unh interoperability lab

Improving Networks Worldwide.

UNH InterOperability Lab

Serial Attached SCSI (SAS)Clause 9

Improving Networks Worldwide.

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SAS Clause 9

Clause 8

• Port Layer– Links SAS Link Layer state machines

with SSP, SMP, and STP state machines

• Operation of the Port Layer is transparent

• No major testable items are be found in Clause 8

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SAS Clause 9

Presentation Topics

• Transport Layer Protocols– SSP

•Frame Types•Sequencing•Command Mapping•Sample Traces

– SMP– STP

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SAS Clause 9

SSP Connections

• First, an SSP Connection is opened between two link partners– One must be an SSP Initiator– The other must be an SSP Target– Determined by bits asserted in the

Identify Address Frames

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SAS Clause 9

SSP Open Frame

• Frame Type– 1 Byte value 0x01, 0x05, 0x06, 0x07, 0x16– 0xF0 through 0xFF are vendor specific– All others are reserved and invalid

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SAS Clause 9

SSP Open Frame

• Hashed Destination and Source Addresses– 4 byte address calculated from the WWNs of

the source and destination– Details on Hash Algorithm and collision

likelihood found in Annex H of the SAS 2.0 Standard

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SAS Clause 9

SSP Open Frame

• TLR Control– Valid for only Command Frames

• Reserved for all other frame types

– Used to communicate support for Transport Layer Retries by initiators

– See Section 9.2.1 of SAS 2.0 Standard for more details

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SAS Clause 9

SSP Open Frame

• Retry Data Frames– Valid only for XFER_RDY Frames


– Set to 1 indicates to initiator to disable Transport Layer Retries for write DATA frames associated with this XFER_RDY

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SAS Clause 9

SSP Open Frame

• Retransmit– Valid for TASK, RESPONSE, and XFER_RDY

Frames• Reserved for all other frame types

– Set to one indicates the frame is a retransmission

• Circumstances described in 9.2.4 of SAS 2.0 Standard

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SAS Clause 9

SSP Open Frame

• Changing Data Pointer– Valid for Retransmitted DATA Frame


– Set to one indicates that DATA OFFSET field may not be sequentially increased

– More details in section 9.2.4.5 of SAS 2.0 Standard

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SAS Clause 9

SSP Open Frame

• Number of Fill Bytes– Valid for DATA and RESPONSE Frames


– Specifies the number of bytes between the Information Unit and the CRC in the frame added to make the size of the frame divisible by 4

– Needed for the CRC calculation to work correctly

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SAS Clause 9

SSP Open Frame

• Initiator Port Transfer Tag– AKA “Tag”– Used for establishing context for

Commands and Tasks– Assigned by Initiators

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SAS Clause 9

SSP Open Frame

• Target Port Transfer Tag– AKA “TPTT”– Used for establishing context for DATA

Writes– Assigned by a target– Optionally implemented by targets

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SAS Clause 9

SSP Open Frame

• Data Offset– Used to discribe where the data is

placed relative to series of data commands

– Valid for only DATA frames• Ignored in all other frames

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SAS Clause 9

SSP Open Frame

• Information Unit– Non-general information unit

• DATA, XFER_RDY, COMMAND...

– Varies by frame type– Contents covered further in this

presentation (slide 20)

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SAS Clause 9

SSP Open Frame

• Fill Bytes– Added only if needed– Used to make frame size divisible by

4 for CRC calculations– Number in command specified by

Number Of Fill Bytes Field

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SAS Clause 9

SSP Open Frame

• CRC – Cyclic Redundancy Check

– CRC is used to detect bit errors inside of transmitted frames

– Transmitter calculates CRC and attaches it to every frame

– Receiver calculates CRC at receiption and if it doesn't match what is received, transmits NAK (CRC ERROR) to the transmitter

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SAS Clause 9

SSP Open Frame

• CRC – Cyclic Redundancy Check– Computed over the entire SSP Frame– See Annex G of SAS 2.0 Standard for

more information on CRC

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SAS Clause 9

SSP Connections

• Once the SSP Connection (see Clause 7) is established, five types of frames can be transmitted inside that SSP connection– DATA– XFER_RDY– COMMAND– RESPONSE– TASK

