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Fibre Channel Overview

OverviewBy providing an overview of the Fibre Channel Protocol, students will be better suited to learn

the concepts and functions of the Cisco MDS 9000 Family switches. These switches are used to

create a Fibre Channel-based storage area network (SAN) and offer specific tools to manage

and troubleshoot Fibre Channel switched fabric networks.

Objectives

This lesson teaches you to identify and describe the characteristics and structure of the Fibre

Channel protocol, in order to demonstrate the fundamental knowledge needed to study the

installation, configuration, and troubleshooting of Fibre Channel-based systems, givenquestions related to specific aspects of this protocol.

Upon completing this lesson, you will be able to:

Describe Fibre Channel protocol basic characteristics and structure

Explain the protocol layers of Fibre Channel

Explain the Fibre Channel frame format

Explain the addressing scheme for Fibre Channel

Explain the functions of Fibre Channel services

Explain the functions of the Fibre Channel Name Server

Explain the Fibre Channel fabric and port login processes

Explain the Fibre Channel exchanges and sequences


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1-34 MDS 9000 Configuration and Troubleshooting (MDSCT) v1.0 Copyright 2003, Cisco Systems, Inc

Explain the Fibre Channel flow control methods

Explain the classes of service in an Fibre Channel network

Learner Skills and Knowledge

To fully benefit from this lesson, you must have these prerequisite skills and knowledge:

Network Storage Architectures

Outline

This lesson includes these sections:

Overview

Fibre Channel Protocol Basics

Fibre Channel Protocol Layers

Fibre Channel Frame Format

Fibre Channel Addressing

Fibre Channel Services

Fibre Channel Name Server

Fibre Channel Fabric and Port Login

Fibre Channel Exchanges and Sequences

Fibre Channel Flow Control

Fibre Channel Class of Service

Summary

Lesson Review


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Copyright 2003, Cisco Systems, Inc Network Storage Technology Overview 1-35

Fibre Channel Protocol BasicsThis section describes the basic characteristics and structure of the Fibre Channel protocol.

Fibre ChannelIntroduction

Fibre Channel is a bi-directional, point-to-point, serial data channel that provides a general

transport mechanism for ULPs such as SCSI, IP, and HIPPI.

Fibre Channel was introduced in order to overcome the physical and protocol limitations of

SCSI, which is limited by distance, speed, number of storage devices per chain, resiliency, lack

of device sharing, and management flexibility.

Fibre Channel offers a greater sustained data rate (1 or 2 G bps; 10 G bps, future), loop or

switched networks for device sharing and low latency, distances of 10 km or greater with

extension devices, virtually unlimited devices in a fabric, non-disruptive device addition, and

centralized management with local or remote access.

2003, Cisco Systems, Inc. All rights reserved. Deploying MDS 9000 Systems v1.0Module 1, Lesson 2 - 5

Fibre Channel - Introduction

Fibre Channel - An integrated set of ANSI standardsdeveloped to combine the best characteristics of bothNetwork I/O and Channel I/O.

Additionally, Fibre Channel overcomes the physical andprotocol limitations of SCSI.

Fibre Channel is a bi-directional, point-to-point, serialdata channel.

It provides a general transport mechanism for UpperLayer Protocols (ULP); e.g., SCSI, IP, HIPPI, etc.


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Fibre Channel - Characteristics

A channel provides a direct or switched point-to-point connection between the communicating

devices, typically hardware intensive, and transports data at high speed with low overhead. A

network is an aggregation of distributed nodes (like workstations, file servers, or peripherals)

with its own protocol that supports interaction among these nodes. A network has a relatively

high overhead since it is software intensive and, consequently, slower than a channel. Networks

can handle a more extensive range of tasks than channels as they operate in an environment of

unanticipated connections, while channels operate among only a few devices with predefinedaddresses.

Fibre Channel attempts to combine the best of these two methods of communication in a new

I/O interface that meets the needs of both channel and network users. Fibre Channel's purpose

is to provide a means for the high-speed transfer of data in a serial link between

supercomputers, mainframes, workstations, desktop computers, storage devices, displays, and

other peripherals. The Fibre Channel protocol does not have its own command set; it simply

manages the data transfer between nodes and thus interoperates with existing upper-level

protocols.

Fibre Channel (FC) is an ANSI standards-based, layered architecture running at 1.0625 Gbps

(100 MBps) or 2.125 Gbps (200 MBps) with a bit error rate of < 10-12. An 8 bit byte to 10 bitcharacter (1 Byte) data encoding process is performed on all data. A BER of 10

-12may seem

like an extremely low error rate; it simply corresponds to one error every 16.6 minutes at

1.0625Gbps.

FC has a copper distance limit of approximately 13 to 30 meters over twisted pair. The longer

distance requires an active interface, which helps smooth the signal. (I.e. DB-9 and HSSDC).

FC can be transmitted over fiber optic distances of up to 550 meters using short wave


Channels Connection Service

Physical Circuits

HW Reliable Transfers

High Speed

Low Latency

Short Distance

Hardware Intense

Networks Connectionless

Logical Circuits

Unreliable Transfers

High Connectivity

Higher Latency

Longer Distance

Software intense

Fibre Channel

High Data Rates 1 and 2Gbps

Circuit and Packet Switched

Reliable Transfers BER


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multimode fiber (MMF) and 10 km over long wave single-mode fiber (SMF). These distances

can be extended with various types of networking devices and transports, which are discussed

elsewhere.


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Fibre Channel Layered Architecture

Fibre Channel has an ANSI-based layered architecture that can be considered a general

transport vehicle for ULPs (such as SCSI command sets, HIPPI data framing, IP and others).

The Physical interface (FC-0) consists of transmission media, transmitters, and receivers and

their interfaces.

FC-1 defines the transmission protocol that includes the serial encoding, decoding, and error

control.

The signaling protocol (FC-2) specifies the rules, and provides mechanisms needed to transfer

blocks of data end-to-end. FC-2 functions include several classes of service, frame format

definition, sequence disassembly and reassembly, exchange management, address assignment,

alias address definition, protocols for hunt group and multicast management, and stacked

connect-requests.

FC-3 provides a set of services that are common across multiple Nx_Ports of a node.

Specifications exist here but are rarely implemented.

FC-4 is the highest level in the Fibre Channel standards set. It defines the mapping between the

lower levels of the Fibre Channel and the IPI and SCSI command sets, the HIPPI data framing,

IP, and other ULPs. Fibre Channel provides a method for supporting a number of ULPs.

The link services represent a mandatory function required by FC-2.


ANSI standards-based, layered architecture

Interface (Transmitter & Receiver)

Common Services

Signaling Protocol

Transmission Protocol

FC-0

Physical

FC-1

FC-2

FC-3

IPI3 SCSI HIPPI IP OthersSBCCSFC-4

Mapping

ULPs IPI3 SCSI IP SBCCS Others

Media

Link Services

FC-PI

Fibre Channel Layered Architecture


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Fibre Channel Transmission Hierarchy

A transmission character is the lowest level in the hierarchy and it uses an 8b/10b encoding

scheme for every byte of data transmitted. By using this encoding scheme it helps to improve

the characteristics of transmitted information, provides adequate transitions to make clock

recovery at the receiver, improves the detection of bit errors, and helps achieve word alignment

with the use of special transmission characters.

A transmission word is a group of four consecutive transmission characters. Some transmission

words have a special transmission character in the beginning that indicates the word is an

ordered set. These can be frame delimiters or convey information between frames. Examples

are start of frame, end of frame, idle, receiver ready, loop initialization, open, and close.

A Fibre Channel frame is variable in length, up to 2,148 bytes, with a payload up to 2,112

bytes. The total frame size must be an even multiple of 4 bytes so that no partial transmission

words can be sent out. Pad bytes of between 0 and 3 are added to the end of the payload to

ensure this need. Start of frame (SOF) and end of frame (EOF) delimiters mark the beginning

and end of the Fibre Channel frame, which also has a 32-bit cyclic redundancy check (CRC) for

error detection.

