Avaya Configuring Frame Relay Services Instrukcja Użytkownika Pobierz pdf (Strona 35)

Frame Relay Overview

117376-A Rev. A 2-15

Figure 2-8. Detecting and Controlling Network Congestion

If you enable the congestion control feature, you can specify the number of

FECN/BECN bits the router receives in a given time period before it stops

transmitting frames. While frames are going across the network, the frame relay

interface checks received packets for FECN and BECN bits set to 1. If the

interface receives the speciﬁed number of bits during the designated time period,

frame relay drops all trafﬁc destined for the PVC where there is congestion. When

the interface no longer receives these congestion notiﬁcations, the router resumes

transmission.

For example, suppose you set the congestion timer to 0.5 seconds and the

congestion count to 3. In this case, if an interface receives 3 FECNs or BECNs

within 0.5 seconds, the node stops sending frames (although it continues to

receive frames for this PVC). If the interface receives no FECNs or BECNs during

the next 0.5 seconds, the router resumes transmission. See Cha

pter 3,

“Customizing Frame Relay,” for instructions on conﬁguring the congestion

parameters.

If you enable congestion control and also enable trafﬁc shaping, you can queue or

throttle congested trafﬁc rather than drop it by choosing that value in the

Congestion Method parameter (see A

ppendix A for the parameter description).

Congestion

direction

BECN

FECN

Frame relay

network

node

Frame relay

network

node

Frame relay

network

node

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Avaya Configuring Frame Relay Services Instrukcja Użytkownika Strona 35