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SAS Clause 9

SSP Frame Types

• DATA– Carries actual data to and from

targets and initiators

• XFER_RDY– Sent by targets giving initiators

permission to transmit data

• COMMAND– Contains CDBs for commands sent by

initiators

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SAS Clause 9

SSP Frame Types

• RESPONSE– Sent at the completion of a command

by targets to initiators. Contains information regarding current status and the command status

• TASK– Sent by initiators to targets to

manage outstanding commands and other non-command related activities

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SAS Clause 9

DATA Frames

• Type: 0x01• Information Unit: Data (Read or

Write)• Originates: From a SSP Initiator or

SSP Target• Information Unit Size: 1 to 1024

Bytes

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SAS Clause 9

DATA Frames Information Unit

• Only contains data

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SAS Clause 9

XFER_RDY Frames

• Type: 0x05• Information Unit: Transfer Ready• Originates: SSP Targets Only• Information Unit Size: 12 bytes

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SAS Clause 9

XFER_RDY Frames Information Unit

• Requested Offset– Specifies an offset in the write data

buffer of the application client which can be transmitted in the context of this XFER_RDY frame.

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SAS Clause 9

XFER_RDY Frames Information Unit

• Write Data Length– Specifies the number of bytes that

may be transmitted within the context of this XFER_RDY frame.

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SAS Clause 9

COMMAND Frames

• Type: 0x06• Information Unit: Command• Originates: SSP Initiator Only• Information Unit Size: 28 to 280

bytes

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SAS Clause 9

COMMAND Frames Information Unit

• Logical Unit Number– Refers to the LUN on the DUT this

command will be routed too

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SAS Clause 9


• Enable First Burst– Set to 1 specifies that the SSP port shall

expect first burst data for the command as defined by the FIRST BURST SIZE field in the Disconnect-Reconnect Mode Page

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SAS Clause 9


• Command Priority– Specifies the importance of the

command relative to other commands with TASK ATTRIBUTE set to 0

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SAS Clause 9


• Task Attribute– Used to control the order of execution

of received commands

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SAS Clause 9


• Task Attribute– Simple: 000b – Relies on COMMAND PRIORITY field

for order of execution via rules defined in SAM-4

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SAS Clause 9


• Task Attribute– Simple: 000b – Relies on COMMAND PRIORITY field

for order of execution via rules defined in SAM-4

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SAS Clause 9


• Task Attribute– Head of Queue: 001b– Specifies the Command is to be

handled according to the HEAD OF QUEUE task attribute defined in SAM-4

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SAS Clause 9


• Task Attribute– Ordered: 010b– Specifies the command is to be

handled according the ORDERED task attribute defined in SAM-4

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SAS Clause 9


• Task Attribute– ACA: 100b– Specifies the command is to be

handled according the rules for an ACA task attribute defined in SAM-4

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SAS Clause 9


• Task Attribute– All other values (011b and 101b-

111b) are reserved and shall be considered invalid

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SAS Clause 9


• Additional CDB Length– Length in Dwords (4 bytes) of the

ADDITIONAL CDB field

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SAS Clause 9


• CDB and Additional CDB Bytes– Together contain the Command

Descriptor/Date Block of the command– Commands are defined in SCSI Command

Standards • SPC, SBC, SSC, etc...

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SAS Clause 9

CDB Example

• Sample CDB – READ (16) Command– Covered in more detail in the SCSI

presentation

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SAS Clause 9

TASK Frames

• Type: 0x16• Information Unit: Task

Management Function• Originator: SSP Initiator only• Information Unit Size: 28 bytes

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SAS Clause 9

TASK Frames Information Unit

• Logical Unit Number– Refers to the LUN on the DUT this

Task Management Function will be routed too

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SAS Clause 9

TASK Frames Information Unit

• Task Management Function– Specifies the type of task

management function

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SAS Clause 9

TASK Frames Information Unit• Task Management Function

– 01h: ABORT TASK: Instructs the LUN to abort the task with the IPTT specified in the TASK Frame

– 02: ABORT TASK SET: Instructions the LUN to abort the task set associated with the ITPT specified in the TASK Frame

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SAS Clause 9


– 04h: CLEAR TASK SET: Instructs the LUN to clear the task set associated with the IPTT specified in the TASK Frame.

