[j-nsp] Finding drops

[adamv0025 at netconsultings.com]

> Jason Lixfeld
> Sent: Monday, January 21, 2019 8:09 PM
> 
> Hi all,
> 
> I’m doing some RFC2544 tests through an MX204.  The tester is connected to
> et-0/0/2, and the test destination is somewhere out there via et-0/0/0.  64
> byte packets seem to be getting dropped, and I’m trying to find where on
> the box those drops are being recorded.
> 
> I’ve distilled the test down to generating 100 million 64 byte (UDP) packets to
> the destination, but the counters on et-0/0/2 read as though they’ve only
> received about 76.6% of those packets.
> 
> If I change the test to send 100 million 100 byte packets, the counters on et-
> 0/0/2 account for all packets.
> 
> I’ve tried looking at various output to find a counter that registers the missing
> packets, but I’m not having any luck.
> 
> Aside from 'show interface et-0/0/2 extensive’, I’ve looked here with no
> luck:
> 
> show interface queue et-0/0/2
> show pfe statistics traffic detail
> show pfe statistics exceptions
> show pfe statistics error
> 
> Somewhere else I should be looking?
>
Maybe any of the show commands in the below, if they show any drops?
https://kb.juniper.net/InfoCenter/index?page=content&id=KB26519&cat=FIREWALL&actp=LIST

I appreciate you're just concerned with packet count at the moment, but what is interesting is that if you change the rate at which you blast the packet at the box (bigger packets = slower PPS rate) the counters align all of a sudden.
That sort of indicates that for the 64B stream the packets are dropped by the platform -do you get the confirmation on the RX end of the tester about the missing packets? Not sure if this is about misaligned counters or actually about dropped packets?
  
How I read your test is that presumably this is 40G in and 40G out the same PFE (back to back packets @ 64B or 100B packets) 
So we should just consider single PFE performance but still the resulting PPS rate is noooowhere near the theoretical PPS budget.
How are the PFEs on 204 linked together (any sacrifices in the PFE BW/PPS budget to account for the fabric)? On MPC7E all 4 PFEs would be connected via fabric.  
So nothing really adds up here...  shouldn't be happening -not at these rates

adam