||(1) Any logical transportation of any form of information across a system or network. It may originate in one or more applications, be carried through any one or more network components, and end in any one or more user applications. (2) The smallest metric of traffic that is visible from the standpoint of a network's traffic routing and management capabilities. The actual implementation of an information flow is therefore highly dependent on the network type of the networks it travels across. For example, if the network uses an IP router type of network architecture, a source and destination IP address pair would define an information flow. If the network is based on an ATM network architecture, a virtual channel identifier defines information flow. The essential characteristic of the information flow in either case is that it represents the traffic aggregation that the network will base its resource allocation and traffic routing mechanisms on. All traffic within an information flow should therefore have similar network quality of service (QoS) requirements.