 48 engineers who will have the need to use an IPv6 address in text. 50 While the IPv6 address architecture [RFC4291] section 2.2 depicts a 51 flexible model for text representation of an IPv6 address, this 52 flexibility has been causing problems for operators ,system 53 engineers, and customers. The following draft will describe the 54 problems that a flexible text representation has been causing. This 55 document also recommends a canonical representation format that best 56 avoids confusion. 58 Table of Contents 60 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 61 1.1. Requirements Language . . . . . . . . . . . . . . . . . . 4 62 2. Text representation flexibility of RFC4291 . . . . . . . . . . 4 63 2.1. leading zeros . . . . . . . . . . . . . . . . . . . . . . 4 64 2.2. zero compression . . . . . . . . . . . . . . . . . . . . . 5 65 2.3. Uppercase or Lowercase . . . . . . . . . . . . . . . . . . 6 66 3. Problems Encountered with the Flexible Model . . . . . . . . . 6 67 3.1. Searching . . . . . . . . . . . . . . . . . . . . . . . . 6 68 3.1.1. General Summary . . . . . . . . . . . . . . . . . . . 6 69 3.1.2. Searching Spreadsheets and Text Files . . . . . . . . 6 70 3.1.3. Searching with Whois . . . . . . . . . . . . . . . . . 7 71 3.1.4. Searching for an Address in a Network Diagram . . . . 7 72 3.2. Parsing and Modifying . . . . . . . . . . . . . . . . . . 7 73 3.2.1. General Summary . . . . . . . . . . . . . . . . . . . 7 74 3.2.2. Logging . . . . . . . . . . . . . . . . . . . . . . . 7 75 3.2.3. Auditing. Case 1 . . . . . . . . . . . . . . . . . . . 8 76 3.2.4. Auditing. Case 2 . . . . . . . . . . . . . . . . . . . 8 77 3.2.5. Unexpected Modifying . . . . . . . . . . . . . . . . . 8 78 3.3. Operating . . . . . . . . . . . . . . . . . . . . . . . . 8 79 3.3.1. General Summary . . . . . . . . . . . . . . . . . . . 8 80 3.3.2. Customer Calls . . . . . . . . . . . . . . . . . . . . 9 81 3.3.3. Abuse . . . . . . . . . . . . . . . . . . . . . . . . 9 82 3.4. Other Minor Problems . . . . . . . . . . . . . . . . . . . 9 83 3.4.1. Changing Platforms . . . . . . . . . . . . . . . . . . 9 84 3.4.2. Preference in Documentation . . . . . . . . . . . . . 9 85 3.4.3. Legibility . . . . . . . . . . . . . . . . . . . . . . 9 86 4. A Recommendation for IPv6 Text Representation . . . . . . . . 10 87 4.1. Handling Leading Zeros . . . . . . . . . . . . . . . . . . 10 88 4.2. "::" usage . . . . . . . . . . . . . . . . . . . . . . . . 10 89 4.2.1. shorten as much as possible . . . . . . . . . . . . . 10 90 4.2.2. one 16bit 0 field . . . . . . . . . . . . . . . . . . 10 91 4.2.3. when "::" can be used twice . . . . . . . . . . . . . 10 92 4.3. Lower Case . . . . . . . . . . . . . . . . . . . . . . . . 10 93 5. Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . 10 94 6. Security Considerations . . . . . . . . . . . . . . . . . . . 11 95 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11 96 8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 11 97 9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 11 98 9.1. Normative References . . . . . . . . . . . . . . . . . . . 11 99 9.2. Informative References . . . . . . . . . . . . . . . . . . 11 100 Appendix A. IPv6 Addresses with Embedded IPv4 Addresses . . . . . 12 101 Appendix B. For developers . . . . . . . . . . . . . . . . . . . 12 102 Appendix C. Prefix Issues . . . . . . . . . . . . . . . . . . . . 12 103 Appendix D. Phonetic Alphabet and Figure Code . . . . . . . . . . 12 104 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 13 106 1. Introduction 108 A single IPv6 address can be text represented in many ways. Examples 109 are shown below. 111 2001:db8:0:0:1:0:0:1 113 2001:0db8:0:0:1:0:0:1 115 2001:db8::1:0:0:1 117 2001:db8::0:1:0:0:1 119 2001:0db8::1:0:0:1 121 2001:db8:0:0:1::1 123 2001:db8:0000:0:1::1 125 2001:DB8:0:0:1::1 127 All the above point to the same IPv6 address. This flexiblity has 128 caused many problems for operators, systems engineers, and customers. 129 The problems will be noted in section 3. Also, a canonical 130 representation format to avoid problems will be introduced in section 131 4. 