A high speed transmission protocol that is implemented in a network device that includes a plurality of modules which are connected by a plurality of high speed links. The protocol includes a transmission link aspect for providing at least one of variable-sized packet based transmission with fixed sized messaging capability and pre-emptive transmission capability and a fabric forwarding aspect supporting at least one of class differentiations for packet flows, a plurality of addressable physical and logical modules, generic multicast forwarding port level indication for physical or logical ports, and explicit parameter for packet-content agnostic fabric operation. The protocol also include a packet processing descriptor aspect for providing at least one of a flexibility for various packet-processing descriptor adaptations and packet processing flow continuity across the network device for system design scalability. The protocol further includes an in-band messaging aspect for providing at least one of congestion management protocols, system resiliency protocols, database synchronization protocols and component access protocols and an encoding aspect for providing a structured header design.