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Community Member

QOS - division of unused bandwidth

Hi,

Can someone explain to me how unused bandwidth (Allocated to a class but not used) is divided when a policy is applied to a interface ?

Is it according to there bandwidth allocation,

2 REPLIES
Community Member

Re: QOS - division of unused bandwidth

Here is a page stating, that unused bandwidth is allocated according to the size of the class.

Can anyone confirm this ?

How much will be allocated to the default class, if has not been assigned a % of bandwidth ?

http://www.cisco.com/warp/public/105/priorityvsbw.html#howisunusedbandwidthallocated

Purple

Re: QOS - division of unused bandwidth

Hi,

That is correct. Classes with bandwidth or priority statements configured will get the first chance to use up any spare bandwidth. If there is still some bandwidth remaining, it will go to class-default.

Consider the following:

policy-map Test

class1

band 128

class2

band 256

If the above polocy is applied to a 512k link and the offered traffic is:

512k for class1 and

512k for class2,

the resulting allocation of bandwidth will be:

class1 will get 128/(128+256)*512 = 171k

class2 will get 256/(128+256)*512 = 341k

Class-default will get nothing.

Hope that helps - pls rate the post if it does.

Paresh

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