133 1.1. Requirements Language 135 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 136 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 137 document are to be interpreted as described in RFC 2119 [RFC2119]. 139 2. Text representation flexibility of RFC4291 141 Examples of flexibility in Section 2.2 of RFC4291 are described 142 below. 144 2.1. leading zeros 146 'It is not necessary to write the leading zeros in an individual 147 field.' 149 In other words, it is also not necessary to omit leading zeros. This 150 means that, it is possible to select from such as the following 151 example. The final 16bit field is different, but all these addresses 152 are the same. 154 2001:db8:aaaa:bbbb:cccc:dddd:eeee:0001 156 2001:db8:aaaa:bbbb:cccc:dddd:eeee:001 158 2001:db8:aaaa:bbbb:cccc:dddd:eeee:01 160 2001:db8:aaaa:bbbb:cccc:dddd:eeee:1 162 2.2. zero compression 164 'A special syntax is available to compress the zeros. The use of 165 "::" indicates one or more groups of 16 bits of zeros.' 167 It is possible to select whether or not to omit just one 16bits of 168 zeros. 170 2001:db8:aaaa:bbbb:cccc:dddd::1 172 2001:db8:aaaa:bbbb:cccc:dddd:0:1 174 In case where there are more than one zero fields, there is a choice 175 of how many fields can be shortened. Examples follow. 177 2001:db8:0:0:0::1 179 2001:db8:0:0::1 181 2001:db8:0::1 183 2001:db8::1 185 ... and more 187 In addition, RFC4291 in section 2.2 notes, 189 'The "::" can also be used to compress leading or trailing zeros 190 in an address.' 192 It is possible to choose whether to compress a leading zero or a 193 trailing zero in a single address. Examples are shown below. 195 2001:db8::aaaa:0:0:1 197 2001:db8:0:0:aaaa::1 199 2.3. Uppercase or Lowercase 201 RFC4291 does not mention about preference of uppercase or lowercase. 202 Various flavors are shown below. 204 2001:db8:aaaa:bbbb:cccc:dddd:eeee:aaaa 206 2001:db8:aaaa:bbbb:cccc:dddd:eeee:AAAA 208 2001:db8:aaaa:bbbb:cccc:dddd:eeee:AaAa 210 ... more combinations 212 3. Problems Encountered with the Flexible Model 214 3.1. Searching 216 3.1.1. General Summary 218 A search of an IPv6 address if conducted through a UNIX system is 219 usually case sensitive and extended options to allow for regular 220 expression use will come in handy. However, there are many 221 applications in the internet today that do not provide this 222 capability. When searching for an IPv6 address in such systems, the 223 system engineer will have to try each and every possibility to search 224 for an address. This has critical impacts especially when trying to 225 deploy IPv6 over an enterprise network. 227 3.1.2. Searching Spreadsheets and Text Files 229 Spreadsheet applications and text editors on GUI systems, rarely have 230 the ability to search for a text using regular expression. Moreover, 231 there are many non-engineers (who are not aware of case sensitivity 232 and regular expression use) that use these application to manage IP 233 addresses. This has worked quite well with IPv4 since text 234 representation in IPv4 has very little flexibility. There is no 235 incentive to encourage these non-engineers to change their tool or 236 learn reagular expression when they decide to go dual-stack. If the 237 entry in the spreadsheet reads, 2001:db8::1:0:0:1, but the search was 238 conducted as 2001:db8:0:0:1::1, this will show a result of no match. 239 One example where this will cause problem is, when the search is 240 being conducted to assign a new address from a pool, and a check was 241 being done to see if it was not in use. This may cause problems to 242 the end-hosts or end-users. This type of address management is very 243 often seen in enterprise networks and also in ISPs. 245 3.1.3. Searching with Whois 247 The whois utility is used by a wide range of people today. When a 248 record is set to the whois database, one will likely check the output 249 to see if the entry is correct. If a entity was recorded as 2001: 250 db8::/48, but the whois ouput showed 2001:0db8:0000::/48, most non- 251 engineers would think that their input was wrong, and will likely 252 retry several times or make a frustrated call to the database 253 hostmaster. If there was a need to register the same address on 254 different systems, and each system showed a different text 255 representation, this would confuse people even more. Although this 256 document focuses on addresses rather than prefixes, this is worth 257 mentioning since problems encountered are mostly equal. 