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Fibre Channel – Chapter 9

Fibre Channel – Chapter 9. Fibre Channel Introduction. Originally developed for mainframe & supercomputing environments to connect together high speed clusters & storage

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Fibre Channel – Chapter 9

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  1. Fibre Channel – Chapter 9

  2. Fibre ChannelIntroduction • Originally developed for mainframe & supercomputing environments to connect together high speed clusters & storage • Development began in 1988 under the auspices of the ANSI T11 committee (device level interfaces) and culminated in the approval of the ANSI standard in 1994 • Besides its use as a very high bandwidth I/O channel technology, there is increasing interest in Fibre Channel as a LAN technology because of its high speed and unique combination of channel & network oriented properties: • Data-type qualifiers for routing data into specific interface buffers • Link-level constructs designed to support individual I/O operations • Support for existing I/O interface specifications (SCSI, HIPPI, etc.) • Full multiplexing capabilities • Peer-to-peer connectivity between any two ports in a FC network • Ability to internetwork with other LAN, WAN, & I/O technologies Class #5: Token Ring LANs & Fibre Channel

  3. Fibre ChannelIntroduction • Comparsion of Fibre Channel with Gigabit Ethernet and ATM [Table 9.1] Class #5: Token Ring LANs & Fibre Channel

  4. Fibre ChannelArchitecture • Designed to provide a common, efficient, high-speed transport to a wide variety of devices through a single port type • Requirements outlined by the Fibre Channel Association: • Full-duplex links over a fiber pair (one transmit/one receive) • Bi-directional performance up to 3.2-Gbps on a single link • Support over distances up to 10 kilometers • Small connectors for high density applications • High-capacity utilization with distance insensitivity • Greater connectivity than existing multi-drop channels • Broad availability at reasonable cost • Support for multiple cost/performance levels, from PCs to clusters • Ability to carry multiple protocols and command sets • The best way to meet such demanding requirements was to develop a transport mechanism based on simple point-to-point links & a switching network Class #5: Token Ring LANs & Fibre Channel

  5. Fibre ChannelTerminology • Fibre Channel, having a different heritage than other LAN/WAN technologies, has different terminology [Table 9.2] • Dedicated Connection: A circuit guaranteed and retained by the fabric for two specified N_Ports • Exchange: The basic mechanism that transfers information, consisting of one or more related non-concurrent sequences in one or both directions • Fabric: The entity that interconnects various N_Ports attached to it and handle the routing of frames • Intermix: A mode of service that reserves the full FC capacity for a dedicated (Class 1) connection but allows the transport of additional connectionless data if space is available • Node: A collection of one or more N_Ports • Operation: A set of one or more, possibly concurrent, exchanges that is associated with a logical construct above the FC-2 layer Class #5: Token Ring LANs & Fibre Channel

  6. Fibre ChannelTerminology (continued) • Fibre Channel, having a different heritage than other LAN/WAN technologies, has different terminology [Table 9.2] • Dedicated Connection: A circuit guaranteed and retained by the fabric for two • Originator: The logical function associated with an N_Ports that initiates an exchange • Port: The hardware entity within a node that performs data communications over a FC link • Responder: The logical function in a N_Port responsible for supporting an exchange initiated by an originator • Sequence: A set of one or more data frames with a common sequence ID transmitted unidirectionally from one N_Port to another N_Port, with a corresponding response, if applicable, transmitted in response to each data frame Class #5: Token Ring LANs & Fibre Channel

  7. Fibre ChannelTerminology • Fibre Channel Elements • The key elements of a FC network are the end devices called nodes and the collection of switching elements called the fabric • Communication between nodes across a FC network consists of transmission of frames across the point-to-point links & fabric • Each node has one or more N_Ports for connection to the fabric • Nodes connect to F_Ports on the fabric via bi-directional point-to-point links • Fabrics can be a single switch or a general collection of switching elements • Frames may be buffered within the fabric, making it possible for nodes to connect to the fabric at different data rates • The fabric is a switched architecture, not a shared access medium, so no MAC issues are encountered and no MAC sublayer is necessary • The FC network scales easily in terms of ports, data rate, and distance covered and through its layered protocol architecture interworks with existing LAN and I/O protocols Class #5: Token Ring LANs & Fibre Channel

