Re: Is TS agreement necessary?

[Joe Touch <touch@ISI.EDU>]

Mark Duffy wrote:
> At 06:08 PM 4/5/02 -0800, Joe Touch wrote:
> 
>>Lars Eggert wrote:
>>
>>>Stephen Kent wrote:
>>>
>>>
>>>>RFC 2401 is reasonably clear in noting that the SPD is nominally per 
>>>>interface. What sort of management interface is provided to a client 
>>>>is up to the vendor, so long as one can achieve the same effects as a 
>>>>per-interface SPD.  Otherwise, the implementation would not be compliant
>>>
>>>As a side note, I misunderstood this for a long time to mean "SPD per 
>>>PHYSICAL interface", which is not sufficient (because of ambiguities via 
>>>multiple matching tunnel-mode SAs in the same per-physical-interface 
>>>SPD). When viewing tunnel mode SAs as virtual interfaces in their own 
>>>right that have separate SPDs associated with them, these problems 
>>>dissapear. Maybe that's part of the confusion around tunnel mode...
>>>Lars
>>
>>Hi, Steve,
>>
>>One of the confusions I have is regarding systems that say they use 
>>these tunnel mode SAs as virtual interfaces. It seems that the tunnel SA 
>>has to be in the SPD of the underlying interface, but they only work if 
>>the SA is in the SPD of the virtual interface (i.e., inside the tunnel). 
>>That seems self-referential... ??
>>
>>Jo
> 
> I'm not Steve but I'll pipe up anyway :-)
> It doesn't seem any problem on the outgoing side -- first the forwarding
> decision selects the outgoing interface (the tunnel).  Then the SPD for
> that virtual interface is consulted (and it has all-wildcard selectors for
> the single tunnel mode SA).  The packet is encapsulated and a new
> forwarding decision made.

As per other mail to PPVPN, the issue is that the SA of the tunnel 
appears in the SPD of the tunnel itself. That seems recursive. It seems 
that the SA of a tunnel should appear in the SPD of the interface (real 
or virtual) that the tunneled packet will be emitted on.

> When we are the IKE responder, there is some potential ambiguity.

I'm not speaking about IKE at all, FWIW.

Joe