Re: BITS

["David T. Perkins" <dperkins@dsperkins.com>]

HI,

Your interpretation of the compliance shows a use with value.
However, to come to the interpretation requires a jump
to come up with "only the bits that are named can have the
values set to '1'". Only careful definition of bit values
would allow a general rule.

On Tue, 28 Oct 2003, C. M. Heard wrote:
> On Tue, 28 Oct 2003, David T. Perkins wrote:
> > Sure, one could "remove bit definitions", but it provides no
> > real value. Likewise, in compliance specifications, but what
> > does it mean, and what are you saying about interoperability
> > when you "remove bits in a compliance specification". What value
> > do you achieve?
> 
> 
> Here is an example.  In the SONET-MIB (RFC 3592) there exists the
> following object definition:
> 
>    sonetMediumLoopbackConfig OBJECT-TYPE
>        SYNTAX      BITS {
>                      sonetNoLoop(0),
>                      sonetFacilityLoop(1),
>                      sonetTerminalLoop(2),
>                      sonetOtherLoop(3) }
>        MAX-ACCESS  read-write
>        STATUS      current
>        DESCRIPTION
>           "The current loopback state of the SONET/SDH interface.  The
>            values mean:
> 
>              sonetNoLoop
>                 Not in the loopback state. A device that is not
>                 capable of performing a loopback on this interface
>                 shall always return this value.
> 
>              sonetFacilityLoop
>                 The received signal at this interface is looped back
>                 out through the corresponding transmitter in the return
>                 direction.
> 
>              sonetTerminalLoop
>                 The signal that is about to be transmitted is connected
>                 to the associated incoming receiver.
> 
>              sonetOtherLoop
>                 Loopbacks that are not defined here."
> 
>        ::= { sonetMediumEntry 8 }
> 
> The ETHER-WIS compliance statement has the following OBJECT clause:
> 
>            OBJECT       sonetMediumLoopbackConfig
>            SYNTAX       BITS {
>                sonetNoLoop(0),
>                sonetFacilityLoop(1)
>                }
>            MIN-ACCESS   read-only
>            DESCRIPTION
>                "Write access is not required, nor is support for values
>                other than sonetNoLoop(0) and sonetFacilityLoop(1)."
> 
> What does this achieve?  It says that an implementation is not required
> to allow bit positions other than the ones listed to be set, even if
> write access is alowed.  Seems useful to me.
> 
> //cmh
> 
>