Flow Control and Read Streaming Proposal

gop at us.ibm.com gop at us.ibm.com
Tue May 2 12:15:43 PDT 2000


* From the T10 Reflector (t10 at t10.org), posted by:
* gop at us.ibm.com
*
Larry,

In proposal 00-142 you use a mode page bit to indicate if a target is to
use read streaming or not. This will not work because, in most cases, there
is only one mode page for all initiators. Because of this if you have one
initiator that supports read streaming and one that does not and the
initiator that supports read streaming turnings it on then the target will
use read streaming with all the initiators. So what do you think will
happen when the target starts streaming read data to an initiator that does
not support read streaming? I think it will detect a protocol error and hit
the bus with a reset.

One way around this would be to not do read streaming but still use the P0
to indicate flow control for reads. When the flow control bit is set the
target would assert the P0 line when it knew it would not be sending any
more packets for that nexus but it would still send the L_Q between each
packet. Initiators that knew this was going to happen could ignore the L_Q
(we would have to make a rule that the target could not change the L_Q
information in this mode) and initiators that know nothing about the mode
would continue to operate even though they know nothing about the mode page
bit.

Bye for now,
George Penokie

Dept Z9V  114-2 N212
E-Mail:    gop at us.ibm.com
Internal:  553-5208
External: 507-253-5208   FAX: 507-253-2880


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