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    Re: iSCSI: synch and steering comments



    
    
    Mallikarjun,
    
    It is clearly communicated in the paragraph above it - but fine I will add
    it here too.
    
    Julo
    
    "Mallikarjun C." <cbm@rose.hp.com> on 30/03/2001 00:54:20
    
    Please respond to cbm@rose.hp.com
    
    To:   ips@ece.cmu.edu
    cc:
    Subject:  Re: iSCSI: synch and steering comments
    
    
    
    
    Julian,
    
    Some comments.
    
    >Answers in text. Thanks, Julo
    >
    >
    ..
    
    >-Suggest adding the following statement to section 1.2.8.2.
    >
    > All conventional, in-order data arrival notifications generated by TCP
    > are passed through to iSCSI by the Synch and Steering layer after
    > appropriate data placements while none of the out-of-order data
    placements
    > that it performs are communicated to upper layers.
    >
    >+++ I have added the following to 1.2.8.2
    >
    >   On the incoming path the Synch and Steering layer does not change the
    >   way TCP notifies iSCSI about in-order data arrival.  All out-of-order
    >   data placements
    >   performed by the Synch and Steering layer are hidden from iSCSI.
    
    Okay, I'd however prefer it to imply that in-order data placement is also
    handled by Synch and Steering in the same sentence, instead of only
    commenting on in-order notifications, and out-of-order placements.
    
    >
    >   I have aloso changed a bit the figure to convey better the fact that
    TCP
    >   and Synch&Steering are related (not strictly layered +++
    
    That's a good idea.
    
    >
    >   ++++
    >
    >-Section 1.2.8.2 states that a Synch and Steering layer is optional.
    > It has to be qualifed that it is optional only for those iSCSI devices
    > which perform connection recovery on header digest errors, since that's
    > how they cope with loss of framing. (I guess this may change in next
    rev?)
    >
    >+++ with the new format I think that we have:
    >
    >- one more chance if we go for format 1 or
    >- drop the connection on header error
    >
    >In both cases we can leave synch and steering optional
    
    Well, that doesn't address the thrust of my comment.  I was implying
    that the draft should make it clear that those implementations which
    don't support Synch and Steering should end the connection on a header
    digest error and/or parity error, and not go into (what Somesh called)
    a speculative mode.
    
    >
    >+++
    >
    >-It appears to me that at least one Synch and Steering layer must be
    > defined/referred to as the minimal implementation in the main draft to
    > enable interoperability, when implementations do implement Synch and
    >Steering.
    >
    >+++ why ? +++
    
    I may be using "interoperability" in a somewhat unconventional sense here.
    While the draft says that Synch and Steering layer is optional, I don't see
    that it requires implementations to always support a "no synch & steering"
    mode, even when they support one type of Synch and Steering layer.  Given
    that
    there's no mandatory Synch and Steering layer either, I don't see how two
    iSCSI boxes that a customer buys are guaranteed to interoperate.  Please
    comment if the draft already implies what I am asking for.
    
    Thanks.
    --
    Mallikarjun
    
    
    Mallikarjun Chadalapaka
    Networked Storage Architecture
    Network Storage Solutions Organization
    MS 5668   Hewlett-Packard, Roseville.
    cbm@rose.hp.com
    
    
    
    


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Last updated: Tue Sep 04 01:05:13 2001
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