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    Re: iSCSI: Aggregation tags in SendTargets



    
    Mark,
    You might want to modify your first rule, it does not take into count the
    condition where a single address can have more then one connection to the
    same session, but only to the same IP address.
    
    .
    .
    .
    John L. Hufferd
    Senior Technical Staff Member (STSM)
    IBM/SSG San Jose Ca
    (408) 256-0403, Tie: 276-0403,  eFax: (408) 904-4688
    Internet address: hufferd@us.ibm.com
    
    
    Mark Bakke <mbakke@cisco.com>@ece.cmu.edu on 05/15/2001 01:06:24 PM
    
    Sent by:  owner-ips@ece.cmu.edu
    
    
    To:   IPS <ips@ece.cmu.edu>
    cc:
    Subject:  iSCSI: Aggregation tags in SendTargets
    
    
    
    
    During the interim meeting, we had discussed a proposal to
    add an aggregation tag to the SendTargets response, indicating
    which (if any) target addresses supported multiple connections
    per session, and which groups of addresses an initiator could
    hope to aggregate a session across.
    
    Aggregation tags were generally well-received; a small modification
    to the proposed method also allows an initiator to know whether
    a single address supports multiple connections per session just
    by itself.
    
    Here is the section that would go into the NDT document.
    
    --
    
    (This would be added to section 4.2, right before the vendor-specific
    paragraph at the end):
    
    
      If an iSCSI target supports multiple connections per session,
      it must indicate this by including an aggregation tag after each
      address, in the form of
    
        TargetAddress=address,tag
    
      Where "tag" is an ASCII, alpha-numeric string indicating an address
      group.  Within a single session, a connection may be requested to any
      combination of TCP addresses that have the same tag.  If an address
      supports multiple connections per session, but does not support
      spanning a session across other addresses, it will have its own
      tag.
    
      Here is an example:
    
        TargetName=fqn.com.acme.diskarray.sn.8675309
        TargetAddress=10.1.0.45:3000,1
        TargetAddress=10.1.1.46:3000,1
        TargetAddress=10.1.0.47:3000,2
        TargetAddress=10.1.1.48:3000,2
        TargetAddress=10.1.1.49:3000
        TargetAddress=10.1.1.50:3000,3
        TargetAlias=Oracle tables
    
      In this example, any of the target addresses can be used to reach
      the same target.  A single-connection session can be established
      to any of these TCP addresses.  A multiple-connection session could span
      addresses .45 and .46, or .47 and .48, but cannot span any other
      combination.  A TargetAddress without a tag (.49) cannot be combined
      with any other address within the same session.  A TargetAddress
      with a tag that is not shared with other addresses supports multiple
      connections per session, but all connections must be to the same
      address.
    
      To make this work, there are a few rules to follow:
    
      A target that does not support spanning sessions across multiple
    addresses
      MUST NOT include the tags.
    
      A target that is accessible via multiple TCP addresses SHOULD include
      all TCP addresses in a SendTargets response.
    
      A target with multiple TCP addresses that supports a session spanning
      multiple TCP addresses MUST indicate TCP address groups using aggregation
      tages in a SendTargets response.
    
      Aggregation tags have no meaning or persistence beyond a particular
      SendTargets response.
    
    
    
    --
    Mark A. Bakke
    Cisco Systems
    mbakke@cisco.com
    763.398.1054
    
    
    
    


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Last updated: Tue Sep 04 01:04:42 2001
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