FEC is occurring at the PHY , below the PCS.
Even if you're not sending any traffic, all the ethernet control frame juju
is still going back and forth, which FEC may have to correct.
I *think* (but not 100% sure) that for anything that by spec requires FEC,
there is a default RS-FEC type that will be used, which *may* be able to be
changed by the device. Could be fixed though, I honestly cannot remember.
On Thu, Apr 18, 2024 at 1:35 PM Aaron Gould <aar...@gvtc.com> wrote:
> Not to belabor this, but so interesting... I need a FEC-for-Dummies or
> FEC-for-IP/Ethernet-Engineers...
>
> Shown below, my 400g interface with NO config at all... Interface has no
> traffic at all, no packets at all.... BUT, lots of FEC hits. Interesting
> this FEC-thing. I'd love to have a fiber splitter and see if wireshark could
> read it and show me what FEC looks like...but something tells me i would need
> a 400g sniffer to read it, lol
>
> It's like FEC (fec119 in this case) is this automatic thing running between
> interfaces (hardware i guess), with no protocols and nothing needed at all in
> order to function.
>
> -Aaron
>
>
> {master}
> me@mx960> show configuration interfaces et-7/1/4 | display set
>
> {master}
> me@mx960>
>
> {master}
> me@mx960> clear interfaces statistics et-7/1/4
>
> {master}
> me@mx960> show interfaces et-7/1/4 | grep packet
> Input packets : 0
> Output packets: 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 | grep rror
> 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 28209
> FEC Uncorrected Errors 0
> FEC Corrected Errors Rate 2347
> FEC Uncorrected Errors Rate 0
>
> {master}
> me@mx960> show interfaces et-7/1/4 | grep packet
> Input packets : 0
> Output packets: 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 | grep rror
> 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 45153
> FEC Uncorrected Errors 0
> FEC Corrected Errors Rate 29
> FEC Uncorrected Errors Rate 0
>
> {master}
> me@mx960> show interfaces et-7/1/4 | grep packet
> Input packets : 0
> Output packets: 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 | grep rror
> 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 57339
> FEC Uncorrected Errors 0
> FEC Corrected Errors Rate 2378
> FEC Uncorrected Errors Rate 0
>
> {master}
> me@mx960>
>
>
> On 4/18/2024 7:13 AM, Mark Tinka wrote:
>
>
>
> On 4/17/24 23:24, Aaron Gould wrote:
>
> Well JTAC just said that it seems ok, and that 400g is going to show 4x
> more than 100g "This is due to having to synchronize much more to support
> higher data."
>
>
> We've seen the same between Juniper and Arista boxes in the same rack
> running at 100G, despite cleaning fibres, swapping optics, moving ports,
> moving line cards, e.t.c. TAC said it's a non-issue, and to be expected,
> and shared the same KB's.
>
> It's a bit disconcerting when you plot the data on your NMS, but it's not
> material.
>
> Mark.
>
> --
> -Aaron
>
>
