68 - minimal conformance requirements

>>   Note that both peers can have their own policies about what addresses
>>   are acceptable to use.  A minimal "mobile client" could have a policy
>>   that says that only the responder's address specified in local
>>   configuration is acceptable.  This kind of client does not have to
>>   send or process ADDITIONAL_*_ADDRESS notifications.  Similarly, a
>>   simple "VPN gateway" that has only a single address, and is not going
>>   to change it, does not need to send or understand
>>   ADDITIONAL_*_ADDRESS notifications.
>>  
>>
>I think we discussed this previously (and I have not
>yet checked what the result of that discussion was).
>However, the above client text sounds a bit too flexible
>in my opinion.
>
I checked issue #46 where we discussed this before.
The conclusion appeared to be that for the gateway the
current text is OK. On the client part I don't think we
decided anything.

However, when thinking about this it seems that even
the gateway part is suspect. It is true that you don't
need the additional addresses on a gateway that is
a responder. However, if this gateway is working in
gateway-to-gateway mode and is an initiator towards
the peer gateway which has multiple addresses, then
we need it.

We could try to describe all this, but I think the cost
of that is greater than simply saying that nodes that
conform to this specification need to be able to understand
the additional addresses. It is another matter what needs
to be sent.

Here's a proposed text change:

   Note that both peers can have their own policies about what addresses
   are acceptable to use.  A minimal "mobile client" could have a policy
   that says that only the responder's address specified in local
   configuration is acceptable.  This kind of client does not have to
   send or process ADDITIONAL_*_ADDRESS notifications.  Similarly, a
   simple "VPN gateway" that has only a single address, and is not going
   to change it, does not need to send or understand
   ADDITIONAL_*_ADDRESS notifications.

=>

   Note that a node that has only a single address at any given time
   does not need to send ADDITIONAL_*_ADDRESS notifications, but
   all nodes that support this specification must understand the reception
   of such notifications. However, nodes MAY have their own policies
   about what addresses are acceptable to use.

--Jari