TCP/IP Tutorial and Technical Overview - IBM Redbooks

Where:
Wildcard-Filter (WF) The Wildcard-Filter style uses the options shared
reservation and wildcard sender selection. This
reservation style establishes a single reservation for all
senders in a session. Reservations from different senders
are merged together along the path so that only the
biggest reservation request reaches the senders.
A wildcard reservation is forwarded upstream to all
sender hosts. If new senders appear in the session, for
example, new members enter a videoconferencing, the
reservation is extended to these new senders.
Fixed-Filter (FF) The Fixed-Filter style uses the option's distinct
reservations and explicit sender selection. This means
that a distinct reservation is created for data packets from
a particular sender. Packets from different senders that
are in the same session do not share reservations.
Shared-Explicit (SE) The Shared-Explicit style uses the option's shared
reservation and explicit sender selection. This means that
a single reservation covers flows from a specified subset
of senders. Therefore, a sender list must be included into
the reservation request from the receiver.
Reservations established in shared style (WF and SE) are mostly used for
multicast applications. For this type of application, it is unlikely that several data
sources transmit data simultaneously, so it is not necessary to reserve QoS for
each sender.
For example, in an audio conference that consists of five participants, every
station sends a data stream with 64 kbps. With a Fixed-Filter style reservation, all
members of the conference must establish four separate 64 kbps reservations
for the flows from the other senders. But in an audio conference, usually only one
or two people speak at the same time. Therefore, it is sufficient to reserve a
bandwidth of 128 kbps for all senders, because most audio conferencing
software uses silence suppression, which means that if a person does not speak,
no packets are sent. This can be realized if every receiver makes one shared
reservation of 128 kbps for all senders.
Using the Shared-Explicit style, all receivers must explicitly identify all other
senders in the conference. With the Wildcard-Filter style, the reservation counts
for every sender that matches the reservation specifications. If, for example, the
audio conferencing tool sends the data packets to a special TCP/IP port, the
receivers can make a Wildcard-Filter reservation for all packets with this
destination port.
Chapter 8. Quality of service 303