When requests are not rejected for either resource use with IP traffic. availability or policy reasons, the incident PATH message There are two significant RSVP messages, PATH and is carried from sender to receiver and a RESV message is RESV. Transmitting applications send PATH messages carried in return. In this case, a reservation is said to be installed. An installed reservation indicates that RSVP- toward receivers. These messages describe the data that will be transmitted and follow the path that the data will aware devices in the traffic path have committed the take. Receivers send RESV messages. These follow the requested resources to the appropriate flow and are path seeded by the PATH messages, back toward the prepared to allocate these resources to traffic belonging senders, indicating the profile of traffic that particular to the flow. This process of approving or rejecting RSVP receivers are interested in. In the case of multicast traffic messages is known as admission-control and is a key QoS flows, RESV messages from multiple receivers are concept. "merged," making RSVP suitable for QoS with multicast Guarantees must be valid end-to-end across multiple traffic. subnets. Lower quality guarantees can be provided As defined today, RSVP messages carry the following without requiring tight coupling between the QoS information: mechanisms in different subnets. However, high quality guarantees require tight coupling between these How the network can identify traffic on a conversa- mechanisms. tion (classification informaton) As an example, it is possible to independently con- Quantitative parameters describing the traffic on the figure devices in each subnet (in a top-down manner) to conversation (data rate, etc.) prioritize some set of traffic (as identified by IP port) The service type required from the network for the above best-effort traffic (BBE service). This will indeed conversation's traffic improve the quality of service perceived by the priori- Policy information (identifying the user requesting