[j-nsp] A conceptual advice on QoS is needed

[Victor Sudakov]

Dear Colleagues,

I have read the "Day One: Deploying Basic QoS" book. There are a
couple of questions left concering EX4200 switches.

1. In a BA classifier, traffic is assigned to a forwarding-class and a
loss-priority. It is quite clear how to use forwarding-classes,
but where and how do I use the loss-priority parameter? I figure it's
probably used as a hook in the scheduler config somewhere, but where
exactly?

Moreover, it seems that when I classify traffic as 
"forwarding-class XXX loss-priority high", it simply gets discarded
on default scheduler-maps.

2. How come I cannot set loss-priority in a port-based classifier?

3.  The book says: "It is strongly advised to ensure that every
forwarding-class for which any traffic may appear on an interface to
which the scheduler-map is applied has a corresponding scheduler. If
no scheduler is identified for a forwarding-class, and traffic arrives
on that interface for that class, it will receive no explicitly
configured service (for example, no buffers, no transmit-rate) and
will therefore suffer very poor service unless the interface is
completely unused by other traffic."

Is it possible to configure a single dummy FIFO egress scheduler which
would be forwarding-classes and loss-priority agnostic? There are
interfaces where I only need to apply rewrite-rules on egress without
prioritizing. 

-- 
Victor Sudakov,  VAS4-RIPE, VAS47-RIPN
sip:sudakov at sibptus.tomsk.ru