[j-nsp] Re: verify QoS operation

[Rainer Clasen]

Guy Davies wrote:
> > -----Original Message-----
> > From: juniper-nsp-bounces at puck.nether.net 
> > [mailto:juniper-nsp-bounces at puck.nether.net] On Behalf Of Rainer Clasen
> > 
> > Erdem Sener wrote:
> > >  show interfaces <interface-name> extensive --> where you 
> > can see how 
> > > much traffic is transmitted/dropped for each queue.
> > 
> > These are outgoing stats. I'm looking for incoming Stats - in 
> > case I can't look at the output counters on the neighboring device.
> 
> A receiving device has no way of knowing how the transmitting device
> implemented classification, queueing, scheduling and congestion
> avoidance for each class of traffic. 

Uhhm, sorry for being inprecise. I actually don't care what the
transmitting device did internally. I do want to know how the emitted
packets (having DSCP or mpls-exp set) match in my incoming BA classifier.


> This decision is made at each hop
> and can be based on different models at each hop, particularly if your
> devices support different queueing, scheduling and congestion avoidance
> algorithms.  Assuming that the packets are marked at the ingress to the
> network, you can see the number of packets arriving marked with a
> particular class based on a particular marking (although I don't think
> JUNOS actually records those stats).  

jepp, these stat's are exactly what I'm looking for.

> However, this gives absolutely no
> indication of whether the transmitting device is actually queueing and
> scheduling packets appropriately (for some value of "appropriate") since
> you have no idea of the rate at which packets for each class are
> arriving at the transmitting device.  Each device is responsible for the
> QoS of outbound packets.  There is little benefit to implementing QoS
> inbound since the resource has already been utilized by the time you get
> to make a choice whether or not to drop a packet.

You're absolutely right. 

It's just that our network crosses some administrative borders - and I
want to check what I'm receiving from another department. Or to put it in
other words: I'm looking for an indication that they're setting the DSCP
properly. Jepp, I can write up a firewall filter + counters to check
this, but it'd be a lot more comfortable to take a quick glance at the
incoming classifer stats ... (which also indicates if my classification
matches their tagging).

Rainer

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