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    RE: iSCSI - bookmarks change



    Section "4. Login Phase" of your previous EMAIL (iSCSI - Login changes and
    the latest agreements) says:
    
    	The login phase is implemented via login request and responses only.
    
    But below you say:
    
    	During the Login Phase ... the Text command
       SHOULD be issued as an immediate command (I=1).
    
    These seem contradictory.
    
    Eddy
    
    -----Original Message-----
    From: Julian Satran [mailto:Julian_Satran@il.ibm.com]
    Sent: Tuesday, September 04, 2001 5:19 AM
    To: ips@ece.cmu.edu
    Subject: iSCSI - bookmarks change
    
    
    Now that text commands are out of login (and we don't have to care too much
    about the immediate version) we can rationalize the bookmarks.
    
    Here is my suggestion for the new text request/response:
    
    
    1.1  Text Command
    
       The Text Command is provided to allow the exchange of information and
       for future extensions. It permits the initiator to inform a target of
       its capabilities or to request some special operations.
    
       A connection SHOULD have only one outstanding text command at any given
       time.
    
    
    
       Byte /    0       |       1       |       2       |       3       |
          /              |               |               |               |
         |7 6 5 4 3 2 1 0|7 6 5 4 3 2 1 0|7 6 5 4 3 2 1 0|7 6 5 4 3 2 1 0|
         +---------------+---------------+---------------+---------------+
        0|X|I| 0x04      |F|B| Rsvd      | Reserved                      |
         +---------------+---------------+---------------+---------------+
        4| Reserved      | DataSegmentLength                             |
         +---------------+---------------+---------------+---------------+
        8| Reserved                                                      |
         +                                                               +
       12|                                                               |
         +---------------+---------------+---------------+---------------+
       16| Initiator Task Tag                                            |
         +---------------+---------------+---------------+---------------+
       20| Reserved                                                      |
         +---------------+---------------+---------------+---------------+
       24| CmdSN                                                         |
         +---------------+---------------+---------------+---------------+
       28| ExpStatSN                                                     |
         +---------------+---------------+---------------+---------------+
       32/ Reserved                                                      /
        +/                                                               /
         +---------------+---------------+---------------+---------------+
       48| Digests if any...                                             |
         +---------------+---------------+---------------+---------------+
         / DataSegment (Text)                                            /
        +/                                                               /
         +---------------+---------------+---------------+---------------+
    
    
    1.1.1     F (Final) Bit
    
       When set to 1 it indicates that this is the last or only text command in
       a sequence of commands; otherwise it indicates that more commands will
       follow.
    
    1.1.2     I - Immediate
    
       During the Login Phase (the current stage part of CNxSG is either
       SecurityNegotiation or LoginOperationalNegotiation), the Text command
       SHOULD be issued as an immediate command (I=1).
    
    1.1.3     B - bookmark bit
    
       The bookmark bit set to 1 tells the target to continue from its last
       bookmark for the specific Initiator Task Tag and thus allows a target to
       transfer a large amount of textual data over a sequence of
       text-command/text-response exchanges.
    
       The bookmark bit set to 0 tells the target that this is a new Text
       request; the target should reset any bookmark it holds on the specific
       Initiator Task Tag.
    
       A target MAY reject an old Bookmark.
    
       Bookmark generation at target is detailed in 2.11.2.
    
       Long text responses are handled as in the following example:
    
          I->T Text SendTargets=all (F=1,B=0)
          T->I Text <part 1> (F=0,B=1)
          I->T Text <empty> (F=1,B=1)
          T->I Text <part 2> (F=0,B=1)
          I->T Text <empty> (F=1,B=1)
          ...
          T->I Text <part n> (F=1,B=0)
    
    1.1.4     Initiator Task Tag
    
       The initiator assigned identifier for this Text Command.
       If the command is sent as part of a sequence of commands (e.g., the
       Login Phase or a sequence of Text commands) the Initiator Task Tag MUST
       be the same for all the commands within the sequence (similar to linked
       SCSI commands).
    
    1.1.5     Text
    
       The initiator sends the target a set of key=value or key=list pairs
       encoded in UTF-8 Unicode. All the text keys and text values specified in
       this document are to be presented and interpreted in the case they
       appear in this document (they are case sensitive). The key and value are
       separated by a '=' (0x3d) delimiter. Every key=value pair (including the
       last or only pair) MUST be followed by null (0x00) delimiter.  A list is
       a set of values separated by comma (0x2c). Large binary items can be
       encoded using their hexadecimal representation (e.g., 8190 is 0x1ffe) or
       decimal representation. The maximum length of an individual value (not
       its string representation) is 255 bytes.
    
       The data lengths of a text command or response MUST NOT exceed 4096
       bytes.  Key names MUST NOT exceed 63 bytes. Key values MUST NOT exceed
       255 bytes.
    
       Character strings are represented as plain text. Numeric and binary
       values are represented using either decimal numbers or the hexadecimal
       0xffff notation. Upper and lower case letters may be used
       interchangeably in hexadecimal notation (i.e., 0x1aBc, 0x1AbC and 0x1ABC
       are equivalent).
    
       The target responds by sending its response back to the initiator. The
       response text format is similar to the request text format.
    
       Some basic key=value pairs are described in Appendix A and Appendix D.
       All keys in Appendix D, except for the X- extension format, MUST be
       supported by iSCSI initiators and targets. Keys in Appendix A MUST be
       supported only when the function they refer to is mandatory to
       implement.
    
       Manufacturers may introduce new keys by prefixing them with X- followed
       by their (reversed) domain name, for example the company owning the
       domain acme.com can issue:
    
          X-com.acme.bar.foo.do_something=0000000000000003
    
       Any other key not understood by the target may be ignored by the target
       without affecting basic function. However the Text Response for a key
       that was not understood MUST be key=NotUnderstood.
    
