iSCSI: synch and steering comments

["Mallikarjun C." <cbm@rose.hp.com>]

Julian,

Following are the comments I have on Synch and Steering in rev05.

-Suggest replacing "it" in the following sentence in section 1.2.8.2, page 23
 (first sentence in a new para):
 
 "According to our model of layering, iSCSI considers the information 
    it delivers (headers and payloads) as a contiguous stream of bytes 
    mapped to the positive integers from 0 to infinity."
 
 with "that a Synch and Steering layer" to make it clear.  The sentence
 is ambiguous about the direction of delivery with the way it is.
 
-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.
 
-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?)
 
-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.
 
-I am somewhat confused about the following statement in section 1.2.8.2:
    "The Synch and Steering Layer is required to add to every sent data 
    item (IP packet, TCP packet or some other superstructure) enough 
    information to enable the receiver to steer it to a memory location 
    independent of any other piece. "
 
 Clearly from the way I understood the markers in Appendix.C, it doesn't
 comply with this requirement.  A more generic statement would be:
    "The Synch and Steering Layer is required to add adequate 
    information to the data stream to enable the receiver to quickly 
    steer the stream to its final memory location, even in the face of 
    discontiguities in the stream. "
--
Mallikarjun 


Mallikarjun Chadalapaka
Networked Storage Architecture
Network Storage Solutions Organization
MS 5668	Hewlett-Packard, Roseville.
cbm@rose.hp.com