Death to I_T_L_Q nexus

George Penokie george.penokie at
Wed Jun 11 08:32:35 PDT 2014

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If don't reached SAM overload yet this proposal should push you over the
edge. Here is the overview:
There has been a long standing problem with the I_T_L_Q nexus as it
combines routing information with a command identifier. The routing part is
the I, the T, and the L. The command identifier is the Q. In addition the
nexus really does not have a satisfactory home in the SAM-5 UML model.
This proposal solves the UML issue by adding a Management Application
Client class that is a “kind of” Application Client class. The new
Management Application Client class has I_T Nexus Identifier attributes and
I_T_L Nexus Identifier attributes. The Management Application Client class
is the class that goes out and finds all the nexuses in the SCSI domain.
The method used for the Management Client class to do this is protocol
specific. For example in SAS the discovery is defined in the SPL standard.
This also separates Q from nexus and replaces that with a standard alone
attribute called a Command Identifier attribute. The effect of this is that
all the I_T_L_Q nexus terms will be replaced with either Command Identifier
or I_T_L nexus and command identifier. This causes extensive changes to
several standards but has the largest effect on SPL, then SAM, then SPC,
and finally SBC. To prevent issues with existing published standards the
term I_T_L_Q nexus will have to remain but it will be defined as being
synonymous with I_T_L nexus plus command identifier.
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Your PDF file will be posted at:
Bye for now,
George Penokie
Avago Technologies
3033 41 St NW
Rochester , MN 55901
george.penokie at

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