Spring 2001

1
Fiber Channel

• Spring 2001
• Prof. Choong Seon HONG

2
Introduction

• I/O channel transfers data between a buffer at
  the source device and a buffer at the destination
  device, moving only the user contents from one
  devices to another, without regard to the format
  or meaning of the data
• I/O channels typically manage transfers between
  processors and peripheral devices, such as disks,
  graphics equipment, CD-ROMs, and video devices.
• Fibre channel is designed to combine the best
  features of both technologies, simplicity and
  speed of channel communications with flexibility
  and interconnectivity that characterize
  protocol-based network communications

3
Introduction (contd)

• Fiber channel allows system designers to combine
  traditional peripheral connection, host-to-host
  interworking, loosely coupled processor
  clustering, and multimedia applications in a
  single multiprotocol interface.
• The types of channel-oriented facilities
  incorporated into the Fiber Channel protocol
  architecture
• Data type qualifiers for routing frame payload
  into particular interface buffers
• Link-level constructs associated with individual
  I/O operations
• Protocol interface specifications to allow
  support of existing I/O channel architectures
  such as SCSI

4
Introduction (contd)

• LAN Technology comparison

5
Fibre Channel Architecture

• Designed to provide a common, efficient
  transport system so that a variety of devices and
  applications can be supported through a single
  port type.
• The ambitious requirements of Fiber Channel
  Association
• Full-duplex links with two fibers per link
• Performance from 100 Mbps to 3.2 Gbps on a
  single link (200 Mbps to 6.4 Gbps per link)
• Support for distance up to 10Km
• Small connectors
• High-capacity utilization with distance
  insensitivity
• Greater connectivity than existing multidrop
  channels
• Broad availability (i.e., standard components)
• Support for multiple cost/performance levels,
  from small systems to super-computers
• Ability to carry multiple existing interface
  command sets for existing channel and network
  protocols

6
Fibre Channel Architecture (contd)

• The solution about requirements
• developing a simple generic transport mechanism
  based on point-to-point links and a switching
• supporting a simple encoding and framing scheme
  that support a variety of channel and network
  protocols

7
Fibre Channel Architecture (contd)

• Fiber Channel Terms

8
Fibre Channel Architecture (contd)

• Fibre Channel Elements
• Nodes
• Fabric

9
Fibre Channel Architecture (contd)

• Fibre Channel Elements (contd)
• Frames may be buffered within the fabric, making
  it possible for different nodes to connect to the
  fabric at different data rates.
• a more general network of fabric element

10
Fibre Channel Architecture (contd)

• Fibre Channel Elements (contd)
• Fabric is responsible for buffering and routing
  frames between source and destinations nodes.
• Fibre channel is more like a traditional
  circuit-switched or packet-switched network.
• not concerned with medium access control (MAC)
  issues
• Fibre channel can readily accommodate new
  transmission media and data rates by adding new
  switches and F_Ports to an existing fabric.

11
Fibre Channel Architecture (contd)

• Fibre Channel Protocol Architecture

12
Fibre Channel Architecture (contd)

• Fibre Channel Levels

13
Fibre Channel Architecture (contd)

• Fibre Channel Protocol Architecture (contd)
• Physical interface and media
• allowing a variety of physical media and data
  rates
• physical media are optical fiber, coaxial cable,
  and shielded twisted pair.
• Transmission protocol
• dealing with the transmission of data between
  N-Ports in the form of frames
• Framing protocol
• related concepts
• Node and N_Port and their identifiers
• Topologies
• Class of services provided by the fabric
• Segmentation of data into frames and reassembly
• Grouping of frames into logical entities called
  sequences
• Sequencing, flow control, and error control

14
Fibre Channel Architecture (contd)

• Fibre Channel Protocol Architecture (contd)
• Common services
• Stripping Making use of multiple N_Ports in
  parallel to transmit a single information unit
  across multiple links simultaneously.
• Hunt Group a set of associated N_Ports at a
  single node
• Multicast delivering to all N_Ports on a
  fabric (broadcast) or to a subset of the N_Ports
  on a fabric
• Mapping FC-4
• Defining the mapping of various channel and
  network protocol to FC-CH
• I/O channel interfaces
• SCSI (simple computer system interface) used to
  support high-capacity and high-data-rate devices,
  such as disks and graphics and video equipment
• HIPPI (high-performance parallel interface)
  used for mainframe/super computer environments

15
Fibre Channel Architecture (contd)

• Network interfaces
• IEEE 802 802 MAC frames map onto Fibre Channel
  frames
• Asynchronous Transfer Mode (ATM)
• Internet Protocol
• FC-4 mapping protocols make use of the FC-PH
  capabilities to transfer upper-layer protocol
  (ULP) information.
• Each FC-4 specification defines the formats and
  procedures for ULP.

