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Re: I-D ACTION:draft-ietf-shim6-applicability-01.txt

Hi Brain,

thanks for your comments...


El 14/06/2006, a las 9:35, Brian E Carpenter escribió:


A few personal comments:


2.  Application scenarios

...

   ...This configuration
is intended to provide protection for the end-site in the event of a 
   failure in some subset of the available transit providers without
   requiring the end-site to acquire provider-independent (PI) address
   space.


I suggest adding:
or requiring any particular cooperation between the transit providers. 

since this seems to be a significant feature of shim6.



ok


3.3.  Address Generation

...

   Stateful address auto-configuration using DHCP [RFC3315] is not
currently supported, because there is no defined mechanism to convey the CGA Parameter Data Structure and other relevant information from the DHCP server to the host. The definition of such mechanisms seems 
   to be quite straightforward in the case of the HBA, ...


Is there a plan to perform this work?
I had the intention of writing a draft but it was not clear to me how useful would this extension be... 

I mean, there are two cases: the HBA and the CGA
The HBA is quite easy to solve, since there is no secret information. However, the resulting addresses would contain a somehow random iid part (as oposed to the case where the dhcp server can assign iid ::1, ::2, ::3 and so on to the hosts in the network) so i am not sure why would be interesting to use dhcp in this case... do you have any hints why this could be interesting?
The CGA case is more complex since there is a private key involved. I this case we can allow the dhcp server to assign a key pair to the host, in which case the dhcp server is actually assigning a address to the host, but we need a secure channel between the server and the host and the problem that the server knew the private key at some point in time. THe other option is that the host conveys the public key to the server. In this case, it is less clear what the dhcp server is actually assigning to the host (since the public key is determined by the host) and what would this be useful for...
So, bottom line is what a HBA/CGA dhcp extension would be useful for and what scenarios/use cases are there for this? 



5.3.  Shim6 and SCTP

...

   ...It is
   recommended that Shim6 is not used for SCTP sessions, and that path
   maintenance is provided solely by SCTP.


What is the mechanism, i.e. how does SCTP tell shim6 to do nothing?
well, i think we discussed about this and my understanding was that there was no need for an explicit notification by the sctp to the shim (this is implementations specific proabbaly...)
That it would be possible for the shim layer to simply not create any context for sctp sockets. In order to do that, the shim6 layer need to have access to the socket information (which i think is implementation specific)
Besides, it would also be possible to define a DONOT_SHIM socket option, but this would require update to use such mechanism
perhaps some other people with more background on this could expand on this... 

regards, marcelo



    Brian