  8. Fibre ChannelTerminology • Basic Fibre Channel Architectural Diagram Class #5: Token Ring LANs & Fibre Channel

  9. Fibre ChannelExample Architecture Class #5: Token Ring LANs & Fibre Channel

  10. Fibre ChannelProtocol Specifications • Fibre Channel Protocol Architecture • The Fibre Channel standard reference model is organized into five levels [Figure 9.3 and Table 9.3] • These are not ‘levels’ in the strict sense of the OSI model but are instead functional groupings of services and/or definitions • The standard does not dictate actual implementations, relationships between the levels, or the specific interfaces between levels • Levels FC-0, FC-1, and FC-2 are defined together in a standard called the Fibre Channel Physical and Signaling Interface (FC-PH) • No final standard has been issued for FC-3 • A number of standards have been developed at FC-4 specifying how Fibre Channel interfaces to existing LAN and I/O technologies Class #5: Token Ring LANs & Fibre Channel

  11. Fibre ChannelProtocol Specifications • Fibre Channel Protocol Architecture (continued) Class #5: Token Ring LANs & Fibre Channel

  12. Fibre ChannelProtocol Specifications • Fibre Channel Protocol Architecture (continued) • Details on the FC-0 level • A variety of physical media and data rates are allowed: • Data rates: 100-Mbps to 3.2-Gbps • Media: fiber optic, coaxial cable, and STP • Distance: 50 m to 10 km depending on data rate and media • The FC-1 level uses a 8B/10B encoding scheme in which 8 bits of data from the FC-2 level are encoded into a 10 bit binary symbol Class #5: Token Ring LANs & Fibre Channel

  13. Fibre ChannelProtocol Specifications • Fibre Channel Protocol Architecture (continued) • The FC-2 level is responsible for the transmission of data between N_Ports, which requires the following: • Addressing of N_Ports • Permissible topologies of the fabric • Classes of service • Segmentation and reassembly of frames as well as higher level grouping of frames (sequences and exchanges) • Sequencing, flow control, and error control • The FC-3 level provides a common set of services across multiple N_Ports • Striping: the process of using multiple ports to transmit a single data unit in parallel • Hunt groups: allows a connection to be established to any available N_Port in the group • Multicast (and broadcast) Class #5: Token Ring LANs & Fibre Channel

  14. Fibre ChannelProtocol Specifications • Fibre Channel Protocol Architecture (continued) • The FC-4 level defines how other protocols interoperate with Fibre Channel (specifically FC-PH) • SCSI – a common device interface standard for computer peripherals • HIPPI – a high speed I/O channel used in mainframe and supercomputing environments • IEEE 802 – how IEEE 802 MAC frames map to Fibre Channel frames • ATM • IP – how to map packets into Fibre Channel frames (RFC 2625) Class #5: Token Ring LANs & Fibre Channel

  15. Fibre ChannelPhysical Media and Topologies • A major strength of Fibre Channel is that it provides a range of options for the physical medium, the data rate on that medium, and the topology of the network • Transmission Media • A special shorthand nomenclature has been developed for FC media – it basically consists of the following: • Speed-Medium-Transmitter-Distance • FC-0 options are listed in Figure 9.4 • Allowable Media Types • Fiber Optic: both SM and both 50m and 62.5m MM • Coaxial Cable: three types of 75 ohm cable are specified, a thick RG-6/U, a thinner RG-59/U, and a miniature coax cable 0.1 inches in diameter • Shielded Twisted Pair: two types of 150 ohm cables are specified for use over short distances at data rates up to 200-Mbps: EIA-568 Type 1 STP: (two shielded twisted pair) or EIA-568 Type 2 STP (four pair STP) Class #5: Token Ring LANs & Fibre Channel

