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[IPsec] WESP #109 - WESP header alignment for IPv6
From: Grewal, Ken <ken.grewal_at_nospam>Date: Thu Sep 24 2009 - 18:13:00 GMT
To: "ipsec@ietf.org" <ipsec@ietf.org>
All,
During the IPsecME interim meeting earlier this week, there was initial consensus from the participants that the WESP header should be aligned on an 8 octet boundary for IPv6 in the following manner.
We will extend the WESP header by a 4 octet reserved field (all zeros) and use a new bit 'X' in the flags field to denote presence (or absence) of this alignment field. This can be depicted as follows:
Existing WESP header:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Next Header | HdrLen | TrailerLen |V|V|E| Rsvd |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Proposed change
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Next Header | HdrLen | TrailerLen |V|V|E|X| Rsvd |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved (zeros) for IPv6 alignment |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
If 'X' is set (value 1), the 4 octet reserved field is present (needed for IPv6). If 'X' is clear (value 0), the 4 octet reserved field is absent (needed for IPv4).
This comment was from AD review of the document and ticket #109 has been generated to track this item.
Any additional feedback?
Thanks,
- Ken
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