IE Lab16, QoS descrepancy

From: Igor M. (imanassypov@rogers.com)
Date: Mon Aug 25 2008 - 14:41:31 ART


Hi,

If anyone has gone through lab 16 of the internetwork expert, I am having troubles understanding their solutions for QoS question 7.1. To remind - R3, R4, R5 where R3 is a hub, R3-R5 is provisioned at 512Kbps while R3-R4 is provisioned at 1024Kbps. Both spokes (R4, & R5) are allowed to burst up to AR if they have credit.

Now, if I calculate the pertaining values for lets say R3-R5 circuit, I come up with
cir = 512000
bc = 5120 (to allow 10ms for Tc)
and be = Tc x (AR - CIR) = 10 x ( 1544 - 512 ) = 10320.
In their solution the same circuit R3-R5 be = 10240.

Where am I wrong in my calculations?

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I.M., M.Eng. P.Eng.

Network Architect

CI Investments

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Blogs and organic groups at http://www.ccie.net



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