| Frame Relay service providers use a
parameter called committed information rate (CIR) to
provision network resources to a Frame Relay user and regulate usage
according to the assigned parameters. A mechanism written for the
Frame Relay protocol exists for letting Frame Relay users know that
congestion has been encountered within the Frame Relay network. This
mechanism relies on the Forward Explicit Congestion Notification (FECN)/Backward
Explicit Congestion Notification (BECN) bits in the Q.922 header of
the frame. The network or the user can selectively set the
discard-eligible (DE) bit in frames, and then drop these frames when
congestion is encountered.
The traffic shaping-over-Frame Relay
feature provides the following capabilities:
- Rate enforcement on a
per-virtual-circuit basis - You can configure a peak rate to
limit outbound traffic to either the CIR or some other defined
value, such as the excess information rate (EIR).
- Generalized BECN support on a
per-VC basis - The router can monitor BECNs and throttle
traffic based on BECN-marked packet feedback from the Frame
Relay network.
- Priority/Custom/Weighted Fair
Queuing (PQ/CQ/WFQ) support at the VC level - This allows
for finer granularity in the prioritization and queuing of
traffic, thus giving you more control over the traffic flow on
an individual VC.
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