The present document contains general guidance on European ENUM trials and the specification for: ? The format@ contents and meaning of the information in the NAPTR records that are held by the ENUM Tier 2 Nameserver providers and accessible by DNS. ? The ways in which ENUM client software should interpret and act upon information obtained from NAPTR records. The present document is intended to enable interoperability between ENUM trials that are organized in different countries. This interoperability enables: ? The same ENUM client software to work with NAPTR records generated by different national trials and this in turn will enable applications that use ENUM to access details of ENUM subscribers in more than one country without additional modifications. ? Organizations to function as ENUM Registrars and ENUM Tier 2 Nameserver Provider in more than one national trial. The present document will therefore add economies of scope to the ENUM trials that will benefit ENUM subscribers@ trial participants@ application service providers and ENUM users. The present document is published as a Technical Specification (TS) at this stage as the contents are unproven. The intention is to update and upgrade the present document in the light of the results obtained from the trials. These requirements are therefore specified for the trial phase only@ and as such impose no constraints on ENUM when implemented on a commercial basis following completion of the trial. Although the present document is focused towards European ENUM trials its use could facilitate interoperability with ENUM trials in other parts of the world.