© 2004 Cisco Systems, Inc. All rights reserved. Printed in USA.
Presentation_ID.scr
999999
© 2004 Cisco Systems, Inc. All rights reserved.
RST-3508
9805_05_2004_c2
Cisco IOS-Based Supervisor
QoS Flow Summary
Shared
Memory
RX
Classify
Police
Queue 1
Queue 2
Queue 3
Queue 4
Rewrite
Info
Sched TX
DBL
Classification Based on:
Default DSCP Port Setting
Port “Trusted” CoS or DSCP
Layer 2/3/4 ACLs
Policing via ACLs
Police Action:
Mark
Drop
Based:
Byte Rate
Burst
(Token Bucket)
Rewrites TOS
Field in IP
Header and
802.1p/ISL
CoS Field
In-Coming
Encapsulation
Can Be 802.1Q,
802.1p, ISL,
or None
Sharing and Shaping
and Strict Priority Q3
to Schedule Between
Output Queues
Out-Going
Encapsulation
Can Be 802.1Q,
802.1p, ISL,
or None
Dynamic Buffer Limiting
(Supervisor II Plus
Supervisor IV
Supervisor V )
Congestion Avoidance
100100100
© 2004 Cisco Systems, Inc. All rights reserved.
RST-3508
9805_05_2004_c2
Tx Queuing and Scheduling
• Queue selection based on “internal DSCP”
Default DSCP on port
Trust CoS/DSCP
Via service policies
• Switch-wide DSCP to Tx queue map, not per-port!
• Shaping: Max rate per queue
• Sharing: Min rate per queue
• Strict priority on queue 3
• All in hardware at wire rate
Sharing,
Strict Priority
Shaping
Ethernet
MAC
DSCP to
Queue Map
Q1
Q2
Q3
Q4
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