Flow Based Precedence and Preemption Methods Without a Priory Signaling

Precedence and preemption (P&P) has its roots in the TDM voice networks, where it can be defined and implemented in a natural setting. Due to the hop-by-hop nature of IP networks, definition and implementation of P&P poses additional challenges. One of the main challenges is keeping the overall P&P architecture simple enough so that the management and operations of the networks do not become overly cumbersome, and that the end-to-end P&P requirements are satisfied across multiple autonomous domains. To this end, the DoD QoS Working Group has defined DoD wide use of the differentiated services code points (DSCP) to indicate the P&P level and the class of service associated with each packet. If P&P is based only on the DSCP value, this architecture may lead to inefficient use of network resources when the network is stressed. But RSVP's scalability problems in backbone networks are well documented in RFC 2208. An alternative method is to treat the packets based on the micro-flow they belong to, in addition to their DSCP value. Advances in ASIC technology make it feasible to recognize and keep the state of the micro-flows for each router while maintaining scalability. Micro-flows are recognized based on attributes such as source and destination IP addresses and port numbers. In addition, other attributes such as packet sizes and packet inter-arrival times make it feasible to recognize the nature of the flows, and thus allow for the allocation of the corresponding network resources without using signaling protocols. This paper will also discuss the application of flow identification techniques in DoD black core networks, where signaling and DSCP values may not be available