[rddp] Last call comments on SCTP RDMA/DDP Adaptation draft

SCTP RDMA/DDP Adaptation draft authors,

Below are my comments on draft-ietf-rddp-sctp-01.txt:

1. Section 2.1, page 5, first paragraph: The last sentence is not clear on whether the mix traffic is allowed on a single stream association or not. Suggest rephrasing the sentence to “An application that needs to mix DDP and non-DDP traffic must use different stream associations for the DDP traffic and non-DDP traffic.”

2. Section 2.2, page 5, second paragraph, third line: grammatical correction. Sentence should be “DDP Segments are used for the messages sent between DDP endpoints.”

3. Section 2.2: The spec does not explicitly state 1:1 mapping of SCTP payload data chunk and DDP Segment. Suggest adding the following “Each DDP Segment is exactly contained in one SCTP payload data chunk with the payload protocol identifier 0x00000001.”

4. Section 2.2.1: This section does not say how DDP-SSN is incremented. Suggest adding the following text “DDP-SSN is increased by one (modulo 65536) with each DDP message submitted to the SCTP layer.”

5. Section 2.1: Need to add a requirement that DDP-SSN for the DDP Segments of a DDP message should be same. Suggest adding the text: “The DDP-SSN field of the Payload Data Chunks of the DDP segments of a DDP Message MUST be the same.”

6. Section 2.2.1: This section does not mention whether DDP-SSN is passed to DDP layer or not. For delivery, it is important. Suggest adding the following text “The adaptation layer passes DDP-SSN to the DDP layer for the in-order delivery of DDP Messages.”

7. Section 2.2.1: Who maintains DDP-SSN, adaptation layer or DDP layer? Please clarify it in this section.

8. Suggest renaming section 2.2.2 to “DDP Segment Payload Data Chunk”.

9. Suggest renaming section 2.2.3 to “DDP Stream Session Control Payload Data Chunk”.

10. Section 2.2.3: This section does not say how the length of the private data is derived. Suggest adding the text “The length of private data is derived from the length of Payload Data Chunk.”

11. Section 6, third paragraph: This sentence combines two conditions: MUST NOT with an exception case. It is little bit confusing. Suggest splitting the sentence into two sentences: “SCTP Data Chunk fragmentation MUST NOT be used for the cases where IP fragmentation is not required. SCTP data chunk fragmentation MAY be used to avoid IP fragmentation.”

12. Section 6, fourth paragraph: Is there any specific formula for deriving the maximum DDP segment size based on the theoretical maximum size of the SCTP Data Chunk?

13. Section 7, third paragraph: in the end says “Typical ULP flow control will exclusively deal with tagged messages,..”. Replace “tagged messages” with “DDP Messages”.

14. Section 7: Is there any requirement on the adaptation layer on passing DDP-SSN to DDP layer? If yes, then please specify (“The adaptation layer SHOULD pass DDP-SSN along with the DDP Segment to the DDP layer.”). If no, then please clarify.

Hemal