Re: [tsvwg] I-D Action: draft-ietf-tsvwg-udp-options-08.txt

[Joe Touch <[e-mail]>]

Hi, Mike,

Many thanks for these detailed comments. They’ll be incorporated in the next rev.

Joe

> On Dec 28, 2019, at 2:53 PM, C. M. Heard <[e-mail]> wrote:
> 
> Hi Joe,
> 
> These comments address only the changes in version -08, as you requested.
> I am sorry that they are so late, but my day job has required all my attention.
> 
> On Thu, Sep 12, 2019 at 9:14 PM Joe Touch wrote
> Hi, all,
> 
> This is a quick update to cover the following:
> 
> - update conventions to cite "standard" caps-only text (was that
> seriously necessary?)
> 
> Thanks for doing that as someone will insist during eventual IESG review
>  
> - remove 'experimentally' throughout; this is standards-track
> 
> Changes look good.
>  
> - add the extended length format
> 
> Changes look good, but I would recommend that another figure,
> to accompany Figure 22, be added to make it clear that the EXP
> option is allowed to use the extended length format.
>  
> - correct the lengths in the summary table
>  
> Changes look good, except for inconsistent capitalization of RESERVED..
> 
> - require post-options area of surplus to be zero-fill
> 
> Change looks good.
> 
> - fix the figure and description of OCS to use a 16-bit checksum
> 
> The work on this section is incomplete, as it does not specify
> that a two-byte pseudo header containing the length of the surplus
> area be conceptually prefixed to the surplus area data. As noted in
> https://tools.ietf.org/html/draft-fairhurst-udp-options-cco-00 <https://tools.ietf.org/html/draft-fairhurst-udp-options-cco-00>,
> that pseudo-header is necessary to fix the most common middlebox
> traversal issue that has been found (i.e., calculating the UDP
> checksum based in the IP payload length instead of the UDP length).
> Since the result will not be an overall ones-complement sum of
> zero, that language needs to be dropped from the draft.
> 
> I would also recommend that the next version of the draft
> explicitly mention that for the purpose of the checksum
> calculation the surplus area needs to be conceptually
> padded by zero bytes that are not actually transmitted
> if its start and/or end are on odd boundaries relative
> to the start of the UDP data area. 
> 
>  
> - define OCS as required when UDP CS != 0
> 
> Changes look good.
> 
>  
> - change ACS from a 16-bit CRC to CRC32c
> 
> Changes look good, but it should be explicitly stated whether it is
> REQUIRED that an option-aware receiver discard a packet with
> an incorrect ACS (which I believe is the intent of the draft) or
> whether it is at the receiver's discretion (presumably not, since
> ACS is listed as one of the options that an options-aware
> implementation is required to support).
>  
> There are more than a few other changes underway based on feedback from
> the last meeting. The concept behind those changes will be posted for
> feedback when developed further for WG feedback before being included in
> the next update.
> 
> I.e., please don't treat the fact that the rest hasn't changed as
> anything beyond "TBD".
> 
> Comments on *these changes* welcome, of course.
> 
> Editorial: section numbers for Echo (6.) and Experimental (6.1) are incorrect.
> 
> Substantive comments later on the proposed path forward presented at IETF 106.
> 
>  Mike Heard