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Fibre Channel over Ethernet Initialization Protocol

What You Will Learn

On June 3, 2009, INCITS T11 approved and released the final revision of FC-BB-5, the T11 standard covering Fibre

Channel over Ethernet (FCoE). Cisco has been actively participating in the definition of FC-BB-5, and the Cisco

Nexus

™

5000 Series Switches have offered an FCoE implementation since the time the T11 committee released a

draft of FC-BB-5 that finalized the FCoE encapsulation (frame format) and data plane aspects. Since then, the T11

committee has focused on the FCoE control plane functions, and specifically on the virtual link establishment and

management functions known as FCoE Initialization Protocol (FIP).

The Cisco Nexus 5000 Series FCoE implementation could establish point-to-point FCoE links to first-generation

converged network adapters (CNAs) without FIP, but FIP is required to build more complex topologies in which

FCoE links can map to an Ethernet path that consists of more than one Ethernet link segment. The final revision of

FC-BB-5 completed the definition of FIP and was soon followed by Cisco

NX-OS Software Release 4.1(3)N1(1), the

first software release for the Cisco Nexus 5000 Series that offers FIP capabilities.

This document describes FIP as it is defined in FC-BB-5 and shows how FIP and FC-BB-5 map to the Cisco Nexus

5000 Series software implementation.

Background

Fibre Channel has established itself in the storage industry as the best-performing and most reliable transport for

block storage. This role is the result of years of innovation and tuning that have built a solid ecosystem of end-to-end

services and tools to satisfy the storage needs of mission-critical applications.

FCoE offers the capability to transport Fibre Channel payloads on top of an Ethernet network. FCoE originates from

the simple observation that as long as the same ecosystem of end-to-end services and tools remains available, and

as long as performance is not affected, users do not have a preference for a physical representation of data on a

wire. By offering equivalent quality-of-service (QoS) semantics, and by presenting the same data-link-layer payloads

to upper-layer services, an Ethernet link can effectively replace a Fibre Channel link at the physical layer.

If the technology offered only this, however, FCoE would not be very interesting. With Fibre Channel frames carried

on an Ethernet cable, the next step is to take these frames and mix them with regular Ethernet frames on the same

wire. By enabling the same Ethernet link to carry both Fibre Channel and Ethernet payloads, FCoE increases

utilization of the physical infrastructure and therefore reduces the total number of network ports that must exist

overall. In this basic model, the Fibre Channel physical layer is replaced by an Ethernet physical layer, Fibre

Channel and Ethernet frames share the same wire, and each switch forwards each individual frame from one ingress

port to one egress port using the forwarding rules that are appropriate: Fibre Channel rules (based on T11 FC-SW)

for Fibre Channel frames, and Ethernet rules (based on IEEE 802.1D) for Ethernet frames.

This model is the approach that the Cisco Nexus 5000 Series followed in incorporating FCoE when the product line

was first released. The one-to-one mapping between a Fibre Channel link and an Ethernet link is a simple way to

build an FCoE network that can potentially extend end to end, from initiators to targets, through a number of

switching points. The switching points can perform switching with Fibre Channel rules and can implement the entire

stack of Fibre Channel services (starting from FC-2). The fabric is just a Fibre Channel fabric that happens to use

Ethernet to encode signals from one point to the next.