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File and Disk Sharing Protocols April 2, 2008 Richard Sharpe

File and Disk Sharing Protocols April 2, 2008 Richard Sharpe Senior Software Engineer | Data Robotics Wireshark Contributor SHARK FEST '08 Foothill College March 31 - April 2, 2008. Agenda. Disk serving/sharing protocols File serving/sharing protocols Ethereal issues.

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File and Disk Sharing Protocols April 2, 2008 Richard Sharpe

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  1. SHARKFEST '08 | Foothill College | March 31 - April 2, 2008 File and Disk Sharing Protocols April 2, 2008 Richard Sharpe Senior Software Engineer | Data Robotics Wireshark Contributor SHARKFEST '08 Foothill College March 31 - April 2, 2008

  2. SHARKFEST '08 | Foothill College | March 31 - April 2, 2008 Agenda • Disk serving/sharing protocols • File serving/sharing protocols • Ethereal issues

  3. File Sharing or Disk Sharing • Network Oriented • Disk or File blocks?

  4. Disk Sharing Basics

  5. Disk Sharing Dimensions • How many Logical Units (LUNs) • Size of each LUN • Does the protocol restrict LUN size • Management • Storage protection • Mirroring or striping or P+Q • Provisioning • Do you back all advertised blocks with real blocks? • When do you alert user more storage is needed? • Mixed LUN sizes? • Shared access?

  6. Disk Sharing/Serving Protocols • Protocol • SCSI • ATA • Proprietary • Transport • USB • FireWire (IEEE1394) • Ethernet • FibreChannel and FibreChannel over Ethernet (FCoE) • Point-to-point cable (SATA, SAS, PATA, Parallel SCSI)

  7. SCSI Introduction • Parallel • 8, 16, and 32-bit cables • Terminators, LVDS, etc • Serial Attached SCSI • USB and FireWire • TCP/IP – ie, iSCSI • SCSI over FibreChannel • SCSI over Ethernet - HyperSCSI

  8. SCSI Standards Architecture www.t10.org/scsi-3.htm

  9. Original SCSI Model • Eight Phases • Bus Free • Arbitration • Selection • Reselection • Command (CDB) • Data • Message • Status

  10. SCSI Data Phases COMMAND • Target requests Command Descriptor Block (CDB) • 6, 10, 12, 16 or variable byte CDBs

  11. SCSI Data Phases, Command 10-Byte CDBs

  12. SCSI Data Phases, Command • 12-Byte CDBs • Provides for 6-byte LBAs • 32-bit transfer sizes • 16-Byte CDBs • Provides for 8-byte LBAs • 32-bit transfer sizes

  13. SCSI Data Phases • Data Transfer • Target requests transfer to or from initiator • Status • Target requests transfer of status to initiator • Message • Target can request transfer of messages • See www.t10.org, eg http://www.t10.org/ftp/t10/drafts/spc2/spc2r20.pdf

  14. USB Storage Details • SCSI over USB Bulk Only Transport • Command Block Wrapper • Wraps CDB (max 16-bytes) • Data in (to host) or data out (from host) • Command Status Wrapper • Wraps the status and residue • No sense data • See: http://www.usb.org/developers/devclass_docs/usbmassbulk_10.pdf

  15. Command Block Wrapper • Sent to Bulk endpoint by the host

  16. Command Status Wrapper • Sent on a Bulk In endpoint by the device

  17. Protocol Dissection Issues • Capture files? • Wireshark understands Linux usbmon captures • Request and response matching • Match data in or data out to requests • Conversations • Using the existing SCSI dissector

  18. Use the source • epan/dissectors/packet-usb-masstorage.c

  19. USB Storage Details

  20. ATA • Serial ATA • ATA over Ethernet (ATAoE) • SATA over FibreChannel • ATA over FireWire? • Why not, given Firewire extension to 3+Gbps?

  21. File Sharing Basics

  22. Create a file Delete a file Rename a file Open a file Read/write a file Lock portions of a file Change permissions Read/write file attributes Extend/truncate a file File Operations

  23. Further File Sharing Dimensions • One tree of files per server or a forest • Namespaces • Single network-wide namespace or one (or more) per server • Stateless vs Stateful • Access permission model • Sharing model • Locking • Caching mechanisms • Performance

  24. File Serving/Sharing Protocols • NFS • NFS v3 • NFS v4 • CIFS/SMB • NetWare • Parallel NFS • Andrew File System • PanFS

  25. NFS v3 • RFC1813 (http://www.faqs.org/rfcs/rfc1813.html) • Improvement of NFS v2 • Stateless • Operates over UDP and TCP • Server does not need to keep client-related state • File handles encapsulate state • Based on XDR and SunRPC • File attributes returned with most calls • Reduces number of calls and round trips

  26. NFS v3 continued • Locking protocol external to NFS v3 • NFS lock manager • Mount protocol separate

  27. NFS v4 • RFC3010 (http://www.faqs.org/rfcs/rfc3010.html) • Servers keep state • Operates over TCP and UDP • Open request establishes state • Lease based, with release on timeout • Compound operations • Locking • Caching and delegation

  28. CIFS/SMB • Originally NetBEUI • Over Ethernet Frame Protocol • Server Message Block protocol • Renamed CIFS in 1996 • State based • TCP connection oriented • NetBIOS header • Forest of trees • Shares are the point of access

  29. CIFS/SMB continued • Sharing defined in the protocol • Read/Write/Delete specified at file open time • Locking part of the protocol • Ranges of bytes can be locked for reading/writing • Client caching protocol part of the protocol • OpLock based (callbacks)

  30. CIFS/SMB Packets Request/Response Protocol • Basic Header fields repeated in request and response • Makes response matching relatively simple

  31. CIFS/SMB Header

  32. packet-smb.c • Now look at the source code • epan/dissectors/packet-smb.c

  33. NetWare • Based on XNS • Internet Packet Exchange Protocol – IPX • Network layer - connectionless • Sequenced Packet Exchange – SPX • Transport protocol – connection oriented • Service Advertisement Protocol • Very popular at one time

  34. Parallel NFS • Extension to NFSv4 (http://www.pnfs.com/) • Allows direct, parallel, access to storage devices • Provides clients with layout information

  35. Andrew File System

  36. PanFS

  37. These Protocols and Ethereal • Protocol dissectors reusable • Capture formats can inject any packet types • Eg, SCSI over FC over Ethernet • State keeping

  38. Problems • More capture file format need to be included • Especially for proprietary tools • USB sniffers • FireWire sniffers • Other sniffer products

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