A Fibre Channel sequence is a series of one or more related FC frames transmitted

unidirectionally between two ports. All frames are part of a sequence and frames within the

same sequence contain the same sequence ID (SEQ_ID). A sequence count (SEQ_CNT) field

identifies individual frames within a sequence and is incremented by 1 for each frame

transmission. This enables proper frame order and verification that all frames have been

received.


Fibre Channel TransmissionHierarchy

Transmission Character

Lowest level using 8b/10b encoding scheme

Transmission Word

Group of four transmission characters

Fibre Channel Frame

Variable length up to 2,148 bytes

Fibre Channel Sequence

Series of one or more related FC framestransmitted in one direction between two ports

Fibre Channel Exchange

Series of one or more non-concurrentsequences between two ports


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A Fibre Channel Exchange is a series of one or more non-concurrent sequences between two

ports. Sequences can be in either direction and must be part of an exchange. An OX_ID field is

assigned by the exchange originator and the RX_ID field is assigned by the exchange

responder.

Analogy

Transmission characters=letters; transmission words=syllables; Fibre Channel frames=words;

Fibre Channel sequences=sentences; and Fibre Channel exchanges=conversations.


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Fibre Channel - Standards

Fibre Channel is structured by a lengthy list of standards. This illustration names just a few.

Like other protocol standards, Fibre Channel builds up from the physical and signaling level.

This foundation branches up and out to include different topology structures (i.e. arbitrated loop

or switched fabric), specifies formats for generic services, and deals with the mapping of upper

layer protocols (UPLs).

There are numerous other FC standards that cover other areas of networking and are governedby the Technical Committee T11 at www.t11.org.


Fibre Channel - Standards

Mapping ProtocolSCSI-FCP

FCP for SCSI-3

FC-LE

Link Encapsulation

FC-FP

Mapping of HIPPI-FP

FC-SB-2

Single Byte

Command Code Set

FC-AVAudio-Video

Physical

and SignalingFC-PH

Physical & Signaling

FC-PH-2

2nd Generation P&S

FC-PH-3

3rd Generation P&S

FC-FG

Fabric Generic

Fabric

FC-SW

Switched Fabric

FC-SW-2

2nd Generation SF

FC-GS-1

Generic Services

FC-GS-2

2nd Generation GS

FC-GS-3

3rd Generation GS

GenericServices

Arbitrated LoopFC-AL

Arbitrated Loop

FC-AL-2

2nd Generation AL

FC-AL-3

3rd Generation AL

FC-PLDA

Private Loop Attached

FC-FLA

Fabric Loop Attached

FC-TapeTape Tech. Report


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Fibre Channel Standard Port Types

An N_Port (Node) connects to another N_Port for point-to-point operation or to an F_Port in a

switched fabric.

An F_Port (Fabric) resides on fabric switches and connects to devices configured as an N_Port.

An NL_Port (Node/Loop) is an attached arbitrated loop (AL) device configuration when

connected to a fabric switch.

An FL_Port (Fabric/Loop) is a fabric switch port configuration when an AL device is

connected.

An E_Port (Expansion) is a connection between fabric switches, typically over extended

distances (> 10km) and utilizes an internal service link (ISL) facility for communication.

A B_Port (Bridge) is a subset of the E_Port, used on bridge devices that interconnect over

backbone WAN like ATM or SONET.

A G_Port (Generic) is a port configuration that can be used as either a node attachment or

expansion port (not common).

Note Auto Mode on the Cisco MDS 9000 is similar to the G_Port configuration but is not a

standard port type.


Fibre Channel Standard Port Types

N_Port: (Node)*

F_Port: (Fabric)*

NL_Port: (Node/Loop)*

FL_Port: (Fabric/Loop)*

E_Port: (Expansion)*

B_Port: (Bridge)

G_Port: (Generic)

* Cisco supported

Fabric Switch

Fabric Switch

FL_Port

B_Port

G_Port

E_Port

F_Port

F_Port

F_Port

E_Port

HostN_Port

StorageN_Port

ServerN_Port

Host NL_Port

Client NL_Port

Server NL_Port

Arbitrated LoopSwitched Fabric

F_Port

EthernetClientN_Port

Storage NL_Port


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Fibre Channel Enhanced Port Types

The figure lists FC enhanced port types, which are unique to Cisco.

SD_PortSPAN Destination. Fabric port set up to be the capture port for switched port

Analyzer (SPAN) traffic.

TE_PortTrunking E_Port. An E_Port capable of carrying multiple VSANs.

TL_PortTranslative Loop. Attached arbitrated loop device that is not fabric aware but can talk

to fabric ports. A TL Port makes a select set of fabric devices appear as private devices on the

loop and makes it also appear to devices on the private loop that they are talking to an on-loop

device when in fact they are talking to an off-loop device. It makes devices on the private loop

appear as public devices to rest of the fabric. Mechanisms independent of nature of fabric

device: N_PORT, public NL_PORT or another private NL_PORT made visible through

translation.

2003, Cisco Systems, Inc. All rights reserved. Deploying MDS 9000 Systems v1.0Module 1, Lesson 2 -11

Fibre Channel Enhanced Port Types

Unique to Cisco:

SD_Port (SPAN Destination)

TE_Port (Trunking)

TL_Port (Translative)

Disk Array FC AnalyzerSD port

TE port

TE port

E port E port

TL portF port

FL portHost

Private Loop

ISL

EISLPort Channel

Public Loop

Disk Array

JBOD

JBOD


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Fibre Channel Fabric And Port Login

In order for any device or switch in the network to be recognized as part of the SAN fabric it

must first login. The first login session is called Fabric_Login or FLOGI. The FLOGI

command exchange is initiated between the Node (device) and the Login_Server, which resides

in the fabric FC switch that the node is connected to. Once the FLOGI is accepted the node can

move on to Port_Login or PLOGI. The PLOGI command exchange is initiated between the

node and the Name_Server, which also resides on the FC switch and appears as a N_Port. Port

parameters are exchanged at that point. These login processes result in the devices having anestablished fabric and Fibre Channel sessions.

The PLOGI process is repeated between the initiator and target so that the storage device can

be seen by the host as a valid and connected entity for sending data to. This requires an

additional login called Process_Login or PRLI. When the PRLI command is accepted the two

devices can request a process like an FC-4 session so the initiator can start sending SCSI

commands.

FLOGIN_Port to Fabric login

PLOGIN_Port to N_Port login

PRLIFC-4 process to FC-4 process login


Fabric andPort Logins

Fibre Channel Fabric And Port Login

FC SwitchLogin Server FFFFFE

Initiator Target

Fabric and

Port Logins

Port Login

Name Server FFFFFC


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Fibre ChannelName_Identifiers

Naming is part of the overall addressing structure for Fibre Channel SANs and is needed for

device identification within the Fibre Channel fabric. Similar to the 48-bit MAC address used

in an Ethernet environment, Fibre Channel IDs (FC_IDs) are used to identify the source and

destination device ports. The fabric switch dynamically assigns a 24-bit port address, FC_ID, or

N_Port_ID to devices as they login. A destination identifier (D_ID) and source identifier

(S_ID) are embedded into the Fibre Channel frame header for routing purposes. However,

World_Wide_Names, which are also a form of fibre channel device identification, are not usedfor transporting frames or routing.

A node is a communicating device, typically one physical interface, which is referenced to as a

Node Port or N_Port.

Each node has a Node_Name, which is assigned by the manufacturer (64-bit or 8-byte). When a

Node_Name is formally registered with IEEE it is considered globally unique and referred to as

a node World-Wide Name (nWWN). These are eight hexadecimal numbers separated by

colons.

A Port_Name is a unique name for a node port (N_Port) within a parent Node (64-bit or 8-

byte), which allows each node and its associated N_Port to be unique. When a Port_Name is

formally registered with IEEE it is considered globally unique and referred to as a port World-

Wide Name (pWWN). These are also eight hexadecimal numbers separated by colons.

A Fabric_Name is the unique identity of the principal fabric switch (64-bit or 8-byte) within a

SAN, which is also assigned by the manufacturer and uses the same format.


Fibre Channel Name_Identifiers

Fibre Channel Name_Identifier is a fixed 64-bit

value used to uniquely identify nodes, ports, and

fabrics whenever a login session is established.

