4-8
Cisco AVVID Network Infrastructure Enterprise Quality of Service Design
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Chapter 4 QoS in an AVVID-Enabled Wide-Area Network
QoS Recommendations for WAN Aggregation Routers
Example 4-2
Four-Classes in Four Queues
ip cef
!
...
!
class-map match-any GOLD-DATA
match ip dscp af21
match ip dscp af22
match ip dscp af23
!
class-map match-any SILVER-DATA
match ip dscp af11
match ip dscp af12
match ip dscp af13
!
class-map match-any <BE-DATA
match ip dscp 2
match ip dscp 4
match ip dscp 6
!
policy-map WAN-EDGE
class GOLD-DATA
bandwidth percent 20
random-detect dscp-based
class SILVER-DATA
bandwidth percent 15
random-detect dscp-based
class <BE-DATA
bandwidth percent 5
random-detect dscp-based
random-detect dscp 2 32 40 10
random-detect dscp 4 28 40 10
random-detect dscp 6 24 40 10
class class-default
fair-queue
For distributed platforms, use ip cef distributed and use:
class <BE-DATA
bandwidth percent 5
random-detect dscp-based
random-detect dscp 2 70 128 10
random-detect dscp 4 58 128 10
random-detect dscp 6 44 128 10
Although it may appear contradictory that less-than-best-effort traffic is assigned a minimum bandwidth
guarantee, the logic is based on the fact that CBWFQ will drop packets from a given class when the link
is congested and the particular queue for the traffic class is full. Therefore, during times of congestion,
all applications designated less-than-best-effort will receive a maximum of 5% of the pipe and then be
dropped. Also, the random-detect thresholds have been adjusted to drop less-than-best-effort traffic in
order of importance (6 before 4 before 2, which corresponds to the AFxy drop-preference model).
This design is more efficient than strict policing, as these bandwidth-intensive, non-critical applications
have the ability to make use of additional bandwidth if it is available.
Note
Remember that this policy does not take effect until it is bound to an interface with a service-policy
statement. Service-policy statements are discussed in the
section.