Re: [IPFIX] Fwd: I-D ACTION:draft-ietf-ipfix-export-per-sctp-stream-04.txt

[Tobias Limmer <Tobias.Limmer at informatik.uni-erlangen.de>]

Hi Benoit, all,

I've also got a few comments on the draft ipfix-export-per-sctp- 
stream-04:


2.3. Limitations:
"This method requires multiple SCTP streams in the association between  
the Exporting and Collecting Process, ideally one per Template."

No - if we had only one Template in the association, we would not need  
multiple SCTP streams.


3.1.1. IPFIX Protocol Specifications Limitation:
"Note that a workaround allowed by the IPFIX specifications [RFC5101]  
is to use only one Template Record per SCTP Transport Session, at the  
cost of multiplying the number of SCTP Transport Sessions when  
multiple Template Records are required."

This paragraph sounds a little misplaced, as it already mentions the  
performance impact. After reading it, I was wondering what other  
method would be proposed in this draft.


4.2. Template Management:
"Any Data Sets associated with a Template Record MUST be sent on the  
same SCTP stream on which the Template Record was sent."

According to rfc5101, an Options Template Record is a Template Record.  
Later in the same section you specify: "When the Options Template and  
associated Data Records are sent in different SCTP streams, [...]".
Isn't this a contradiction, or am I missing something here?


4.5. The Collecting Process's Side:
"3. A Data Record is received unreliably although it is expected to be  
sent reliably (due to a previously received Data Record associated  
with the Data Record Reliability Options Template)."

Is it possible for the receiving side of a SCTP connection to  
determine which SCTP messages were sent unreliably? I did not find any  
indication of that in rfc3758. The receiving side only knows if  
complete messages or fragments are skipped.


4.5. The Collecting Process's Side:
"In the case where the Exporting Process does not support the [...]"

This paragraph is a duplicate.


6. Examples:
In Figure 3, you seem to use the Options Reliability Template 257  
(defined in Figure 1) that was received in another stream. A small  
remark would be good which indicates, that all streams belong to the  
same SCTP association.


Thanks,
Tobi



--
Dipl.-Inf. Tobias Limmer
Chair for Computer Networks and Communication Systems
Universität Erlangen-Nürnberg
Martensstr. 3, D-91058 Erlangen, Germany
Phone: +49-9131-8527931  Fax: +49-9131-8527409
eMail: limmer .at. informatik.uni-erlangen.de
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