Article ID: 123551, created on Nov 16, 2014, last review on Oct 6, 2015

  • Applies to:
  • Odin Business Automation Standard 4.5

Symptoms

The value field of a DNS record can not exceed 255 characters. As a result, it is not possible to create a DKIM record with a 2048 bits key cause it requires 411 characters.

Cause

As stated if RFC 1035, maximal length of a TXT DNS records is 255 bytes. OBAS handles such kind of records with length not greater than 255 bytes without errors.

However to get around this limitation, per RFC 4408 a TXT or SPF record is allowed to contain multiple strings, which should be concatenated together by the reading application.

3.1.3.  Multiple Strings in a Single DNS record

As defined in [RFC1035] sections 3.3.14 and 3.3, a single text DNS
   record (either TXT or SPF RR types) can be composed of more than one
   string.  If a published record contains multiple strings, then the
   record MUST be treated as if those strings are concatenated together
   without adding spaces.  For example:

   IN TXT "v=spf1 .... first" "second string..."

MUST be treated as equivalent to

   IN TXT "v=spf1 .... firstsecond string..."

SPF or TXT records containing multiple strings are useful in
   constructing records that would exceed the 255-byte maximum length of
   a string within a single TXT or SPF RR record.

Resolution

The feature request PBAS-29730 has been submitted to implement RFC 4408 specifications in future OBAS versions.

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