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

Hi,

I have now reviewed the three documents in the ROHC over IPsec solution.
I will comment here on some high level issues that may require document
updates, however not necessarily in this document. Please consider if
the fix is more appropriate in any of the other two documents.

1. I find there is a lack of discussion of how to handle Path MTU for
these ROHC inside of a IPsec SA. The issue to me is the variable size
compressed packet. That makes the actual MTU seen on the ingress of the
processing to jump up and down depending on what type of ROHC packet is
created for a particular packet. To me it appears that the MTU with ROHC
enabled in a IPsec SA is less than without ROHC when sending IR.

There must be some discussion about this issue. How it affects path MTU
discovery, what to do about it so that one don't get spurious IP
fragmentation or MTU losses for packets with DF bit set.

2. I understand that one the negotiation mechanism is sufficient to
ensure that the decompressor doesn't get a profile or more CID then it
can handle. However, wouldn't it be suitable to recommend at least some
basic set of functionality that is mandatory to support to ensure better
interoperability and minimal achieved functionality.

3. When I read this document I get the impression that it would be
suitable to be published as a proposed standard because it defines so
much how things shall interact. So can you please motivate why you think
Informational is more suitable?

4. Section 6.

The Next Header field of the security protocol header
   (e.g., ESP, AH) is populated with a "ROHC" identifier,

Considering that you are having so much other references, why not a
reference to where this one is defined? Also should it not say: ...
"ROHC" protocol number?


cheers

Magnus Westerlund

IETF Transport Area Director & TSVWG Chair
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