259 3.1.4. Searching for an Address in a Network Diagram 261 Network diagrams and blue-prints contain IP addresses of systems. In 262 times of trouble shooting, there may be a need to search through a 263 diagram to find the point of failure (for example, if a traceroute 264 stopped at 2001:db8::1, one would search the diagram for that 265 address). This is a technique quite often in use in enterprise 266 networks and managed services. Again, the different flavors of text 267 representation will result in a time-consuming search, leading to 268 longer MTTR in times of trouble. 270 3.2. Parsing and Modifying 272 3.2.1. General Summary 274 With all the possible text representation ways, each application must 275 include a module, object, link, etc. to a function that will parse 276 IPv6 addresses in a manner that no matter how it is represented, they 277 will mean the same address. This is not too much a problem if the 278 output is to be just 'read' or 'managed' by a network engineer. 279 However, many system engineers who integrate complex computer systems 280 to corporate customers will have difficulties finding that their 281 favorite tool will not have this function, or will encounter 282 difficulties such as having to rewrite their macro's or scripts for 283 their customers. It must be noted that each additional line of a 284 program will result in increased development fees that will be 285 charged to the customers. 287 3.2.2. Logging 289 If an application were to ouput a log summary that represented the 290 address in full (such as 2001:0db8:0000:0000:1111:2222:3333:4444), 291 the output would be highly unreadable compared to the IPv4 output. 292 The address would have to be parsed and reformed to make it useful 293 for human reading. This will result in additional code on the 294 applications which will result in extra fees charged to the 295 customers. Sometimes, logging for critical systems is done by 296 mirroring the same traffic to two different systems. Care must be 297 taken that no matter what the log output is, the logs should be 298 parsed so they will mean the same. 300 3.2.3. Auditing. Case 1 302 When a router or any other network appliance machine configuration is 303 audited, there are many methods to compare the configuration 304 information of a node. Sometimes, auditing will be done by just 305 comparing the changes made each day. In this case, if configuration 306 was done such that 2001:db8::1 was changed to 2001:0db8:0000:0000: 307 0000:0000:0000:0001 just because the new engineer on the block felt 308 it was better, a simple diff will tell you that a different address 309 was configured. If this was done on a wide scale network, people 310 will be focusing on 'why the extra zeros were put in' instead of 311 doing any real auditing. Lots of tools are just plain diffs that do 312 not take into account address representation rules. 314 3.2.4. Auditing. Case 2 316 Node configurations will be matched against a information system that 317 manages IP addresses. If output notation is different, there will 318 need to be a script that is implemented to cover for this. An SNMP 319 GET of an interface address and text representation in a humanly 320 written text file is highly unlikely to match on first try. 322 3.2.5. Unexpected Modifying 324 Sometimes, a system will take an address and modify it as a 325 convenience. For example, a system may take an input of 326 2001:0db8:0::1 and make the output 2001:db8::1 (which is seen in some 327 RIR databases). If the zeros were inputed for a reason, the outcome 328 may be somewhat unexpected. 