Node_Name is assigned by the manufacturer

Example; 12:34:56:78:9A:BC:DE:F1

Port_Name is also assigned by the manufacturer for aN_Port within a Node using the same format

Fabric_Name is the identity of the principal fabric switch,again manufacturer assigned with the same format

World Wide Name

Value format recognized by IEEE to be globally unique

Node_Name (nWWN) and Port_Name (pWWN)


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A World Wide Name has two components, pWWN and nWWN. WWN is a unique number

format assigned by the Name Assignment Authority (NAA). Other name formats, not following

these unique formats, are called Fibre Channel Names (FCN).


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Fibre ChannelNames

Fibre Channel names are used primarily for identification of the fabric, nodes, and ports within

the SAN fabric.

Independent of any ULP or OS

Information logged into Name_Server

Port query, logs, and soft zoning

Principal Switch WWN is the Fabric_Name. Selection of a unique Principal Switch within a

fabric is through Exchange Fabric Parameters (EFPs), based on lowest priority and if same,

lowest local switch WWN (VSAN WWN), when there are at least two switches forming a

fabric and lasts for 2*FSTOV (= 10) seconds.

Domain ID Allocation and Distribution

Principal switch allocates unique domains to all switches in the fabric. Allocation of a

maximum of 239 domains. Identification of Principal Links (Upstream + Downstream ports),

across which domain requests are propagated. Distributing the allocated list of domains by the

Principal Switch across the fabric.

FC_ID allocation: Allocate and free up FC_IDs based on requests. A single FC_ID (~64k

FC_IDs) for F/N ports. An Area (256 FC_IDs) for FL ports (and for some F_Ports because of

interoperability issues). Freed FC_IDs can be cached based on the corresponding WWNs. The

same FC_ID is allocated for a given WWN on a best-effort basis.


Fibre Channel Names

Fibre Channel names are used primarilyfor identification within the SAN fabric.

Independent of any ULP or OS

Information logged into Name_Server

Port queries, logs, and soft zoning

Principal

Fabric Switch

E_Port

Fabric Switch

E_Port NodeN_PortF_PortNode N_Port F_Port

Fabric_Name

Node_NameNode_Name

Port_Name Port_Name

Port_Name Port_Name


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Fibre Channel Name Formats

A World Wide Node Name uniquely identifies each device.

A World Wide Port Name uniquely identifies each port in that device.

VSIDVendor Specified ID.

First four bits identify the Name Assignment Authority (NAA).

Remaining 60 bits are determined by the format in NAA ID field.The 48 LSBs are based on IEEE 802.1A Universal LAN MAC Address (ULA) and become the

IEEE Organizational Unique ID (OUI).

For a complete list of NAA identifiers, refer to pg 113 of FC-PH rev 4.3.


Name_Identifier Formats

NAA Name

Name_Identifier (64 bits)

60 bit field

48 bits12 bits

NAA ID4 bits

IEEE IEEE OUI for nodezeros0 0 0 1

IEEE OUI for node or fabricN_Port

0 0 1 0IEEE

Extended F_Port

IP IP address (32 bits)Zeros (28 bit)0 1 0 0

IEEE Registered VSID (36 bits)IEEE ID (24 bit)0 1 0 1

IEEE Registered

Extended

VSID (36 bits)IEEE ID (24 bit)

0 1 1 0 VSID Extension(64 bits)

Bits 63 .. 60 59 ... 0

Fibre Channel Name Formats

First four bits identify the Name Assignment Authority (NAA) Remaining 60 bits are determined by the NAA ID field

The 48 LSBs are based on IEEE 802.1A MAC Address (ULA)


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FC Network Topologies

Arbitrated loop (AL) networks are based on loop hubs and/or fabric switches that have loop

capabilities. Bandwidth is shared equally between all connected devices of which there is a

limit of 126. The more active devices connected the less available bandwidth.

AL is the most deployed topology of SANs but Fabric deployments are growing and becoming

the preferred method because of the equal bandwidth allocation to each connection is at line

speed and the flexibility in network topologies. However, fabrics are more complicated to

configure and manage.

Switched fabrics have a theoretical address support for over 16 million connections, compared

to AL at 126, but that exceeds the practical and physical limitations of the switches that make

up a fabric. Nonetheless, switched fabric networks have more flexibility in their topologies and

can be configured to support zoning, which is a form of VLAN in the Fibre Channel world.


FC Network Topologies

Point-to-Point Node-to-Node

Arbitrated Loop Shared FCtransport, supporting up to 126devices and 1 fabric port

Switched Fabric Any-to-any FCnetworked topology, theoreticallysupporting millions of connections

Arbitrated Loop Switched Fabric

NL-port

NL-port N-port

F-port

N-port N-port

NL-port

FL-port

N-port N-port N-port

TE-port

E-port

TE-port

F-portF-port

F-port

F-port

N-port

E-port

SD-port

N-port N-port

Point-to-Point

NL-port

FL-port


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Fibre Channel - Classes of Service

Various classes of service are set up between end points in order to ensure proper data

transport, based on application. Class of service is established between connecting devices

during the initial call setup.

Class of ServiceApplication examples:

Class 1Streaming data for tape backup or video requires dedicated connection with sustained

full bandwidth.

Class 2Online Transaction Processing (OLTP) or relational database transactions require

acknowledgments of frames but not dedicated bandwidth. Commonly used behind Class 3.

Class 3Sacrificed reliability for reduced overhead and better performance. Widely used in

arbitrated loop networks because of temporary dedicated connections and in-order delivery

with this topology.

Class 4Time-sensitive applications with support for multiple virtual circuits (VCs) between

connections and variable QoS requirements for each VC (example: Real-time video

broadcasts).

Class 6Video Broadcast applications from central video server and multiple video recipients.(Multicast)

Note Class (5) exists but is not defined.


Fibre Channel - Classes of Service

Class 1 Dedicated connection with assumed full bandwidth Confirmation of delivery or notification of non-delivery

Not widely implemented by fabric switches but some AL networks

Class 2 Connectionless format that does not require dedicatedbandwidth but does require acknowledgement of frame delivery

Mission critical applications (data integrity) or small datatransactions (bursty traffic)

Class 3 Also connectionless, like Class 2, but no frame delivery ACKs

Similar to UDP/IP datagram, which relies on upper-level protocols

Most commonly used

Class 4 Connection-oriented (virtual circuits) not widely implemented

Fractional bandwidth with Quality of Service (QoS) parameters andconfirmation of delivery or notification of non-delivery

Class 6 Connection-oriented with delivery acknowledgements Deploys multicast server (multicast video) as a central point for

individual ACKs from multiple broadcast recipients


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Fibre Channel Protocol LayersThis section explains the five different layers of the Fibre Channel protocol.

Fibre ChannelProtocol Layers

Fibre Channel Protocol (FCP) layers are similar to those of the OSI model where it starts with

the lower level physical connections and runs up through the upper layer protocol. FC-0 and

FC-1 can be thought of as the physical layer, where FC-2 is similar to the Media Access

Control (MAC) layer or the lower part of the data link layer in the OSI model. FC-3 is under

development for devices that have more than one port such as for striping, where data is

transmitted out all ports at the same time in order to increase bandwidth. FC-4 defines how

upper-layer protocols are mapped onto and transmitted over Fibre Channel, similar to the

transport layer in the OSI model.

ANSI standards-based, layered architecture:

FC-0Physical interface (copper or optical), signaling, and media and transmitter/receiver

specs.

FC-1Link level control and data encoding, 8 bit byte to 10 bit character (1 Byte), and Linkmaintenance.

FC-2Format, segmentation, reassembly of frames, flow control, and class of service (frame

format, sequence and exchange management, login/logout, flow control and class of service,

and segmentation and reassembly of frames).

FC-3Common services and services for multiple ports on the same node.


Fibre Channel - Protocol Layers

Fibre Channel Protocol (FCP) Layers

FC-0

Physical media specs and signaling

FC-1

Link maintenance and data encoding

FC-2

Frame format, login, sequence, exchange,flow control, and class of service

FC-3

Common services for multiple ports

FC-4

Upper Layer Protocol (UPL) mapping


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FC-4Upper-layer protocol interface between FC and other protocols (SCSI-3, IP, HIPPI,

ATM-AAL5, etc.) SCSI-FCP (Fibre Channel Protocol for SCSI-3).


