initiator retransmission of DATA frames with transport layer retries

Deglin, Rich Richard_Deglin at adaptec.com
Mon Jul 25 14:08:00 PDT 2005


* From the T10 Reflector (t10 at t10.org), posted by:
* "Deglin, Rich" <Richard_Deglin at adaptec.com>
*
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I have not been able to clearly make out the meaning of this phrase in
sec 9.2.4.5.2:
=20
"For both reads and writes, the CHANGING DATA POINTER bit is set to one
in the first retransmitted DATA frame
and CHANGING DATA POINTER bit is set to zero in subsequent DATA frames."
=20
Consider the following scenario:
=20
1. Initiator transmits write command to target
2. Target transmits XFER_RDY frame to initiator (TPTT =3D A, offset =3D =
X,
RETRANSMIT =3D 0)
3. Initiator transmits DATA frames for TPTT =3D A
4. Initiator receives NAK for one of the write DATA frames and prepares
to retransmit the DATA frames
5. Target retransmits XFER_RDY frame to initiator (TPTT =3D B, offset =
=3D X,
RETRANSMIT =3D 1)
6. Initiator abandons its retransmission for TPTT =3D A and begins
transmission for TPTT =3D B
=20
Q: does initiator set the CHANGING_DATA_POINTER bit in the first DATA
frame of the transmission for TPTT =3D B?
=20
Rich Deglin
Principal Software Engineer
Vitesse Semiconductor, Inc.

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I have not been able to clearly make out the meaning = of this phrase in sec 9.2.4.5.2:

 

For both reads and writes, the = CHANGING DATA POINTER bit is set to one in the first retransmitted DATA = frame

and CHANGING DATA POINTER = bit is set to zero in subsequent DATA frames.

 

Consider the following = scenario:

 

1. Initiator transmits = write command to target

2. Target transmits = XFER_RDY frame to initiator (TPTT =3D A, offset =3D X, RETRANSMIT =3D = 0)

3. Initiator transmits DATA = frames for TPTT =3D A

4. Initiator receives NAK = for one of the write DATA frames and prepares to retransmit the DATA = frames

5. Target retransmits = XFER_RDY frame to initiator (TPTT =3D B, offset =3D X, RETRANSMIT =3D = 1)

6. Initiator abandons its retransmission for TPTT =3D A and begins transmission for TPTT =3D = B

 

Q: does initiator set the CHANGING_DATA_POINTER bit = in the first DATA frame of the transmission for TPTT =3D = B?

 

Rich Deglin

Principal Software = Engineer

Vitesse= Semiconductor, Inc.

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