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Network Working Group                                          A. FarrelRequest for Comments: 5513                            Old Dog ConsultingCategory: Informational                                     1 April 2009IANA Considerations for Three Letter AcronymsStatus of This Memo   This memo provides information for the Internet community.  It does   not specify an Internet standard of any kind.  Distribution of this   memo is unlimited.Copyright Notice   Copyright (c) 2009 IETF Trust and the persons identified as the   document authors.  All rights reserved.   This document is subject toBCP 78 and the IETF Trust's Legal   Provisions Relating to IETF Documents in effect on the date of   publication of this document (http://trustee.ietf.org/license-info).   Please review these documents carefully, as they describe your rights   and restrictions with respect to this document.   This document may contain material from IETF Documents or IETF   Contributions published or made publicly available before November   10, 2008.  The person(s) controlling the copyright in some of this   material may not have granted the IETF Trust the right to allow   modifications of such material outside the IETF Standards Process.   Without obtaining an adequate license from the person(s) controlling   the copyright in such materials, this document may not be modified   outside the IETF Standards Process, and derivative works of it may   not be created outside the IETF Standards Process, except to format   it for publication as an RFC or to translate it into languages other   than English.Abstract   Three Letter Acronyms (TLAs) are commonly used to identify components   of networks or protocols as designed or specified within the IETF.  A   common concern is that one acronym may have multiple expansions.   While this may not have been an issue in the past, network   convergence means that protocols that did not previously operate   together are now found in close proximity.  This results in   contention for acronyms, and confusion in interpretation.  Such   confusion has the potential to degrade the performance of the   Internet as misunderstandings lead to misconfiguration or other   operating errors.Farrel                       Informational                      [Page 1]

RFC 5513                          TLAs                        April 2009   Given the growing use of TLAs and the relatively small number   available, this document specifies a Badly Construed Proposal (BCP)   for the management of a registry of TLAs within the IETF, and the   procedures for the allocation of new TLAs from the registry.1.  Introduction   A Three-Letter Acronym (TLA) is a popular form of abbreviation   usually based on the initial letters of a three-word term.  A formal   definition of a TLA is provided inSection 2.   TLAs are particularly popular within the Internet community where   they serve as abbreviations in the spoken and written word.  As their   popularity has grown, the measure of the value of an RFC (q.v.) is   not only its successful implementation, interoperability, and   deployment, but also the number of TLAs included in the text.   For example, the Transmission Control Protocol (itself a TLA - TCP)   [RFC0793] is extremely successful.  The specification contains no   fewer than 20 distinct TLAs (although it should be noted that some   are simple abbreviations rather than proper acronyms).  On the other   hand, the Internet Stream Protocol Version 2 [RFC1819] is ambiguously   referred to using the TLA ST2, and also as STII which is clearly not   a TLA.  Further, the STII specification contains only 12 distinct   TLAs, and it should be no surprise that STII has been far less   successful than TCP.   A common concern amongst diligent protocol implementers is that one   acronym may have multiple expansions.  While this may not have been   an issue in the past, network convergence means that protocols that   did not previously operate together are now found in close proximity.   Not only does this result in contention for acronyms, and confusion   in interpretation of specification, it also leads to many wasted   hours trying to select appropriate and suitably-unique names for   variables within source code implementations.  Such confusion has the   potential to degrade the performance of the Internet as   misunderstandings lead to coding errors, compilation failures,   misconfiguration, and other operating errors.   Furthermore, it should be noted that we are rapidly approaching World   Acronym Depletion (WAD).  It has been estimated that, at the current   rate of TLA allocation, we will run out by the end of September this   year.  This timescale could be worsened if there is the expected   growth in demand for mobile acronyms, IP-TLAs, and TLA-on-demand.   According to the definition provided inSection 2, there are 36**3 -   10**3 = 45656 TLAs in total.  This number will so easily be depleted   that we must institute some policy for conservation.Farrel                       Informational                      [Page 2]

RFC 5513                          TLAs                        April 2009   The Internet Assigned Numbers Authority (IANA, helpfully, a four-   letter acronym - although note that a four-letter acronym is an FLA   and hence is, in its own way, a TLA) maintains registries of names   and numbers for use within the Internet in order to avoid duplicate   allocation of one of those names or numbers and the consequent   confusion and failed interoperability that would arise.  It is,   therefore, wholly appropriate that the IANA should manage the   assignment and use of TLAs within the Internet.   This document specifies a Badly Construed Proposal for the management   of a registry of TLAs within the IETF, and the procedures for the   allocation of new TLAs from the registry.1.1.  RFC Editor Terminology List   It is worth observing that the RFC Editor currently maintains a list   of common terms, abbreviations, and acronyms.  While this list is   highly useful for the construction of documents, it does not provide   unambiguous interpretation of acronyms.2.  Formal Definition of TLA   Acronym - a word made up of the initial letters of the words in a      phrase.      For example, IETF is an acronym formed from the first letters of      the phrase International Essential Tremor Foundation [URL-IETF].   Three Letter Acronym (TLA) - an acronym comprising exactly three      letters.      For example, RFC is a TLA formed of the first letters of the      phrase Rugby Football Club [URL-CARDIFF].   For our usage, we also allow digits within a TLA.  Thus, P2P is an   acronym meaning Purchase to Pay [URL-P2P].  The digits 2 and 4 are   specially used by clever people who have noticed that, when spoken,   they sound like the words 'to' and 'for'.  Whether this is helpful   may be left as an exercise for the user considering the brief   conversation, below.   A - Do you use the Internet Streams Protocol?   B - Yes.  Do you use ST, too?   A - No, I use ST2.   B - That's interesting.  C uses ST2, too.   A - I have a car horn application called Toot-toot.   B - Really? Do you use ST2 to Toot-toot, too?Farrel                       Informational                      [Page 3]

