A system comprising: a Tree Hierarchy Constructor Unit, configured to construct a tree hierarchy representation that corresponds to distributed enforcement of a Quality-of-Service, QoS, policy on incoming packets that are intended for transmission towards a destination, said tree hierarchy representation comprises a hierarchical tree of Policy Objects; wherein each Policy Object includes a pair of a Condition and a corresponding Treatment; wherein a Policy Object that is located on an upper level in the tree is a defined as a Parent of a Policy Object located on a lower level of that tree; wherein a Policy Object that is located on lower level of the tree is defined as a Child of a Policy Object located on an upper level of that tree; wherein a parent Policy Object can have one or more children Policy Object; whereas a child Policy Object has only a single parent Policy Object; wherein said tree hierarchy representation is utilized by at least two separate Processing Units, PUs, (551, 552) comprised in the system and which are configured to separately process different packets that are intended for transmission towards said destination; a Policy Object Association Unit, configured to associate between a first set of instances of parent and child Policy Objects of QoS enforcement, and a first PU; and to separately associate between (i) a second set of instances of said parent and child Policy Objects of QoS enforcement, and (ii) a second PU; a Cross-PU Instances Synchronization Unit, configured to automatically determine that the first PU caused modification of said first set of instances of said parent and child Policy Objects that are utilized by the first PU, and to dynamically cause a corresponding modification to said second set of instances of said parent and child Policy Objects that are utilized by the second PU. a Tree Hierarchy Constructor Unit, configured to construct a tree hierarchy representation that corresponds to distributed enforcement of a Quality-of-Service, QoS, policy on incoming packets that are intended for transmission towards a destination, said tree hierarchy representation comprises a hierarchical tree of Policy Objects; wherein each Policy Object includes a pair of a Condition and a corresponding Treatment; wherein a Policy Object that is located on an upper level in the tree is a defined as a Parent of a Policy Object located on a lower level of that tree; wherein a Policy Object that is located on lower level of the tree is defined as a Child of a Policy Object located on an upper level of that tree; wherein a parent Policy Object can have one or more children Policy Object; whereas a child Policy Object has only a single parent Policy Object; wherein said tree hierarchy representation is utilized by at least two separate Processing Units, PUs, (551, 552) comprised in the system and which are configured to separately process different packets that are intended for transmission towards said destination; a Policy Object Association Unit, configured to associate between a first set of instances of parent and child Policy Objects of QoS enforcement, and a first PU; and to separately associate between (i) a second set of instances of said parent and child Policy Objects of QoS enforcement, and (ii) a second PU; a Cross-PU Instances Synchronization Unit, configured to automatically determine that the first PU caused modification of said first set of instances of said parent and child Policy Objects that are utilized by the first PU, and to dynamically cause a corresponding modification to said second set of instances of said parent and child Policy Objects that are utilized by the second PU.