Re: RE: AD review of draft-ietf-rddp-sctp-04

On Jun 23, 2006, at 21:43, Caitlin Bestler wrote:
> Lars Eggert wrote:
>> Section 6.1., paragraph 2:
>>> The Payload Data Chunks for a given session, when sequenced by  
>>> their DDP-SSN, MUST follow one of the patterns defined in this  
>>> section.
>>
>>    The sequence patterns in the remainder of this section don't
>>    include any DDP-SSNs? How can compliance thus be established?
>
> All SCTP Data Chunks generated by the DDP/SCTP Adaptation have a
> DDP-SSN. Therefore all messages specified in this draft have DDP-SSNs.

Right, but I was trying to raise a different question. Let me try again:

"The payload data chunks [...], when sequenced by their DDP-SSN, MUST  
follow one of the patterns defined in this section."

I read this sentence as: "This section will show sequences of packets  
together with their DDP-SSNs. Valid sessions MUST follow one of these  
DDP-SSN sequences.

Did I get the meaning correctly?

If yes, my comment was that the section doesn't actually talk about  
DDP-SSNs at all.

> The rules for formulating the DDP-SSN are already clear. The
> fact that the messsages are sequenced clearly mandates what
> the DDP-SSNs would be.

Ah. So they are assumed to be implicitly clear. I think this is  
problematic, because in the beginning of this section, the drafts  
says that valid exchanges MUST follow on of the DDP-SSN sequences,  
but then doesn't explicitly define them. Explicitly defining the  
valid packet exchanges together with the DDP-SSNs in these sections  
allows implementors to easily verify whether they are in compliance.

> Since implementations are not likely to generate the DDP-SSNs
> at the layer discussed in these sequence sections, I do not
> see the value of repeating this information here.

Hm. Maybe I simply got hung up on the phrasing here ("when sequenced  
by their DDP-SSN")?

Lars
-- 
Lars Eggert                                     NEC Network Laboratories