Subject: [Hipsec] Updating moskowitz-hip-07: IPv4 pseudo header

From: [email-masked] (Pekka Nikander)
Date: Fri Sep 5 05:56:00 2003

draft-moskowitz-hip-07.txt currently specifies as follows:

6.1.2 CRC

    The checksum field is located at the same location within the header
    as the checksum field in UDP packets, enabling hardware assisted
    checksum generation and verification. Note that since the checksum
    covers the source and destination addresses in the IP header, it must
    be recomputed on HIP based NAT boxes.

    ....

    In case of using IPv4, the the IPv6 pseudo header format [10] is
    still used, but in the pseudo-header source and destination addresses
    are IPv4 addresses expressed in IPv4-in-IPv6 format [3].

Now, do we really think that the IPv4 practise is the right one?
If we have an IPv4 NAT box, it must explicitly know about how to
update the HIP pseudo header, and the processing is different from
the standard IPv4 TCP and UDP pseudo-header cases.  That foils the
statement above about being able to use hardware assisted checksum
generation and verification.

I propose that we change the text as follows:

    In case of using IPv4, the IPv4 UDP pseudo header format [RFC768]
    is used.  In the pseudo header, the source and destination
    addresses are those used in the IP header, the zero field is
    obviously zero, the protocol is the HIP protcol number (TBD),
    and the length is calculated as in the IPv6 case.

This would require a small change to the current implementations.

Opinions?

--Pekka Nikander

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From: [email-masked] (Miika Komu)
Date: Fri Sep 5 07:08:04 2003

> This would require a small change to the current implementations.

Sounds reasonable to me.

-- 
Miika Komu              [email-masked]          http://www.iki.fi/miika/