  16. Fibre ChannelPhysical Media and Topologies • Topologies • The most general FC topology is the fabric (switched) topology • Four basic topologies [Figure 9.5] are available in Fibre Channel: point-to-point, fabric, arbitrated loop (no hub), and arbitrated loop with hub • Point-to-point connects two end nodes with no switches or routing • The fabric topology can contain an arbitrary number of switches, some connecting to nodes and others that just provide transport between other switches • The fabric topology allows for easy scalability • In the fabric topology the overhead on nodes is minimized; they are only responsible for managing the point-to-point link to their local switch • Each port requires a unique address to allow frames to be delivered to the proper destination Class #5: Token Ring LANs & Fibre Channel

  17. Fibre ChannelPhysical Media and Topologies • Topologies (continued) • The arbitrated loop topology allows up to 126 nodes to be connected in a simple, low-cost loop • The ports on the loop are a special kind called NL_Ports because they must perform special functions associated with loop management • Operation is roughly equivalent to other token ring protocols • There is a token acquisition protocol controlling loop access • The fabric & loop topologies can be connected as long as one node can act as both an arbitrated loop & a fabric node that participates in routing decisions on the fabric • The topology of a given FC network is discovered automatically as part of network initialization Class #5: Token Ring LANs & Fibre Channel

  18. Fibre ChannelPhysical Media and Topologies • Fibre Channel Topologies (continued) Class #5: Token Ring LANs & Fibre Channel

  19. Fibre ChannelFraming & Classes of Service • Framing Protocol • The FC-2 layer defines the rules for the transfer of frames between nodes, comparable to the OSI data link layer • FC-2 specifies the types of frames, procedures for the exchange of frames, frame formats, flow control, and classes of service • Classes of Service • FC-2 defines multiple classes of service; these classes are determined by the way communication is established between two ports and their flow control and error control capabilities • Five classes of service are currently defined: • Class 1: Acknowledged Connection-oriented service • Class 2: Acknowledged Connectionless service • Class 3: Unacknowledged Connectionless service • Class 4: Fractional Bandwidth Connection-oriented service • Class 6: Unidirectional Connection service Class #5: Token Ring LANs & Fibre Channel

  20. Fibre ChannelFraming & Classes of Service • FC-2 Classes of Service • Class 1 Service (Acknowledged Connection-oriented service) • Provides a dedicated path through the fabric which behaves to the end nodes like a point-to-point link • Also provides a guaranteed data rate with sequenced delivery of frames • The end node requests the setup of a Class 1 service connection using a special start-of-frame delimiter (SOFc1) • Class 1 service is advantageous for long constant bandwidth transfers of data (e.g. - streaming backups over a network) Class #5: Token Ring LANs & Fibre Channel

  21. Fibre ChannelFraming & Classes of Service • FC-2 Classes of Service (continued) • Class 2 Service (Acknowledged Connectionless service) • Provides an acknowledged data transmission service without the overhead of setting up a connection through the fabric • Acknowledgements frames are returned by the receiving port, if a delivery cannot be made due to congestion a busy frame is returned • This is not the case with frames that cannot be delivered due to frame errors • Sequenced delivery is not guaranteed; frames can take different paths through the fabric if possible • Multiplexing of frames from different sources and/or destinations is allowed • Class 2 service is good for Storage Area Networks (SANs) Class #5: Token Ring LANs & Fibre Channel

  22. Fibre ChannelFraming & Classes of Service • FC-2 Classes of Service (continued) • Class 3 Service (Unacknowledged Connectionless service) • Provides a basic datagram service with no connection setup • No guaranteed nor acknowledged delivery • Good for short bursts of data or delivery of multicast/broadcast data • Class 4 Service (Fractional Bandwidth Connection-oriented service) • Provides a service similar to Class 1 but also provides Quality of Service (QoS) guarantees and reservations • Allows the specification of guaranteed bandwidth & bounded latency • QoS parameters established separately for each direction • Good for time-critical & real-time applications like videoconferencing • Class 6 Service (Unidirectional Connection service) • Provides the reliable unicast delivery found in Class 1 but also supports reliable multicast and preemption • Good for video streaming and broadcasting Class #5: Token Ring LANs & Fibre Channel

