07-16-2008 08:21 AM - edited 03-03-2019 10:45 PM
Hi, I'm interested in how folks implement max-reserved-bandwidth with their qos(strict priority/CBWFQ/etc.)
any help is appreciated
Solved! Go to Solution.
07-16-2008 03:55 PM
Yes, default class should be working.
On many Cisco routers, bandwidth in the default class configures a FIFO queue. Without it, normal default is flow based fair-queue. Also on most routers, default class flow queues compete for bandwidth with defined classes. However, the LLQ, when there's congestion, preempts all the other queues (up to its defined cap).
07-16-2008 09:03 AM
Hi,
The sum of all bandwidth allocation on an interface should not exceed 75 percent of the available bandwidth on an interface. The remaining 25 percent of bandwidth is used for overhead, including Layer 2 overhead, control traffic, and best-effort traffic, so If you need to allocate more than 75 percent for CBWFQ and IP RTP Priority, you can use the this command,
here is an example, below we have 3 different classes (HTTP/FTP/ICMP)in addition to the default class, i will allocate 500k for each class and only 44k for the default class,
since CBWFQ can not allocate more than 75% of the interface bandwidth the above bandwidth allocation doesn't comply with default bandwidth of serial interfaces which is 1544 (1544x25/100=386 so 1544-386=1158) so 1158 is the maximum available bandwidth for allocation on this interface, so the router will never accept policy-map with bandwidth over than 1158 unless we use max-reserved-bandwidth command.
PE1#conf t
PE1(config)#class-map http
PE1(config-cmap)#match protocol http
PE1(config-cmap)#class-map ftp
PE1(config-cmap)#match protocol ftp
PE1(config-cmap)#class-map icmp
PE1(config-cmap)#match protocol icmp
PE1(config)#policy-map qos
PE1(config-pmap)#class http
PE1(config-pmap-c)#bandwidth 500
PE1(config-pmap-c)#class ftp
PE1(config-pmap-c)#bandwidth 500
PE1(config-pmap-c)#class icmp
PE1(config-pmap-c)#bandwidth 500
PE1(config-pmap-c)#class class-default
PE1(config-pmap-c)#bandwidth 44
PE1(config-pmap)#int s2/1
PE1(config-if)#service-policy output qos
I/f Serial2/1 class icmp requested bandwidth 500 (kbps), available only 158 (kbps)
PE1#show queueing int s2/1 | inc Bandwidth
Available Bandwidth 1158 kilobits/sec
PE1(config-if)#max-reserved-bandwidth 100
PE1(config-if)#do show queueing int s2/1 | inc Bandwidth
Available Bandwidth 1544 kilobits/sec
PE1(config-if)#service-policy output qos
PE1(config-if)#do show queueing int s2/1 | inc Bandwidth
Available Bandwidth 0 kilobits/sec
Best Regards,
Mounir Mohamed
07-16-2008 09:25 AM
Thanks for the the information. My concern is with how I need to implement the command. I have a config similar to :
Building configuration...
Current configuration : 281 bytes
!
interface GigabitEthernet0/1
description WLAN VLAN 10.226.70.x/24 (10.226.70.4)
ip address 10.26.7.1 255.255.255.0
duplex auto
speed auto
no snmp trap link-status
max-reserved-bandwidth 95
service-policy output VOICE-WAN
##########sh class-map
Class Map match-any class-default (id 0)
Match any
Class Map match-any VOICE (id 1)
Match ip dscp ef (46)
Match ip dscp cs3 (24)
Match ip dscp af31 (26)
Match protocol rtp audio
Class Map match-all KEHTrfc (id 2)
Match access-group name KTEmlHP3k
#######sh policy-map
Policy Map VOICE-WAN
Class VOICE
Strict Priority
Bandwidth 500 (kbps) Burst 12500 (Bytes)
Class class-default
Flow based Fair Queueing
Bandwidth 0 (kbps)
exponential weight 9
class min-threshold max-threshold mark-probablity
----------------------------------------------------------
0 - - 1/10
1 - - 1/10
2 - - 1/10
3 - - 1/10
4 - - 1/10
5 - - 1/10
6 - - 1/10
7 - - 1/10
rsvp - - 1/10
does the max-reserved-bandwidth give more bandwidth to the default class?
07-16-2008 09:56 AM
By default free or unallocated bandwidth available for overhead and best-effort traffic which is handled by the default-class (class-default) so Yes if you use this command the reset of bandwidth will increased and so class-default will use more bandwidth.
07-16-2008 10:16 AM
okay, that's great...
Now, as noted above in the sh class-map command there is no bandwidth assigned to the default class. Does this mean that the default class is working or not?
07-16-2008 03:55 PM
Yes, default class should be working.
On many Cisco routers, bandwidth in the default class configures a FIFO queue. Without it, normal default is flow based fair-queue. Also on most routers, default class flow queues compete for bandwidth with defined classes. However, the LLQ, when there's congestion, preempts all the other queues (up to its defined cap).
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