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    iSCSI: Wrapping up SendTargets



    
    Dear Discovery Enthusiasts-
    
    The SendTargets threads are winding down, so I would like
    to see if we have a rough consensus on a few things.
    
    
    I've read through all of the threads on whether to
    keep SendTargets in iSCSI, and I believe there is
    a rough concensus that we should keep it in, carefully
    limit its growth, and recommend that functionality
    beyond the basic reporting of the targets and addresses
    available be implemented using standard discovery
    protocols instead.  On looking through responses from
    Josh, Steph, Larry, Paul, Julian, Mallikarjun, John,
    Kaladhar, Jim, and Marjorie, I have seen 7 (I include
    myself in this count) in favor of keeping SendTargets
    but limiting its growth, one in favor of dropping
    SendTargets, and three with no comment on SendTargets.
    
    For adding discovery functionality beyond basic reporting
    of available targets and addresses, I have seen 5
    (again, including myself) in favor of using SLP for
    future discovery, one in favor of using iSNS for future
    discovery, two in favor of either SLP or iSNS, and 
    three with no comment.
    
    I realize that this doesn't constitute calling consensus,
    and I'm not the person to do it, but I wanted to point out
    where most people who have responded seem to be headed,
    so that others who wish to be heard are motivated to
    comment.
    
    
    Anyway, that said, I would like to see SendTargets stay
    in the draft, mainly for the same reasons that several
    others already stated:
    
      SendTargets shares the same authentication as iSCSI.
    
      SendTargets provides a simple, low-risk path to building
      interoperable, minimal-configuration iSCSI implementations.
    
      SendTargets builds on the existing iSCSI login and text
      commands, and will be the smallest-footprint and -effort
      way to implement this basic functionality.
    
    The first reason given above is the most important.
    
    I believe that we should limit extensions to it as much as
    possible, for instance, we should not attempt to return
    certificates and other information.  Implementations that
    wish to do fancier things like these would implement one
    of the other discovery mechanisms.  We could go as far
    as atrophying SendTargets later, but I think that John is
    right, that it would be a decision to be made later (iSCSIv2).
    
    That said, I do agree that Julian is correct from a philosophical
    point of view; discovery really belongs outside the protocol.  
    This is a direction we need to pursue.  I absolutely agree with
    Julian that we have to be careful not to let something like
    SendTargets turn into a management protocol. It would be "easy
    to do" :-).
    
    I see a mild consensus toward SLP as a good direction for
    moving forward with discovery beyond simple target reporting.
    The SLP folks themselves intended for hosts to be able to
    behave in the Unicast manner we are trying, and are interested
    in updating the SLP API to handle this.  However, I think that
    it would be best to use SendTargets for now, while we both
    make sure that the right SLP API is developed, and that we
    can solve the problem of authentication schemes.
    
    
    On ReportPortalGroups
    
    I did not hear anyone say we didn't need this functionality; most
    seemed to say the we either "at least" need ReportPortalGroups
    if we don't have SendTargets, or that SendTargets was assumed,
    and ReportPortalGroups is a subset.
    
    I agree that this is necessary functionality, but that if we
    can assume that we still have SendTargets, ReportPortalGroups
    is really a subset.  Paul mentioned just using:
    
      SendTargets <iscsi-target-name>
    
    would be the same as ReportPortalGroups.  This might help
    avoid the feature creep that some of the responders feared.
    
    Anyway, either way of doing ReportPortalGroups (making it its
    own command or making it part of SendTargets) is fine with me.
    I think that the consensus was that as long as we have SendTargets,
    we should use it for the ReportPortalGroups functionality.
    
    
    On the Growth of SendTargets
    
    A few people mentioned concern about TargetAlias and digital
    certificates.  TargetAlias is returned by the target upon login
    anyway, so I could live with removing it from SendTargets, and
    letting the higher-level discovery/management mechanisms deal
    with it.  I think that the same goes for certificates.  As we
    figure out how our customers really want to do security for iSCSI,
    we may have other mechanisms in place for handling these.
    
    This should help keep SendTargets from growing.  Stating that
    it is limited to name, address, and aggregation information (just
    what is required to connect) should keep it right where it is,
    and the future discovery mechanisms can take over from there.
    
    So here's what I think we have:
    
      Now    - Keep SendTargets, document it in the iSCSI spec, and
               declare its limitation to just what is needed to
               connect to a target (name, address, aggregation).
    
               Define ReportPortalGroups functionality as a subset
               of SendTargets.
    
      Future - Pursue SLP as the "standard discovery", allowing for
               other solutions such as iSNS as appropriate.
    
    Do we have rough consensus on either of the above, at least
    on the "Now" part?
    
    Once we have consensus on that, we can continue the threads
    on aggregation tags, which targets should provide SendTargets,
    and whether or not we need iterators.
    
    Anyway, I have to apologize in advance; I will be out of
    the office until the 18th, so I am sort of throwing this out
    on the list and running away.
    
    
    Regards,
    
    -- 
    Mark A. Bakke
    Cisco Systems
    mbakke@cisco.com
    763.398.1054
    


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Last updated: Tue Sep 04 01:04:32 2001
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