16
9.2 Physical Media and Topologies

• Major strengths of Fibre Channel
• Providing a range of options for the physical
  medium, data rate on that medium, and the
  topology of the network.
• Transmission media

17
Physical Media and Topologies (contd)

• Two most common implementations
• 110-TW-S-EL and 100-M5-I-SL
• FC-0 Nomenclature

18
Physical Media and Topologies (contd)

• Topologies
• Fabric (switched)
• Fabric is responsible for routing between
  N_Ports and error detection
• Point-to-point topology
• Arbitrated loop topology
• low cost topology for connecting up to 126 nodes
  in a loop
• containing the functions of both both N_Ports
  and F_Ports (NL_Ports)
• operating in a manner roughly equivalent to the
  token ring protocols

19
Physical Media and Topologies (contd)

• Topologies (contd)
• Five applications of Fibre Channel

20
9.3 Framing protocols

• Defining the rules for the exchange of
  higher-layer information between nodes
• Specifying types of frames, procedures for their
  exchange, and formats
• Similar to the data link layer function
• Class of Service
• Class 1 Acknowledged Connection Service
• providing a guaranteed data rate through a
  dedicated path
• containing a special start-of-frame delimiter
  referred to as SOFc1
• alerting the fabric that a connection is
  requested.
• the fabric allocates a circuit between N_Ports
• the destination N_Port can then transmit an ACK
  indicating its acceptance

21
Framing protocols (contd)

• Class 2 Acknowledged Connectionless Service
• analogous to the acknowledged connectionless LLC
  service
• no dedicated physical or logical connection
• useful for data transfers to and from a
  mass-storage system shared system among a number
  of workstations
• used for a storage area network (SAN)
  configuration
• Class 3 Unacknowledged Connectionless Service
• Allowing data to be sent rapidly to multiple
  devices attached to the fabric
• useful for interworking ad for multicast and
  broadcast transmission

22
Framing protocols (contd)

• Class 4 Fractional Bandwidth Connection-Oriented
  Service
• providing acknowledged connection-oriented
  service
• enabling establishment of virtual connections
  with bandwidth reservation for predictable QoS
  including guaranteed throughput and bounded
  end-to-end delay
• appropriate for time-critical and real-time
  applications, including audio and video
• Class 6 Unidirectional Connection Service
• providing the reliable unicast delivery of Class
  1
• supporting reliable multicast and preemption

23
Framing protocols (contd)

• Building Block Hierarchy

24
Framing protocols (contd)

• Frames
• Three types of data frames
• FC-4 Device Data used to transfer higher-layer
  data units from supported FC-4 protocols, such as
  IEEE 802, SCSI, and IP
• FC-4 Video Data transferred by an N-Port
  directly to or from a video buffer without first
  directing them to an intermediate storage
  location
• Link data used to transfer link application
  information between N_Ports.
• Three types of link control frames for
  sliding-window flow control mechanism
• Link Continue (acknowledge)
• Link Response
• Link Command
• Sequences
• FC-2 places no limit on the size of the unit,
  called a sequence
• Each data frame includes a sequence ID in its
  header
• When error is detected, FC-2 identifies the
  sequence containing error is retransmitted.

25
Framing protocols (contd)

• Exchanges
• a mechanism for organizing multiple sequences
  into a higher-level construct for the convenience
  of applications
• For example, in Fibre Channel standard for SCSI
  support, the various command, data transfer, and
  response sequences assoiciated with an individual
  disk operation are grouped into a single exchange
• Allowing SCSI logic to treat all transport
  functions of the operation as a single atomic
  unit for tracking and error recovery.

