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When a direct link between QSFP-100GBASE-SR4(740-058734) and QSFP-100G-SR4-T2(740-061405) is Up with normal Diagnostics Optics Monitoring data (DOM) on both QSFP types, the "FEC Corrected Errors" rate may be seen to be increasing on the interfaces.
This article clarifies that an incrementing "FEC Corrected Errors" rate is normal for a link that is running Forward Error Correction (FEC) because it indicates that the errored bits have been corrected by FEC already.
An experimental test result is shown as follows. FEC91 is RS-FEC, which is compliant with IEEE 802.3-2015 Clause 91.
Test Topology
FPC 10 : FPC3-SFF-PTX-1X
PIC 0 : 10x100/10x40/40x10GE
Xcvr 0 QSFP-100G-SR4-T2 (740-061405) ------ MMF ------ Xcvr 1 QSFP-100GBASE-SR4 (740-058734)
Xcvr 2 QSFP-100G-SR4-T2 (740-061405) ------ MMF ------ Xcvr 3 QSFP-100GBASE-SR4 (740-058734) The following outputs show the FEC supporting hardware and highlight the incrementing FEC Corrected Errors rate counter.
User@ptx3000> show chassis hardware
Hardware inventory:
Item Version Part number Serial number Description
Chassis JN1260BC8AJC PTX3000
Midplane REV 27 750-044645 ACPG6953 Backplane
FPM REV 02 760-059087 ACNX8519 Front Panel Display
PSM 0 REV 06 740-044981 1EDK5161015 AC 12V Power Supply
PSM 1 REV 06 740-044981 1EDK5161026 AC 12V Power Supply
PSM 2 REV 06 740-044981 1EDK5161030 AC 12V Power Supply
PSM 3 REV 06 740-044981 1EDK5040298 AC 12V Power Supply
Routing Engine 0 REV 12 740-026942 P737A-006333 RE-DUO-2600
Routing Engine 1 REV 12 740-026942 P737A-006300 RE-DUO-2600
CB 0 REV 06 750-058864 ACPN2836 Control Board
CB 1 REV 06 750-058864 ACPN2840 Control Board
FPC 10 REV 40 750-057064 ACPJ9207 FPC3-SFF-PTX-1X
CPU BUILTIN BUILTIN SMPC PMB
PIC 0 REV 06 750-070203 BCAJ3689 10x100/10x40/40x10GE
Xcvr 0 REV 01 740-061405 1ECQ11150LC QSFP-100G-SR4-T2
Xcvr 1 REV 01 740-058734 1ACQ111401P QSFP-100GBASE-SR4
Xcvr 2 REV 01 740-061405 1ECQ11150H1 QSFP-100G-SR4-T2
Xcvr 3 REV 01 740-058734 1ACQ11460EN QSFP-100GBASE-SR4
User@ptx3000> show chassis pic fpc-slot 10 pic-slot 0
FPC slot 10, PIC slot 0 information:
Type 10x100/10x40/40x10GE
State Online
PIC version 1.6
Uptime 7 minutes, 55 seconds
PIC port information:
Fiber Xcvr vendor Wave- Xcvr JNPR
Port Cable type type Xcvr vendor part number length Firmware Rev
0 100GBASE SR4 MM JUNIPER-AVAGO AFBR-89CDDZ-JU1 850 nm 0.0 REV 01
1 100GBASE SR4 MM JUNIPER-FINISAR FTLC9551REPM-J3 850 nm 0.0 REV 01
2 100GBASE SR4 MM JUNIPER-AVAGO AFBR-89CDDZ-JU1 850 nm 0.0 REV 01
3 100GBASE SR4 MM JUNIPER-FINISAR FTLC9551REPM-J3 850 nm 0.0 REV 01
User@ptx3000> show interfaces et-10/0/0 extensive
Physical interface: et-10/0/0, Enabled, Physical link is Up
Interface index: 129, SNMP ifIndex: 504, Generation: 132
Link-level type: Ethernet, MTU: 1514, Speed: 100Gbps, BPDU Error: None,
Loop Detect PDU Error: None, Loopback: Disabled, Source filtering: Disabled,
Flow control: Enabled
Device flags : Present Running
Interface flags: SNMP-Traps Internal: 0x4000
Link flags : None
CoS queues : 8 supported, 8 maximum usable queues
Hold-times : Up 0 ms, Down 0 ms
Damping : half-life: 0 sec, max-suppress: 0 sec, reuse: 0, suppress: 0, state: unsuppressed
Current address: 08:b2:58:66:d3:a7, Hardware address: 08:b2:58:66:d3:a7
Last flapped : 2019-09-18 08:36:29 IST (00:12:49 ago)
Statistics last cleared: Never
Traffic statistics:
Input bytes : 0 0 bps
Output bytes : 0 0 bps
Input packets: 0 0 pps
Output packets: 0 0 pps
IPv6 transit statistics:
Input bytes : 0
Output bytes : 0
Input packets: 0
Output packets: 0
Input errors:
Errors: 0, Drops: 0, Framing errors: 0, Runts: 0, Policed discards: 0, L3 incompletes: 0,
L2 channel errors: 0, L2 mismatch timeouts: 0, FIFO errors: 0, Resource errors: 0
