ARIN's RESTful Whois Directory Service Available 26 June

Posted: Thursday, 24 June 2010

ARIN is deploying an improved Whois service called Whois-RWS on 26 June 2010. Included in the deployment are the following services that provide the general public with access to ARIN's registration data:

  • a RESTful Web Service (RWS)
  • a NICNAME/WHOIS port 43 service
  • a user-friendly web site (

When using Whois-RWS you will notice some differences in behavior for certain queries and corresponding result sets on the NICNAME/WHOIS TCP port 43 service. These minor differences are documented at:

ARIN’s Directory Service for registration data has used the NICNAME/WHOIS protocol since its inception. The limitations of the NICNAME/WHOIS protocol are well known and documented in RFC3912. Whois-RWS was created as an alternative to the ARIN Whois and will provide much richer functionality and capability to the community.

Whois-RWS can easily be integrated into command line scripts, or it can be used with a web browser, which makes it applicable for programmatic consumption and accessible for interactive use. ARIN will continue to maintain services for the NICNAME/WHOIS protocol on TCP/43. This is achieved by using a proxy service to translate traditional ARIN Whois queries into Whois-RWS queries. However, ARIN recommends use of the RESTful Web Service.

Those who choose to use the Whois-RWS Proxy will find it has many features unavailable over the existing Whois service, including:  

  • Support for new query types such as CIDR queries
  • Better feedback for ambiguous queries
  • More finely scoped record type queries
  • Options for NICNAME/WHOIS clients that re-interpret traditional parameters used by ARIN's service.
  • RESTful URL references, useful for embedding into documents and email
  • Better grouping of record types and delineation of results

Another major benefit is that data from ARIN’s registration database is distributed to the Whois-RWS servers many times throughout the day, versus the once-a-day update of ARIN’s previous Whois service. Changes will be reflected more quickly through Whois-RWS, so query results will be more current than the previous Whois service.

ARIN continues to welcome community participation on the Whois-RWS mailing list, and we invite you to subscribe and provide feedback to:


Mark Kosters
Chief Technology Officer
American Registry for Internet Numbers (ARIN)