Subject: [Seamoby] CARD: Address length in L2-ID parameter

From: Marco Liebsch <[email-masked]>
Date: Fri, 10 Oct 2003 18:54:07 +0200

"...L2 id suboption should have address length field which MUST be
used at least with with L2 type = 0x00."

Maybe I misunderstood the issue, but the actual address length can
be calculated from the L2-ID sub-option's Length indicator, which
is always present, isn't it?

address length = Sub-option length - 5 octets

marco 

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From: Henrik Petander <[email-masked]>
Date: Mon, 20 Oct 2003 04:11:10 +0300 (EEST)

Hi Marco,

> is always present, isn't it?

Yes, but the sub-option is padded to be a multiple of 32 bits long, based
on the way I understood 5.1.3. For example a 48-bit MAC address (and the
L2 id subotion) would not end on a 32-bit boundary without 8 bits of
padding.  And if you don't know the length of the address, you can't
determine where the padding starts.

To correct this there are IMO three alternatives: 1. the boundary
restriction needs to be relaxed or 2. the length of the address needs to
be specified in the packet format or 3. L2 type specification should be a
MUST and type 0x00 should be removed.

Henrik

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From: Marco Liebsch <[email-masked]>
Date: Wed, 22 Oct 2003 18:15:34 +0200

Hi Henrik,

>MUST and type 0x00 should be removed.
Thanks for the clarification. Of course, you are right.
Referring to the recent issue on the assignment of L2-type values, I 
must admit that
your option 1 or 2 are the candidates I would go for. Since we said that 
individual
sub-options should take care about 32-bit boundary alignment, relaxing 
this for the
L2-ID is not consistent. Hence, it won't be a problem to have another 
byte after the
L2-type field, which indicates the real length of the L2-ID field 
without padding.
However, having 2 length fields in one parameter doesn't look good, but 
might be the
best compromise.

What's the opinion of others? Any preferences here?

marco