Re: constant FEC errors juniper mpc10e 400g

[Tom Beecher <beecher () beecher cc>]

Notes I found that I took from smart optical people :

"PAM4 runs at much lower SNRs than NRZ, because you're trying to read 4
distinct voltage levels instead of 2.Even the cleanest system will have
some of that, so the only way to make it usable is to have FEC in place."



On Wed, Apr 17, 2024 at 4:01 PM Fredrik Holmqvist / I2B <fredrik () i2b se>
wrote:

> Hi.
>
> Looks like normal behavior:
>
>
> https://supportportal.juniper.net/s/article/PTX-FEC-corrected-errors-increasing-on-link-between-QSFP-100GBASE-SR4-740-058734-and-QSFP-100G-SR4-T2-740-061405?language=en_US
>
> "An incrementing FEC Corrected Errors counter is normal for a link that
> is running FEC. It just indicates that the errored bits have been
> corrected by FEC. "
>
> "Therefore, the incrementing FEC Corrected Errors counter might only be
> indicating an interoperability issue between the optics from ......"
>
> ---
> Fredrik Holmqvist
> I2B & BBTA tjänster AB
> 08-590 90 000
>
> On 2024-04-17 21:36, Aaron Gould wrote:
> > 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