[Sis-dtn] Positive reception claim vs. Negative reception claim in LTP Report Segment preparation and processing

[Felix.Flentge at esa.int]

Ah, yes, of course you are right.

We will look into the negative ACK as part of our LTPv2 prototyping 
activity.

Regards,
Felix



From:   "구철회" <chkoo at kari.re.kr>
To:     <Felix.Flentge at esa.int>
Cc:     "sis-dtn at mailman.ccsds.org" <sis-dtn at mailman.ccsds.org>
Date:   04/04/2022 11:58
Subject:        RE: Re: [Sis-dtn] Positive reception claim vs. Negative 
reception claim in LTP Report Segment preparation and processing
Sent by:        chkoo at kari.re.kr



Hi Felix,

I think current LTP spec quite works well with negative claim also. 
Consider below reception claim according to the LTP spec but negative 
claim.

lower bound = 0
upper bound = 7000
negative reception claim count = 1
offset = 1000
length = 2000

it means a receiver is requesting block of segements which starts at 1000 
and length is 2000, i.e., 1000 ~ 2999, for retransmission.
A sender can safely remove 2 blocks, i.e., 0 - 999 and 3000 - 7000. I 
think it is simpler, lower overhead and *importantly* easier to calculate 
(acutally no painful for localizing the target segment position).

Cheol
--------- 원본 메일 ---------
보낸사람 : <Felix.Flentge at esa.int>
받는사람 : "구철회" <chkoo at kari.re.kr>
참조 : "sis-dtn at mailman.ccsds.org" <sis-dtn at mailman.ccsds.org>
받은날짜 : 2022-04-04 (월) 17:40:24
제목 : Re: [Sis-dtn] Positive reception claim vs. Negative reception claim 
in LTP Report Segment preparation and processing
Hi Cheol, 

interesting question. One thing I can think of is that the positive claims 
would allow you to free memory earlier while for negative claims you need 
to wait until the end of a session. 

Regards, 
Felix 



From:        "구철회 via SIS-DTN" <sis-dtn at mailman.ccsds.org> 
To:        "sis-dtn at mailman.ccsds.org" <sis-dtn at mailman.ccsds.org> 
Date:        04/04/2022 10:15 
Subject:        [Sis-dtn] Positive reception claim vs. Negative reception 
claim in LTP Report Segment preparation and processing 
Sent by:        "SIS-DTN" <sis-dtn-bounces at mailman.ccsds.org> 


Greetings, 
 
This is Cheol. I am developing an LTP reference implementation. During 
reading the LTP specification (RFC-5326), the preparation of reception 
claim in Report Segment makes me confusing about why it is positive claim 
not negative claim for segments that were not received successfully (i.e., 
NAK).
 
For reference, CFDP’s NAK PDU has the negative claim structure when it is 
requested to report missing PDUs. Does anyone know about the background of 
choosing the positive claim for NAK operation in LTP?
I think negative claim is simpler and more efficient in terms of overhead 
for sender and receiver both.
I like to listen experts’ opinion on LTP operation and honestly hope it to 
be changed in newly coming LTP spec.
 
Cheol

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