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Hi,
I have some questions on iSCSI
Markers which are not clear to me from the specification. Can one of you please
clarify or answer:
1. The marker interval value like RFMarkInt,
SFMarkInt, IFMarkInt etc, are they value in dwords (for example, a value of 1
means interval of 4 bytes) or are they in bytes but you have to make sure that
they are multiple of 4?
2. Is the position of the first marker in a
TCP connection in a direction (initial sequence value + IFMarkInt
value)?
3. Is the relative offset of the next
nearest start of the iSCSI message header that is in the marker is counting
the beginning of the marker or is it relative to the end of the
marker?
4. If there are multiple markers at negotiated
marker intervals before the beginning of next iSCSI message header (in between
two iSCSI messages), is it required to check the content validity of the
next marker with respect to the previous marker or do you take the content
of the latest marker identified as valid value?
5. The iSCSI PDUs being always multiple of 4
bytes, does it imply in any way that the TCP sequence # needs to be also
at a 4-byte boundary alignment before starting placement of
markers?
6. As I understood from the specification -01, the
idea of using Urgent pointer to identfy iSCSI message boundary in TCP
stream is also to help an external protocol analyzer to be able to
identify and sync correctly from a iSCSI message boundary at any point of
time when it is asked to sample. With the marker scheme, it seems that the
protocol analyzer needs to start sampling right at the beginning of the iSCSI
log-in phase to be able to identify the markers and hence the iSCSI message
boundary etc. Is my understanding correct?
Thanks
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