Transcript
Fiber Channel
Gruppo Reti TLC
[email protected] http://www.telematica.polito.it/ STANDARD LAN - 1
Fibre Channel • Born to interconnect mainframes and servers to storage systems • Speed up to Gb/s using 8B/10B encoding on monomodal fibers @ 1300 nm • Up to 10 km • Physical medium: fibERs, but not only… • Interoperability with SCSI, Internet Protocol (IP), … • Standard ANSI X3.230-1994 STANDARD LAN - 2
Scenarios
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Scenarios
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Reference model Channels IPI
SCSI
Networks HIPPI
802.2
IP
ISO/OSI ATM
FC-4
Common Services
FC-3
Framing Protocol/Flow Control
FC-2
Encode/Decode
FC-1
Transport
Data Link
Physical
133 Mb/s 266 Mb/s 531 Mb/s 1062 Mb/s
FC-0 STANDARD LAN - 5
FC-0 layer
• Physical layer – Defines all physical properties: “Fibre” (misspelled to mean fiber but also copper) – Equivalent to OSI-1
• Requirement: BER smaller than 10-12 STANDARD LAN - 6
FC-1 layer • Line coding according to 8B/10B transmission encoding – Important scheme (adopted later in Gigabit Ethernet) – 8 bits words are transmitted using 10 bits symbols • • • •
Error detection (disparity control) Synchronization recovery and locking 100% D.C. voltage balance Additional line symbols are available and used for signaling (framing, sequence number) STANDARD LAN - 7
FC-2 Layer • Functions: – Framing – Sequence control – Flow Control – Manages several classes of services – Login/Logout between apparatus – Topology management – Segmentation and Reassembly
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FC-2 Layer • Several PDUs are defined 2: – Ordered Set: 4 byte long, used for signaling (SOF, EOF, R_RDY,…) – Frame: base data unit, up to 2148 byte (36B+2112B) – Sequence: 1 or more frames (similar to the sentence) – Exchange: 1 or more sequences (similar to a dialog)
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FC-2 Layer
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FC-2: frame format
4 bytes Start of Frame
24 bytes Frame header
CTL
Source Address
0-2112 bytes Data Field 0-64 bytes Optional header
Destination Type Address
0-2048 bytes Payload
Seq_Cnt
4 bytes 4 bytes CRC End Error of Check Frame
Seq_ID Exchange_ID
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FC-3 and FC-4 Layer • FC-3: not completely defined. Often not implemented. (e.g. multicast management) • FC-4: specifies how to interface upper layer protocols to fibre channel – Small Computer System Interface (SCSI) – Internet Protocol (IP) – High Performance Parallel Interface (HIPPI) – Asynchronous Transfer Mode - (ATM-AAL5) – Intelligent Peripheral Interface - 3 (IPI-3) (disk and tape) STANDARD LAN - 12
Fibre Channel Topologies • Topologies: – Point-to-point – Arbitrated loop – Fabric
• Different interfaces (ports) are defined – Node port: N_Port – Loop port: L_Port – Switch port: F_Port – … and combinations (FL_Port, …) STANDARD LAN - 13
Point-to-point N_port
N_port
• Only two N_ports with direct connection – Bidirectional – Dedicated capacity
• A link setup is required STANDARD LAN - 14
“Arbitrated Loop” topology L_port
L_port
• Most common solution: – Simple – Shared medium
• Up to 127 ports (all L_ports)
L_port
L_port
• Distributed access scheme • No limit on channel holding time • Optional fairness algorithms are available STANDARD LAN - 15
Access scheme • Every device has an Arbitrated Loop Physical Address (AL_PA) • When data must be transmitted – A reservation message is sent first ARBx (x= AL_PA) along the whole ring – When an ARB message is received back, the device • Is the owner of the ring, and can start the connection setup with another L_Port • After that, a point-to-point channel is created
– If more than a device sends an ARB message: • The highest priority ARB is retransmitted (ARBy goes over if y
