Wildcard-Filter (WF) Style

Wildcard-Filter (WF) Style

The WF style is a shared reservation style with implicit sender selection. Since all reservations are sharing the same resource allocation, the amount of resource that needs to be reserved is equal to the largest value of the resource requested by all receivers. The WF style is represented by the equation

WF(*{Q})

with the asterisk signifying a wildcard sender selection and Q signifying the flowspec. The symbol Q, or flowspec, is essentially the QoS or amount of bandwidth requested by the receiver. The network in Figure 10-4 shows a WF scenario. The receivers are requesting bandwidth for a particular session that is supported by sources 1,2, and 3. The receivers don’t care from which source the data arrives so all are using the wildcard specification WF(*{Q}). Receiver 1 is requesting 500K and sends a WF(*{500K}) RSVP request to router A.

Figure 10-4: WF(*{Q}) reservation style example

Router A receives only one WF request and attempts to allocate the bandwidth on the input interface, E0, and the output interface, S0. For reservation requests, input and output interfaces refer to the direction of the reservation request flow. The data flow from the sources will reverse the direction of these interfaces. For the following examples, assume the routers have the resources to satisfy reservation requests. Since the request is a shared reservation request, router A will allocate the largest of the requested allocations. With only one request, the allocation will equal what receiver 1 requested. The same argument applies to routers C and D and receivers 2 and 3. Router C will allocate 300K on the E0 and E1 interfaces, while router D will allocate 200K on the E0 and E1 interfaces. Router A will receive one reservation request on interface S2 for 500K and two reservation requests for 200K and 300K on interface E0. Router A will allocate 500K on interface S2. The largest of the two requests, 300K, is received on interface E0. On interfaces S0 and S1, Router A has to be able to handle the largest of the three requests received. For this case, a 500K allocation is reserved on the S0 and S1 interfaces and the reservation is forwarded toward the sources. Routers E and F only receive an RSVP request for 500K. This amount will be allocated on all interfaces between the sources and the receivers. The bandwidth allocations for the WF example network in Figure 10-4 are listed in Table 10-2.

Table 10-2: Bandwidth Allocations for the Wildcard-Filter Style Example

Router

Interface E0

Interface E1

Interface S0

Interface S1

Interface S2

A

300K

500K

500K

500K

B

500K

500K

C

300K

300K

D

200K

200K

E

500K

500K

F

500K

500K