Requirements of a Generic Segmentation and Reassembly Building Block

The main focus of this report is the investigation and analysis of the requirements of a Segmentation And Reassembly (SAR) building block for a Network Processor. The SAR block should be generic enough to accommodate both ATM and IP traffic and cover a variety of protocols and applications. A data unit travelling a network can be split into parts (segmented), combined with other data units (multiplexed), and rejoined into one (reassembled) several times and in different ways during its time in the network. Such a packet manipulation depends on the size of the packet, the Quality of Service (QoS) requirements of the application that transmits the data unit, the type of the network protocol, the transport layer, the rate and configuration of the lines it traverses, and the capabilities of the network nodes, among others. A network node that supports both ATM and IP transport protocols, a number of line configurations and a number of application areas should therefore be able to first recognize and second manipulate (segment, mix and reassemble) data units in a specific way that depends on various network parameters. A SAR function that can be generic enough to handle all these protocols in an efficient way is a considerable advantage, if not a requirement, in a flexible system. However, a prerequisite for its architectural definition is a well defined set of requirements, which is established in this report.