The MPLS WG Archive

[Kireeti Kompella <kireeti@juniper.net>]

> If the IGP advertises the Reserved bandwidth per priority, then what are
> the mechanism/equations to deduce the Unreserved bandwidth per priority?

>From the expired ISIS document:

5.6 Sub-TLV 11: Unreserved bandwidth
                ^^^^^^^^^^
   
   This sub-TLV contains the amount of bandwidth reservable on this
   direction on this link.  Note that for oversubscription purposes,
   this can be greater than the bandwidth of the link.          
   
   Because of the need for priority and preemption, each head end needs 
   to know the amount of reserved bandwidth at each priority level.
   Thus, this sub-TLV contains eight 32 bit IEEE floating point numbers.
   The units are bytes (not bits!) per second.  The values correspond to
   the bandwidth that can be reserved with a holding of priority 0
   through 7, arranged in increasing order with priority 0 occurring at
   the start of the sub-TLV, and priority 7 at the end of the sub-TLV.

>From the expired OSPF document:

2.5.8  Unreserved Bandwidth
       ^^^^^^^^^^

   The Unreserved Bandwidth sub-TLV specifies the amount of bandwidth
   not yet reserved at each of the eight priority levels, in IEEE
   floating point format.  Each value will be less than or equal to the
   maximum reservable bandwidth.  The units are bytes per second.

   The Unreserved Bandwidth sub-TLV is TLV type 8, and is 32 octets in
   length.

Kireeti.