The MPLS WG Archive

["Cucchiara, Joan" <JCucchiara@Brixnet.com>]

Tom,

> 
> >I also question why this extra variable is required to
> >convey the label space membership attributes.
> >
> >If  mplsInterfaceConfIndex is zero, then it uneqivocally
> >has the attributes 'in global label space' and 'not in
> >local label space'.
> >
> >If mplsInterfaceConfIndex is non-zero, that it uneqivocally
> >has the attribute 'in local label space' and the 'in
> >global label space' variable arbitrates that (optional)
> >attribute.
> 
>          Yes, but there are cases in ATM where an interface needs
> to be part of both label spaces. This is why we have
> provided two separate variables here.

The combination of the index and ONE of these
objects would (I think) allow all combinations.  For example,

mplsInterfaceConfIndex
SYNTAX   InterfaceIndexOrZero
DESCRIPTION
   "...A non-zero index for an entry indicates the ifIndex for
    the corresponding interface entry in (of) the MPLS-layer in
    the ifTable.  Note that the global label space may apply to
    several interfaces, and therefore the configuration of
    the global label space interface parameters will
    apply to all of the interfaces that are participating in
    the global label space."

It has been stated that there will be at most 1 occurance
of mplsInterfaceConfIndex == 0 in this table.

Which means that the entry represents the perPlatform Label Space.

Further, a non-zero value represents the ifIndex (with ifType of
mpls(166)) represents a perInterface Label Space for that
"mpls interface".

Additionally, there are two objects:

mplsInterfaceIsGlobalLabelSpace
SYNTAX  TruthValue
DESCRIPTION
   "This value indicates whether or not this interface
   participates in the global label space."

and 

mplsInterfaceIsLocalLabelSpace
SYNTAX  TruthValue
DESCRIPTION
   "This value indicates whether or not this interface
   uses in the local or per-interface label space."

As far as I can tell the object 'mplsInterfaceIsLocalLabelSpace'
is redundant with a non-zero value of 'mplsInterfaceConfIndex'.

Here are the possible combinations

GlobalLabelSpace:

   mplsInterfaceConfIndex == 0
   mplsInterfaceIsGlobalLabelSpace == TRUE

Combo (GlobalLabelSpace and LocalLabelSpace)

   mplsInterfaceConfIndex == non-zero, ifIndex value
   mplsInterfaceIsGlobalLabelSpace == TRUE

LocalLabelSpace

   mplsInterfaceConfIndex == non-zero, ifIndex value
   mplsInterfaceIsGlobalLabelSpace == FALSE

NOT Possible

   mplsInterfaceConfIndex == 0
   mplsInterfaceIsGlobalLabelSpace == FALSE.

Are the above all that are necessary?   If not,
could the other possibilities be given?

Here are suggestions for what they are worth.

*  Replace the term GlobalLabelSpace with PerPlatformLabelSpace
   throughout the MIB.

*  Replace the term LocalLabelSpace with PerInterfaceLabelSpace
   throughout the MIB.

*  Remove the object mplsInterfaceIsLocalLabelSpace

*  Reword the description for the object mplsInterfaceIsGlobalLabelSpace as:

mplsInterfacePerPlatformLabelSpaceAlso  OBJECT-TYPE
SYNTAX  TruthValue
MAX-ACCESS  read-only
STATUS   current
DESCRIPTION
   "If the value of the 'mplsInterfaceConfIndex is non-zero, and
   the value of this object is 'true' then the interface represented
   by this entry also participates in the PerPlatform Label Space as
   described in Section 3.14 of the MPLS Architecture.

   If the value of the 'mplsInterfaceConfIndex is zero, then this entry
   indicates is for the PerPlatform Label Space and 
   the value of this object must be 'true'."

-Joan



> 
>          --Tom
> 
>