  23. Fibre ChannelFrames, sequences, and exchanges • There is much more to the FC-2 layer than frames & classes of service; it defines a set of functional building blocks for higher layer services • Also defines a number of protocols used to implement services at a port • Typical protocols are creating or terminating a connection, transferring data, etc. • Protocols consist of an exchange of information between N_Ports, which in turn consists of sequences, and sequences a composed of a related set of frames Class #5: Token Ring LANs & Fibre Channel

  24. Fibre ChannelFrames, sequences, and exchanges Class #5: Token Ring LANs & Fibre Channel

  25. Fibre ChannelFrames, sequences, and exchanges (continued) • There are two general types of frames: data and control • The three types of data frames are used to transfer higher level information between N_Ports • FC-4 Device Data: used to transfer higher-layer data units from protocols specified in FC-4 standards (IP, SCSI, etc.) • FC-4 Video Data: used to transmit streamed video between buffers without an intermediate storage • Link Data: used to support higher level control information between N_Ports • There are currently three types of link control frames defined: • Link Continue: functions as an acknowledgement in Fibre Channel sliding-window based data transfer • Link Response: used as a negative acknowledgement in FC sliding-window based data transfer • Link Command: A reset command used to reinitialize the sliding-window based transfer mechanism Class #5: Token Ring LANs & Fibre Channel

  26. Fibre ChannelFrames, sequences, and exchanges (continued) • Sequences • With Fibre Channel a maximum frame size is imposed at the FC-2 layer but is transparent to higher layers • Higher layers set down chunks of data to FC-2, which may need to break them up into a sequence of frames • The sequence of data frames needed to carry a single higher-layer chunk of data may also be accompanied by one or more link control frames for acknowledgement • FC-2 provides the segmentation and reassembly that supports the transmission of sequences as well as error control • Errors in a frame that belongs to a sequence causes the retransmission of that whole sequence (and any others transmitted after it – go back N ARQ) Class #5: Token Ring LANs & Fibre Channel

  27. Fibre ChannelFrames, sequences, and exchanges (continued) • Exchanges • Exchanges are mechanisms for organizing multiple sequences into a higher-level construct to allow easier interfacing to applications • Examples of exchanges are SCSI disk operations like a read or write • Can involve either a unidirectional or bi-directional transfer of sequences • Within a given exchange, only a single sequence can be active (though sequences from different exchanges can be simultaneously active) Class #5: Token Ring LANs & Fibre Channel

  28. Fibre ChannelFrames, sequences, and exchanges (continued) • Protocols • An exchange is tied to a protocol that provides a specific service for higher levels • Some common protocols that may be used by any higher application: • Fabric Login: executed upon initialization of an N_Port, requires the exchange of the N_Port address, classes of service supported, and flow-control parameters • N_Port Login: the exchange of service parameters between a pair of N_Ports before data exchange (buffer space, service classes supported, etc.) • N_Port Logout: the termination of a connection between a pair of N_Ports Class #5: Token Ring LANs & Fibre Channel

  29. Two levels of credit are in use with Class 1 & 2 services -- end-to-end and node-to-switch Class 4 may have the same flow control as Classes 1 and 2; can’t find a good answer because most current equipment only supports class 2 & 3 Fibre ChannelFraming & Classes of Service • Flow Control • Fibre Channel provides a sophisticated set of flow control mechanisms at two ‘levels’: end-to-end and buffer-to-buffer • The key to the FC flow control mechanisms is the concept of credit: credit is negotiated at login and denotes the number of unacknowledged frames allowed at any time • End-to-End Flow Control • This type of flow control paces the flow of frames between N_Ports • Requires acknowledgements to operate, so end-to-end flow control can be used only with Class 1 and Class 2 services Class #5: Token Ring LANs & Fibre Channel

