Dell Brocade G620 Brocade 8.0.1 Fabric OS Administratiors Guide - Page 103

Forward error correction, FEC limitations

Page 103 highlights

Performing Advanced Configuration Tasks 7. Enter the switchEnable command to re-enable the switch. With any of these settings, detection of duplicate PWWNs results in a RASLog. Ports that are restricted become persistently disabled, marked with the reason "Duplicate Port WWN detected". Forward error correction Forward error correction (FEC) provides a data transmission error control method by including redundant data (error-correcting code) to ensure error-free transmission on a specified port or port range. When 10/16G FEC is enabled, it can correct one burst of up to 11-bit errors in every 2112-bit transmission, whether the error is in a frame or a primitive. When 32G FEC is enabled, it can correct up to 7 symbols in every 5280-bit transmission. A symbol consists of 10 bits, so there are 528 symbols in every 5280-bit transmission. Since FEC is optional, the Transmitter Training Signal (TTS) was extended to include a means to negotiate FEC capabilities. FEC is negotiated and activated when both sides of the link have FEC enabled. The FEC active indicator in the Fabric OS indicates whether or not FEC was successfully negotiated or not. FEC uses unused bits within the signaling protocol to generate an Error Correcting Code (ECC) and correct bits as needed. The following considerations apply to FEC: ∙ FEC is always active on ports operating at 32 Gbps speed based on the standard, regardless of the FEC settings on the switch. ∙ FEC is supported on E_Ports on 16 Gbps-capable switches at 10/16G speeds. ∙ FEC is supported on the N_Ports and F_Ports of an Access Gateway using RDY, Normal (R_RDY), or Virtual Channel (VC_RDY) flow control modes. ∙ FEC is supported on F_Ports if the device attached to it supports FEC. ∙ FEC is enabled by default. ∙ FEC enables automatically when negotiation with a switch detects FEC capability. ∙ FEC persists after driver reloads and system reboots. ∙ FEC functions with features such as QoS, trunking, and BB_Credit recovery. FEC limitations The following limitations apply to Forward Error Correction (FEC): ∙ FEC is configurable only on 16 and 32 Gbps-capable switches (Brocade 6505, 6510, 6520, G620, M6505, 6547, 6548, 7840, and the Brocade DCX 8510 and X6 Director family). 32 Gbps is supported only with Fabric OS 8.0.0 and later. FEC is mandatory for ports operating at 32 Gbps speed and hence enabled by default. ∙ For switch-to-adaptor connections, FEC is supported only on QLogic BR-1860 and BR-1867 with driver v3.2.x on the Fabric Adapter ports operating in HBA mode connected to 16- and 32- Gbps Brocade switches running Fabric OS 7.1 and later. ∙ FEC is supported only on link speeds of 10-Gbps, 16-Gbps, and 32-Gbps regardless of whether the platform is FEC-capable. ∙ To connect between a switch and an HBA at 16 or 32 Gbps, both sides must be in the same mode (fixed speed, and FEC on or off) for them to communicate at that rate. If only one port has FEC enabled, neither port will be able to see the other. If the ports are in dynamic mode, then they may connect, but not at 16 or 32 Gbps. ∙ FEC is not active unless enabled when the HBA port speed changes to less than 16 or 32 Gbps. ∙ DWDM in transparent mode supports FEC. Enabling forward error correction Use the following procedure to enable FEC. Brocade Fabric OS Administration Guide, 8.0.1 53-1004111-02 103

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7.
Enter the
switchEnable
command to re-enable the switch.
With any of these settings, detection of duplicate PWWNs results in a RASLog. Ports that are restricted become persistently
disabled, marked with the reason "Duplicate Port WWN detected".
Forward error correction
Forward error correction (FEC) provides a data transmission error control method by including redundant data (error-correcting code) to
ensure error-free transmission on a specified port or port range. When 10/16G FEC is enabled, it can correct one burst of up to 11-bit
errors in every 2112-bit transmission, whether the error is in a frame or a primitive. When 32G FEC is enabled, it can correct up to 7
symbols in every 5280-bit transmission. A symbol consists of 10 bits, so there are 528 symbols in every 5280-bit transmission.
Since FEC is optional, the Transmitter Training Signal (TTS) was extended to include a means to negotiate FEC capabilities. FEC is
negotiated and activated when both sides of the link have FEC enabled. The FEC active indicator in the Fabric OS indicates whether or
not FEC was successfully negotiated or not. FEC uses unused bits within the signaling protocol to generate an Error Correcting Code
(ECC) and correct bits as needed.
The following considerations apply to FEC:
FEC is always active on ports operating at 32 Gbps speed based on the standard, regardless of the FEC settings on the switch.
FEC is supported on E_Ports on 16 Gbps-capable switches at 10/16G speeds.
FEC is supported on the N_Ports and F_Ports of an Access Gateway using RDY, Normal (R_RDY), or Virtual Channel
(VC_RDY) flow control modes.
FEC is supported on F_Ports if the device attached to it supports FEC.
FEC is enabled by default.
FEC enables automatically when negotiation with a switch detects FEC capability.
FEC persists after driver reloads and system reboots.
FEC functions with features such as QoS, trunking, and BB_Credit recovery.
FEC limitations
The following limitations apply to Forward Error Correction (FEC):
FEC is configurable only on 16 and 32 Gbps-capable switches (Brocade 6505, 6510, 6520, G620, M6505, 6547, 6548,
7840, and the Brocade DCX 8510 and X6 Director family). 32 Gbps is supported only with Fabric OS 8.0.0 and later. FEC is
mandatory for ports operating at 32 Gbps speed and hence enabled by default.
For switch-to-adaptor connections, FEC is supported only on QLogic BR-1860 and BR-1867 with driver v3.2.x on the Fabric
Adapter ports operating in HBA mode connected to 16- and 32- Gbps Brocade switches running Fabric OS 7.1 and later.
FEC is supported only on link speeds of 10-Gbps, 16-Gbps, and 32-Gbps regardless of whether the platform is FEC-capable.
To connect between a switch and an HBA at 16 or 32 Gbps, both sides must be in the same mode (fixed speed, and FEC on or
off) for them to communicate at that rate. If only one port has FEC enabled, neither port will be able to see the other. If the ports
are in dynamic mode, then they may connect, but not at 16 or 32 Gbps.
FEC is not active unless enabled when the HBA port speed changes to less than 16 or 32 Gbps.
DWDM in transparent mode supports FEC.
Enabling forward error correction
Use the following procedure to enable FEC.
Performing Advanced Configuration Tasks
Brocade Fabric OS Administration Guide, 8.0.1
53-1004111-02
103