Reserving bandwidth on an interface
The Maximum Bandwidth TLV indicates the maximum outbound bandwidth that can be used on the interface. Maximum Bandwidth is the operating speed of the port. This reflects the actual physical bandwidth of the interface. You cannot configure this TLV.
The Maximum Reservable Bandwidth TLV indicates the maximum bandwidth that can be reserved on the interface. The Maximum Reservable Bandwidth must be configured; there is no default.
The Unreserved Bandwidth TLV indicates the amount of bandwidth not yet reserved on the interface. This TLV consists of eight octets, indicating the amount of unreserved bandwidth (in kilobits per second) at each of eight priority levels. The octets correspond to the bandwidth that can be reserved with a hold priority of 0 through 7, arranged in increasing order, with priority 0 occurring at the start of the TLV, and priority 7 at the end of the TLV. The value in each of the octets is less than or equal to the maximum reservable bandwidth. The Unreserved Bandwidth TLV itself is not user-configurable, although it is affected by modifications to the reservable bandwidth on an interface, as well as changes to LSPs.
You can configure the maximum reservable bandwidth as an absolute value. It is mandatory to configure the maximum reservable bandwidth if you want to use bandwidth reservation functionality.