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Question 12/17 – Abstract Syntax Notation One (ASN.1), Object Identifiers (OIDs) and associated registration
(Continuation of Q.10/17)


Additional Recommendations, where needed, will be developed to accommodate advances in technology and additional requirements from users of the ASN.1 notation, its encoding rules, and additional requirements from users and providers of registration authorities for international object identifiers.

ASN.1 has proved to be the notation-of-choice for many ITU-T standardization groups, many of which continue to produce requests for additional functionality in the ASN.1 Recommendations and for correction of residual ambiguities and lack of clarity in the more recent additions and amendments to those Recommendations (maintenance).

Object identifiers (OIDs) have proved a very popular namespace based primarily on a tree-structure of hierarchical registration authorities identified by integer value. Its recent extension to International OIDs allowing arcs to be identified by Unicode labels is also in demand for various applications, and is likely to produce requirements for further development and extension.

There is a continuing requirement to provide advice and assistance to other study groups, external standards development organizations (SDOs) and countries on both ASN.1 notational matters but increasingly on the management of the OID namespace. It is expected that the need for help and advice will increase with the introduction of international OIDs. There is therefore a need for an ITU-T "ASN.1 & OID Project" with an appointed project leader to provide such advice and assistance.

Recommendations under responsibility of this Question as of 1 December 2008: X.660, X.662, X.665, X.666, X.667, X.668, X.669, X.670, X.671, X.680, X.681, X.682, X.683, X.690, X.691, X.692, X.693, X.694, X.695, X.891, X.892 and X.893.


Study items to be considered include, but are not limited to:

  1. What enhancements are required to the Abstract Syntax Notation One (ASN.1) and its associated encoding rules to meet the needs of future applications?
  2. What additional encoding rule support is needed to provide for the requirements of the many applications using ASN.1?
  3. What additional packed encoding rules (PER) encoding instructions are needed to allow protocol specifiers to vary those encoding rules?
  4. Are there requirements for additional generic applications of ASN.1 in addition to X.891, X.892 and X.893?
  5. What additional Recommendations are needed to provide linkage between ASN.1 and other notations for schema definition, particularly (but not exclusively) related to eXtensible Markup Language (XML) mark-up?
  6. What further work needs to be done to ensure that the semantic underpinning of ASN.1 is sufficient to support the "ASN.1 tools" industry with a well-defined and unambiguous specification of the ASN.1 notation for all possible input specifications?
  7. What further developments are needed in OIDs to support the work of network aspects of identification (NID) and identity management (IdM) in other groups and to integrate the different naming schemes in use in the world?
  8. What specifications are needed to support the provision of resolvers related to international OID tree?
  9. What additional registration authorities or their procedures are needed to support the work of this and other Questions?
  10. What collaboration, beyond current agreements, is required with other bodies producing de jure or de facto standards to ensure that ITU-T work on ASN.1 and OIDs remains a leader in the area of provision of notations for protocol definition and for unambiguous naming?
  11. What changes are needed to the ASN.1 notation to allow the further use of ISO/IEC 10646 characters?
  12. What support is needed for ASN.1 to play a role in the sensing and alerting of events caused by climate change?


Tasks include, but are not limited to:

  1. Further the work on support for the IETF “oid:” Internationalized Resource Identifier (IRI) scheme and its registration with the Internet Assigned Numbers Authority (IANA).
  2. Provide updated Recommendations for X.660-, X.670-, X.680- X.690- and X.890-series throughout the study period in response to user needs, producing new editions when appropriate.
  3. When there is a need to improve data transfer, assist other Questions in all study groups in the provision of ASN.1 modules equivalent to XML schemas defined in ITU-T Recommendations (existing or under development), particularly in low bandwidth situations.
  4. Consider extending the ASN.1 notation to allow the further use of ISO/IEC 10646 characters.
  5. Under the responsibility of the ASN.1 & OID Project Leader:
    • Provide general advice to users of ASN.1 and OIDs;
    • Promote the use of ASN.1 and international OIDs within other study groups and external standards development organizations (SDOs);
    • Help the TSB to provide and maintain a web-based database of ASN.1 modules defined in ITU-T Recommendations;
    • Help countries with the establishment and maintenance of a national registration authorities for OIDs (including international OIDs).


Recommendations: H.200-series, H.323, T.120, X.400-series, X.500-series, X.700-series, X.880-series, X.900-series, Z-series and many others

Questions: All ITU-T Questions related to the above Recommendations

Study groups: All study groups that use ASN.1 or OIDs, or that have identification needs in relation to NID or IdM

Standardization bodies: ISO/IEC JTC 1/SC 6 and all ISO/IEC WGs that use ASN.1 or OIDs; OMG; IETF; W3C; OASIS


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Updated : 2009-01-28