Re: [tsvwg] New Version Notification for draft-touch-tsvwg-udp-options-05.txt

["C. M. Heard" <[e-mail]>]

On Fri, Mar 17, 2017 at 6:03 PM, Joe Touch <[e-mail]> wrote:
> The queue has closed, but I have a new version of UDP options 06 that
> will post as soon as it opens (why do we still do this?)
>
> Here's a pointer in the meantime:
>
> http://www.isi.edu/touch/pubs/draft-touch-tsvwg-udp-options-06.txt
>
> It includes Mike's nice observation about combining FRAG and LITE,
> clarifies some nits about what happens in each order, etc.
>
> I tried to keep things simple, so LITE comes first when it's used, FRAG
> stops processing until reassembly, and things pick up after reassembly
> with options included after the last fragment. I think that's clean...

Agreed, I like the way you have done this, with the final fragment being
indicated by including a checksum. That said, the following text:

>> A host SHOULD indicate FRAG support by transmitting an
   unfragmented datagram using the Fragmentation option (e.g., with
   Offset and M both zero), except when encoded as LITE.

needs to be adjusted owing to elimination of the M bit in favor of a
whole-datagram checksum.

Regarding the whole-datagram checksum: it would IMHO be appropriate to
be very specific as to what it is. I would propose the standard Internet
checksum without a pseudo-header, with the value 0x0000 indicating the
absence of a checksum.

Other comments:

In section 5.4, was a decision made as to what the CRC16 is? Details
will be needed in order to ensure interoperability.

In Section 9, third paragraph, you may want to make the following change:

OLD:
   This feature is also inconsistent with the UDP application interface
   [RFC768] [RFC1122].
NEW:
   This feature is also inconsistent with the UDP application interface
   [RFC1122].

in view of the following text in RFC 768:

IP Interface
-------------

The UDP module  must be able to determine  the  source  and  destination
internet addresses and the protocol field from the internet header.  One
possible  UDP/IP  interface  would return  the whole  internet  datagram
including all of the internet header in response to a receive operation.
Such an interface  would  also allow  the UDP to pass  a  full  internet
datagram  complete  with header  to the IP to send.  The IP would verify
certain fields for consistency and compute the internet header checksum.

Thanks and regards,

Mike Heard