TCP/IP Tutorial and Technical Overview - IBM Redbooks

To establish a reservation with RSVP, the receivers send reservation requests to
the senders, depending on their system capabilities. For example, a fast
workstation and a slow PC want to receive a high-quality MPEG video stream
with 30 frames per second, which has a data rate of 1.5 Mbps. The workstation
has enough CPU performance to decode the video stream, but the PC can only
decode 10 frames per second. If the video server sends the messages to the two
receivers that it can provide the 1.5 Mbps video stream, the workstation can
return a reservation request for the full 1.5 Mbps. But the PC does not need the
full bandwidth for its flow because it cannot decode all frames. So the PC may
send a reservation request for a flow with 10 frames per second and 500 kbps.
RSVP operation
A basic part of a resource reservation is the path. The path is the way of a packet
flow through the different routers from the sender to the receiver. All packets that
belong to a specific flow will use the same path. The path gets determined if a
sender generates messages that travel in the same direction as the flow. Each
sender host periodically sends a path message for each data flow it originates.
The path message contains traffic information that describes the QoS for a
specific flow. Because RSVP does not handle routing by itself, it uses the
information from the routing tables in each router to forward the RSVP
messages.
Chapter 8. Quality of service 297