Receive Data Field Size - Cisco MDS 9000 Series Configuration Manual

Receive Data Field Size

The Buffer-to-Buffer Credit Recovery feature can be used on any nonarbitrated loop link. This feature is most
useful on unreliable links, such as Metropolitan Area Networks (MANs) or WANs, but can also help on
shorter, high-loss links, such as a link with a faulty fiber connection.
Note The Buffer-to-Buffer Credit Recovery feature is not compatible with the distance extension (DE) feature, also
known as buffer-to-buffer credit spoofing. If you use intermediate optical equipment, such as dense
wavelength-division multiplexing (DWDM) or Fibre Channel bridges that use DE on Inter-Switch Links
(ISLs) between switches, then buffer-to-buffer credit recovery on both sides of an ISL must be disabled.
The following are the guidelines and restrictions for the Buffer-to-Buffer Credit Recovery feature:
• E ports
• F ports
Receive Data Field Size
You can configure the receive data field size for Fibre Channel interfaces. The default data field size is 2112
bytes, which supports frame lengths up to 2148 byte, the maximum size of Fibre Channel frames.
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• This feature is enabled by default on ISLs (E ports).
• This feature works on an ISL between a Cisco switch and a peer switch from any vendor, provided
this feature is supported on the peer switch.
• This feature is supported only on links that are in R_RDY flow control mode. It is not supported
on links that are in ER_RDY flow control mode.
• This feature is enabled by default on F ports.
• This feature works on an F port between a Cisco switch and a peer device from any vendor, provided
this feature is supported on the peer device.
Note
Some host bus adapters (HBAs) do not support the Buffer-to-Buffer Credit
Recovery feature. Others support this feature at only certain speeds. Check with
your HBA vendor about the exact configurations supported.
• N-Port ID Virtualization (NPIV) ports do not support buffer-to-buffer credit recovery for Cisco
N-Port Virtualizer (Cisco NPV) switch logins.
Configuring Interface Buffers