– 08h: LOGICAL UNIT RESET: Instructs the LUN to perform a reset

– 10h: I_T NEXUS RESET: Instructs the LUN to perform an I_T NEXUS RESET

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SAS Clause 9


– 20h: Reserved– 40h: CLEAR ACA: Instructs the LUN to

perform a Clear ACA function– 80h: QUERY TASK: Instructs the LUN

to perform a QUERY TASK function on the command associated with the IPTT specified in the TASK Frame

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SAS Clause 9

RESPONSE Frames

• Type: 0x07• Information Unit: Response

Information Unit• Originator: SSP Target only• Information Unit Size: 24 to 1024

bytes

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SAS Clause 9

RESPONSE Frames Information Unit

• Status Qualifier & Status– Format Determined by DATAPRES

Field

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SAS Clause 9

RESPONSE Frames Information Unit

• Datapres– Specifies if no data, response data, or

sense data is contained in this frame

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SAS Clause 9

REPSONSE Frames Information Unit

• Sense Data Length– Length of any Sense Data contained

within this frame

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SAS Clause 9


• Response Data Length– Length of any Response Data

contained within this frame

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SAS Clause 9


• Response Data– # of bytes specified of Response Data

• Sense Data– # of bytes specified of Sense Data

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SAS Clause 9

Response Data Field

• Additional Response Information– Contains information regarding

certain Task Management Functions as defined in SAM-4

– Reserved otherwise

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SAS Clause 9

Response Data Field

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SAS Clause 9

Sequences of SSP Frames

• Test Unit Ready and other Non-Data Commands

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SAS Clause 9


• Write Command Sequence

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SAS Clause 9


• Read Command Sequence

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SAS Clause 9


• Task management sequence

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SAS Clause 9

SAS Mapping

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SAS Clause 9

SAS Mapping

• All SCSI Commands are located in the CDB and Additional CDB Bytes Field of a SSP Command Frame

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SAS Clause 9

Sample Write Command Sequence

• Initiator sends command to target• Target returns XFER_RDY• Initiator send data to target• Target returns response when data

transmission is complete

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SAS Clause 9

Sample Read Command Sequence

• Initiator sends command to target• Target immediately begins transmitting

data• Target transmits response frame when

data transmission is complete

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SAS Clause 9

Presentation Topics


• Frame Types• Sequencing• Command Mapping• Sample Traces

– SMP– STP

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SAS Clause 9

SMP Frames

• SMP Frame Type– Specifies the frame type– 40h – SMP Request – SMP Initiators Only– 41h – SMP Response – SMP Targets Only

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SAS Clause 9

Major SMP Functions• REPORT GENERAL

– Returns general information

• DISCOVER– Returns specific information about

specified phy

• REPORT ZONE PERMISSION TABLE– Returns zone permission descriptors

requested (Current, Shadow, Saved, or Default)

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SAS Clause 9

Major SMP Functions• CONFIGURE ZONE PERMISSION

TABLE– Allows the configuration of the zone

permission descriptors

– ENABLE DISABLE ZONING– Turns zoning on or off on at the

expander device

– REPORT BROADCAST– Returns the Broadcast Descriptors

specified

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SAS Clause 9

Major SMP Functions• ZONED BROADCAST

– Instructs the zoning device to broadcast the specified zones

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SAS Clause 9

SMP Frames

• Frame Dependent Bytes– Varies based on the Type of SMP Frame– Size always divisible by 4 bytes for CRC

calculation

• CRC for error detection

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SAS Clause 9

Presentation Topics


• Frame Types• Sequencing• Command Mapping• Sample Traces

– SMP– STP

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SAS Clause 9

STP Connections• SATA Devices transmit an initial FIS

upon a Link Reset– Expander Devices will not forward this FIS to

STP Initiators– Create a Block of Shadow Registers to hold

this information which is reported upon request from an SMP Initiator using the SMP REPORT PHY SATA function

– All Communication between STP Initiators and SATA Devices is done via rules established in the SATA Standard

– SATA BIST Requests shall not be forwarded to SATA Targets by Expander Devices

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