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Protocol Layer FC-0

The FC-PI standard describes the physical link, the lowest level in a Fiber Channel system.

A link is composed of two unidirectional optical fibers or four electrical wires. The link never

stops carrying the data. When two ports are not communicating data they send idles to each

other, making sure that the link stays active. LCF = link control facility.

FC-0 does not detect transmit code violations, invalid ordered sets or any alteration of encoded

bit stream. A hardware facility that attaches to an end of a link and manages transmission andreception of data. It is contained within each FC_Port. Before a link comes up, Port A must

send to Port B AND Port B must send to Port A, PLUS additional link initialization steps.

Cable Types: Electrical (varieties of shielded and unshielded Twisted Pair)

Optical fibers (single or multiple mode)

Single mode is 9 microns with loss budget of 14db, over a distance of 10KM

Multimode is 50 or 62.5 microns with a loss budget of 6db, over a distance of 500m

Media Converters:

MIA (Media Interface Adapter)

Hot or non-hot pluggable

External converters


Tx

Rx Rx

Tx

Link

Outbound Outbound

Inbound Inbound

PORT A PORT B

LCF LCF

Protocol Layer FC-0

A Fibre Channel port connects toa topology via a link

FC-0 level of FC-PI specificationdescribes the FC link

FC-0 provides an optical fiber orelectrical signal interface


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GBICS: Electrical or optical

General laser transmitter characteristics are specified in the form of transmitter eye diagram

mask. These includes rise time, fall time, pulse overshoot, undershoot and ringing. All of them

shall be controlled to prevent signal degradation.

If its electrical, there will be two RX and two TX wires.


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Protocol Layer FC-1

Fibre Channel layer FC-1 provides three primary functions:

Encoding and decoding the 8b/10b data transmission code scheme patented by IBM

Ordered sets, which provide unique transmission words for signaling and control functions

Implementing link level protocols


FC-1 provides three primary functions:

Encoding and decoding

8b/10b data transmission code schemepatented by IBM

Ordered sets

Provide unique transmission words forsignaling and control functions

Implementing link level protocols

Protocol Layer FC-1


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Fibre Channel Transmission Code

8-bit data bytes are encoded into 10 bit transmission words.

Bit synchronization is easier to achieve

Receiver and transmitter design is simplified

Provides error detection at layer 1

Distinguish control and data characters

The primary reason to encode is to improve the transmission characteristic of information.

Ensures that sufficient transitions are present in serial bit stream so clock recovery is

possible.

Increases the likelihood of detecting single or multiple bit errors that may occur.

Some of the special character patterns assist in word alignment.

Maintain a balance between ones and zeros transmitted, ensuring that the receiving signal

is free of any DC-component (running disparity)

To prevent excessive DC-component and run length problems, only characters containing six

ones and four zeros, five ones and five zeros and four ones and six zeros are allowed. The rest

are invalid characters. Transmission characters always have either:


D0

Dn

Data Clock

Driver/Transmitter

Parallel Input Serial Output Media Output

8b/10b Data

Encoder

Tx Byte

Parallel/Serial

Converter

(Serializer)

Fibre Channel Transmission Code

Data transmitted over Fibre Channel is encoded 8bits at a time into a 10 bit transmission characterand then sent serially by bit.

The 10 bit transmission code supports all 256 eightbit combinations. There are 1024 10 bit patterns.

There are 12 special characters defined by the8b/10b encoding scheme but only one of them(K28.5) is used by Fibre Channel.


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6 ones and 4 zeros = Positive disparity

4 ones and 6 zeros = Negative disparity

5 ones and 5 zeros = Neutral disparity

The CRD is fed back to the encoder to select appropriate encoding of the next character to

balance number of ones and zeros. Normally a word consists of four 8 bit bytes (32 bits). When

each 8 bit is encoded prior to the transmission, the resulting word consists of 40 bits

representing four 10 bit transmission characters.


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Fibre Channel Ordered Sets

A Fibre Channel transmission word consist of an ordered set of four transmission characters.

Ordered sets are used to distinguish between Fibre Channel control information from data.

They also provide bit and word synchronization.

An ordered set is a transmission word starting with a K28.5 special character. This is a 10-bit

character that doesnt have a corresponding 8-bit value. It has a 7-bit value and is the only

transmission character to have (5) 1s or (5) 0s in a row.

Frame DelimiterUsed to mark the beginning and end of the frame. It also marks the first

and last frame along with the Class of Service.

Primitive SignalsWhen there is no data on the wire, fill words are used to maintain

synchronization. Also indicates events or actions.

Primitive SequenceUsed to establish and maintain the link. Indicates state changes.


Start-of-Frame

End-of-Frame

Transmission Word

Ordered Set

(K28.5, Dxx.y, Dxx.y, Dxx.y)

Data Word

(Dxx.y, Dxx.y, Dxx.y, Dxx.y)

Primitive Signals

IDLE

ARB(x)ARB(F0)

ARB(FF)

R_RDY

VC_RDYCLS

OPN

DHDMRK(Tx)SYN x,y,z

Not Operational (NOS)

Offline (OLS)

Link Reset (LR)

Link Reset Resp (LRR)

Loop Init (LIP)Loop Port Bypass (LPB)

Loop Port Enable (LPE)

Non-Fill WordFill Word Primitive SequenceFrame Delimiter

Fibre Channel Ordered Sets

FC-1 Ordered Sets: Frame Delimiters

Primitive Signals

Primitive Sequences


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Fibre ChannelFrame Delimiters

SOF is used to:

Mark the beginning of the frame

Indicate whether it is the first frame of the sequence

Indicate the class of service

EOF is used to:

Mark the end of frame

Indicate the last frame of sequence

Indicate the class of service

EOF has both negative and positive running disparity, ensuring that every frame ends with

negative running disparity. CRD is forced negative by EOF and remains negative after each

ordered set.


Fibre Channel Frame Delimiters

Frame Delimiters

Identify start and end of frame (SOF and EOF)

Start of Frame (SOF)

Beginning of a frame

Indicates beginning of a sequence

Indicates the class of service

End of Frame (EOF)

Beginning of a frame

Indicates beginning of a sequence

Indicates the class of service


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Fibre ChannelPrimitive Signals

Primitive signals indicate events at the sending port and are entities that can be Fill words

like ARB (Attribute) or IDLE (Idle), or Control words like R_RDY (Receiver Ready), OPN

(Open), or CLS (Close).

The FC-AL, FC-PH, and follow-on standard enhancements define these signals for the different

port events.


Fibre Channel Primitive Signals

Primitive Signals

Indicate events at the sending port

FC-PH standard defined two primitive signals when twonodes are not communicating

Idle (IDLE)

Receiver_Ready (R_RDY)

FC-AL, FC-AL2 and enhancements to FC-PH standards(FC-PH2 and FC-PH3) have added to the list of primitivesignals


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Job Aid: List of Primitive Signals

This job aid provides a list of the primitive signals, their abbreviations, and the FC standard

document that defines them.


Job Aid: List of Primitive Signals

Primitive Signal

Arbitrate (Fairness & Init)

Arbitrate (Alternate to IDLE)

Clock Sync X

Clock Sync Y

Clock Sync Z

CLOSE

Dynamic Half Duplex

Idle

Mark

Open Full Duplex (pt-pt)

Open Half Duplex (pt-pt)

Abbr.

ARB(F0)

SYNx

ARB(FF)

SYNy

SYNz

CLS

IDLE

DHD

MRK(tx)

OPN(yx)

OPN(yy)

Document

Arbitrate ARB(x) FC-AL

FC-AL

FC-PH3

FC-AL2

FC-PH3

FC-PH3

FC-AL

FC-PH

FC-AL2

FC-AL

FC-AL

FC-AL

Open Broadcast Replicate

Open Selective ReplicateReceiver Ready

Virtual Circuit Ready

OPN(fr)

OPN(yr)R_RDY

VC_RDY

FC-AL

FC-ALFC-PH

FC-PH2


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Fibre Channel Primitive Sequences

Primitive sequences are used to establish and maintain a link between two fibre channel ports.

These sequences continue to be transmitted until a response has been received and the link

becomes active.


