[j-nsp] DSCP-marked traffic mysteriously being dropped by MX960

[Wayne Tucker]

On Mon, Jul 23, 2012 at 8:02 AM, John Neiberger <jneiberger at gmail.com> wrote:
>
> Well, we have applied the scheduler map to the interface but we're
> still seeing 100% drops in queue 1, which is where CS2 is hitting. It
> is literally dropping every packet in queue 1, but I don't understand
> enough about what I'm seeing to understand why.
>
>  Queue counters:       Queued packets  Transmitted packets      Dropped packets
>     0 HSD, BASIC-D                4775                 4775                    0
>     1 MNGMT, VOIP-                4913                    0                 4913
>     2 UET, CDN, VO                   0                    0                    0
>     3 VOIP-BEARER,                  81                   81                    0

It looks like you're mapping multiple classes to the same queue.  I
try to avoid doing that - from what I recall it comes with an added
requirement that all forwarding classes in that queue use the same
scheduler.

I noticed in your previous output that you're setting the
loss-priority for the management traffic to high - are you sure you
want to do that?  It's a little counter-intuitive, but loss-priority
high is the traffic you want to drop before low (or medium, etc.).
Depending on the drop profile used it's pretty much guaranteed to not
get any resources in cases like this where there is no applicable
scheduler (the aggressive settings keep the packets from even getting
into a queue).  In fact, it's probably why you're seeing these drops
in the first place - the drop profile for loss-priority low is usually
liberal enough that the packets still get queued and forwarded.

>                 classifiers {
>                     dscp DSCPV4-CLASSIFIER;

Can you paste the config for DSCPV4-CLASSIFIER?

:w