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FCoE Overview

FCoE Overview. IEEE CommSoc/SP Chapter Austin, Texas, May 21 2009 Tony Hurson tony.hurson@ieee.org. Networked Storage History. SCSI Read, Write over FC. FC Fabric Port Terminology. FC Routing. Ethernet Routing. Dynamic Scheme: Source Learning

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FCoE Overview

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  1. FCoE Overview IEEE CommSoc/SP Chapter Austin, Texas, May 21 2009 Tony Hurson tony.hurson@ieee.org

  2. Networked Storage History

  3. SCSI Read, Write over FC

  4. FC Fabric Port Terminology

  5. FC Routing

  6. Ethernet Routing • Dynamic Scheme: Source Learning • If unicast DstMAC is not in lookup table, flood frame to all ports except its source port. • Note source port of SrcMAC in lookup table, if not already present • Age/invalidate lookup entries • Similar flooding behavior for multicast • Precludes loops in fabric

  7. FC Frame Format

  8. Protocol Stack History and Comparison

  9. Lossless Ethernet – via PAUSE

  10. FCoE Early Deployment Example

  11. FCoE Frame Format

  12. FCoE Endpoint Model

  13. FCoE Switch Functional Model

  14. Converged Ethernet • AKA Data Center Bridging (DCB). Run up to four major traffic classes on single 10 GbE fabric. In order of market prevalence: • Networking (TCP/IP, lossy). • Block Storage (lossless FCoE, or lossless/lossy iSCSI). • Management (“heartbeat” traffic, low bandwidth, but must get through). • Inter-Process Communication (clustered computing: high bandwidth, low latency, lossless preferred).

  15. Groundwork for DCB • IEEE 802.1Qaz – ETS & DCBX – bandwidth allocation to major traffic classes (Priority Groups); plus DCB management protocol. • IEEE 802.1Qbb – Priority PAUSE. Selectively PAUSE traffic on link by Priority Group. • IEEE 802.1Qau – Dynamic Congestion Notification.

  16. IEEE 802.1Qaz Enhanced Transmission Selection • Support at least 3 Priority Groups/traffic classes • PGs identified by Priority field of existing 802.1Q VLAN Tag • Configured Bandwidth per PG has 1% resolution • PG15 has limitless bandwidth (use sparingly!, for Management) • Work Conservation – if the wire’s free, use it.

  17. ETS Configuration Example • PG0 (Storage): 40% of port b/w • PG1 (Networking): 20% of port b/w • PG2 (IPC): 40% of port b/w • PG15 (mgmt): limitless • If a PG underutilizes, others can fill the space. • Typical implementation: DWRR.

  18. IEEE 802.1Qbb Priority PAUSE

  19. IEEE 802.1Qau Dynamic Congestion Control Background • Lossless fabrics are prone to congestion spreading (congestion trees). • Ethernet-FC gateways with their different port speeds (10 GbE; 8 Gbps) are natural bottlenecks. • ETS Work Conservation model adds fuel to fire. • Solution: switches/endpoints notify traffic sources of incipient congestion, via feedback messages; sources reduce rates accordingly.

  20. Congestion Notification in Action

  21. Congestion Control at Endpoint Transmit

  22. FCoE Summary • Presents new, but very familiar, PHY and Link Layers for FC. • Core switching discipline remains FC-SW-5. • Higher FC layers almost completely unchanged (that’s the legacy value!) • Biggest Ethernet-level requirement: lossless fabric. • Part of Converged Ethernet initiative – lots of ancillary activity at IEEE.

  23. Further Reading • FCoE: www.t11.org • IEEE 802.1Q(az|au|bb): www.ieee.org • Thank you! Questions?

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