ENUM Implementation Redux

1
ENUM Implementation Redux

• Wilhelm Wimmreuter
• Wilhelm.wimmreuter_at_siemens.com
• The person to blame for the I-D is
• Lawrence Conroy
• Lwc_at_roke.co.uk

2
Things we have done

• Theres an I-D that summarises our ENUM
  implementation experiences - it is
  lthttp//www.ietf.org/internet-drafts/draft-conroy-
  enum-experiences-01.txtgt
• This is tied to the presentation made at the last
  IETF - that was lthttp//www.ietf.org/proceedings/0
  3nov/slides/enum-2/index.htmlgt
• The mapping between the issues raised in that
  presentation and the I-D is presentation issues
  1-8 are covered in sections 2.1, 2.3, 2.6, 2.9,
  2.8, 2.7, 2.5, and 2.4 of the I-D, respectively
• However, theres always one more issue, and a
  clarification, so

3
Things we have seen

• NEW Issue 9 (Section 2.2) - RegExp Case
  Insensitivity Flag
• Some people add the RegExp case insensitivity
  flag ('i' on the end of a RegExp field value) to
  NAPTRs
• Given that, with ENUM, we're dealing with an
  E.164 Number as an Application Unique String,
  this is pointless
• However, it does quite effectively break some
  clients that assume that the last character is a
  RegExp delimiter
• Thus, for clients, expect such legally correct
  idiocy and check the last and prior characters
  for a delimiter - the i flag has no effect for
  ENUM, so can be ignored as the last character
  after the delim. Dont just look for a trailing
  i, as it is a legal delimiter, and some person
  will use both someday
• For registrants, don't do it.

4
For the email-challenged

• Clarification on Issue 4 (2.9) -
• ORDER consideration across non-final domain
  traversal
• This is a special case of ORDER consideration in
  discarded NAPTRs
• NAPTRs can be made into a single list, sorted
  first on ORDER field values and then on
  PREFERENCE field values, to be processed one by
  one
• If a NAPTR is discarded if inappropriate for the
  client (unsupported ENUMSERVICE or resultant URI
  scheme) then the client may continue with the
  next. It might consider every NAPTR in a
  domain, if all others with a better ORDER
  PREFERENCE have been discarded
• Thus, for Registrants, don't assume that a NAPTR
  will be ignored if it has a lower ORDER value
  than others - they may have all been discarded as
  inappropriate for the client making the ENUM
  evaluation.