Re: [Tsv-art] Tsvart last call review of draft-ietf-6lo-minimal-fragment-07

Joerg Ott <ott@in.tum.de> Thu, 30 January 2020 11:20 UTC

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To: "Pascal Thubert (pthubert)" <pthubert@cisco.com>, Joerg Ott <jo@acm.org>, "tsv-art@ietf.org" <tsv-art@ietf.org>
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From: Joerg Ott <ott@in.tum.de>
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Date: Thu, 30 Jan 2020 12:20:39 +0100
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Subject: Re: [Tsv-art] Tsvart last call review of draft-ietf-6lo-minimal-fragment-07
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Hi Pascal,

wow, this is a super-fast fix.  Looks all good to me.

Best,
Jörg

On 30.01.20 12:01, Pascal Thubert (pthubert) wrote:
> Many thanks Joerg!
> 
> Please see below:
> 
>> Generally, the document is in good state and almost ready to publish. A few
>> nits, one on protocol state management below:
>>
>> Nits:
>>
>> The text uses both "6lo fragments" and "6LoWPAN fragments".
> 
> Changed to 6LoWPAN fragments everywhere
> 
> 
>>
>> Section 5, end of 1st para:
>> "Since the datagram_tag is uniquely associated to the source Link-Layer
>> address of the fragment, the forwarding node MUST assign a new
>> datagram_tag from its own namespace for the next hop and rewrite the
>> fragment header of each fragment with that datagram_tag."
>>
>> This sentence is correct but it comes after the description of handling
>> subsequent fragments, rather than the first one, and subsequent ones should,
>> of course, not receive a new datagram_tag. Maybe move the sentence further
>> up or make explicit reference to the first fragment.
> 
> Great point, moved up.
> 
>>
>> Sect. 5, bullet list, "* a datagram_size"
>> Just as a remark, this does not seem to be used. It *could* be used to check if
>> a fragment beyond the end of the packet arrives, but has otherwise no
>> (documented) meaning. The draft should spell out its purpose.
> 
> Since we did not use it the simplest is to remove it 😊
> 
>>
>> Sect. 5, bullet list, "a timer that allows discarding the stale FF state after some
>> timeout"
>> Surely needed, but no advice is given. There is generally no explicit statement
>> when to discard the state. What should an implementation do to interoperate,
>> given that upstream multiplexing of packet fragments from multiple sources
>> can yield diverse intervals between consecutive fragments? Would this be the
>> same timer previously used for reassembly? If so, maybe just state this.
> 
> Great point again! Does the below work, added to the bullet?
> "
> The duration of the timer should be longer than that which covers the reassembly at the receiving end point.
> "
> 
>>
>> Sect. 7, 2nd bullet: "attck" -> "attack"
>>
> 
> Fixed!
> 
> 
> Many thanks again, Joerg. I posted 09 with the above. Please let me know if we are OK?
> 
> All the best
> 
> Pascal
> 
> 
> 
> 
> 
>