  30. Fibre ChannelFlow Control (continued) • End-to-End Flow Control • Three types of acknowledgements are possible in a Class 1 or Class 2 service • ACK_1: acknowledges one data frame & decrements the credit count by 1 • ACK_N: acknowledges N data frames & decrements the credit count by N • ACK_0: acknowledges a whole sequence, decrementing the credit count by the number of frames in the sequence Class #5: Token Ring LANs & Fibre Channel

  31. Fibre ChannelFlow Control (continued) • End-to-End Flow Control (continued) • Acknowledgement types cannot be mixed; if ACK_1 is initially used for a Class 1 connection than it must be used for the duration of the connection • Busy and Reject control frames are used for flow control • The F_BSY frame indicates the fabric is busy and cannot deliver a frame • The P_BSY frame indicates the destination port is busy and cannot accept a frame; the sender will try a predefined number of times to retransmit the frame • With the Reject (F_RJT and P_RJT) frames, delivery of the data frame is being denied (for some reason other than congestion) • When a frame belonging to a sequence is rejected the whole sequence must be retransmitted Class #5: Token Ring LANs & Fibre Channel

  32. Fibre ChannelFlow Control (continued) • Buffer-to-buffer Flow Control • This is flow control across a pair of ports connected by a point-to-point link, assuring that buffers are available in the ports at either end of the link • This mechanism is also applicable to all classes of service (including Class 3 datagram service) • A single type of control signal, the R_RDY frame, is used for buffer-to-buffer flow control • As a data frame is transmitted across the link, the sender increments its credit count for the link • At the receiving port the data frame is buffered as received • As soon as the data frame is switched to another port’s buffer on the switch, the receiving port sends back the R_RDY frame to the sending port • When the sending port receives the R_RDY frame it decrements the credit count, opening its send window by one frame Class #5: Token Ring LANs & Fibre Channel

  33. Fibre ChannelFraming & Classes of Service • Frame Format [Figure 9.10] • The Fibre Channel Frame contains five general fields: • Start Delimiter • Frame Header • Data • Cyclic Redundancy Check (CRC) • End Delimiter Class #5: Token Ring LANs & Fibre Channel

  34. Fibre ChannelFraming & Classes of Service • Frame Format - Start of Frame Delimiter • The start of Frame Delimiter includes a four byte set of non-data symbols denoting the start of a frame and allowing synchronization • The SOF delimiter comes in several varieties, each of which will specify the frame’s type and class of service • Examples are SOF Class 1 connection (SOFc1), SOF normal (for data frames), and SOF fabric (for control frames in the fabric) Class #5: Token Ring LANs & Fibre Channel

  35. Fibre ChannelFraming & Classes of Service • Frame Format - FC- 2 Frame Header • Contains the control data required at this level; consists of the following fields: • Routing control: contains two subfields, one that denotes the type of frame (device data, link control, etc.) and the type of data within the frame • Destination Identifier: destination N_Port or F_Port • FC uses two levels of addressing: a globally unique identifier (world wide port/node names) & a lower level port identifier • World wide/port name is used by higher layers and for network management • Port identifier is the 3-byte that is used for frame routing that consists of three parts: domain, area, and port • The hierarchical addressing structure facilitates routing and management of the fabric • A mechanism for mapping between the two addresses is necessary Class #5: Token Ring LANs & Fibre Channel

  36. Fibre ChannelFraming & Classes of Service • Frame Format - FC- 2 Frame Header • Contains the control data required at this level; consists of the following fields: • Source Identifier: source N_Port or F_Port • Type: if the routing control field specifies an FC-4 frame, then this field specifies the payload protocol (SCSI, IP, etc.) • This field and the Route control field allow the destination N_Port to deliver the data to the correct higher layer ‘user’ • Frame control: contains control information relating to frame content • Is frame a retransmission? Is frame part of a sequence? • Sequence ID: unique identifier for a sequence used for all frames belonging to it • Data Field control: specifies which, if any, of four optional headers are present Class #5: Token Ring LANs & Fibre Channel

