Subject: [core] Benoit Claise's No Objection on draft-ietf-core-block-19: (with COMMENT)

From: "Benoit Claise" <[email-masked]>
Date: Thu, 21 Apr 2016 05:32:28 -0700

Benoit Claise has entered the following ballot position for
draft-ietf-core-block-19: No Objection

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COMMENT:
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   CoAP is based on datagram transports such as UDP, which limit the
   maximum size of resource representations that can be transferred
   without creating unreasonable levels of IP fragmentation.

CoAP is based on UDP, right? So isn't it?
NEW:
   CoAP is based on UDP datagrams, which limit the
   maximum size of resource representations that can be transferred
   without creating unreasonable levels of IP fragmentation.

And ...

OLD:
   Using fragmentation (either at the adaptation layer or at
   the IP layer) for the transport of larger representations would be
   possible up to the maximum size of the underlying datagram protocol
   (such as UDP),

NEW:
   Using fragmentation (either at the adaptation layer or at
   the IP layer) for the transport of larger representations would be
   possible up to the maximum size of the underlying datagram protocol
   (UDP),

Note that they might exist other instances.

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From: Carsten Bormann <[email-masked]>
Date: Thu, 21 Apr 2016 14:41:32 +0200

Hi Benoit,

CoAP is often run on DTLS (which is then generally run on UDP, but can
also be run on, say, SMS).

> Note that they might exist other instances.

I think the generality here is warranted; as UDP is indeed by far the
most important underlying protocol, we are only discussing that one, so
the cost of that generality is low.

Grüße, Carsten

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From: Benoit Claise <[email-masked]>
Date: Thu, 21 Apr 2016 14:48:36 +0200

Hi Carsten,

Am I correct that rfc7252 only specifies UDP (and DTLS)?

Regards, Benoit.
> .

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From: Carsten Bormann <[email-masked]>
Date: Thu, 21 Apr 2016 15:41:00 +0200

> Am I correct that rfc7252 only specifies UDP (and DTLS)?

That is correct.  RFC 7252 also has a lot of this generality-infused
text, as in:

3.  Message Format

   CoAP is based on the exchange of compact messages that, by default,
   are transported over UDP (i.e., each CoAP message occupies the data
   section of one UDP datagram).  CoAP may also be used over Datagram
   Transport Layer Security (DTLS) (see Section 9.1).  It could also be
   used over other transports such as SMS, TCP, or SCTP, the
   specification of which is out of this document's scope.  (UDP-lite
   [RFC3828] and UDP zero checksum [RFC6936] are not supported by CoAP.)

(One transport that we are working on right now is TLS and/or TCP; the
block-wise protocol is used here both to avoid head-of-line blocking and
to stay compatible with the message sizes RFC 7252 recommends based on
UDP/DTLS.)

Grüße, Carsten