HP FlexNetwork 6600, Руководство по настройке

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Configuring FR QoS
Overview
On a FR interface, you can use generic QoS services to perform traffic policing, traffic shaping,
congestion management, and congestion avoidance. You can also use FR-specific QoS
mechanisms, including FR traffic shaping, FR traffic policing, FR congestion management, FR
discard eligibility (DE) rule list, and FR queuing management.
FR QoS is more flexible than generic QoS. It works on a per PVC basis, and generic QoS works on
a per interface basis. For more information about Frame Relay, see
Layer 2—WAN Configuration
Guide .
Figure 44 FR QoS implementation
FR QoS uses these parameters:
•
CIR ALLOW —Average transmission rate guaranteed on a VC. When no congestion occurs,
CIR ALLOW is guaranteed for data transmission.
•
CIR —Minimum transmitting rate that an FR VC provides. CIR is guaranteed for data
transmission even if congestion occurs in the network.
•
CBS —Traffic that an FR VC is committed to transmit within the interval of Tc. When congestion
occurs in the network, transmitting traffic of the CBS size is guaranteed by the FR network.
•
EBS —Maximum traffic that can exceed CBS on an FR VC within the interval of Tc. When
congestion occurs in the network, the traffic of EBS is dropped first. Transmitting traffic of the
EBS size is not guaranteed by the FR network.
FRTS
The functionality of FRTS
Frame relay traffic shaping (FRTS) limits the outgoing traffic rate and smoothes bursts for PVCs so
they can transmit traffic at a nearly constant rate.
FRTS applies to the outgoing interface of a switch. You can use FRTS to remove the bottleneck
created when the input rate of a device is slower than the output rate of the sending device.
As shown in Figure 45 , Router B transmits packets to Router A at 128 kbps, whereas the maximum
interface rate of Router A is only 64 kbps. This traffic rate disparity creates a bottleneck at the
interface that connects Router A to the FR network. To avoid packet loss, you can use FRTS at the
outgoing interface Serial 2/0/1 of Router B so the interface can transmit packets constantly at 64
kbps when no congestion is present. Even if congestion occurs in the network, Router B can still
transmit packets at the rate of 32 kbps.