[j-nsp] QoS when there is no congestion

[Jason Healy]

On Nov 14, 2016, at 6:19 PM, Ross Halliday <ross.halliday at wtccommunications.ca> wrote:
> 
> This is called a "microburst", and WILL cause packet delay and reordering if the buffer isn't large enough. Anyone operating an IP SAN should be familiar with this concept. This is a big issue issue with switches used for iSCSI, such as the Cisco 3750s we started out with (despite common notions, QoS actually has to be enabled as the 'default'/'disabled' buffers are insufficient to deal with microbursts).

We're actually starting to experience this now.  We have a QFX with 10g and 1g links, and seeing significant drops on the 1g interfaces when traffic arrives on a 10g.  We have QoS enabled on our WAN connection, but haven't put it on the internal interfaces (where the drops are).

Do you have links to guidelines for basic QoS guidelines where you have this mismatched interface speed?  I haven't had a lot of luck finding out things like underlying buffer size, so that makes troubleshooting a little tricky.

Thanks,

Jason