The purpose of the VPN label is to demultiplex VPN traffic
arriving at the PE. From this point of view, any allocation policy,
ranging from a separate label per route to a single label per site,
fulfils the functional requirement. For most scenarios, one label per
site provides the required functionality with the minimum amount
of state. At the other extreme, one label per route can provide per/
destination statistics and good visibility into the CE–CE traffic
matrix. The cost is the extra state maintained, which can make
troubleshooting difficult, as we have argued in the Foundations
chapter in the context of LDP. Therefore, unless the functionality is
needed, an approach that creates less state is preferable.