Reference Guide

Chapter 3 Transport Layer Implementation Details
Serial Attached SCSI (SAS)
DLT-S4 Interface Reference Guide 21
Serial Attached SCSI (SAS) 3
For more in information about SAS task management, (see chapter 2,
Task Management).
Transport Layer Retries 3 DLT-S4 tape drives support Transport Layer Retries as indicated in the
MODE SENSE Logical Unit Control Page. It is not possible to turn off
support of Transport Layer Retries.
This section describes implementation specific details of the Transport
Layer retires for DLT-S4 tape drive.
Data In Information Unit
Retries
3
When the SDLT-S4 detects that the host did not successfully receive the
Data In IU, it will resend the Data In IU. The retransmitted Data In IU will
have the following new information in the SSP Frame Header:
• The Changing Data Pointer bit is set to 1
• The Target Port Transfer Tag is set to a new value
The SDLT-S4 will attempt to retransmit the Data In IU up to two times.
Transfer Ready
Information Unit Retries
3
When the SDLT-S4 detects that the host did not successfully receive the
Transfer Ready IU, it will resend the Transfer Ready IU. The
retransmitted Transfer Ready IU will have the following new information
in the SSP Frame Header:
• The Retransmit Bit is set to 1
• The Target Port Transfer Tag is set to a new value
The SDLT-S4 will attempt to retransmit the Transfer Ready IU up to two
times.
Response Information
Unit Retries
3
When the SDLT-S4 detects that the host did not successfully receive the
Response IU, it will resend the Response IU. The retransmitted Response
IU will have the following new information in the SSP Frame Header:
• The Retransmit Bit is set to 1
The SDLT-S4 will attempt to retransmit the Response IU up to two times.