CBWFQ Congestion Allocations

Hi GS:

Question about the exact behaviors of CBWFQ.

Say you have this policy-map:

class TEST1
priority percent 15
class TEST2
bandwidth percent 30
class TEST3
bandwidth percent 30
class class-default
fair-queue
random-detect

So I understand the following:

TEST1 no congestion -> EF treatment for up to 15%, Can send up to line rate
with normal treatment (assuming none of the other classes are sending)

TEST1 congestion -> LLQ treatment for up to 15%, policed for greater than
15%

TEST2 no congestion -> Can Send Up To Line Rate (assuming none of the other
classes are sending)

TEST2 congestion -> AF treatment for up to 30%, excess ????

TEST3 no congestion -> Can Send Up To Line Rate (assuming none of the other
classes are sending)

TEST3 congestion -> AF treatment for up to 30%, excess ????

For TEST2/TEST3 congestion scenario, I see this statement from Cisco

http://www.cisco.com/en/US/tech/tk543/tk757/technologies_tech_note09186a0080103eae.shtml

If class-default does not need it, the unused bandwidth is available for use
by class TEST1 and class TEST2 (they use different names for their classes).
If both classes need the bandwidth, they share it in proportion to the
configured rates. In this configuration, the sharing ratio is 30:30 or 1:1

Instead of trying to word my questions, if someone could elaborate the
allocations in the following scenarios, it would be immensely helpful.

1) Scenario#1
TEST1 is sending traffic at exactly at 100% of line rate
TEST2 is sending traffic at exactly at 100% of line rate
TEST3 is sending traffic at exactly at 100% of line rate
class-default is sending traffic at exactly 100% of line rate

How is the bandwidth going to be allocated between them?

2) Scenario#2
TEST1 is sending traffic at exactly at 15% of line rate
TEST2 is sending traffic at exactly at 42.5% of line rate
TEST3 is sending traffic at exactly at 42.5% of line rate
class-default is sending traffic at exactly 50% of line rate

How is the bandwidth going to be allocated between them?

Also, I don't think the max-reserved-bandwidth assists in determining how
much bandwidth the default class gets when congestion occurs, but not sure?

Thanks very much,

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Received on Tue Sep 21 2010 - 11:32:59 ART