Bandwidth reservation relates to the way the bandwidth is to be allocated (the reservation type), and the technique used to select senders (the sender selection). The reservation type may be distinct for individual data flows, or may be shared among multiple data flows. The selection of the senders may be explicit (meaning that individual senders are identified individually), or it may be a wildcard selection that implicitly selects all the senders to a session. This table shows the reservation styles that are defined for the various Sender Selection-Reservation Type combinations:
┌─────────────────────────────────────────────────────────────────┐ │Sender Selection Reservation Type Reservation Style │ ├─────────────────────────────────────────────────────────────────┤ │explicit distinct Fixed-Filter (FF) │ ├─────────────────────────────────────────────────────────────────┤ │explicit shared Shared-Explicit (SE) │ ├─────────────────────────────────────────────────────────────────┤ │wildcard distinct (none defined) │ ├─────────────────────────────────────────────────────────────────┤ │wildcard shared Wildcard-Filter (WF) │ └─────────────────────────────────────────────────────────────────┘
The fixed filter (FF) style specifies a distinct flow for each sender. The bandwidth reservations are made separately for each flow. Parameters in the reservation specify each sender explicitly.
With the shared explicit (SE) style, each of the senders is specified explicitly in the reservation message, but the reserved bandwidth is shared by all the senders wherever they can be merged upstream from the receiver.
The wildcard filter (WF) style specifies a single reservation of bandwidth which is to be shared by all the senders. This type of reservation is propagated upstream to all senders as they become senders in the RSVP session. Besides there being a single bandwidth reservation for all the senders to the receiver that makes the reservation, the other receivers in the same multicast group will have their bandwidth reservations merged as well. The "largest" such reservation for the session at any point in the multicast tree determines how much bandwidth is reserved at that point in the tree.
The wildcard and shared explicit styles are primarily useful for multicast applications where the data sources are unlikely to transmit simultaneously.