Definitions of Textual Conventions (TCs) for Bidirectional Forwarding Detection (BFD) Management
draft-ietf-bfd-tc-mib-08

Not really a blocking factor (DISCUSS), but it would nice if the situation would be clarified. 
As mentioned by Bert Wijnen, part of the MIB doctors review:

   BfdIntervalTC ::= TEXTUAL-CONVENTION
    DISPLAY-HINT  "d"
    STATUS        current
    DESCRIPTION
        "The BFD interval in microseconds."
    SYNTAX Unsigned32 (0..4294967295)


  If you see it used in, for example

    bfdSessDesiredMinTxInterval OBJECT-TYPE
        SYNTAX     BfdIntervalTC
        MAX-ACCESS read-create
        STATUS     current
        DESCRIPTION
            "This object specifies the minimum interval, in
             microseconds, that the local system would like to use
             when transmitting BFD Control packets. The value of
             zero(0) is reserved in this case, and should not be
             used."
        REFERENCE
            "Section 4.1 from Katz, D. and D. Ward, Bidirectional
             Forwarding Detection (BFD), RFC 5880, June 2012."
        ::= { bfdSessEntry 25 }

   Then what value is added by using a TC. In fact you can even question if it
   is not conflicting, because according to the TC description clause I would
   expect zero to be a valid interval value, where as here it describes
   that zero is a special value and should not be used. So it is only special
   Since it should NOT BE used, or does zero mean something special?
   Assuming zero SHOULD NOT be used. I personally would just do:

    bfdSessDesiredMinTxInterval OBJECT-TYPE
        SYNTAX Unsigned32 (1..4294967295)
        MAX-ACCESS read-create
        STATUS     current
        UNITS      microseconds
        DESCRIPTION
            "This object specifies the minimum interval that the local
             system would like to use when transmitting BFD Control packets.
        REFERENCE
            "Section 4.1 from Katz, D. and D. Ward, Bidirectional
             Forwarding Detection (BFD), RFC 5880, June 2012."
        ::= { bfdSessEntry 25 }

BENOIT: the alternative is to have the following TC and to simplify the defintion
   BfdIntervalTC ::= TEXTUAL-CONVENTION
    DISPLAY-HINT  "d"
    STATUS        current
    DESCRIPTION
        "The BFD interval in microseconds."
    SYNTAX Unsigned32 (1..4294967295)



   In case zero has special meaning I would do:
    bfdSessDesiredMinTxInterval OBJECT-TYPE
        SYNTAX Unsigned32 (0 | 1..4294967295)
        MAX-ACCESS read-create
        STATUS     current
        UNITS      microseconds
        DESCRIPTION
            "This object specifies the minimum interval that the local
             system would like to use when transmitting BFD Control packets.
             The value zero has been reserved for a special meaning:
             <describe what zero means>
        REFERENCE
            "Section 4.1 from Katz, D. and D. Ward, Bidirectional
             Forwarding Detection (BFD), RFC 5880, June 2012."
        ::= { bfdSessEntry 25 }

looks like mib doctors et al have no discussion going on that will result in changes.