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QoS bandwidth budget

I have this QoS policy:

class-map match-all Video-Control1

match access-group name Video-Control1

class-map match-any Prec5

match ip precedence 5

match ip rtp 16384 16383

class-map match-all Video-RTP1

match access-group name Video-RTP1

class-map match-all VoIP-RTP1

match access-group name VoIP-RTP1

class-map match-any Patch-management

match access-group name patch-servers

class-map match-all VoIP-Control1

match access-group name VoIP-Control1

!

!

policy-map QoS-Policy1

class Video-Control1

priority percent 5

class Video-RTP1

bandwidth 420

class VoIP-RTP1

priority percent 40

class VoIP-Control1

bandwidth 30

class Patch-management

class class-default

fair-queue

set dscp default

ip access-list extended Video-Control1

deny ip any any fragments

permit tcp any any range 5555 5587 dscp cs6

permit tcp any any eq 1720 dscp cs6

ip access-list extended Video-RTP1

deny ip any any fragments

permit udp any any range 2326 2837 dscp cs4

ip access-list extended VoIP-Control1

deny ip any any fragments

permit tcp any any range 2000 2002 dscp af31

permit tcp any any eq 1720 dscp af31

permit tcp any any range 11000 11999 dscp af31

permit udp any any eq 2427 dscp af31

permit tcp any any eq 2428 dscp af31

permit tcp any any eq 2748

ip access-list extended VoIP-RTP1

deny ip any any fragments

permit udp any any range 16384 32768 dscp ef

ip access-list extended patch-servers

permit ip host 10.16.5.25 any

permit ip host 10.16.5.30 any

sh policy-map interface

Serial2/0/2:0

Service-policy output: QoS-Policy1

Class-map: Video-Control1 (match-all)

0 packets, 0 bytes

5 minute offered rate 0 bps, drop rate 0 bps

Match: access-group name Video-Control1

Queueing

Strict Priority

Output Queue: Conversation 264

Bandwidth 5 (%)

Bandwidth 76 (kbps) Burst 1900 (Bytes)

(pkts matched/bytes matched) 0/0

(total drops/bytes drops) 0/0

Class-map: Video-RTP1 (match-all)

0 packets, 0 bytes

5 minute offered rate 0 bps, drop rate 0 bps

Match: access-group name Video-RTP1

Queueing

Output Queue: Conversation 265

Bandwidth 420 (kbps)Max Threshold 64 (packets)

(pkts matched/bytes matched) 0/0

(depth/total drops/no-buffer drops) 0/0/0

Class-map: VoIP-RTP1 (match-all)

17515 packets, 1120960 bytes

5 minute offered rate 0 bps, drop rate 0 bps

Match: access-group name VoIP-RTP1

Queueing

Strict Priority

Output Queue: Conversation 264

Bandwidth 40 (%)

Bandwidth 614 (kbps) Burst 15350 (Bytes)

(pkts matched/bytes matched) 684/43776

(total drops/bytes drops) 0/0

Class-map: VoIP-Control1 (match-all)

0 packets, 0 bytes

5 minute offered rate 0 bps, drop rate 0 bps

Match: access-group name VoIP-Control1

Queueing

Output Queue: Conversation 266

Bandwidth 30 (kbps)Max Threshold 64 (packets)

(pkts matched/bytes matched) 0/0

(depth/total drops/no-buffer drops) 0/0/0

Class-map: Patch-management (match-any)

0 packets, 0 bytes

5 minute offered rate 0 bps

Match: access-group name patch-servers

0 packets, 0 bytes

5 minute rate 0 bps

Class-map: class-default (match-any)

22590 packets, 5371873 bytes

5 minute offered rate 0 bps, drop rate 0 bps

Match: any

Queueing

Flow Based Fair Queueing

Maximum Number of Hashed Queues 256

(total queued/total drops/no-buffer drops) 0/0/0

QoS Set

dscp default

Packets marked 22297

Now when I add up the bandwidth allocated by this policy I come up with 1110kbps. The interface shows 1536kbps.

When I try to allocate 384 kbps to:

class Patch-management

bandwidth 384

I get:

I/f Serial2/0/2:0 class Patch-management requested bandwidth 384 (kbps), available only 12 (kbps)

What gives?

-mike

1 ACCEPTED SOLUTION

Accepted Solutions

Re: QoS bandwidth budget

Mike,

What you are seeing is the normal behavior. Router, by default, only allows 75% of available bandwidth for bandwidth allocation on an interface and it reserves the other 25% for best effort and control traffic. You can change this behavior with the command 'max-reserved-bandwidth (%)' under the interface. This would allow you to allocate more bandwidth (up to 100%) for QOS traffic. However, be careful when using this command as you don't want to starve the control & best effort traffic of any bandwidth.

http://www.cisco.com/univercd/cc/td/doc/product/software/ios124/124tcr/tqos_r/qos_m1ht.htm#wp1141987

HTH

Sundar

1 REPLY

Re: QoS bandwidth budget

Mike,

What you are seeing is the normal behavior. Router, by default, only allows 75% of available bandwidth for bandwidth allocation on an interface and it reserves the other 25% for best effort and control traffic. You can change this behavior with the command 'max-reserved-bandwidth (%)' under the interface. This would allow you to allocate more bandwidth (up to 100%) for QOS traffic. However, be careful when using this command as you don't want to starve the control & best effort traffic of any bandwidth.

http://www.cisco.com/univercd/cc/td/doc/product/software/ios124/124tcr/tqos_r/qos_m1ht.htm#wp1141987

HTH

Sundar

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