[storm] David Black's review of draft-ietf-storm-rdmap-ext-04
"Black, David" <david.black@emc.com> Sat, 06 July 2013 01:03 UTC
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From: "Black, David" <david.black@emc.com>
To: "storm@ietf.org" <storm@ietf.org>
Date: Fri, 05 Jul 2013 21:03:03 -0400
Thread-Topic: David Black's review of draft-ietf-storm-rdmap-ext-04
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Subject: [storm] David Black's review of draft-ietf-storm-rdmap-ext-04
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As I previously indicated, the authors should revise what they can reasonably edit this coming week and submit a -05 version of this draft by the midnight UTC cutoff on Monday, July 15 [WARNING - that's midnight Greenwich (Zulu) Time, not any US Time and not British Summer Time!]. I'm happy to carry any of the comments below over to become initial WG Last Call comments on that -05 version due to the severe delays in dealing with this draft. Surprising omission - the term "atomic" is never defined (!). No, the definition is not obvious ... a crucial question (which could be answered by a definition or in Section 5.3) is: "Atomic with respect to what?". There are atomic operations defined in other contexts that are atomic only with respect to other atomic operations (and not atomic wrt other non-atomic operations), and I think considerably more is intended here. Section 7 does not appear to be sufficient, as it describes behavior from the viewpoint of a single operation issuer, which does not include behavior with respect to operations that may have been issued from elsewhere, including local memory access by the Remote Peer. Section 4 - say how large the Atomic Request and Atomic Response headers are. Section 4.1 - I think Figure 1 actually contains 3 fields - the two Control Fields and the Invalidate STag field (see Figure 4 in RFC 5040). It would be helpful to add some text below the figure to indicate which bytes are which field (this is also a problem in RFC 5040). Appendix A helps, but the field delineations really need to be here. Throughout section 5 - these operations are specified in terms of "destination address". Would it be better to talk about "buffer offset"? Section 5: The discovery of whether the Atomic Operations are implemented or not is outside the scope of this specification and it should be handled by the ULPs or applications. That's just asking for an IESG Discuss position :-). At least say something about how discovery could work. Moreover, what's wrong with just trying an atomic operation? If the operation fails, the resulting error will be: 0x0/0x2/0x06, Remote Operation Error / Unexpected OpCode It looks like a FetchAdd with Add Data=0 is a no-op that could safely be used for this purpose, providing a simple robust discovery mechanism. As part of this, I would add a requirement that if any of the atomic operations are supported, then all of them MUST be supported, so that the FetchAdd no-op can be used to discover all of them. Section 5.1.1: The "multiple fields of selectable length" text in the Add Mask description is not clear - I see how this works, but an example that uses an Add Mask to designate multiple fields would help. the FetchAdd pseudo code contains a lot of doubled complement operations, e.g., carry = !(!(sum & 2)) - why is that not carry = sum & 2 ?? Section 5.1.2 This sentence in the last paragraph is problematic standing by itself: Additionally an error MUST be surfaced and a terminate message MUST be generated. I think that needs to be combined with the previous sentence to introduce a bullet list of what has to happen when a non-64-bit-aligned address is used: If a Swap Atomic Operation is attempted on a target buffer address that is not 64-bit aligned, then: o The operation MUST NOT be performed, o The Responder's memory MUST NOT be modified, o The result MUST be surfaced as an error, and o A terminate message MUST be generated. In addition, it's important to say which error is generated. Section 8.2 indicates 0x0/0x2/0x07, Remote Operation Error / Catastrophic error, localized to RDMAP Stream - say that here also. Section 5.1.3 Same comments as last paragraph in Section 5.1.2 This section uses "Original Remote Data Value". Sections 5.1.1 and 5.1.2 use "Original Remote Data". All three should use the same term, and based on Section 5.2.2, "Original Remote Data Value" appears to be correct. Section 5.2.1 Request Identifier: 32 bits. The Request Identifier specifies a number that is used to identify Atomic Operation Request Message. The use of this field is implementation dependent and outside the scope of this specification. That's not right. This identifier is returned in the response and used by the Requestor to associate the response to the request. The Requestor can choose any value it likes that enables it to do that, and the details of how those values are generated is outside the scope of this specification, but their use is definitely in scope. Section 10, IANA Considerations: 0x9, Immediate Data with SE, [RFCXXXX] Spell out SE as "Solicited Event" Section 10.1 This one's my fault, partly. The specification of the new registry is based on a version of the rddp registries draft that was subsequently changed (e.g., the Assignment Policy paragraph needs to be removed. See the -02 version of the rddp registries draft for text to use as a model: http://tools.ietf.org/id/draft-ietf-storm-rddp-registries-02.txt I'd suggest working from Section 3.5 in that -02 version. Thanks, --David ---------------------------------------------------- David L. Black, Distinguished Engineer EMC Corporation, 176 South St., Hopkinton, MA 01748 +1 (508) 293-7953 FAX: +1 (508) 293-7786 david.black@emc.com Mobile: +1 (978) 394-7754 ----------------------------------------------------
- [storm] David Black's review of draft-ietf-storm-… Black, David
- Re: [storm] David Black's review of draft-ietf-st… Sharp, Robert O
- Re: [storm] David Black's review of draft-ietf-st… Black, David
- Re: [storm] David Black's review of draft-ietf-st… Sharp, Robert O
- Re: [storm] David Black's review of draft-ietf-st… Black, David
- Re: [storm] David Black's review of draft-ietf-st… Sharp, Robert O
- Re: [storm] David Black's review of draft-ietf-st… Black, David