  37. Fibre ChannelFraming & Classes of Service • Frame Format - Frame Header (continued) • Contains the control data required at this level; consists of the following fields: • Sequence count: A unique number assigned sequentially to each frame in a sequence (for flow control and proper reassembly of frames within a sequence) • Originator Exchange Identifier: a unique identifier assigned to the higher layer initiator of an exchange • Responder Exchange Identifier: a unique identifier assigned to the higher layer destination of an exchange • Parameter: used in different ways for link control and data frames • Link control frames carry information specific to the control function in this field • Data frames may carry an address meaningful to the upper layer protocol Class #5: Token Ring LANs & Fibre Channel

  38. Fibre ChannelFraming & Classes of Service • Frame Format - Data Field • Contains user data in a multiple of four bytes chunks up to a maximum of 2112 bytes • Can also include one or more optional headers whose presence is denoted in the Data Field control field: • Expiration Security optional header: can carry an expiration date for the frame and well as other security data over and above the FC-PH standard • Optional Network Header: may be used by a bridge or gateway node interfacing to an external network to allow tunneling (includes 8 bit source and destination network addresses) • Optional Association Header: may help specify an upper layer process (or group of processes) associated with an exchange • Optional Device Header: if used the format is specified by the upper layer protocol used with the frame Class #5: Token Ring LANs & Fibre Channel

  39. Fibre ChannelFraming & Classes of Service • Frame Format - CRC & End Delimeter • CRC field: the error detection algorithm is the same 32 bit CRC used with FDDI and IEEE 802 • End of Frame Delimiter • A four byte field denoting the end of the frame • The EOF field may be modified by a switch in the fabric if it finds an error in the frame or some other condition that invalidates the frame • There are three different EOF delimiters for valid frames: • EOFt denotes the end of a valid sequence • EOFdt is used with Class 1 service to indicate that the frame is the last frame on the logical connection (i.e. – the connection is being terminated) • EOFn is used to denote successful transmission of frames not covered by the first two Class #5: Token Ring LANs & Fibre Channel

  40. Fibre ChannelExamples of Equipment • Fibre Channel Equipment Manufacturers • High-end (“Director-Class”) Switches • Brocade Silkworm 2400 (http://www.brocade.com/products/directors/silkworm_24000/index.jsp) • McData Intrepid 6140 (http://www.mcdata.com/products/hardware/director/6140.html) • Low-end (“Edge”) Switches • EMC DS-16B3(http://www.emc.com/pdf/products/connectrix/connectrix_DS_16B2.pdf) • Cisco MDS 9120 (http://www.cisco.com/en/US/products/ps5993/index.html) • Host-Bus Adapters (HBA) • HP Storageworks FCA-2408 2Gbps PCI-X (http://h18006.www1.hp.com/products/storageworks/fca2408/index.html) • Qlogic QLA2200L 1Gbps PCI (http://www.qlogic.com/support/product_resources.asp?id=118) Class #5: Token Ring LANs & Fibre Channel

  41. IEEE 802.3 Family of LAN ProtocolsHomework & Reading • Homework #4 - Due in four weeks (3/22) • The idea of using Ethernet as a service provider technology is very attractive, but it lacks much of the functionality needed in that environment. Research a technology called Resilient Packet Ring (RPR) and write 1-1.5 pages on what its goals are and what functionality it provides. • Fibre Channel continues to evolve as a networking technology: research and write 1-1.5 pages on two different enhancements are currently being developed (e.g. – higher speeds, new higher layer mappings, etc.) • Redo OPNet Lab #1 using a 16-Mbps Token Ring instead of ethernet; answer all questions except #4. • Reading • This week’s material: Stallings chapters 8 and 9 • Next week: SONET, ATM, & ATM LANs (chapter 11) Class #5: Token Ring LANs & Fibre Channel

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