QoS - RSVP bandwidth and flow reservations

When implementing RSVP as a QoS mechanism, we use the ip rsvp bandwidth command on participating routers to reserve resources along the communication path.

In its most basic form, this command specifies two values:

  • The maximum amount of bandwidth, in kb/s, that can be allocated by RSVP flows. The range is from 1 to 10000000.
  • The maximum amount of bandwidth, in kb/s, that may be allocated to a single flow. The range is from 1 to 10000000.

An example of the command on a particular interface is as follows:

Router(config-if)#ip rsvp bandwidth 256 64

This command reserves a total of 256 kb/s for all RSVP flows, and reserves a maximum of 64 kb/s for each individual flow.

Thus, this interface can support RSVP flows of up to 64 kb/s each, and can support a total flow bandwidth of 256 kb/s.

That means that the interface can support four flows of 64 kb/s each, or eight flows of 32 kb/s each or a combination of two flows of 64 kb/s each and four flows of 32 kb/s each, and so on. As long as the total bandwidth of all the flows does not surpass 256 kb/s.

Any attempts at creating individual flows larger than 64 kb/s or creating a number of flows that will surpass a total of 256 kb/s will fail.