Re: [lisp] Proposed change to draft-ietf-lisp-05.txt

[Margaret Wasserman <mrw at sandstorm.net>]

On Sep 25, 2009, at 5:10 PM, Noel Chiappa wrote:
> > I think, for example, that we may return the answer to the source  
> > RLOC
> > in the outer header, right?
>
> Err, what answer? Map-Registers are not acknowledged.

Oh, right.  Sorry.  Please ignore my other comment about where the  
reply will be sent, as well...

> > Why is this set to 0? ... Why include the field in the Map-Register
> > message if it will always be 0?
>
> Ummm, I think I might be the cause of that - unless it's there because
> there's a desire to make all the control packets look similar (i.e.  
> include a
> nonce field).
>
> When the issue of replay protection was raised, since replay is  
> generally an
> on-path attack, I was trying to add a 'hook' to the Map-Register  
> packet that
> would allow us to add replay protection _later_, without changing  
> the packet
> format. (I.e. defer adding the _mechanism_ to deal with that attack  
> till
> later, since it's an unlikely attack; but at the same time, putting  
> a field
> in now would avoid interoperability problems - or using another  
> opcode for a
> new format Map-Register - later. I.e. a cheap thing to do now -  
> since we're
> chaning the packet format _anyway_ - to avoid a painful change  
> later.) I had
> worked out a mechanism using a nonce, so perhaps that's what this is?
>
> But that's something of a guess!

I'm not sure that I agree with setting aside this big block in the  
message to add replay protection later, but that isn't a blocking  
issue for me.  If we are setting aside this field for later use,  
though, it should be labeled "reserved for later use", not "nonce".

Margaret