Re: [Tsv-art] Tsvart last call review of draft-ietf-dots-rfc8782-bis-05

tuexen@fh-muenster.de Mon, 22 March 2021 09:04 UTC

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Date: Mon, 22 Mar 2021 10:04:17 +0100
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To: mohamed.boucadair@orange.com
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Subject: Re: [Tsv-art] Tsvart last call review of draft-ietf-dots-rfc8782-bis-05
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> On 22. Mar 2021, at 07:42, <mohamed.boucadair@orange.com> <mohamed.boucadair@orange.com> wrote:
> 
> Hi Michael, 
> 
> Thank you for the review.
> 
> The motivation was used as it was the key element in the discussion in Section 3.3.3 of RFC1122, but you made a fair comment.
> 
> ==
>         DISCUSSION:
>              Picking the correct datagram size to use when sending data
>              is a complex topic [IP:9].
> 
>              (a)  In general, no host is required to accept an IP
>                   datagram larger than 576 bytes (including header and
>                   data), so a host must not send a larger datagram
>                   without explicit knowledge or prior arrangement with
>                   the destination host.
> ==
> 
> We can update the text as follows: 
> 
> OLD: 
>   assume a PMTU of 576 bytes for IPv4 datagrams, as every IPv4 host
>   must be capable of receiving a packet whose length is equal to 576
>   bytes as discussed in [RFC0791] and [RFC1122].
> 
> NEW:
>   assume a PMTU of 576 bytes for IPv4 datagrams (see Section 3.3.3 of [RFC1122]).
Hi Med,

let me try to get my point clear:

You can use Section 3.3.3 of [RFC1122] to motivate that the sender should
not send datagram larger than 576, since there is no guarantee that the
receiver has resources to reassemble and process it. But RFC 1122 makes
no statement about the path. As far as I know there is no safe value for
a PMTU you can derive from a specification.


So maybe:
NEW:
  assume a PMTU of 576 bytes for IPv4 datagrams (see Section 3.3.3 of [RFC1122]
  for support at the receiver).

Best regards
Michael
> 
> Cheers,
> Med
> 
>> -----Message d'origine-----
>> De : Michael Tüxen via Datatracker [mailto:noreply@ietf.org]
>> Envoyé : lundi 22 mars 2021 00:33
>> À : tsv-art@ietf.org
>> Cc : dots@ietf.org; draft-ietf-dots-rfc8782-bis.all@ietf.org; last-
>> call@ietf.org
>> Objet : Tsvart last call review of draft-ietf-dots-rfc8782-bis-05
>> 
>> Reviewer: Michael Tüxen
>> Review result: Ready with Nits
>> 
>> This document has been reviewed as part of the transport area review
>> team's ongoing effort to review key IETF documents. These comments
>> were written primarily for the transport area directors, but are copied
>> to the document's authors and WG to allow them to address any
>> issues raised and also to the IETF discussion list for information.
>> 
>> When done at the time of IETF Last Call, the authors should consider
>> this review as part of the last-call comments they receive. Please
>> always CC tsv-art@ietf.org if you reply to or forward this review.
>> 
>>> From a transport perspective, there is one minor issue:
>> Section 7.3 provides a motivation for using a path MTU for IPv4 of 576
>> bytes.
>> The motivation refers to the requirement that a receiver is capable of
>> receiving IPv4 packets of that size, however they can be received
>> fragmented.
>> While it is acceptable to use 576 bytes as the minimum PMTU, the
>> motivation does not hold.
>> 
> 
> 
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