Congestion Management; De Rule List - HP A6600 Configuration Manual

 WFQ
 CBQ
 RTPQ
 PVC PQ
Of these queuing mechanisms, FIFO, PQ, CQ, WFQ, CBQ, and RTPQ are universal queuing mechanisms.
For more information, see
PVC PQ can only be applied on FR interfaces. PVC priority queues fall into the following types: top, middle,
normal, and bottom, in descending priority order. The packets from a certain PVC must be assigned to one
PVC priority queue, and the packets from PVCs are assigned to PVC priority queues on the interface as
configured. PVC PQ dequeues and sends packets in the high-priority queue and then packets in the
low-priority queue.
FR PVC queuing mechanisms include FIFO, PQ, CQ, WFQ, CBQ, and RTPQ. Only RTPQ can coexist with
another queuing mechanism. Among these queuing mechanisms, the A6600 routers support only FIFO.
With FRTS enabled on an interface, only FIFO, RTPQ, or PVC PQ is available on the interface.

Congestion management

FR congestion management can process FR packets when congestion occurs in the network. It drops the
packets with the DE flag bits set to 1 and notifies other routers on the network about the congestion.
FR congestion management is applied on the outgoing interface of an FR switching device. If no congestion
occurs, the FR switching device forwards the FR packets without any processing. If congestion occurs, packets
with the FE flag bits set to 1 are dropped. With forward packets to be forwarded, the FECN flag bits in the
FR packet headers are set to 1. With backward packets on the same PVC, the BECN flag bits in the FR packet
headers are set to 1. If no backward packets is transmitted within a period, the router automatically transmits
the packets with the BECN flag bits set to 1 to the calling DTE.
Figure 44 FR congestion management implementation
DTE
Router A

DE rule list

In an FR network, packets with the DE flag bits set to 1 are dropped first when congestion occurs in the
network. DE rule lists are applied on the FR PVCs of a router, with each DE rule list containing multiple DE
rules. If a packet transmitted over the PVC matches the rules in the DE rule list, its DE flag bit is set to 1. The
packet is dropped first when congestion occurs in the network.
―Configuring congestion
Data flow direction
BECN
DCE NNI
FECN
Router B
management.‖
Frame-Relay
帧中继网络
Frame relay
network
network
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