1. A method comprising: receiving a data unit at an ingress line interface of a network device; at the ingress line interface, performing a lookup into a classification table, associated with the ingress line interface, based on header information of the data unit; identifying a class of the received data unit based on the performed lookup; at the ingress line interface, obtaining a service tag based on the class of the data unit, where the service tag includes a redirect subcommand field, the redirect subcommand field including a subcommand, used by a service module of the network device, to specify further processing required by the data unit, or provide an indication for assigning the data unit to at least one of a component or a service sub-module of the network device; identifying at the ingress line interface, based on information included in the obtained service tag, the service module of the network device; sending, based on identifying the service module, the service tag and the data unit, across a switch fabric of the network device from the ingress line interface to the service module in the network device; performing a service for the data unit at the service module of the network device based on the subcommand; determining whether the data unit requires further processing; and upon determining the data unit requires no further processing, clearing fields of the service tag, and sending the data unit to a network address originally included in a data unit descriptor.