Cisco-Router--ATM-Query

Q1) When to use any of above mentioned ?
Q2) How to calculate value for CBR or VBR-RT ?

For e.g :

ID(config)#interface ATM6/0.777 point-to-point
ID(config-subif)# pvc att-per 1/777
ID(config-if-atm-vc)#vbr-rt ?
  <1-44209>  Peak Cell Rate(PCR) in Kbps

ID(config-if-atm-vc)#vbr-rt 8000 ?
  <1-8000>  Average Cell Rate in Kbps

ID(config-if-atm-vc)#cbr ?
  <1-44209>  Peak Cell Rate in Kbps

ID(config-if-atm-vc)#cbr 44000 ?


If i have 2Mb PVC and 45Mb PVC ..please guide me how to calculate values ..

LVL 6
SanjeevlokeAsked:
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lucasrgCommented:
well the qos on atm work like this.


cbr is constant bit rate so you just have to configure the rate you don't need to do bust or any other value.


VBR-RT is variable bit rate for real time application like voice so you have to configure a minimal and a maximal values the minimal is to keep ATM from starting to drop cells with is bad for a voice application and this kind of cell are less likely to be dropped by the switch than the VBR-NRT which are used for video application.

there are other call UBR and ABR that are used for internet circuits because the only use the available bandwidth.

to calculate the values what you do is that you divide the value ten times and that would be the burst or the maximal values for the VBR circuits.


i hope this helps.
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SanjeevlokeAuthor Commented:
Q1) When to use any of above mentioned ?

CBR/VBR-RT/VBR-NRT
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ArneLoviusCommented:
it has been a while (+10 years) since I worked with ATM circuits....

this has a reasonable description of the different classes http://en.wikipedia.org/wiki/Asynchronous_Transfer_Mode

are you provisioning the circuits as a provider or subscriber?

some more context would be useful

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SanjeevlokeAuthor Commented:
As a subscriber...
I want to understand QoS part on ATM interface like CBR,VBR-RT and VBR-NRT
possible scenarios when to use CBR,VBR-RT and VBR-NRT.

and how to calculate values to specified  for 2mb,10mb ,45Mb circuits .
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SanjeevlokeAuthor Commented:
OK
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