330 3.3. Operating 332 3.3.1. General Summary 334 When an operator sets an IPv6 address of a system as 2001:db8:0:0:1: 335 0:0:1, the system may take the address and show the configuration 336 result as 2001:DB8::1:0:0:1. A distinguished engineer will know that 337 the right address is set, but an operator, or a customer that is 338 communicating with the operator to solve a problem, is usually not as 339 distinguished as we would like. Again, the extra load in checking 340 that the IP address is the same as was intended, will result in fees 341 that will be charged to the customers. 343 3.3.2. Customer Calls 345 When a customer calls to inquire about a suspected outage, IPv6 346 address representation should be handled with care. Not all 347 customers are engineers nor have the same skill in IPv6 technology. 348 The NOC will have to take extra steps to humanly parse the address to 349 avoid having to explain to the customers that 2001:db8:0:1::1 is the 350 same as 2001:db8::1:0:0:0:1. This is one thing that will never 351 happen in IPv4 because IPv4 address cannot be abbreviated. 353 3.3.3. Abuse 355 Network abuse is reported along with the abusing IP address. This 356 'reporting' could take any shape or form of the flexible model. A 357 team that handles network abuse must be able to tell the difference 358 between a 2001:db8::1:0:1 and 2001:db8:1::0:1. Mistakes in the 359 placement of the "::" will result in a critical situation. A system 360 that handles these incidents should be able to handle any type of 361 input and parse it in a correct manner. Also, incidents are reported 362 over the phone. It is unnecessary to report if the letter is an 363 uppercase or lowercase. However, when a letter is spelled uppercase, 364 people tend to clarify that it is uppercase, which is unnecessary 365 information. 367 3.4. Other Minor Problems 369 3.4.1. Changing Platforms 371 When an engineer decides to change the platform of a running service, 372 the same code may not work as expected due to the difference in IPv6 373 address text representation. Usually, a change in a platform (e.g. 374 Unix to Windows, Cisco to Juniper) will result in a major change of 375 code, but flexibility in address representation will increase the 376 work load which will again, result in fees that will be charged to 377 the customers, and also longer down time of systems. 379 3.4.2. Preference in Documentation 381 A document that is edited by more than one author, may become harder 382 to read. 384 3.4.3. Legibility 386 Capital case D and 0 can be quite often misread. Capital B and 8 can 387 also be misread. 389 4. A Recommendation for IPv6 Text Representation 391 A recommendation for a canonical text representation format of IPv6 392 addresses is presented in this section. The recommendation in this 393 document is one that, complies fully with RFC 4291, is implemented by 394 various operating systems, and is human friendly. 396 4.1. Handling Leading Zeros 398 Leading zeros should be chopped for human legibility and easier 399 searching. Also, a single 16 bit 0000 field should be represented as 400 just 0. Place holder zeros are often cause of mis-reading. 402 4.2. "::" usage 404 4.2.1. shorten as much as possible 406 The use of "::" should be used to its maximum capability (i.e. 2001: 407 db8::0:1 is not very clean). 409 4.2.2. one 16bit 0 field 411 "::" should not be used to shorten just one 16bit 0 field for it 412 would tend to mislead that there are more than one 16 bit field that 413 is shortened. 415 4.2.3. when "::" can be used twice 417 When cases where it is possible to use "::" in two or more different 418 sections of an address, implementation to shorten the side with more 419 16bit 0 fields are more common (i.e. latter is shortened in 2001:0:0: 420 1:0:0:0:1). When the length of 16bit 0 fields are equal (i.e. 2001: 421 db8:0:0:1:0:0:1), the former is usually shortened. One idea to avoid 422 any confusion, is for the operator to not use 16bit field 0 in the 423 first 64 bits. By nature IPv6 addresses are usually assigned or 424 allocated to end-users as longer than 32 bits (typicaly 48bit or 425 longer). 