Cisco Cisco Nexus 5010 Switch Libro bianco

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Introduction

This document provides design guidelines for implementing a unified data center fabric using Cisco Nexus

5000

Series Switches and QLogic second-generation converged network adapters (CNAs). Unified fabric implies that

multiple types of network traffic can be present on the same physical link: for example, the fabric may transport both

LAN and SAN traffic simultaneously over 10 Gigabit Ethernet. To achieve this unified approach, Fibre Channel over

Ethernet (FCoE) is used to transport storage traffic over an Ethernet network.

The Cisco Nexus 5000 Series offers the first unified fabric switches in the networking industry. They are field proven,

with more than 1000 customers and more than a year in the market. These powerful 10 Gigabit Ethernet LAN

switches can operate as fully functional SAN switches. Along with other products in the Cisco Nexus Family, the

Cisco Nexus 5000 Series can provide a data center access layer solution for connectivity to Gigabit Ethernet, 10

Gigabit Ethernet, and Fibre Channel ports.

CNAs are multifunction adapters with the characteristics of traditional network interface cards (NICs) and Fibre

Channel host bus adapters (HBAs). The QLogic QLE8100 family of CNAs is leading the second generation of CNAs

with significant enhancements in performance, power utilization, and server-platform applicability. Together,

QLE8100 adapters and the Cisco Nexus 5000 Series create a consolidated and optimized solution for server

connectivity in the data center.

This design guide provides a brief protocol discussion as well as configuration guidelines for implementing a unified

fabric with FCoE. For a more complete description of the FCoE protocol defined in the FC-BB-5 standard, please visit

http://www.t11.org/index.html

FCoE Protocol

FCoE provides a mechanism for transporting Fibre Channel frames on top of an Ethernet infrastructure. At a high

level, unaltered Fibre Channel frames are encapsulated in an Ethernet header and sent along a lossless Ethernet

fabric and decapsulated when they reach their target. Because no protocol conversion or state tables are required,

FCoE is considered to be a gatewayless technology. The FCoE architecture is completely based on the Fibre

Channel protocol. It provides the same host-to-switch and switch-to-switch connectivity as Fibre Channel fabrics.

FCoE also provides the same level of management and security found in Fibre Channel today with the use of zoning,

port world wide name (pWWN)–based port security, etc.

Because the transmission of Fibre Channel frames requires a lossless transport, an Ethernet network used to

transport FCoE frames must also provide the same lossless characteristics found in today’s Fibre Channel SANs.

These characteristics are provided by using Priority Flow Control (PFC), a revised implementation of the IEEE 802.3X

Ethernet standard known as Pause and currently passing through the standards body as IEEE 802.1Qbb.

PFC allows you to pause specific classes of service (CoSs) based on an IEEE 802.1p CoS value. FCoE traffic is

marked with a specific CoS value that corresponds to a no-drop class. When congestion occurs in the network, a

pause frame for the specified CoS value is sent to the server adapter, pausing the FCoE traffic. This approach is

similar to the buffer-credit flow control used in Fibre Channel fabrics.

In native Fibre Channel, initiators and targets log into the domain and name servers in Fibre Channel networks to

receive their Fibre Channel ID (FCID) so they can begin communicating on the fabric. In the same way, FCoE hosts

log into an FCoE fabric through a switching element found in the Cisco Nexus 5000 Series Switches. This element is

called the Fibre Channel forwarder (FCF). The FCF acts as the logical Fibre Channel switch for the end-host login

requests. After hosts are logged into an FCF, all traffic must pass through that FCF to reach its target. The Cisco

Nexus 5000 Series Switches can run in both switch mode and N-port virtualization (NPV) mode, which will be

discussed in the solution sections of this guide.