RE: issue 11 -- window size

> -----Original Message-----
> From: [email protected] 
> [mailto:[email protected]] On Behalf Of Bill Sommerfeld
> Sent: Wednesday, March 30, 2005 2:57 PM
> To: Jari Arkko
> Cc: [email protected]
> Subject: Re: [Mobike] issue 11 -- window size
> 
> On Wed, 2005-03-30 at 09:30, Jari Arkko wrote:
> > For the purpose
> > of making progress, let me propose one approach. If the 
> decision was 
> > "do it outside the window", would people have problems with that?
> 
> (I'm reading mail out of order)
> 
> I don't have a problem with that. 
> 
> One encoding which makes this clear would be to allocate a 
> new IKEv2 Exchange Type and specify that it has a distinct 
> Message ID space distinct from the space used by the existing 
> four types (see section 3.1 of draft-ietf-ipsec-ikev2-17.txt).  

I'm still considering this, but at the moment, I don't like this.  Granted,
it's unlikely two IKE peers would ever exhaust the message ID space, so
reserving a portion of this space shouldn't cause us to run out of "regular"
IKEv2 message IDs.  However, an implementation might set its window size to
5 because it really does only want to handle 5 messages at a time.  So now
what if we have this distinct message ID space, and the implementation needs
to consider the fact that it can only handle 5 messages.  So it needs to
split this between "regular" IKE messages and MOBIKE messages?

I prefer your earlier suggestion of reserving one or two message IDs from
the window for mobility purposes.  Consider a roaming client that gets a
notify from a security gateway (SGW) saying the SGW's window size is 5.  The
client should know that it's capable of mobility and consequently reserve a
message ID for MOBIKE messages.  Just because a peer sends a notification
about a window size doesn't mean that an implementation needs to fill up the
window.

-g

> (An alternative would be to grab one or more of the Flags 
> bits, but they are somewhat more scarce..)
> 
> 					- Bill
> 
> 
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