Re: constant FEC errors juniper mpc10e 400g

[Matt Erculiani <merculiani () gmail com>]

At some point, an error rate would exceed the ability of forward error
correction (FEC) overhead to compensate, resulting in CRC errors. You're
not seeing those so all is technically well.

It's not so much how many packets come in with errors that causes a
problem, but what percentage of each packet is corrupted. The former is
usually indicative of the latter though.

Just as Tom said, we're talking about a whole new animal than the NRZ we're
used to inside the building. Long-haul and DCI folks deal with this stuff
pretty regularly. The secret is keep everything clean and mind your bend
radii. We won't get away with some of what we used to get away with.

-Matt

On Wed, Apr 17, 2024 at 1:49 PM Aaron Gould <aaron1 () gvtc com> wrote:

> fec cliff?  is there a level of fec erros that i should be worried about
> then?  not sure what you mean.
>
> -Aaron
> On 4/17/2024 2:46 PM, Matt Erculiani wrote:
>
> I'm no TAC engineer, but the purpose of FEC is to take and correct errors
> when the port is going so fast that errors are simply inevitable. Working
> as Intended.
>
> Easier (read: cheaper) to build in some error correction than make the
> bits wiggle more reliably.
>
> No idea if that rate of increment is alarming or not, but you've not yet
> hit your FEC cliff so you appear to be fine.
>
> -Matt
>
> On Wed, Apr 17, 2024 at 1:40 PM Dominik Dobrowolski <
> dobrowolski.domino () gmail com> wrote:
>
> > Open a JTAC case,
> > That looks like a work for them
> >
> >
> > Kind Regards,
> > Dominik
> >
> > W dniu śr., 17.04.2024 o 21:36 Aaron Gould <aaron1 () gvtc com> napisał(a):
> >
> > > We recently added MPC10E-15C-MRATE cards to our MX960's to upgrade our core to 400g.  During initial testing of the 
> > > 400g interface (400GBASE-FR4), I see constant FEC errors.  FEC is new to me.  Anyone know why this is occurring?  
> > > Shown below, is an interface with no traffic, but seeing constant FEC errors.  This is (2) MX960's cabled directly, 
> > > no dwdm or anything between them... just a fiber patch cable.
> > >
> > >
> > >
> > > {master}
> > > me@mx960> clear interfaces statistics et-7/1/4
> > >
> > > {master}
> > > me@mx960> show interfaces et-7/1/4 | grep rror | refresh 2
> > > ---(refreshed at 2024-04-17 14:18:53 CDT)---
> > >   Link-level type: Ethernet, MTU: 1514, MRU: 1522, Speed: 400Gbps, BPDU Error: None, Loop Detect PDU Error: None, 
> > > Loopback: Disabled, Source filtering: Disabled,
> > >     Bit errors                             0
> > >     Errored blocks                         0
> > >   Ethernet FEC statistics              Errors
> > >     FEC Corrected Errors                    0
> > >     FEC Uncorrected Errors                  0
> > >     FEC Corrected Errors Rate               0
> > >     FEC Uncorrected Errors Rate             0
> > > ---(refreshed at 2024-04-17 14:18:55 CDT)---
> > >   Link-level type: Ethernet, MTU: 1514, MRU: 1522, Speed: 400Gbps, BPDU Error: None, Loop Detect PDU Error: None, 
> > > Loopback: Disabled, Source filtering: Disabled,
> > >     Bit errors                             0
> > >     Errored blocks                         0
> > >   Ethernet FEC statistics              Errors
> > >     FEC Corrected Errors                 4302
> > >     FEC Uncorrected Errors                  0
> > >     FEC Corrected Errors Rate               8
> > >     FEC Uncorrected Errors Rate             0
> > > ---(refreshed at 2024-04-17 14:18:57 CDT)---
> > >   Link-level type: Ethernet, MTU: 1514, MRU: 1522, Speed: 400Gbps, BPDU Error: None, Loop Detect PDU Error: None, 
> > > Loopback: Disabled, Source filtering: Disabled,
