Avaya Configuring Frame Relay Services Bedienungsanleitung PDF herunterladen (Seite 60)

Configuring Frame Relay Services

2-30

117376-C Rev. 00

CIR Configuration Guidelines

Consider the following when you configure traffic shaping.

• In general, the value you assign to the B

should equal 1/4 of the CIR to avoid

excessive queuing and dropped packets.

• If, however, you are sending frames that exceed the size of the B

, data travels

very slowly because the router must use multiple time periods to

accommodate the packet size and avoid exceeding the CIR. If setting the B

1/4 of the CIR yields a value lower than packet size, set the B

to 1/3 or even

1/2 of the CIR.

For example, a typical TFTP frame is 548 bytes. If the CIR is 16,000 bits, the

configured according to the 1/4 guideline would be 4,000 bits, or 500

bytes, which is not big enough to accommodate a TFTP frame. If you set the

to 16,000/2, or 1/2 CIR, the result is 8,000 bits, or a packet size of 1,000

bytes, which works, but may result in excessive queuing because the T

is 1/2

second. If you set the B

to 16,000/3 or 1/3 of CIR, the result is a B

of 5,333

bits or 666 bytes, much closer to the 548 TFTP frame size.

• If you cannot predict the typical frame size, monitor frame relay shaping

statistics for numbers of large frames and dropped frames. If either of these

numbers is increasing constantly or dramatically, adjust the B

to a higher

value in small increments.

WCP and CIR Enforcement

Consider the following when you are determining the best configuration for your

network:

• Data compression maximizes throughput and increases reliability.

• Traffic shaping increases reliability, controls congestion, and prioritizes

traffic.

• Compression and traffic shaping together maximize reliability, but at the

expense of throughput.

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Avaya Configuring Frame Relay Services Bedienungsanleitung Seite 60