Fibre Channel Primitive Sequences

Primitive Sequences

Establish and maintain fibre channel links

Require a minimum of three consecutive same orderedset before action is taken

FC-PH defines four primitive sequences during linkinitialization and failure recovery

Not_Operational (NOS)

Offline (OLS)

Link_Reset (LR)

Link_Reset_Response (LRR)

A link is active (AC) when idles are transmitted andrecognized by the receiver


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Example: Primitive Sequences Link Recovery

This example illustrates the primitive sequences for a link recovery between two fibre channel

ports after a link failure.


Example: Primitive Sequences LinkRecovery

IDLEOperational Link Idles and R_RDY Recognized

IDLE

IDLELink Reset Response

Link Reset Recognized

LRR

LRRLink Reset

Remove Class_1 Connection

Reset F_Port

OLS Recognized

LR

LROffline State

Internal Port Failure

Transmitter Power Down, Perform Diags, or PerformInitialization

Receiver shall ignore Link Error or Link Failure

OLS

OLSNon Operational State

Link Failure

NOS

Transmit inResponse

MeaningCurrentlyTransmitting


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Fibre ChannelLink Failure, Recovery, and Initialization

An N_port or F_Port might be in one of four primary operational states and associated substate

depending on the state of the port.

1. Active state

2. Link recovery state

LR transmit substate (LR1)

LR receive substate (LR2)

LRR receive substate (LR3)

3. Offline state

OLS transmit substate (OL1)

OLS receive substate (OL2)

Wait for OLS substate (OL3)

4. Link failure state

NOS receive substate (LF1)

NOS transmit substate (LF2)


Link FailureCondition

NOS

OLS

LR

Idle

LRR

Idle

Port A Port B

LF2

OL3

OL1

LF1

LR1

OL2

LR3

LR2

AC

AC

ACAC

Link Fail

Link Initialized

Link Reset

Active

Initialize

Offline

Fibre Channel Link Failure, Recovery,And Initialization


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Protocol Layer FC-2

Fibre Channel layer FC-2 provides six primary functions; frame format and structure,

login/logout sessions between ports, sequence management, exchange management, flow

control, and class of service.


Protocol Layer FC-2

FC-2 provides six primary functions Frame format and structure

Login/logout sessions between ports

Sequence management

Exchange management

Flow control

Class of service


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Fibre Channel Frame FormatThis topic explains the frame format of the Fibre Channel protocol.

Fibre ChannelFrame Format

Start of Frame (SOF)Single 4-byte word that describes the class of service used and if it is

one frame only or the first of a series of frames.

Frame Header (24-bytes)CLT (Control Field) Frame Content/Control Information, S_ID

(Source) and D_ID (Destination) Addressing, Type: Data Type (Command, Control or

Content), and Seq_Cnt, Seq_ID, Exchange_ID (Position within a series)

Data Field(0 to 2,112 bytes or 0 528 words) Optional 64-byte Header and Variable data

length framing format allows for various application requirements while balancing overhead

and payload. Frame padding occurs here when data is not divisible evenly by 4-bytes. Fill bytes

are added for proper frame assembly.

Cyclic Redundancy Check or CRC Error Check (4-bytes or 32-bit)Verifies data integrity

within the frame. Note that CRC is run before data goes through the 8bit to 10bit encoder and

the CRC is itself encoded later as part of all the frame contents.End of Frame (EOF)Notification that the frame is complete. Specific EOF is determined by

the Class of Service and sequence with other frames.

Minimum size of an FC frame is 36 bytes. Maximum size is 2,148 bytes or 1 Buffer Credit.

Link utilization is maximized by the use of frame sequences and exchanges between

communicating devices. This also reduces the overhead needed for setting up and tearing down


Idles SOFFrame

Header

Data FieldCRC EOF Idles

Frame

Content

0-528 Transmission Words

(4B)(4B)(0-2112B)(24B)(4B)

2,148 bytes max.

R_CTL D_ID

Byte 0Word

0

1

2

3

4

5

S_IDCS_CTL

TYPE

SEQ_ID DF_CTL

F_CTL

SEQ_CNT

OX_ID RX_ID

Parameter

Byte 1Byte 2Byte 3

Data FieldOptionalHeader

Fibre Channel Frame Format


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of logical connections. Error correction is limited to the sequence level in Fibre Channel. A

failed CRC means an entire sequence of frames are retransmitted rather than track for an

individual frame, thus further minimizing overhead during frame transport.

All FC-2 frames follow the frame format shown above. An FC-2 frame is composed of a SOF

delimiter, frame content, and an EOF delimiter. The frame content is composed of a

Frame_Header, Data_Field, and CRC. Unless otherwise specified, the term frame refers to a

FC-2 frame.

The FC Standard refers to transmitting at least two consecutive IDLE words after the End of

Frame (EOF) and also a port must transmit six primitive signals between each EOF and next

SOF, at least four of them must be IDLE words.

FC does not recognize any unit of data less than a word. Hence if the payload does not end on

the word boundary, fill bytes are used. The maximum number of fill bytes used is 3 to comply

with the Fibre Channel requirements.


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Fibre Channel Frame Header

Routing Control (R_CTL) is a one byte field that contains two four-bit sub fields.

Routing (bits 31 28)

0000Device_Data frame

0010Extended Link_Data Frame

0011FC-4 Link_Data Frame0100Video_Data Frame

1000Basic Link_Data Frame

1100Link_Control Frame

OthersReserved

Information (bits 27 24)

0000Uncategorized information

0001Solicited Data

0010Unsolicited Control

0011Solicited Control

0100Unsolicited Data

0101Data Descriptor

0111Command Status


R_CTL Routing D_ID 24bits Destination_ID

0781516232431Word

0

1

2

3

4

5

S_ID 24 bits Source_IDCS_CTL 8 bits

Class Spec.

TYPE 8 bits

Data Structure

SEQ_ID 8 bitsSequence_ID

DF_CTL 8 bitsData Field

F_CTL 24 bits Frame_Control

SEQ_CNT 16 bits Sequence_Count

OX_ID 16 bits Originator Exchange_ID RX_ID 16 bits Responder Exchange_ID

Parameter Specific to frame type

Uniquely identifies the frame

Byte 0Byte 1Byte 2Byte 3

Fibre Channel Frame Header

Frame Header First field of the frame content

Immediately following the SOF


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OthersUnspecified

Routing Bits differentiate frames based on function or service within an N_Port or F_Port.

Video data frames contain payload information, while the Link_Data frames contain request

and reply commands. The information field is dependant on the Routing field value.

TYPE is a one byte field that identifies the protocol that is being carried by the frame when the

frame is Data Frame (FT-1). For Link Control Frame (FT-0), the TYPE field is reserved.

Type values assigned to a number of FC documents to implement document specific protocol:

x00Basic Link Services, x01Extended Link Services, x05IP over FC (RFC-2625),

x08SCSI FCP, x20FC-GS, x25SNMP

Each N_Port has a native N_Port Identifier, which is unique within the address domain of a

Fabric. An N_Port determines its address FC_identifier during the login process. Address

Identifiers in the range of xFFFFF0 xFFFFFF are well known addresses and reserved for the

following functions. FFFFF0 FFFFF9Reserved; FFFFFAManagement Server;

FFFFFBTime Server; FFFFFCDirectory Server; FFFFFDFabric Controller;

FFFFFEFabric Login Server; FFFFFFBroadcast. S_ID, D_ID, SEQ_ID, and SEQ_CNT

together uniquely identify the frame.


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Fibre Channel Optional Header

If present the, Network_Header is the first 16 bytes of the data field and is only present in the

first data frame of the first sequence.

The Network_Header may be used for routing between Fibre Channel networks of different

Fabric address spaces, or Fibre Channel and non-Fibre Channel networks.

The Association_Header is provided to support system architectures that require more than two

levels of identifiers, (i.e., X_ID and SEQ_ID) and is only present in the first data frame of thefirst sequence.

The contents of the Device_Header are controlled by the ULP. If the Device_Header is present,

it will be either in the first Data frame or in all Data frames of a Sequence.

If a Device_Header is present for a ULP that does not require it, the related FC-4 may reject the

frame with the reason code of TYPE not supported.