       Text operations are usually meant for parameter setting/negotiations but
       can be used also to perform some long lasting operations.
    
       Text operations that will take a long time should be placed in their own
       Text command.
    
    1.2
    
    Text Response
    
       The Text Response PDU contains the target's responses to the initiator's
       Text Command. The format of the Text field matches that of the Text
       Command.
    
    
       Byte /    0       |       1       |       2       |       3       |
          /              |               |               |               |
         |7 6 5 4 3 2 1 0|7 6 5 4 3 2 1 0|7 6 5 4 3 2 1 0|7 6 5 4 3 2 1 0|
         +---------------+---------------+---------------+---------------+
        0|1|1| 0x24      |F|B| Rsvd      | Reserved                      |
         +---------------+---------------+---------------+---------------+
        4| Reserved      | DataSegmentLength                             |
         +---------------+---------------+---------------+---------------+
        8| Reserved                                                      |
         +                                                               +
       12|                                                               |
         +---------------+---------------+---------------+---------------+
       16| Initiator Task Tag                                            |
         +---------------+---------------+---------------+---------------+
       20| Reserved                                                      |
         +---------------+---------------+---------------+---------------+
       24| StatSN                                                        |
         +---------------+---------------+---------------+---------------+
       28| ExpCmdSN                                                      |
         +---------------+---------------+---------------+---------------+
       32| MaxCmdSN                                                      |
         +---------------+---------------+---------------+---------------+
       36/ Reserved                                                      /
        +/                                                               /
         +---------------+---------------+---------------+---------------+
       48| Digests if any...                                             |
         +---------------+---------------+---------------+---------------+
         / DataSegment (Text)                                            /
        +/                                                               /
         +---------------+---------------+---------------+---------------+
    
    1.2.1     F (Final) Bit
    
       When set to 1 in response to a text command with the Final bit set to 1
       the F bit indicates that the target has finished the current stage of
       the operation or the whole operation.  Otherwise if set to 0 in response
       to a text command with the Final Bit set to 1 it indicates that the
       target has more work to do (invites a follow-on text command).  A text
       response with the F bit set to 1 in response to a text command with the
       F bit set to 0 is a protocol error.
    
       A text response with a F bit set to 1 MUST NOT contain key=value pairs
       that may require additional answers from the initiator.
    
    1.2.2     B - bookmark Bit
    
       Whenever a target can't transfer all the remaining text data in a single
       Text response, it attempts to set an internal bookmark. If successful,
       the target associates the bookmark with the Initiator Task Tag.  The
       target indicates that it holds a bookmark for the specific Initiator
       Task Tag by setting the bookmark (B) bit to 1 in the Text response. The
       target resets the internal bookmark associated with a given Initiator
       Task Tag if it receives a Text request with the specified Initiator Task
       Tag with the bookmark bit set to 0.  When a target can't transfer all
       the text data in a single text response and it cannot set an internal
       bookmark it rejects the Text request with an appropriate Reject code. A
       target may reset its internal bookmark(s) after some time in order to
       reclaim resources associated with the bookmark and reject subsequent
       Text requests with the bookmark bit set to 1.
    
       When all the text data fit in a single Text response the bookmark bit of
       the response is set to 0 and the bookmark associated with the Initiator
       Task Tag is reset.
    
    1.2.3     Initiator Task Tag
    
       The Initiator Task Tag matches the tag used in the initial Text Command
       or the Login Initiator Task Tag.
    
    1.2.4     Text Response Data
    
       The Text Response Data Segment contains responses in the same key=value
       format as the Text Command and with the same length and coding
       constraints. Appendix A and Appendix D lists some basic Text Commands
       and their Responses.
    
       Although the initiator is the requesting party and controls the
       request-response initiation and termination the target can offer
       key=value pairs of its own as part of a sequence and not only in
       response to an identical key=value pair offered by the initiator.
    
       A Key=value pair must be confined to a given text response even in the
       presence of bookmark - i.e., it must start and end within one Text
       Response.
    
    
    
    The Reject Reasons table looks like:
    
    1.1.1     Reason
    
       The reject Reason is coded as follows:
    
    
       +------+-----------------------------------------+------------------+
       | Code | Explanation                             | Can the original |
       | (hex)|                                         | PDU be re-sent?  |
       +------+-----------------------------------------+------------------+
       | 0x01 | Format Error                            | no               |
       |      |                                         |                  |
       | 0x02 | Data (payload) Digest Error             | yes  (Note 1)    |
       |      |                                         |                  |
       | 0x03 | Data-SNACK Reject                       | yes              |
       |      |                                         |                  |
       | 0x04 | Protocol Error (e.g., SNACK request for | no               |
       |      | a status that was already acknowledged) |                  |
       |      |                                         |                  |
       | 0x05 | Command not supported in this session   | no               |
       |      | type                                    |                  |
       |      |                                         |                  |
       | 0x06 | Immediate Command Reject - too many     | yes              |
       |      | immediate commands                      |                  |
       |      |                                         |                  |
       | 0x07 | Bookmark Reject - No bookmark for this  | no               |
       |      | Initiator Task Tag                      |                  |
       |      |                                         |                  |
       | 0x08 | Bookmark Reject - Can't generate        | yes              |
       |      | bookmark - out of resources             |                  |
       |      |                                         |                  |
       | 0x0f | Full Feature Phase Command before login | no               |
       +------+-----------------------------------------+------------------+
    
    
     Comments?
    
     Julo
    
    


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Last updated: Wed Sep 05 11:17:06 2001
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