Extension header vs destiantion option

[marcelo bagnulo braun <marcelo@it.uc3m.es>]

Hi,

I guess we also need to understand the differences between using a new 
SHIM extension header to carry the context tag or use a new Destination 
option for carrying it.

We have discussed this issue in the design team, and as far as i 
remember. people that were involved in the design on MIPv6 argued for 
using a new extension header rather than using a destination option. 
The reasons for that, AFAIU, are the problems that appeared when using 
the destination option. These were basically due to the fact that 
Destination options are no ordered within the Destination Option 
extension header. This result that it is not clear how to build the 
destination option header, and that since the context tag determines if 
the addresses are rewritten, then the resulting behavior may be 
affected depending on the order in which destination options are 
placed.
In addition there is the issue brought by Iljitsch, about the 
destination option header being processed after the IPSec related 
header. This seems to be in opposition with the architecture of the 
shim, where the shim resides below the IPsec.
However, if a new extension header is used, then the order is perfectly 
defined and could be placed properly w.r.t. IPSec.

I guess that Erik or Jari could expand on this topic, but AFAIU, we 
should consider a new Extension header rather than a Destiantion 
option.

Comments?

regards, marcelo