Frame

HeaderData Field CRC

Frame Content

(4B)(24B) (16B) (32B) (16-64B)

Network

Header

Assoc.

Header

Device

Header

Fibre Channel Optional Header

FC Frame Payload (02,112B)

One of these three headers

DF_CTL is a one byte field in the frameheader that specifies the presence of anoptional header

When present, optional headers are partof the FC frame payload

Network Header

Association Header

Device Header


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Fibre Channel AddressingThis topic explains the Fibre Channel protocol addressing scheme.


24-bit addressing scheme enables us to a maximum of more than 16 million addresses.

However, some of the addresses are reserved for specific services.

In point-to-point topology the address is assigned by the N port with Higher MAC address

In case of private arbitrated loop topology, only the lowest 8 bits are used, which limits us to

have only 127 devices. The FC_ID is acquired during loop initialization.

The switch fabric topology uses all 24 bits for addressing and the address is assigned by the

fabric when Nx_port login.

When two ports communicate, the destination and source ID are contained in the header and

routing decision are made based on the destination ID field.

A Fibre Channel ID is logically broken into three elements: Domain, Area and Port. The

Domain field represents one or more switch in a single domain but in most of the current

manufacturers implementation, the domain field represents a single switch and hence each

switch has its own domain.

Domain Controllers are assigned the reserved N_Port address FF FC xx (xx = Domain_ID)

The Area_ID field represents N_Ports, within and attached to a single switch or an Arbitrated

loop of NL_Ports attached to a single FL_Port. A single Arbitrated loop shall have exactly one

single Area ID.


Source (S_ID) and Destination (D_ID) FC_IDs use a six character 24-bit hexadecimal addressing scheme

Maximum of 239 switches per domain

Used for frame routing within the fabric network

Point-to-point; assigned unique address by each N_Port

Arbitrated Loop; assigned at loop initialization

Switched Fabric; dynamically assigned by the fabric

AL_PA0000

AL_PAAreaDomain

PortAreaSwitch Domain

8 bits 8 bits 8 bits

Switched Fabric

Private Loop

(no fabric switch)

Public Loop

(connected to switch)

0x0000Point-to-Point X=0 or 1



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A Port_ID represents:

a single N_Port within a Domain/Area;

the valid AL_PA of a single NL_Port or FL_Port on an arbitrated loop.

N_ports and E_ports get one port ID.

F ports dont get any IDs.

FL ports in public AL gets 0x00 port ID.

The FC Well Known Addresses are reserved for special functions. Each of these functions

reside within the switch.


Fabric F_Port, Fabric Login databaseFEFFFF

N_Port of fabric controllerFDFFFF

Well Known AddressF0-FC,FFFFFF

Reserved00-EFFFFF

Reserved00-FFFD-FEFF

ReservedF0-FFFCFF

N_Port of domain controller. Port_ID is the Domain_ID01-EFFCFF

Reserved00FCFFMulticast & Broadcast00-FFFBFF

Reserved00-FF00-FAFF

Reserved00-FF00-FFF0-FE

N_Port & E_Port. Port_ID=00 for FL port for public devices255 address

00-FF00-FF01-EF

Reserved00-FF01-FF00

ReservedNon AL_PA0000

Private Loop NL_PortAL_PA0000

Used during FLOGI000000

DescriptionPort_IDArea_IDDomain_ID

Fibre Channel Addressing (Cont.)

FC_ID includes Domain, Area, and Port

N_Port example; 0x01FF00 (value is always prefixed by a 0x)


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Fibre Channel ServicesThis section explains the different functions of Fibre Channel protocol services.

Fibre ChannelServices

Basic link service commands support low level functions like aborting a sequence (ABTS) and

passing control bit information. Login is not required prior to a Basic Link Services command.

Basic link service timeout is 2 * R_A_TOV (Resource Allocation Time Out Value).

The ABTS frame shall be used by the Sequence Initiator

a) to request that the Sequence Recipient abort one or more Sequences.

b) or Sequence Recipient to request that the ABTS Recipient abort the entire Exchange.

Extended Link Services (ELS) are performed in a single exchange. Most of ELSs are

performed as a two sequence exchange. A request from the originator and a response from the

responder. ELS service requests are not permitted prior to a port login except the fabric login or

FLOGI.

A sequence initiator shall transmit an ELS sequence in order to solicit the destination Nx_Port

to perform a link-level function or service. Unless otherwise noted, Extended Link Service

requests shall not be issued prior to completion of N_Port Login.

ELS Command Examples: N_Port Login (PLOGI), F_Port Login (FLOGI), Logout

(LOGO), Process Login (PRLI ), Process Logout (PRLO), State Change Notification (SCN),

Registered State Change Notification (RSCN ), State Change Registration (SCR), Loop

Initialize (LINIT).


Basic Link Services

Extended Link Services

Generic Services

Exchange & Sequence Mgmt.

Frame Structure

Class of Service & Flow Control

8b/10b Encode/Decode

Ordered Sets

Link Control Protocols

Physical Interface

Optical & Electrical Interfaces

Cables, Connectors

Fibre Channel Level 1

FC-1


FC-0


FC-2

Fibre Channel - Services

Basic Link Services

Low-level functions

Port login not required

Extended Link Services

Login, logout,initialize, registration,notification

Port login required

except for FabricLogin (FLOGI)

Generic Services

Numerous servicesusing FC-CT astransport protocol

Port login required


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Generic Services include: Directory Service, Management Services, Alias Services, Time

Services, and Key Distribution Services. FC-CT (Fiber Channel Common Transport) protocol

is used as a transport media for these services. FC-GS shares a Common Transport (CT) at the

FC-4 level and the CT provides access to the services. Port login is required for generic

services.


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Fibre Channel Extended Link Services

Two Extended Link Services (ELS) are Login and Logout.

The login procedure is a method by which an Nx_Port establishes its operating environment

with a Fabric, if present, and other destination Nx_Ports with which it communicates. Once

login has occurred the port can begin exchange of parameters.

Fabric Login and Port Login are both accomplished with a similar procedure using different

D_IDs and possibly different S_IDs. Process login used to connect to Upper Layer Protocol(ULP).

After the login session a port may originate or respond to exchanges. A Port that originates an

exchange is the Exchange Originator and a port that replies to an exchange is the Exchange

Responder. A port may have multiple open Exchanges to one or multiple other ports.

One or more Information Units are transported during an exchange. The First_Sequence bit in

F_CTL field of the frame header alerts the receiving port that a new exchange is being

originated. A port must establish a login session before performing upper-level operations. The

login session may be established implicitly or explicitly by using port login ELS.

After the login process, all information is transferred within the context of an open exchange.

Exchanges are never created unless there is information unit to send.

Logout/login sessions are long-lived and last for multiple exchanges, depending on the

application.


Fibre Channel Extended Link Services

Login

Fibre Channel defines three types of login sessions

Fabric LoginSession between N_Port and F_Port

Port LoginSession between two N_Ports and fabricservices

Process LoginUsed to establish a session between theprocesses on the two N_Port.

Login sessions occur after the link is active and idles areflowing in both directions

After login, a port may originate or respond to exchanges

Logout

Login sessions are long-lived and last for multiple exchangesdepending on the application


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Fibre Channel Generic Services

Fibre Channel generic services share a common transport (CT) at the FC-4 level. The CT

provides access to a service (e.g., Directory Service) with a set of service parameters. It also

provides another level of multiplexing that simplifies the server-to-server communication for a

distributed service. Fibre Channel generic services do not require a high performance

communication channel as do high performance I/O protocols such as SCSI, IP, VI, etc.

Generic services facilitate the transfer of status and configuration info between FC devices. FC-

CT IU (Fibre Channel Common Transport Information Unit) is the common FC sequence used

to transfer information between a client and a server. CT-IU also keep tracks of sequence

management & error detection and recovery.

