Post on 04-Jun-2018
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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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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.
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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
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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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Copyright 2003, Cisco Systems, Inc Network Storage Technology Overview 1-37
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.
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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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Copyright 2003, Cisco Systems, Inc Network Storage Technology Overview 1-39
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.
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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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Copyright 2003, Cisco Systems, Inc Network Storage Technology Overview 1-41
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.
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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.
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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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Copyright 2003, Cisco Systems, Inc Network Storage Technology Overview 1-43
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.
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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
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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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Copyright 2003, Cisco Systems, Inc Network Storage Technology Overview 1-45
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.
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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.
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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.
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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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Copyright 2003, Cisco Systems, Inc Network Storage Technology Overview 1-49
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.
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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.
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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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Copyright 2003, Cisco Systems, Inc Network Storage Technology Overview 1-51
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.
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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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Copyright 2003, Cisco Systems, Inc Network Storage Technology Overview 1-53
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
2003, Cisco Systems, Inc. All rights reserved. Deploying MDS 9000 Systems v1.0Module 1, Lesson 2 -20
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
2003, Cisco Systems, Inc. All rights reserved. Deploying MDS 9000 Systems v1.0Module 1, Lesson 2 -21
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:
2003, Cisco Systems, Inc. All rights reserved. Deploying MDS 9000 Systems v1.0Module 1, Lesson 2 - 22
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.
2003, Cisco Systems, Inc. All rights reserved. Deploying MDS 9000 Systems v1.0Module 1, Lesson 2 - 23
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.
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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.
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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.
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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.
2003, Cisco Systems, Inc. All rights reserved. Deploying MDS 9000 Systems v1.0Module 1, Lesson 2 - 27
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.
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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)
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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.
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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
2003, Cisco Systems, Inc. All rights reserved. Deploying MDS 9000 Systems v1.0Module 1, Lesson 2 - 32
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
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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.
2003, Cisco Systems, Inc. All rights reserved. Deploying MDS 9000 Systems v1.0Module 1, Lesson 2 - 34
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.
Fibre Channel Addressing
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.
2003, Cisco Systems, Inc. All rights reserved. Deploying MDS 9000 Systems v1.0Module 1, Lesson 2 -36
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
Fibre Channel Addressing
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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.
2003, Cisco Systems, Inc. All rights reserved. Deploying MDS 9000 Systems v1.0Module 1, Lesson 2 - 37
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).
2003, Cisco Systems, Inc. All rights reserved. Deploying MDS 9000 Systems v1.0Module 1, Lesson 2 -39
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
Fibre Channel Level 0
FC-0
Fibre Channel Level 2
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.
2003, Cisco Systems, Inc. All rights reserved. Deploying MDS 9000 Systems v1.0Module 1, Lesson 2 -40
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
2003, Cisco Systems, Inc. All rights reserved. Deploying MDS 9000 Systems v1.0Module 1, Lesson 2 - 41
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.).
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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.
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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)
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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.
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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)
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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.
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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.
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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)
13-17 Class 2 Service Parameters (16 bytes)
18-21 Class 3 Service Parameters (16 bytes)
22-25 Class 4 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.
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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.
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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.
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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.
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N_Port
Device
N_Port
Device
ULP Parameters