3com 3031 Instruccion De Instalación

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HAPTER

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RAME

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Besides the Frame Relay PVC queues, the Frame Relay interface also owns an 
interface queue. In the case that the Frame Relay traffic shaping is not enabled, 
there will only be the Frame Relay interface queue. After it is enabled, both Frame 
Relay PVC queues and the Frame Relay interface queue will exist. Their relations 
are illustrated in the following figure.

Figure 250   Frame Relay queuing

The Frame Relay PVC queuing types include 

■

FIFO (first-in first-out queuing), 

■

PQ (priority queuing), 

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CQ (custom queuing), 

■

WFQ (weighted fair queuing), 

■

CBQ (class-based queuing),

■

RTPQ (real-time transport protocol priority queuing),

■

PVC PQ (PVC priority queuing)

Among them, FIFO, PQ, CQ, WFQ, CBQ and RTPQs are general queues. For the 
detailed introduction, refer to Part XI “QoS”. 

PVC PQ can only be applied on the Frame Relay interface. There are four types of 
PVC priority queues: top, middle, normal and bottom. Their queueing priorities are 
listed in descending order. The packets on the same PVC can only enter one type 
of PVC priority queues, and the packets on different PVCs enter different PVC 
priority queues on the interface, depending on the priorities of the PVCs. The PVC 
PQ transmitting policy is as follows: Based on the queueing priority, transmit the 
packets in the queue with low priority after those in the queue with high priority 
are transmitted.

Frame Relay virtual circuit queuing may be FIFO, PQ, CQ, WFQ, CBQ and RTPQ. 
Only RTPQ can coexist with others. 

When Frame Relay traffic shaping is enabled, only FIFO, RTPQ and PVC PQ are 
available

Frame Relay congestion management can process the Frame Relay packets 
whenever there is network congestion. It will discard the packets that are marked 
with the DE flag bit. At the same time, it will notify other devices on the network 
about the congestion. 

PVC Queue

Interface queue