> > >     Bit errors                             0
> > >     Errored blocks                         0
> > >   Ethernet FEC statistics              Errors
> > >     FEC Corrected Errors                 8796
> > >     FEC Uncorrected Errors                  0
> > >     FEC Corrected Errors Rate             146
> > >     FEC Uncorrected Errors Rate             0
> > > ---(refreshed at 2024-04-17 14:18:59 CDT)---
> > >   Link-level type: Ethernet, MTU: 1514, MRU: 1522, Speed: 400Gbps, BPDU Error: None, Loop Detect PDU Error: None, 
> > > Loopback: Disabled, Source filtering: Disabled,
> > >     Bit errors                             0
> > >     Errored blocks                         0
> > >   Ethernet FEC statistics              Errors
> > >     FEC Corrected Errors                15582
> > >     FEC Uncorrected Errors                  0
> > >     FEC Corrected Errors Rate             111
> > >     FEC Uncorrected Errors Rate             0
> > > ---(refreshed at 2024-04-17 14:19:01 CDT)---
> > >   Link-level type: Ethernet, MTU: 1514, MRU: 1522, Speed: 400Gbps, BPDU Error: None, Loop Detect PDU Error: None, 
> > > Loopback: Disabled, Source filtering: Disabled,
> > >     Bit errors                             0
> > >     Errored blocks                         0
> > >   Ethernet FEC statistics              Errors
> > >     FEC Corrected Errors                20342
> > >     FEC Uncorrected Errors                  0
> > >     FEC Corrected Errors Rate             256
> > >     FEC Uncorrected Errors Rate             0
> > >
> > > {master}
> > > me@mx960> show interfaces et-7/1/4 | grep "put rate"
> > >   Input rate     : 0 bps (0 pps)
> > >   Output rate    : 0 bps (0 pps)
> > >
> > > {master}
> > > me@mx960> show interfaces et-7/1/4
> > > Physical interface: et-7/1/4, Enabled, Physical link is Up
> > >   Interface index: 226, SNMP ifIndex: 800
> > >   Link-level type: Ethernet, MTU: 1514, MRU: 1522, Speed: 400Gbps, BPDU Error: None, Loop Detect PDU Error: None, 
> > > Loopback: Disabled, Source filtering: Disabled,
> > >   Flow control: Enabled
> > >   Pad to minimum frame size: Disabled
> > >   Device flags   : Present Running
> > >   Interface flags: SNMP-Traps Internal: 0x4000
> > >   Link flags     : None
> > >   CoS queues     : 8 supported, 8 maximum usable queues
> > >   Schedulers     : 0
> > >   Last flapped   : 2024-04-17 13:55:28 CDT (00:36:19 ago)
> > >   Input rate     : 0 bps (0 pps)
> > >   Output rate    : 0 bps (0 pps)
> > >   Active alarms  : None
> > >   Active defects : None
> > >   PCS statistics                      Seconds
> > >     Bit errors                             0
> > >     Errored blocks                         0
> > >   Ethernet FEC Mode  :                 FEC119
> > >   Ethernet FEC statistics              Errors
> > >     FEC Corrected Errors               801787
> > >     FEC Uncorrected Errors                  0
> > >     FEC Corrected Errors Rate            2054
> > >     FEC Uncorrected Errors Rate             0
> > >   Link Degrade :
> > >     Link Monitoring                   :  Disable
> > >   Interface transmit statistics: Disabled
> > >
> > >   Logical interface et-7/1/4.0 (Index 420) (SNMP ifIndex 815)
> > >     Flags: Up SNMP-Traps 0x4004000 Encapsulation: ENET2
> > >     Input packets : 1
> > >     Output packets: 1
> > >     Protocol inet, MTU: 1500
> > >     Max nh cache: 75000, New hold nh limit: 75000, Curr nh cnt: 1, Curr new hold cnt: 0, NH drop cnt: 0
> > >       Flags: Sendbcast-pkt-to-re
> > >       Addresses, Flags: Is-Preferred Is-Primary
> > >         Destination: 10.10.10.76/30, Local: 10.10.10.77, Broadcast: 10.10.10.79
> > >
> > >
> > > --
> > > -Aaron
>
> --
> Matt Erculiani
>
> --
> -Aaron

-- 
Matt Erculiani