Re: AD comments on draft-ietf-rohc-hcoipsec-10

Carl Knutsson writes:
> RTP profile can in worst-case add up to around 20 bytes. Header
> compression works best for small packets. Large packets that doesn't fit
> the MTU because of the overhead could be sent uncompressed or over a
> channel without ROHC. The overhead for the uncompressed profile is only
> a few bytes. This overhead is added to the PMTU field.

With ROHC over IPsec there is already a way to express uncompressed
packets without any overhead (i.e. if next header is ROHC protocol
then packet is compressed with ROHC, if not then it is uncompressed),
so sending uncompressed packets does not add any more overhead than
what IPsec already adds.

The amount of overhead for IPsec is per SA, as it depends on the
protocol (ESP/AH) and about the algorithms selected for that SA, so
adding ROHC overhead there should be easy. The ROHC overhead should
take account the normal ROHC maximum header expansion and the ROHC ICV
length.
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