Methods, apparatus and articles of manufacture for advertising network layer reachability information specifying a quality of service for an identified network flow are disclosed. Example methods disclosed herein to specify quality of service for network flows include receiving network layer reachability information including a first quality of service class specified for a first network flow, the network layer reachability information having been advertised by a first network element that is to receive the first network flow. Such example methods can also include updating an incoming packet determined to belong to the first network flow to indicate that the incoming packet belongs to the first quality of service class, the incoming packet being received from a second network element. Such example methods can further include, after updating the incoming packet, routing the incoming packet towards the first network element.