Configure "linear-red-profiles" on an ATM interface

[Samuel]

Hi Group,

I would like to configure "linear-red-profiles" on an ATM interface. I have found only this technical document: http://www.juniper.net/techpubs/software/junos/junos85/swconfig85-network-interfaces/id-10790945.html#id-10790945.

It is not very clear how to configure the different statements (high-plp-max-threshold, low-plp-max-threshold, queue-depth, high-plp-threshold and low-plp-threshold).

I would like to configure CoS to differentiate two kinds of traffic in a queue. 20% of "high-plp" and 80% of "low-plp".

Thanks for your help and explanations.

Regards,

Samuel

[davidjdv]

Hello Samuel,

The principal is the following: a linear-red profile has the following parameters:

- queue-depth: maximum queue-depth in cells - above this value, packets are always dropped

- high(/low)-plp-threshold: percentage of queue-depth, above which packets start to be dropped randomly

- high(/low)-plp-max-threshold: percentage of queue-depth, above which packets are dropped with 100% probability

Between the 2 thresholds the drop probability is linear (hence the name). 

 These parameters are associated with queues (= forwarding-classe) in the scheduler-map.

Here is a config example:

linear-red-profiles {
   be_red_2mb queue-depth 1040 high-plp-threshold 1 low-plp-threshold 25 high-plp-max-threshold 25 low-plp-max-threshold 100;
} 
forwarding-class be {
   priority low;
   transmit-weight percent 20;
   linear-red-profile be_red_2mb; 
}

In this example, when the queue-depth (of the BE class) reaches roughly 63 cells (half-way between 1 and 25%) then we drop high-PLP packets with a 50% chance - but we do not start dropping low-PLP packets before about 125 cells.

High-PLP packets will always be dropped when the queue exceeds 1010 cells whereas low-PLP packets can completely fill the queue.

Regards,

/david 

Message Edited by davidjdv on 09-08-2009 09:37 PM

[Samuel]

Thanks David!