'Deep packet inspection--Use cases, requirements and architectures', by Christof Wehner, Emerson Network Power, which was published in the EE Times recently, noted that there are several requirements that are common across the different use cases.
Some may be only partly applicable, while others are always applicable. Among the requirements that cut across most use cases are Transparency , High Throughput , High (Enough) Processing Capabilities , Low Latency , High Availability and Scalability.