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Introduction to Fibre Channel over Ethernet 1Posted to the Cisco Learning Network www.cisco.com/go/learningnetwork 2008 Cisco Systems, Inc. All rights reserved.

Introduction to FibreChannel over Ethernet

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2Posted to the Cisco Learning Network www.cisco.com/go/learningnetwork 2008 Cisco Systems, Inc. All rights reserved.

What is FCoE?

Conceptually, Fibre Channel over Ethernet (FCoE) can bebroken down into three components:

Encapsulation of a Native Fibre Channel Frame into anEthernet frame

The extension of Ethernet to become a lossless fabricThe replacing of a Fibre Channel link with MAC addresses

in a lossless Ethernet fabric

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Why the Need for FCoE?

Evolving business requirements

Enterprises have a need for these abilities:

High speed

High density

Low latency

Consolidated networks

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FCoE is a New Proposed Standard

Being developed by the International Committee forInformation Technology Standards (INCITS) T11committee

Maps Fibre Chanel natively over Ethernet

Independent of Ethernet forwarding scheme

Current proposal

Leverages lossless Ethernet fabric

Maintains the Fibre Channel operational model

Includes newly approved frame format

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FCoE Requirements Keep Fibre Channel and Ethernet forwarding orthogonal

No need to change Ethernet forwarding to support FCoE.Keep the model agnostic to the forwarding used in Ethernet.

Possibility to have the FCoE forwarder function only on a

subset of the switches composing an Ethernet network Ability to enable FCoE forwarding on a per-VLAN basis

VLANs and virtual storage area networks (VSANs)

assigned from the same numbering space

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FCoE Terminology

Ethernet HBA: an FCoE-enabled host bus adapter

(HBA)

FCoE forwarder: the function inside a switch performingthe Fibre Channel data and control planes

Possibly providing Fibre Channel services to Ethernet HBAs

FCoE gateway: the function inside a switch performingthe encapsulation and decapsulation of Fibre Channel

frames in Ethernet frames Inter-Fabric router: a function that is performing Fibre

Channel routing among different Fibre Channel fabrics

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FC-4 -Protocol Map

FC-2 -Framing

FC-0 -Physical

FC-1 -Data (Encoding /Decoding

FC-3 -Services

Fibre Channel Stack

IEEE 802.3Layers

Fibre ChannelLevels

(unchanged)

FC-4 -Protocol Map

FC-3 -Services

FC-2 -Framing

FCoE

FCoE Mapping

2 - MAC

1 - Physical

From Fibre Channel to FCoE

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Destination MAC Address

Source MAC Address

IEEE 802.1Q Tag

ET = FCoE Ver Reserved

Reserved

Reserved

4 bits

12 bits

Reserved SOFEncapsulated Fibre Channel Frame

(including FC-CRC)

ReservedEOF

8 bits

8 bits

Ethernet FCS

Frame Format

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Architectural Differences with IP Routing

FCoE forwarder and IP router

Like an IP router, an FCoE forwarder forwards Fibre Channel framesbased on a Layer 3 lookup.

That is, based on the D_ID (Domain_ID)

Unlike an IP router, an FCoE forwarder forwards Fibre Channel

frames in a single VLAN. An IP router forwards IP packets across different VLANs

Fibre Channel router and IP router

Like an IP router, a Fibre Channel router forwards Fibre Channelframes across different VLANs.

Unlike an IP router, a Fibre Channel router performs some addresstranslation functions.

For example, a rewrite of the D_ID or the S_ID

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FCoE: FC over Ethernet

Fibre Channel carried over DCE as a Layer 3 protocol

Data Center Ethernet

FCoE

Fibre Channel

SCSI

IP

TCP

Applications

UDP

An FCoE forwarder is explicitly addressed by an Ethernet HBA

(via the Fibre Channel MAC address).

An FCoE forwarder receives FCoE frames addressed to its Fibre Channel MAC addressand forwards them based on the D_ID of the encapsulated Fibre Channel frame.

An FCoE forwarder rewrites the source address and destination address of an FCoEframe.

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FCoE Packaging FCoE may be added:

to an Ethernet switch

to a Fibre Channel switch

The result is two different Fibre Channel forwarder logical models:

Type C (connected)

A Fibre Channel forwarder in a VLAN is logically coupled with oneEthernet bridge function attached to all Ethernet ports of theswitch belonging to that VLAN.

For example, FCoE implemented on top of an Ethernet switch.

Type D (disconnected)

A Fibre Channel forwarder in a VLAN is logically coupled withmore than one Ethernet bridge function, each attached to asubset of the Ethernet ports of the switch belonging to that VLAN.

For example, FCoE implemented in line cards of a Fibre Channelswitch.

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Summary

FCoE is the encapsulation of native Fibre Channel into an Ethernetframe.

Need for FCoE is due to evolving business requirements.

FCoE is being developed by INCITS T11.

FCoE must utilize jumbo frames (or the 2.5K baby jumbo).

Fibre Channel forwarder forwards frames based on a Layer 3lookup.

FCoE may be added to an Ethernet switch or to a Fibre Channelswitch.

Encapsulation of Fibre Channel frames occurs through themapping of Fibre Channel onto Ethernet.

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Documents

Cisco Fcoe