Subject: Gen-ART telechat review of draft-ietf-6man-udpzero-06

From: Richard Barnes <[email-masked]>
Date: Mon, 8 Oct 2012 14:16:55 -0400

I have been selected as the General Area Review Team (Gen-ART) reviewer for this draft (for background on Gen-ART, please see http://www.alvestrand.no/ietf/gen/art/gen-art-FAQ.html).

Please wait for direction from your document shepherd or AD before posting a new version of the draft.

Document: draft-ietf-6man-udpzero-06
Reviewer: Richard Barnes
Review Date: 2012-10-08
IETF LC End Date: 2012-10-02
IESG Telechat date: 2012-10-11

Summary:  Ready

Comment:

In general, the document is well-written and seems to cover the relevant considerations well.  I agree with Barry's DISCUSS that the restrictions in Section 5.1 should be general to all usages of UDP zero checksums, and not specific to tunnels.

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From: Masataka Ohta <[email-masked]>
Date: Tue, 09 Oct 2012 15:12:52 +0900

> Document: draft-ietf-6man-udpzero-06

It's interesting that the draft denies the following statements
in RFC2765:

   Fragmented IPv4 UDP packets that do not contain a UDP checksum (i.e.
   the UDP checksum field is zero) are not of significant use over
   wide-areas in the Internet and will not be translated by the
   translator.

While the draft considers only tunnels and states:

   IPv6 middlebox
   deployment is not yet as prolific as it is in IPv4. Thus, relatively
   few current middleboxes may actually block IPv6 UDP with a zero
   checksum.

interactions between the draft and existing implementations
of RFC2765 will be quite exciting.

The following statement of the draft:

      The computed checksum
      value may be cached (before adding the Length field) for each flow
      /destination and subsequently combined with the Length of each
      packet to minimise per-packet processing.

is bogus, because searching cache means a lot more effort than
recomputing checksum.

							Masataka Ohta