3Com MSR 50 Series Configuration Manual page 1714

1714 C 91: F
HAPTER RAME
R Q S C
ELAY O ONFIGURATION
and interval Tc = CBS / CIR ALLOW = 125 ms. When the interval is in the range of
0 to 250ms, DTE will transmit packets to DCE at 64 kbps and DCE will normally
forward these packets at 64 kbps. When the interval is in the range of 250 to 500
ms, DTE will transmit packets at 100 kbps, and DCE will forward them at 100
kbps. In this case, however, the flag bit of DE in the headers of packets exceeding
CBS will be set to 1. After 500 milliseconds, DTE will transmit the packets to DCE
at 150 kbps, and DCE will forward them at 128 kbps. As for the packets
exceeding CBS but within CBS + EBS, the flag bit of DE in their headers will be set
to 1, and the packets exceeding CBS + EBS will be discarded directly.
Frame Relay queuing management
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. Frame Relay PVC queues may
be defined without Frame Relay traffic shaping is enabled, but it will only be
functional after the traffic shaping is enabled. Their relations are illustrated in the
following figure.
Figure 493 Frame Relay queuing
The Frame Relay PVC queuing types include:
FIFO (First-In First-Out Queuing)
■
PQ (Priority Queuing)
■
CQ (Custom Queuing)
■
WFQ (Weighted Fair Queuing)
■
CBQ (Class-Based Queuing)
■
RTPQ (Realtime Transport Protocol Priority Queuing)
■
PVC PQ (PVC Priority Queuing)
■
Among them, FIFO, PQ, CQ, WFQ, CBQ and RTPQ are general queues. For the
detailed introduction, refer to
PVC PQ can only be applied on the Frame Relay interface. It is applied on a Frame
Relay interface. There are four types of PVC priority queues: top, middle, normal
and bottom. Their queuing 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
"Congestion Management Policies" on page 1649.