QOS issue

Unanswered Question
Aug 27th, 2008

I have a network to the brach through tunnel over ISP.I notice class default is gulping most of my BW.So i tried to shape it using ''shape peak ''. I notice my ping to that branch started droping. My question is, does that means other traffic too like http ,exchange will be droped?

2.I configure a class-map .when i tried to add it to the tunnel int ,its says CBWFQ not allowed.please proffer a solution.

3.which is better, bandwidth percent,shaping and priority.

I have this problem too.
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Giuseppe Larosa Wed, 08/27/2008 - 11:00

Hello Just,

1) shaping provides buffering of exceeding traffic ICMP has a max time to wait for a response (and not dropping that is policing)

try to use an extended ping and increase the time to wait for an answer (ping timeout)

2) mark traffic with different IP precedence values on the lan interface. define a service-policy with class maps matching on IP precedence values (TOS value is copied on the external header by default)

apply this second CBWFQ service-policy to the output wan interface

3) use bandwidth percent outgoing, priority is for LLQ and should be used only for voip traffic. Remenber to verify that the bandwidth value is correct and reflects the real link speed

Hope to help

Giuseppe

Just Kennie Mon, 09/01/2008 - 01:19

1. why cant i add my policy map to the tunnelinterface.what need to be done.

2.You have not really answered my question as regards default traffic shaping.WHAT EFFECT DOES SHAPING DEFAULT TRAFFIC TO 8000 HAVE ON MY USEFUL TRAFFIC LIKE HTTP EXCHANGE.(REMEMBER I SAID ITS MAKING PING TIMEOUT,WILL OTHERS TOO SUFFER).

3.If i match three different traffic under same class map,and set BW % to 20.Does this mean they will share the 20,or each will have 20.

1. Can you post the output of the message you are seeing when applying it to the tunnel interface. By default a tunnel interface has a bandwith of 9k so you would need increase the bandwidth statement to match the linkspeed. Then you might want to use max-reserve-bandwitdth command on that interface since it will only use 75% by default. Post output and lets see what you are seeing.

2. Shaping all default traffic to 8000 depending on what shaping you are using - peak or average - will have a detrimental effect on all traffic not matched by the policies other than the class class-default traffic.

For instance, if you are doing the following:

class-map Voice

match ip dscp 46

class-map Video

match ip dscp 34

policy-map Mike

class-map Voice

bandwidth 96

class-map Video

bandwidth 384

class class-default

shape average 8000

interface tunnel 0

bandwidth 1536

max-reserve-bandwidth 100

service-policy output Mike

All traffic not matching the first 2 classes will be subject to matching in the default class, which in this example will be a peak shaper (8k - 16k) by default that will shape all other non-classified traffic to that limit. That will destroy you TCP applications as well as ICMP. Remember CIR is in b/s second unlike bandwidth statement which is in Kb/s.

3. So if you did this

class-map match-any MATCH-3

match ip dscp 46

match ip dscp 24

match ip dscp 34

policy-map Queue

class-map MATCH-3

bandwidth percent 20

interface serial0/3/0

bandwidth 1536

max-reserve-bandwidth 100

service-policy-output MATCH-3

Any traffic with the marking 24, 46, or 34 will get access to all 20 percent of the 1536Kbps on the interface or roughly 307Kb/s. However, if 3 traffic types are simultaneously on the interface they will all be placed in the same queue and will have a FIFO queue for the bandwidth. If WRED is enabled on the queue and the traffic is TCP based, then the DSCP values will affect who gets dropped first during congestion of the QUEUE. Remember, non of this will occur until the interface itself becomes congested.

Shapers = Always in effect

Queues = Only in effect when congestion on the interface occurs

Policers = Always in effect

Marking = Always in effect

HTH

mike

Marwan ALshawi Wed, 10/08/2008 - 04:59

to answer ur first question as the second one has been answer

the tunnel interface not a physical interface (virtual) and dose not include real bandwidth assigned to it so that the policy map will not work on it unlike other interfaces

I can assign a CBWFQ policy under the shaper

interface Tunnel1

bandwidth 512

ip address 1.1.1.1 255.255.255.0

tunnel source FastEthernet0/0

tunnel destination 10.1.1.1

service-policy output testtest

policy-map testtest

class class-default

shape peak 512000

service-policy Queue

policy-map Queue

class class-default

bandwidth 480

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