Information that a FC-CT IU delivers:

Type of ServiceName Service (FC), Alias Service (F8), Management Service (FA), Time

Service (FB), Key Service (F7), and Vendor Unique (00-1F)

Type of TransactionRequest for Service by a ClientFirst Seq of a exchange, Response

from server for a servicelast Seq of an exchange, and Unsolicited IU about an event

Mode of TransactionSynchronous or asynchronous for multiple request. (asynchronous

mode is always used for unsolicited IU)

Class of ServiceClass 1, Class 2, Class 3, Class 4, or Class 6 and Maximum Size of an IU

FC-CT is a protocol used exclusively for use with Fibre Channel generic services defined in

FC-GS. It has its own FC-4 mapping. Query is used by the host to get information about other

nodes in the fabric from the name server. Register allows a host to put its own information in


Generic Services facilitate the transfer ofstatus and config info between FC devices.

FC-CT IU is the common transport protocol usedfor generic services between client and server

Request and Response FC-CT Information Units

- Type of Service

- Type of Transaction

- Mode of Transaction

- Class of Service

- Max Size of an IU

FC-CT IUs also keep track of sequencemanagement, error detection, and recovery

Fibre Channel Generic Services


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the name server. De-Register removes a hosts entries form the name server. Accept gives

requested info back. Reject gives reason (not found, busy, etc.).

Directory ServiceDistributed database service for all nodes and ports connected to the

fabric. Name server login information. This service is provided through well-known address

hex FFFFFC.

Management ServiceAccess to discovered configuration info, including inventory and zone

info. Fabric configuration server, fabric zone server, and un-zoned name server fall under this

service. All three are separate databases that help with topology discovery, zone configuration,and name server information across the fabric. This service is provided at WKA identifier, hex

FFFFFA. Fabric Configuration Server is currently supported by Cisco, Brocade, McData,

QLogic, and Inrange. Fabric Zone Server is currently supported by all vendors except Brocade.

Alias ServiceManages the registration and deregistration of Alias IDs for both hunt groups

and multicast groups. The Alias Service is not involved in the routing of frames for any group.

This service may be internal or external to the fabric, but, in either case, it is addressed by

means of the well-known address identifier, hexFFFFF8.

Time ServiceProvided to serve time information that is sufficient for managing expiration

time. This service is provided at the well-known address identifier, hex FFFFFB.

Key Distribution ServiceOffers a mechanism for the secure distribution of secret encryptionand/or authentication keys. Secure distribution is accomplished through the use of a Key Server

that utilizes data encryption techniques and verification protocols. The underlying assumption

of this service is that the client contains no keys at start-up other than a distribution key that is

unique to the client. This service is provided at WKA identifier, hex FFFFF7.

Support of all generic services allows for the discovery and understanding of other attached

devices supporting FC-GS-3. (Switches, HBAs, etc.).


FC-GS-3 is an in-band management facilityspecification defined by ANSI T11 workgroup.

Specifies generic services for FCP (Fibre ChannelProtocol)

Support of generic services enables the discoveryand the understanding of other fabric attacheddevices supporting the FC-GS-3 specification

- Directory Service

- Management Service

- Alias Service

- Time Service- Key Distribution Service

Fibre Channel Generic Services (Cont.)


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Fibre Channel Name ServerThis topic explains the functions of a Fibre Channel name server.

Fibre ChannelName Server

Fibre Channel name server is used by Nx_Ports to register port attributes or query for directory

information on other fabric connected ports. Once registered, other ports attributes are

available to that Nx_Port.

Each switch contains its own resident Name Server, called a distributed name server (dNS) and

each dNS is responsible for the name entries associated with the domain(s) assigned to the

switch.

A client Nx_Port communicates its Name Service request (as defined in FC-GS-3) to the entry

switch via the well-known address (xFFFFFC). The dNS within the local Switch services the

request by making any needed requests of other dNSs contained by the other switches, if the

required information is not available locally;

A dNS may maintain local data copies. Integrity of locally copied data is maintained via

Registered State Change Notification (RSCN). This implies that all switches shall distributeRSCN throughout the fabric whenever a change takes place in their local dNS database;

The communication between dNSs to acquire the requested information is transparent to the

original requesting client;

Partial responses to dNS queries are allowed. If an Entry Switch sends a partial response back

to an Nx_Port it shall set the partial response bit in the CT (common transport) header.


Each fabric switch has a resident name servercalled distributed Name Server (dNS)

Each dNS is responsible for the name entries ofthe domain(s) it is associated with

Three types of requests are defined for theName Server:

- Get Object (Query)

- Register Object (Only one object at a time)

- Deregister Object (One global de-registrationrequest)

Fibre Channel Name Server


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Directory Service is used to discover information about Nodes & ports attached to fabric.

There are three types of requests defined for the Name Server:

Get Object (Query)

Register Object (Only one object at a time)

Deregister Object (One global de-registration request)

The name server appears as an N_Port located at Well Known Address (WKA) xFFFFFC.

The name server is available to other N_Ports and NL_Ports, once they have completed Fabric

and Port Login. The port attributes will be registered with the name server after FLOGI.

(Node_Name, Port_ID, Port_Name, Port Type, Fabric_Name, and Class of Service)

Port attributes:

Port Identifier (24 bit Address Assigned by Switch Fabric)

Switch Port_Name (World Wide Name)

Class of Service (2,3)

Port Type (N, NL)

Node attributes:

Node_Name (World Wide Name)


Name Server appears as an N_Port located atWKA xFFFFFC

Available to other N_Ports and NL_Ports, once

they have completed Fabric and Port Login RSCN notification is used to update the changes

to other name servers

Name Server requests are managed throughRequest CT_IUs and Response CT_IUs

When a port logout occurs, the Name Server(fabric) deregisters all objects (attributes)associated with that port

Fibre Channel Name Server (Cont.)


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IP Address

FC-4 Protocol Support (SCSI,IP)

Initial Process Associator

Vendor-specific information

Registered State Change Notification (RSCN) is used to update any changes to all name servers

within a zone. If zone exist, the Name Server restricts access to information within that zone.

All name server requests are managed through Request CT_IUs and Response CT_IUs.

When a port logout occurs, the Name Server (fabric) deregisters all port objects (attributes)

associated with that port.


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Fibre ChannelName Server Objects

Each N_Port & NL_Port has a primary and secondary key.

Port Identifier (primary key) is the FC address identifier dynamically assigned to the port

during Fabric Login

Clients register with the name server database by sending a registration request containing Port

Identifier or Node_Name (FC-GS-3)

* implies that the contents of these bytes are not defined and not restricted by the name server.

Port type is N_Port, NL_Port. B_Port, E_Port, FL_Port etc.

Hard Address is defined in FC-PH-2 in Discovery Address (ADISC) extended link service

Separate Query is done for each Name Server Object.


Fibre Channel Name Server Objects

N_Ports & NL_Ports have Primary and Secondary Keys Port Identifier (Primary Key) is the FC Address Identifier

dynamically assigned to the port during Fabric Login

Clients register with the name server database bysending a registration request containing Port Identifieror Node_Name

Primary Key Indexed Fields Secondary Key Indexed Fields

Port_ID Port_NameIP Address (Node)

Initial Process Assoc

Symbolic Node Name*Class of Service

FC-4 TypeSymbolic Port Name*

Port TypeIP Address (Port)

Fabric Port Name

Hard AddressFC-4 Descriptor*

FC-4 Features

Node_NameNode_Name

Name Server objects maintained by a Name Server database at each switch


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Fibre Channel Fabric and Port LoginThis section explains Fibre Channel device fabric login and port login, logout and query.

Fibre ChannelFabric Login

Fabric Login is used by the N_Port to discover, if a fabric is present. If fabric is present, it

provides operating characteristics associated with the fabric. (service parameters like max.

frame size) The fabric also assigns or confirms (if trying to reuse an old ID), the N_Port

Identifier of the port initiating the login and initializes the BB_Credit value.

N_Ports perform fabric login by transmitting the FLOGI extended link service command to the

well known address of xFFFFFE of the Fabric F_Port and exchanges service parameters such

as; BB_Credit, Maximum Payload Size, and Class of Service supported.

The FLOGI Manager supports Fabric Login(FLOGI) and other F, FL mode services as defined

in FC-FS, FC-AL-2, FC-MI. FLOGI processing involves the allocation of a FC_ID through the

Domain Manager, configuring routes for this FC_ID through the RIB Manager, configuring the

zone server and ACL Managers, configuring the firmware with negotiated BB_Credit,

registration with the Name Server, and interaction with the Port Manager to update port state.

