3Com 10014299 manual Kbps CI R ALLOWº£ 64 Kbps

Configure Frame Relay QoS 261

Figure 85 Frame Relay traffic policing

	DTE	DCE	NNI	Frame-relay
	S0	S0
Router			Router	network
A	192 kbps	64 kbps	B
	CIR ALLOW = 64 kbps
		CBS = 8000 bit

EBS = 8000 bit

As shown in the above figure, Router A at the user side transmits packets at 192 kbps to Router B at the switching side. However, Router B only wants to provide the 64 kbps bandwidth for Router A. In this case, you need to configure the Frame Relay traffic policing at the DCE side of Router B.

Frame Relay traffic policing can only be applied on the DCE interface on a router. It can monitor the traffic transmitted from the DTE side. When the traffic size is smaller than CBS, the packets can be normally transmitted, and the router will not process the packets. When the traffic size is larger than CBS and smaller than EBS

+CBS, the packets can be normally transmitted. In this case, however, as for those packets in the traffic exceeding CBS, the router will mark the flag bit of DE in the Frame Relay packet headers to 1. When the traffic size is larger than CBS + EBS, the router will transmit the traffic within CBS + EBS, and discard the traffic exceeding CBS + EBS. As for the traffic of EBS which is the size exceeding CBS, the router will mark the flag bit of DE in the Frame Relay packet headers to 1.

Figure 86 Fundamentals of Frame Relay traffic policing

	RATE
150	Kbps
CI R ALLOW+EI Rº£ 128	Kbps			Discarded
100	Kbps			DE
CI R ALLOWº£ 64 Kbps
			Transmit
	0ms	125ms	250ms 375ms	500ms 625ms	750ms	TI ME

As shown in the above figure, the parameters of Frame Relay traffic policing are respectively set to be: CIR ALLOW = 64 kbps, CBS = 64000 bit, EBS = 64000 bit, and interval Tc = CBS / CIR ALLOW = 1s. When the interval is in the range of 0 to 2s, 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 2 to 4ms, 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 4 seconds, 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.