Lossless Ethernet; Logical Link Up/Down; Converged Network Adapters - Cisco AP775A - Nexus Converged Network Switch 5010 Configuration Manual

Information About FCoE

Lossless Ethernet

Standard Ethernet is a best-effort medium which means that it lacks any form of flow control. In the event of
congestion or collisions, Ethernet will drop packets. The higher level protocols detect the missing data and
retransmit the dropped packets.
To properly support Fibre Channel, Ethernet has been enhanced with a priority flow control (PFC) mechanism.

Logical Link Up/Down

The optional N5K-M1404 or N5K-M1008 expansion modules provide native 1/2/4-Gigabit Fibre Channel
ports to connect the Cisco Nexus 5000 Series switch to other Fibre Channel devices. On a native Fibre Channel
link, some configuration actions (such as changing the VSAN) require that you reset the interface status.
When you reset the interface status, the switch disables the interface and then immediately reenables the
interface.
If an Ethernet link provides FCoE service, do not reset the physical link because this action is disruptive to
all traffic on the link.
The logical link up/down feature allows the switch to reset an individual virtual link. The logical link down
is signaled with a FIP Clear Virtual Link message.
For pre-FIP CNAs, the switch sends a DCBX message to request the CNA to reset only the virtual Fibre
Channel interface.
If the CNA does not support the logical link level up/down feature, the CNA resets the physical link. In
Note
this case, all traffic on the Ethernet interface is disrupted.
DCBX-based FC Logical Link Status signaling only applies to FCoE sessions to pre-FIP CNAs.

Converged Network Adapters

The following types of CNAs are available:
• Hardware adapter
• FCoE software stack
Two generations of CNAs are supported by the Cisco Nexus 5000 Series switch:
• A FIP adapter uses the FIP to exchange information about its available capabilities and to negotiate the
• A pre-FIP adapter uses DCBX to exchange information about its available capabilities and to negotiate
OL-16597-01
◦ Works with the existing Fibre Channel host bus adapter (HBA) driver and Ethernet Network
Interface Card (NIC) driver in the server.
◦ Server operating system view of the network is unchanged; the CNA presents a SAN interface and
a LAN interface to the operating system.
◦ Runs on existing 10-Gigabit Ethernet adapters.
configurable values with the switch.
the configurable values with the switch.
Cisco Nexus 5000 Series Switch CLI Software Configuration Guide
Lossless Ethernet
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