Junos OS

Can someone explain the significance of yellow differential delay alarms?  i have read the docs, and they give to references for setting the yellow/red thresholds.   the default for a red alarm is 60ms, can someone explain why?

thanks

stine

Hi Stine,

When a particular constituent link in a bundle has a disproportionate delay, its "differential delay" could be considered harmful.  As the ml fragments are received, they have to be reassembled in sequential order.  If a particular link is introducing a large amount of delay, that can cause poor performance for the entire bundle.  It could also cause packet loss.

The operator can choose to configure two thresholds (yellow and red) for this.  The operator can also configure an action to remove, or stop transmitting on the link, when the red threshold is crossed.

http://www.juniper.net/techpubs/software/junos/junos92/swconfig-services/configuring-the-link-services-differential-delay.html#id-12545995

Regards,

Ben

Thanks, that is what i gleaned from the juniper docs and the FRF16.1 document.

I just wasn't completely sure of the implications of upping the red alarm value to 120 (from the default of 60).

stine

The current JUNOS default for red alarm is 120ms. It was increased from from 60ms to 120ms in JUNOS 8.1 release.  If you are on an earlier release, it is probably safe to increase your red alarm value to match the current JUNOS default of 120ms.

thanks, we increased yellow to 60 and red to 120, and have seen no adverse impact on customer traffic.

stine

One other thought.   If you have varying differential delay report on BOTH links in a 2-link bundle, what should we suspect????   I can see where a particular link causing yellow differential delay alarms, but not both of them alternately