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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: iSCSI - Change proposal Removing the X bitJulian, In response to your below proposed changes : 1) I am in favor of your proposal to remove task re-assign and simply re-issue the command on a new connection. 2) Regarding the removal of X bit, I suggest that the bit be made reserved and the position of the I bit and opcode be retained as is. Thanks, Santosh Julian Satran wrote: > > Dear colleagues, > > We intend to publish very soon version 09 of the draft in its current > format (not many changes) and postpone the editorial changes (already under > way) for 10. > > One of the latest change proposal involves removing the X bit. > > The X bit has been used in several types of restart/replay but is somewhat > made redundant by the removal > of the command replay. > > This involves removing the X bit from request byte 0 and either making it > reserved or "shifting left" the rest of the general-use bits (I and the > direction bit). > > It also involves mandating a cleaning NOP. > > The cleaning NOP is needed in order to "flush out" old command PDU that can > be left over by simple sequences like the one in the following scenario: > > 2 connections > > On connection 1 I->T c1,c2,c3 > On connection 2 I->T c4,c5,c6 > > Targets receives everything and acts on commands but responses are sluggish > and initiators sees only an ack for > c1. It then retransmits c2, and c3 while there answer are in flight back > after which the connection is almost dead and not used by initiator. > > After a complete wrap around, involving only connection 2, the target > suddenly gets c2, c3 in a correct window and acts on them. > > The need to clean-up old PDUs is common to all protocols that use a > sequence that wraps and we suggested cleaning up using a NOP. We will > mandate a cleaning NOP only on connections that had at least one "retry". > > It looks like we might e able also to abandon the task management - > reassign function and do it with a reissue (with the same NOP cleanout > implication) since retiring the replay function makes the reassign > unambiguous (reissuing a command, after logout, on a new connection - > implies reassign). > > Please comment - I need your input urgently. > > Julo -- ################################## Santosh Rao Software Design Engineer, HP-UX iSCSI Driver Team, Hewlett Packard, Cupertino. email : santoshr@cup.hp.com Phone : 408-447-3751 ##################################
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