Data Center I/O Consolidation - Cisco Nexus 5500 Series Configuration Manual

Overview

Data Center I/O Consolidation

For FCoE traffic, the Ethernet link must provide a lossless service. Ethernet links on Cisco Nexus devices
provide two mechanisms to ensure lossless transport for FCoE traffic: link-level flow control and priority
flow control.
IEEE 802.3x link-level flow control allows a congested receiver to signal the far end to pause the data
transmission for a short period of time. The pause functionality is applied to all the traffic on the link.
The priority flow control (PFC) feature applies pause functionality to specific classes of traffic on the Ethernet
link. For example, PFC can provide lossless service for the FCoE traffic and best-effort service for the standard
Ethernet traffic. PFC can provide different levels of service to specific classes of Ethernet traffic (using IEEE
802.1p traffic classes).

Data Center I/O Consolidation

I/O consolidation allows a single network technology to carry IP, SAN, and IPC traffic. FCoE is the single
network technology that allows I/O consolidation. The upper Fibre Channel layers are unchanged, so the Fibre
Channel operational model is maintained. FCoE network management and configuration is similar to a native
Fibre Channel network.
Cisco Nexus devices use FCoE to carry Fibre Channel and Ethernet traffic on the same physical Ethernet
connection between the switch and the server. At the server, the connection terminates to a converged network
adapter (CNA). The adapter presents two interfaces to the server's operating system (OS): one Ethernet NIC
interface and one Fibre Channel host bus adapter (HBA) interface.
The server OS is not aware of the FCoE encapsulation (see the following figure). At the switch, the incoming
Ethernet port separates the Ethernet and Fibre Channel traffic (using EtherType to differentiate the frames).
Ethernet frames and Fibre Channel frames are switched to their respective network-side interfaces.
Figure 1: I/O Consolidation
Cisco Nexus 5500 Series NX-OS Fundamentals Configuration Guide, Release 7.x
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