The Response to FLOGI is ACCept which indicates a fabric is present. When an ACC with a

S_ID of xFFFFFE is received and OX_ID is same then that means:

If the common service parameters indicate that the response came from Fabric, then the FLOGI

is complete and the ACC contains the fabrics service parameter. The D_ID contains the

N_Port address assigned by the fabric. If the common service parameters indicate that the

response came from a N_Port, that means no fabric is present and the Port Login (PLOGI)


Fibre Channel Fabric Login

FLOGI (Fabric Login)

Determines the presence or absence of a fabric

Fabric present:

Negotiates operating parameters associated with theport and fabric

Assigns or confirms the N_Port Identifier of the portinitiating the login

Fabric not present:

Indicates to the requesting N_Port of a point-to-pointtopology

Initialize BB_Credit value


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should be performed. If F_BSY or P_BSY is received, the FLOGI originator should retry later.

If F_RJT or P_RJT then examine the error code and take appropriate action: Class of Service

not supported or Invalid S_ID. If a fabric is not present, it indicates to the requesting N_Port

that it is connected to a point-to-point topology.


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Fibre ChannelFLOGI Parameters

A new N Port Fabric Login source address 00 00 00, destination address FF FF FE. An existing

N_Port Fabric Login source address XX YY ZZ, destination address FF FF FE where XX YY

ZZ is the address requesting.

Following the link initialization, during FLOGI, the Nx_Port uses the source ID (S_ID) of

x000000 or x0000AL_PA, meaning that the port is unidentified. The F_Port responds from

Fabric Login Server (xFFFFFE) with assigned N_Port Identifier (xXXXXXX).

FLOGI commands contains the Nx_Ports service parameters which includes BB_Credit and the

maximum size of the frame.

Login with the fabric is required for all Nx_Ports, regardless of the class supported.

communication with other Nx_Ports shall not be attempted until the Fabric Login procedure is

complete.


FLOGI (Service Parameters)Command = x04 or x51

S_ID = x000000 or x0000AL_PA

D_ID = xFFFFFE

FLOGI (Service Parameters)

Command = x02

S_ID = xFFFFFE

D_ID = xXXXXXX

Nx_Port

Device

F_Port

FabricSwitch

Fibre Channel FLOGI Parameters

Nx_Port uses source ID (S_ID) of x000000 orx0000AL_PA, meaning that the port is unidentified

F_Port responds from Fabric Login Server (xFFFFFE)with assigned N_Port Identifier (xXXXXXX)

FLOGI commands contain Nx_Port service parameters,including BB_Credit and the maximum frame size


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Job Aid: FLOGI Commands And Service Parameters

This job aid shows the word count in a sequence and bit order within those words for the Fabric

Login (FLOGI) commands and service parameters.


Job Aid: FLOGI Commands AndService Parameters

Bits 7-0Bits 15-8Bits 23-16Bits 31-24Word

000000Command 040

1-4 Common Service parameters (16 bytes)

5-6 N_Port Name (8 bytes)

7-8 Node Name (8 bytes)

9-12 Class 1 Service Parameters (16 bytes)




26-29 Vendor Version Level (16 bytes)


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Fibre Channel - FLOGI General Operation

1. Host sends an FLOGI.

2. Port manager gets an FC-ID from Domain manager.

3. Name server adds an entry.

4. Zone server programs the permitted list.

5. Switch responds with an ACC.6. An RSCN (Registered State Change Notification) is generated.

Database of attributes of devices: Commonly usedPWWN, FC-ID, FC4-TYPE, Port type.

Dynamically updates database as devices join/leave the SAN. Fully compliant with FC-GS3 ,

FC-SW2 and FC-MI. Maintains a database per VSAN. Maintains all the attributes of the

directly connected devices. Maintains most frequently used attributes of the remote devices.

Dynamically discovers the initiator/target characteristics. Implements Soft Zoning.

The name server should provide non-disruptive service.

Upgrading software should not affect the service.

The service should be available continuously across restart and switchover.

Name server stores its local database entries in a persistent storage.

Upon restart/switchover, it queries other switches to get all the remote entries.

Recovers FC-4 type and FC-4 features registrations that were in progress during

restart/switchover.


Name Server

RSCN tonetwork

Login Server

3

61

4

Zone Server

2

5

Fibre Channel - FLOGI General Operation

1. Host sends a FLOGI to Login Server2. Domain Manager assigns the hosts FC_ID

3. Name Server adds the hosts

4. Zone Server programs the permitted list

5. Switch responds with an ACC

6. An RSCN is generated

Host DomainManager

Fabric Switch


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Fibre ChannelPort Login

After completing the Fabric Login, the N_port does a Port Login to the name server. The name

server appears as an N_Port, located at well-known address FFFFFC, to other ports. The name

server is used by N_ports and NL_Ports to register and discover Fibre Channel attributes.

Attributes that can be registered with the name server include port identifier, port name, node

name, IP address of the port, port type and FC-4 types supported by the port. The Nx_Port can

register, deregister or query the name server database after the Port Login.

N_Port Login allows two N_Ports to establish a session and exchange service parameters and

proceeds following the Fabric Login. N_Port login is required before performing an ULP

operations.

N_Port login performs three functions: It provides service parameters of the destination N_Port.

It initializes End-End Credit, and in point-to-point topologies BB_Credits are initialized.

The port manager supports configuration and initialization of FC interfaces, coordinates with

various services like FLOGI Mgr, Domain Mgr, VSAN Mgr, WWN Mgr, Port Channel Mgr,

Zone Server, ACL Mgr, SPAN, TL Port Mgr, Module firmware etc., generates interface state

change notifications and SNMP Traps, provides APIs to access various runtime and

configuration data, implements SW_ILS services: ELP, ESC and EPP on E-ports, and

implements Trunking and provides support for Port Channels. EPP (Exchange of Peer

Parameters) is a SW_ILS service used mainly for Trunking.

Four extended link services that support port login:

N_Port Login (PLOGI)Two N_Ports establish a session and exchange service parameters.

N_Port Logout (LOGO)To end a session between two end ports.


Fibre Channel Port Login

ELS supported for N_Port N_Port Login (PLOGI)

Establishes a session between two end ports

N_Port Logout (LOGO)

Ends a current session between two end ports

N_Port Discover (PDISC)

Verifies service parameters between two end ports

Address Discover (ADISC)

Discovers the mechanism used to define the otherports address (by switches, jumper or hard coded)


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N_Port Discover (PDISC)To verify existing service parameters between two end ports.

Address Discover (ADISC)To discover the mechanism used to define the other ports

address (by switches, jumper or hard coded).


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Fibre ChannelPLOGI Parameters

N_Port Login allows two N_Ports to establish a session and exchange service parameters and

proceeds following the Fabric Login.

N_Port login is required before performing an ULP operations. It provides service parameters

of the destination N_Port and initializes flow control credits.

TLVs (Type Length Value).

BB_Credit (Point-to-Point) primarily used in Class 3 connections.

End-End Credit (Fabric only) primarily used in Class 1 connections.


N_Port

Device

N_Port

DeviceFlow Control Parameters

Service Parameters

Fibre Channel PLOGI Parameters

PLOGI (Port Login) Proceeds following the Fabric Login

Required before performing any ULP operations

Provides service parameters of the destination N_Port

Initializes flow control parameters

TLVs

BB_Credits

EE_Credits


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Fibre ChannelProcess Login

The Process Login (PRLI) ELS request shall be used to establish the operating environment

between a group of related processes at the originating Nx_Port and a group of related

processes at the responding Nx_Port.

Establishing the operating environment may include the establishment of image pairs and the

exchange of service parameters.

PRLI is used to communicate process service parameters from originator to responder N_Port.

PRLI is dependant on the FC-4 Protocol mapping for a specific upper-level protocol and is

defined during the FC-4 mapping process.

A process login remains in affect until a process logout occurs. The number of concurrent

process logins in effect at an Nx_Port is a function of the Nx_Port facilities available. Process

login is separate from N_Port Login.


N_Port

Device

N_Port

Device

ULP Parameters

Date post:	04-Jun-2018
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