Output errors:
Carrier transitions: 1, Errors: 0, Drops: 0, Collisions: 0, Aged packets: 0, FIFO errors: 0,
HS link CRC errors: 0, MTU errors: 0, Resource errors: 0
Egress queues: 8 supported, 4 in use
Queue counters: Queued packets Transmitted packets Dropped packets
0 0 0 0
1 0 0 0
2 0 0 0
3 0 0 0
Queue number: Mapped forwarding classes
0 best-effort
1 expedited-forwarding
2 assured-forwarding
3 network-control
Active alarms : None
Active defects : None
PCS statistics Seconds
Bit errors 0
Errored blocks 0
Ethernet FEC Mode : FEC91
Ethernet FEC statistics Errors
FEC Corrected Errors 0
FEC Uncorrected Errors 0
FEC Corrected Errors Rate 0
FEC Uncorrected Errors Rate 0
User@ptx3000> show interfaces et-10/0/1 extensive
Physical interface: et-10/0/1, Enabled, Physical link is Up
Interface index: 130, SNMP ifIndex: 505, Generation: 133
Link-level type: Ethernet, MTU: 1514, Speed: 100Gbps, BPDU Error: None,
Loop Detect PDU Error: None, Loopback: Disabled, Source filtering: Disabled,
Flow control: Enabled
Device flags : Present Running
Interface flags: SNMP-Traps Internal: 0x4000
Link flags : None
CoS queues : 8 supported, 8 maximum usable queues
Hold-times : Up 0 ms, Down 0 ms
Damping : half-life: 0 sec, max-suppress: 0 sec, reuse: 0, suppress: 0, state: unsuppressed
Current address: 08:b2:58:66:d3:ab, Hardware address: 08:b2:58:66:d3:ab
Last flapped : 2019-09-18 08:36:28 IST (00:12:55 ago)
Statistics last cleared: Never
Traffic statistics:
Input bytes : 0 0 bps
Output bytes : 0 0 bps
Input packets: 0 0 pps
Output packets: 0 0 pps
IPv6 transit statistics:
Input bytes : 0
Output bytes : 0
Input packets: 0
Output packets: 0
Input errors:
Errors: 0, Drops: 0, Framing errors: 0, Runts: 0, Policed discards: 0, L3 incompletes: 0,
L2 channel errors: 0, L2 mismatch timeouts: 0, FIFO errors: 0, Resource errors: 0
Output errors:
Carrier transitions: 1, Errors: 0, Drops: 0, Collisions: 0, Aged packets: 0, FIFO errors: 0,
HS link CRC errors: 0, MTU errors: 0, Resource errors: 0
Egress queues: 8 supported, 4 in use
Queue counters: Queued packets Transmitted packets Dropped packets
0 0 0 0
1 0 0 0
2 0 0 0
3 0 0 0
Queue number: Mapped forwarding classes
0 best-effort
1 expedited-forwarding
2 assured-forwarding
3 network-control
Active alarms : None
Active defects : None
PCS statistics Seconds
Bit errors 0
Errored blocks 0
Ethernet FEC Mode : FEC91
Ethernet FEC statistics Errors
FEC Corrected Errors 15583531
FEC Uncorrected Errors 0
FEC Corrected Errors Rate 21816
FEC Uncorrected Errors Rate 0
User@ptx3000> show interfaces et-10/0/2 extensive
Physical interface: et-10/0/2, Enabled, Physical link is Up
Interface index: 131, SNMP ifIndex: 643, Generation: 134
Link-level type: Ethernet, MTU: 1514, Speed: 100Gbps, BPDU Error: None,
Loop Detect PDU Error: None, Loopback: Disabled, Source filtering: Disabled,
Flow control: Enabled
Device flags : Present Running
Interface flags: SNMP-Traps Internal: 0x4000
Link flags : None
CoS queues : 8 supported, 8 maximum usable queues
Hold-times : Up 0 ms, Down 0 ms
Damping : half-life: 0 sec, max-suppress: 0 sec, reuse: 0, suppress: 0, state: unsuppressed
Current address: 08:b2:58:66:d3:af, Hardware address: 08:b2:58:66:d3:af
Last flapped : 2019-09-18 08:36:28 IST (00:12:59 ago)
Statistics last cleared: Never
Traffic statistics:
Input bytes : 0 0 bps
Output bytes : 0 0 bps
Input packets: 0 0 pps
Output packets: 0 0 pps
IPv6 transit statistics:
Input bytes : 0
Output bytes : 0
Input packets: 0
Output packets: 0
Input errors:
Errors: 0, Drops: 0, Framing errors: 0, Runts: 0, Policed discards: 0, L3 incompletes: 0,
L2 channel errors: 0, L2 mismatch timeouts: 0, FIFO errors: 0, Resource errors: 0
Output errors:
