Re: constant FEC errors juniper mpc10e 400g

[Joel Busch via NANOG <nanog () nanog org>]

In my reading the 400GBASE-R Physical Coding Sublayer (PCS) always 
includes the FEC. This is defined in clause 119 of IEEE Std 802.3-2022, 
and most easily seen in "Figure 119–2—Functional block diagram" if you 
don't want to get buried in the prose. Nothing there seems to imply that 
the FEC is optional.

I'd be happy to be corrected though. It may well be that there is a 
method to reading these tomes, that I have not discovered yet. It is the 
first time I dove deep into any IEEE standard.

Best regards
Joel

On 17.04.2024 21:47, Tom Beecher wrote:
> Isn't FEC required by the 400G spec?
>
> On Wed, Apr 17, 2024 at 3:45 PM Aaron Gould <aaron1 () gvtc com 
> <mailto:aaron1 () gvtc com>> wrote:
>
>     __
>
>     i did.  Usually my NANOG and J-NSP email list gets me a quicker
>     solution than JTAC.
>
>     -Aaron
>
>     On 4/17/2024 2:37 PM, Dominik Dobrowolski 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
> >     <mailto: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  <http://10.10.10.76/30>, Local: 10.10.10.77, Broadcast: 10.10.10.79
> >
> >         -- 
> >         -Aaron
>     -- 
>     -Aaron

--
Joel Busch, Network

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