26
Framing protocols (contd)

• Example of Exchange Usage

27
Framing protocols (contd)

• Flow Control
• End-to-End Flow control
• used between two communicating N_Ports
• Each of the two N_Ports in a communication
  provides credit for a certain number of frames
• Used mechanism is a Credit_Count number of
  outstanding unacknowledged frames to the
  allocated credit of each type
• requiring some form of acknowledgment
• just used in Class 1 and Class 2
• Buffer-to-Buffer Flow Control
• used between two ports connected by a single
  point-to-pint link
• regulating traffic between an N_Port and the
  F_Port to which it is attached

28
Framing protocols (contd)

• Flow Control (contd)
• The concept of credit
• Prior to communication between two N_Ports
  (end-to-end) and between adjacent ports
  (buffer-to-buffer), each communicating port is
  allocated a credit during the initialization
  procedure.
• The transmitting port limits the number of
  outstanding unacknowledged frames to the
  allocated credit of each type and adjusts the
  credit according to the responses received.
• Used mechanism Credit_Count
• Initially 0
• Increased by 1 for each transmitted data frame
  and decreased by 1 for each acknowledgement of a
  data frame
• Count represents the number of outstanding data
  frames that have not been acknowledged and is
  not permitted to exceed the corresponding maximum
  credit negotiated at login

29
Framing protocols (contd)

• Flow Control Model end-to-end flow control

30
Framing protocols (contd)

• Flow Control Model Buffer-to-Buffer flow
  control

• The upper part of the figure indicating the use
  of R_RDY to regulate the flow of data frames
• The lower part indicating that R_RDY is also
  used to acknowledge receipt of control frames
  across the link

31
Framing protocols (contd)

• Frame Format

32
Framing protocols (contd)

• Frame Format (contd)
• Start of Frame Delimiter
• Including nondata symbols to assure recognition
  of the beginning of a new frame
• A number of different SOF delimiters, depending
  on the class of service and type of frame

33
Framing protocols (contd)

• Frame Format (contd)
• Frame Header
• Containing the bulk of the control information
  needed to manage the FC-2 protocol
• Routing Control (R_CTL)
• routing subfield (4 bits) indicating the type
  of frame (e.g., device data, video data, link
  control)
• information category subfield indicating the
  type of data contained in the frame (e.g.,
  solicited/unsolicited data, solicited/unsolicited
  control)
• Destination ID the address of destination
  N_Port or F_Port
• Source ID The address of the source N_Port or
  F_Port
• Type when R_CTL indicates the this is an FC-4
  frame, identifying the specific FC-4 frame type
  (e.g., SCSI, IEEE 802, IP)
• Frame Control containing control information
  relating to frame content
• Sequence ID

34
Framing protocols (contd)

• Frame Format (contd)
• Frame Header (contd)
• Data Field Control (DF_CTL) specifying the
  presence or absence of each of the four optional
  headers at the beginning of the data field for
  device data or video data frames
• Sequence Count the first frame of a sequence
  has sequence count 0
• Originator Exchange Identifier A unique ID
  assigned by the originator of an exchange.
• Responder Exchange Identifier A unique ID
  assigned by the responder of an exchange.
• Parameter For link control frames, the
  parameter field carries information specific to
  the individual link control frame
• Fibre channel uses a 24-bit address to uniquely
  identify each port This address has three
  components (e.g., domain, area, and port)
• Enabling an easily managed hierarchical address
  structure for use by the fabric.

35
Framing protocols (contd)

• Frame Format (contd)
• Data field
• A maximum of 2112 bytes
• Including an optional payload and zero or more
  of the following optional headers
• Expiration Security Header including an
  expiration time and security-related information
  that is beyond the scope of the FC-PH standard
• Network Header May be used by a bridge or
  gateway node that interfaces to an external
  network 8-byte network destination address and
  an 8-byte network source address
• Association Header May be to identify a
  specific process or group of processes within a
  node associated with an exchange
• Device Header determined by a level above FC-2
  

36
Framing protocols (contd)

• Frame Format (contd)
• CRC Field
• 32-bit cyclic redundancy check (CRC)
• End of Delimiter
• Indicating the end of the frame transmission
• EOF may be modified by an intervening fabric
  element to indicate that the frame is invalid or
  the frame content was corrupted and this
  transmission truncated.
• EOFt
• EOFdt
• EOFn
• EOFni
• EOFdti
• EOFa terminating a frame that is partial due to
  a malfunction in a link facility during
  transmission