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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
It is imperative that DSCP classification be performed on all packets prior to their arriving at the WAN
edges. This allows queueing and congestion-avoidance to be performed at the WAN edge based strictly
on DSCP markings, which reduces WAN aggregator CPU overhead.
Note
The default class-map match setting is match-all. Therefore, when you attempt to classify
mutually-exclusive traffic flows (such as differing DSCP values), it is important to explicitly use the
match-any
qualifier when defining the class-map.
shows how four classes of traffic (gold, silver, bronze, and less-than-best-effort) can be
classified into three queues.
Example 4-1
Four Classes in Three Queues
ip cef
For distributed platforms, use ip cef distributed.
!
...
!
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
!
policy-map WAN-EDGE
class GOLD-DATA
bandwidth percent 25
random-detect dscp-based
class SILVER-DATA
bandwidth percent 15
random-detect dscp-based
class class-default
fair-queue
random-detect dscp-based
random-detect dscp 0 96 128 10
The queue depth and thresholds are increased for the default
random-detect dscp 2 70 128 10
queue. This allows more traffic and increases the portability (to
random-detect dscp 4 58 128 10
Frame Relay Traffic-Shaping [FRTS] interfaces and VIP platforms)
random-detect dscp 6 44 128 10
of the configuration.
The best effort traffic and the less-than-best-effort traffic (DSCP 2, 4, 6) share the default queue, but the
random-detect thresholds have been adjusted such that less-than-best-effort traffic is dropped
significantly sooner than regular best-effort traffic.
shows how four classes of traffic (gold, silver, bronze, and less-than-best-effort) can be
classified into four queues.