This attribute specifies the priority at which a path is established.
Zero is the highest priority and four is the lowest. When PORS
establishes a path through the network, it uses the setupPriority
attribute to determine its potential for bumping established paths to
acquire their bandwidth. The holdingPriority, a complementary
attribute of this attribute, specifies the priority a path maintains once
it is established. A new path can bump an existing path if the new
path's setupPriority is higher (numerically less) than the existing
path's holdingPriority.