Re: [tsvwg] draft-tuexen-tsvwg-sctp-zero-checksum-02 adoption

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> On 11. Apr 2023, at 19:15, Nils Ohlmeier <[e-mail]> wrote:
> 
> Hello,
> 
> I’m supporting adoption of draft draft-tuexen-tsvwg-sctp-zero-checksum-02, because it is going to be useful for all WebRTC endpoints out there to have the option to skip the checksum step.
> 
> I also reviewed the draft. The only concern I found is this sentence:
> 
> "Since the lower layer of SCTP can not be IPv4 or IPv6 as specified in [RFC9260] or UDP as specified in [RFC6951], no problems with middle boxes expecting correct CRC32c checksums in the SCTP packets are expected.”
> 
> Which confuses me, because it sounds to me like this is trying to say that SCTP over IPv4 or IPv6 can not be done. Which obviously doesn’t make any sense. But I honestly fail to parse what this sentence is suppose to tell me (besides no problems with middle boxes is expected).
Hi Nils,

the sentences before the one you cite state that you can only use the zero checksum feature
if the lower layer of SCTP provides an integrity protection at least as good as using CRC32c.

This is true for SCTP over DTLS, but not for SCTP over UDP over IP or SCTP over IP. So you
can not use zero checksum in these cases. This is important, since this means that firewalls
or NATs will not see the zero checksum and therefore don't drop such packets. It was reported
that some middleboxes drop SCTP packets having an incorrect CRC32c.

Any suggestion how to improve the text you find hard to parse?

Best regards
Michael
> 
> Best
>  Nils Ohlmeier