427 4.3. Lower Case 429 Recent implementations tend to represent IPv6 address as lower case. 430 It is better to use lower case to avoid problems such as described in 431 section 3.3.3 and 3.4.3. 433 5. Conclusion 435 The recommended format of text representing an IPv6 address is 436 summarized as follows. 438 (1) omit leading zeros 440 (2) "::" used to their maximum extent whenever possible 442 (3) "::" used where shortens address the most 444 (4) "::" used in the former part in case of a tie breaker 446 (5) do not shorten one 16bit 0 field 448 (6) use lower case 450 Hints for developers are written in the Appendix section. 452 6. Security Considerations 454 None. 456 7. IANA Considerations 458 None. 460 8. Acknowledgements 462 The authors would like to thank Jan Zorz, Randy Bush, Yuichi Minami, 463 Toshimitsu Matsuura for their generous and helpful comments. 465 9. References 467 9.1. Normative References 469 [RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing 470 Architecture", RFC 4291, February 2006. 472 9.2. Informative References 474 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 475 Requirement Levels", BCP 14, RFC 2119, March 1997. 477 [RFC3493] Gilligan, R., Thomson, S., Bound, J., McCann, J., and W. 478 Stevens, "Basic Socket Interface Extensions for IPv6", 479 RFC 3493, February 2003. 481 [RFC4038] Shin, M-K., Hong, Y-G., Hagino, J., Savola, P., and E. 482 Castro, "Application Aspects of IPv6 Transition", 483 RFC 4038, March 2005. 485 [RFC5156] Blanchet, M., "Special-Use IPv6 Addresses", RFC 5156, 486 April 2008. 488 Appendix A. IPv6 Addresses with Embedded IPv4 Addresses 490 IPv4-Compatible IPv6 address and IPv4-Mapped IPv6 address are defined 491 that carry an IPv4 address in the low-order 32 bits of the address. 492 These addresses have special representation that combine hexadecimal 493 and decimal notations. IPv4-Compatible IPv6 address is deprecated. 494 Although the use of IPv4-Mapped IPv6 address is not recommended due 495 to security and portability problems, the text representation method 496 noted in this document should be applied for the hexadecimal part. 498 Appendix B. For developers 500 We recommend that developers use display routines that conform to 501 these rules. For example, the usage of getnameinfo() with flags 502 argument NI_NUMERICHOST in FreeBSD 7.0 will give a conforming output. 503 The function inet_ntop() of FreeBSD7.0 is a good C code reference, 504 but should not be called directly. See RFC4038 for details. 506 Appendix C. Prefix Issues 508 Problems with prefixes are just the same as problems encountered with 509 addresses. Text representation method of IPv6 prefixes should be no 510 different from that of IPv6 addresses. 512 Appendix D. Phonetic Alphabet and Figure Code 514 The use of Phonetics Alphabet is essential for complete accuracy in 515 voice communications. For example, ITU Phonetic alphabet and Figure 516 Code is as follows (extracted hexadecimal from it): 518 +-----------+------------+----------------------+ 519 | Character | Word | Pronunciation | 520 +-----------+------------+----------------------+ 521 | 0 | Nadazero | NAH-DAH-ZAY-ROH | 522 | 1 | Unaone | OO-NAH-WUN | 523 | 2 | Bissotwo | BEES-SOH-TOO | 524 | 3 | Terrathree | TAY-RAH-TREE | 525 | 4 | Kartefour | KAR-TAY-FOWER | 526 | 5 | Pantafive | PAN-TAH-FIVE | 527 | 6 | Soxisix | SOK-SEE-SIX | 528 | 7 | Setteseven | SAY-TAY-SEVEN | 529 | 8 | Oktoeight | OK-TOH-AIT | 530 | 9 | Novenine | NO-VAY-NINER | 531 | A | Alfa | AL FAH | 532 | B | Bravo | BRAH VOH | 533 | C | Charlie | CHAR LEE or SHAR LEE | 534 | D | Delta | DELL TAH | 535 | E | Echo | ECK OH | 536 | F | Foxtrot | FOKS TROT | 537 +-----------+------------+----------------------+ 539 Authors' Addresses 541 Seiichi Kawamura 542 NEC BIGLOBE, Ltd. 543 14-22, Shibaura 4-chome 544 Minatoku, Tokyo 108-8558 545 JAPAN 547 Phone: +81 3 3798 6085 548 Email: kawamucho@mesh.ad.jp 550 Masanobu Kawashima 551 NEC AccessTechnica, Ltd. 552 800, Shimomata 553 Kakegawa-shi, Shizuoka 436-8501 554 JAPAN 556 Phone: +81 537 23 9655 557 Email: kawashimam@necat.nec.co.jp