Subject: [Hipsec] SHIM6 adopting HIP packet format & small change to the format

From: Pekka Nikander <[email-masked]>
Date: Mon, 10 Oct 2005 09:41:41 +0200

In the SHIM6 interim meeting in Amsterdam, SHIM6 tentatively adopted  
the HIP packet format for the SHIM6 protocol proposal, with two  
little modifications in order to adopt the format better for SHIM6  
purposes.  This was a practical decision, with the intention of  
making it easier to create SHIM6/HIP hybrids for research purposes.   
Furthermore, the tentative decision does NOT mean that SHIM6 would,  
at this time, co-ordinate with HIP about packet type or parameter  
numbers, meaning that the HIP WG have to adopt to SHIM6 numbers if  
hybrid compatibility is needed.  However, the aim is to keep the path  
open for perhaps adopting more from HIP to SHIM6 in some future date.

The two tentative SHIM6 packet formats are as follows:

PAYLOAD:

     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  |       0       |1|       Reserved              |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                      Receiver Context Tag                     |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

CONTROL:

     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  |  Hdr Ext Len  |0|     Type    |Type specific|0|
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |           Checksum            |    Type specific format       |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                    Type specific format                       |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

The current HIP packet format is as follows:

     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   | Header Length |  Packet Type  |  VER. |  RES. |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |          Controls             |           Checksum            |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

In order to be compatible with SHIM6, we would need to do the following
changes:

- either
   - flip the places of RES. and VER. and make sure VER. is odd, or
   - take one bit from RES and make it one (I am adopting this)

- make the first bit of Packet Type to be zero
- flip the places of Checksum and Controls

The resulting new HIP packet format would be as follows:

     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   | Header Length |0| Packet Type |  VER. | RES.|1|
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |           Checksum            |           Controls            |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

What do you think?  Are we willing to do these changes?

--Pekka

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From: Miika Komu <[email-masked]>
Date: Mon, 10 Oct 2005 11:56:30 +0300 (EEST)

> - flip the places of Checksum and Controls

Was there some functional reason for the flips? I guess it is fine.

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

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From: Julien Laganier <[email-masked]>
Date: Mon, 10 Oct 2005 11:04:45 +0200

0                   1                   2                   3

> What do you think?  Are we willing to do these changes?

I am fine with these changes.

--julien

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From: Julien Laganier <[email-masked]>
Date: Mon, 10 Oct 2005 11:04:45 +0200

0                   1                   2                   3

--julien

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From: Pekka Nikander <[email-masked]>
Date: Mon, 10 Oct 2005 11:21:29 +0200

> Was there some functional reason for the flips? I guess it is fine.

The checksum and controls changed place so that SHIM6 packet type  
specific content can be continuous.

--Pekka