Carrier transitions: 1, Errors: 0, Drops: 0, Collisions: 0, Aged packets: 0, FIFO errors: 0,
HS link CRC errors: 0, MTU errors: 0, Resource errors: 0
Egress queues: 8 supported, 4 in use
Queue counters: Queued packets Transmitted packets Dropped packets
0 0 0 0
1 0 0 0
2 0 0 0
3 0 0 0
Queue number: Mapped forwarding classes
0 best-effort
1 expedited-forwarding
2 assured-forwarding
3 network-control
Active alarms : None
Active defects : None
PCS statistics Seconds
Bit errors 365
Errored blocks 365
Ethernet FEC Mode : FEC91
Ethernet FEC statistics Errors
FEC Corrected Errors 4756489624
FEC Uncorrected Errors 640004
FEC Corrected Errors Rate 5832363
FEC Uncorrected Errors Rate 0
User@ptx3000> show interfaces et-10/0/3 extensive
Physical interface: et-10/0/3, Enabled, Physical link is Up
Interface index: 132, SNMP ifIndex: 644, Generation: 135
Link-level type: Ethernet, MTU: 1514, Speed: 100Gbps, BPDU Error: None,
Loop Detect PDU Error: None, Loopback: Disabled, Source filtering: Disabled,
Flow control: Enabled
Device flags : Present Running
Interface flags: SNMP-Traps Internal: 0x4000
Link flags : None
CoS queues : 8 supported, 8 maximum usable queues
Hold-times : Up 0 ms, Down 0 ms
Damping : half-life: 0 sec, max-suppress: 0 sec, reuse: 0, suppress: 0, state: unsuppressed
Current address: 08:b2:58:66:d3:b3, Hardware address: 08:b2:58:66:d3:b3
Last flapped : 2019-09-18 08:36:28 IST (00:13:04 ago)
Statistics last cleared: Never
Traffic statistics:
Input bytes : 0 0 bps
Output bytes : 0 0 bps
Input packets: 0 0 pps
Output packets: 0 0 pps
IPv6 transit statistics:
Input bytes : 0
Output bytes : 0
Input packets: 0
Output packets: 0
Input errors:
Errors: 0, Drops: 0, Framing errors: 0, Runts: 0, Policed discards: 0, L3 incompletes: 0,
L2 channel errors: 0, L2 mismatch timeouts: 0, FIFO errors: 0, Resource errors: 0
Output errors:
Carrier transitions: 1, Errors: 0, Drops: 0, Collisions: 0, Aged packets: 0, FIFO errors: 0,
HS link CRC errors: 0, MTU errors: 0, Resource errors: 0
Egress queues: 8 supported, 4 in use
Queue counters: Queued packets Transmitted packets Dropped packets
0 0 0 0
1 0 0 0
2 0 0 0
3 0 0 0
Queue number: Mapped forwarding classes
0 best-effort
1 expedited-forwarding
2 assured-forwarding
3 network-control
Active alarms : None
Active defects : None
PCS statistics Seconds
Bit errors 0
Errored blocks 0
Ethernet FEC Mode : FEC91
Ethernet FEC statistics Errors
FEC Corrected Errors 348021
FEC Uncorrected Errors 0
FEC Corrected Errors Rate 532
FEC Uncorrected Errors Rate 0
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.
It should be possible to connect QSFP-100GBASE-SR4 and QSFP-100G-SR4-T2 with each other because connecting any pair of 100G SR4 optics is supported as long as they conform to the 100GBASE-SR4 IEEE 802.3 standard. Therefore, the incrementing FEC Corrected Errors counter might only be indicating an interoperability issue between the optics from Finisar and FIT (FIT used to be Avago) because Juniper uses both vendors for each of the SKUs.
Below are the vendor part numbers that have been shipped for both 100G SR4 SKUs:
QSFP-100G-SR4-T2 (740-061405) FIT: AFBR-89CDDZ-JU1 Finisar: FTLC9551REPM-J1 QSFP-100GBASE-SR4 (740-058734) FIT: AFBR-89CDDZ-JU2 Finisar: FTLC9551REPM-J3
FEC Corrected Errors is not a problem because it only indicates a possible vendor interoperability issue between Finisar and FIT. Hence no action is required.
However, if the FEC Uncorrected Errors rate is high, it certainly indicates a problem. If FEC Uncorrected Errors increase, open a Support case for troubleshooting the issue.
Note: If the FEC Uncorrected Errors rate is low (<BER 10^-12), there should not be any real problems as per the IEEE 802.3 standard.
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