RFC 5513                          TLAs                        April 2009   Note, however, that an acronym made up entirely of digits might be   frowned upon.   Lastly, we must consider case-sensitivity.  Although acronyms often   include upper or lowercase letters, no assumptions should be made   about the interpretation of the acronym based on the case of its   letters, so that both QOS and QoS clearly refer to the Queen of the   South football club [URL-QOS] and [URL-QoS].2.1.  A Note on Vocalization   Acronyms are often articulated as words in spoken text.  This can be   helpful in generating a cosy feel or a marketing buzz around a   concept that offers a less-favorable reality.  For example, Claws and   Teeth (CAT) can be pronounced "cat" making it seem quite cuddly.   Other acronyms are always spelled out in order to avoid accidental   misinterpretation or litigation.  For example, do not refer to your   neighbor's Daughter or Granddaughter as anything other than their   D-O-G.   But care should be taken with vocalization, as well.  It will be   noted that some letters have more syllables than the words they are   used to represent.  In these cases, acronyms are to be avoided.   Thus, the world wide web must never be assigned the acronym WWW.   Finally, a word of caution about attempting to pronounce acronyms as   words.  This can lead to serious injury for the inexperienced unless   they happen to be native speakers of Czech.  Do not try to say XML in   front of your mother-in-law, and don't attempt to talk about Open   Office dot Org in polite company.3.  Backward and Forward Compatibility   It should be obvious to most RFC readers (MRRs) that TLAs are already   widely used in Internet specifications.  This work is not intended to   unnecessarily invalidate existing RFCs, although where such   invalidation is necessary or desirable, this work can be used for   that purpose.   In order to support existing documents, IANA is required to search   all existing RFCs for every existing acronym usage (EAU), but may   filter that search to exclude non-TLAs.   It will be noted that, as a result of that search, many duplicate   meanings will be discovered.  For example, "OAM" will be found in a   large number of RFCs, yet its meaning may be as diverse as "on a   mission", "order of Australia medal", and "orbital angular momentum".Farrel                       Informational                      [Page 4]

RFC 5513                          TLAs                        April 2009   This contention is best resolved by the judgement of Solomon -- each   acronym usage will be allocated its share of the letters currently in   use.  If there are three uses of an acronym, they will get one letter   each; two existing uses would get one-and-a-half letters each; etc.4.  IANA Considerations4.1.  New Registry   The Internet TLA Registry (ITR) should track the following   information:      - TLA      - Unique interpretation      - Defining RFC4.2.  Reserved Values   Certain key values are reserved.  That is, they are allocated in the   registry by this document and may not be used for any other purpose.      Acronym   Expansion                             Reference      --------+-------------------------------------+-----------      TLA       Two Letter Acronym                    [RFC5513]      TBD       Two Be Deleted                        [RFC5513]      RFC       Ready for Compost                     [RFC5513]      PoS       Not particularly good                 [RFC5513]      VPN       Very possibly no use                  [RFC5513]      TCP       Totally bad proposal                  [RFC5513]      USA       Universal Source of Acronyms          [RFC5513]      NBG       This document                         [RFC5513]      BCP       Badly construed proposal              [RFC5513]4.3. Allocation Policy   IANA shall apply the following allocation policies according to   [RFC5226].   Experimental Use      All TLAs of the form XX* where * is any letter or digit.   First Come First Served      All TLAs of the form X**, Y**, or Z** where * is any letter or      digit.  Excepted from this are the TLAs of the form XX* as above.   IETF Review      All other TLAs.Farrel                       Informational                      [Page 5]

RFC 5513                          TLAs                        April 20095.  Security Considerations   Many security algorithms are identified by TLAs.  It is a clear   requirement that someone implementing, for example, MD5 should be   understood to have encoded the well-known Maybe-Decrypted-   Deciphered-Decoded-Disambiguated-and-Degraded algorithm, and not any   other security algorithm with the same acronym.6.  Acknowledgements   I would like to thank the MPLS-TP design team for holding seemingly   endless meetings during which the need for this document became   apparent.   Thanks to Daniel King for noticing that this document is a BCP.7.  References7.1.  Normative References   [RFC5226]     Narten, T. and H. Alvestrand, "Guidelines for Writing                 an IANA Considerations Section in RFCs",BCP 26,RFC5226, May 2008.7.2.  Informative References   [RFC0793]     Postel, J., "Transmission Control Protocol", STD 7,RFC793, September 1981.   [RFC1819]     Delgrossi, L., Ed., and L. Berger, Ed., "Internet                 Stream Protocol Version 2 (ST2) Protocol Specification                 - Version ST2+",RFC 1819, August 1995.   [URL-IETF]    International Essential Tremor Foundation,http://www.essentialtremor.org/   [URL-CARDIFF] Cardiff Rugby Football Club,http://www.cardiffrfc.com/   [URL-P2P]     eProcumentStotl@nd,http://www.eprocurementscotland.com/Home/ePS-Service/P2P   [URL-QOS]     Queen of the South Football Club,http://www.qosfc.com/   [URL-QoS]     Queen of the South Football Club,                 ahttp://www.qosfc.com/Farrel                       Informational                      [Page 6]

RFC 5513                          TLAs                        April 2009Author's Address   Adrian Farrel   Old Dog Consulting   EMail: adrian@olddog.co.ukFarrel                       Informational                      [Page 7]