Re: [lisp] Benjamin Kaduk's No Objection on draft-ietf-lisp-gpe-12: (with COMMENT)

["Fabio Maino (fmaino)" <[e-mail]>]

Hi Ben, 
I have just posted -rev 13 (https://www.ietf.org/id/draft-ietf-lisp-gpe-13.txt) that should address your comments as described in my previous email. 

Please, find attached the diff with -rev 12. 

Thanks again,
Fabio

On 1/6/20, 2:37 PM, "Fabio Maino (fmaino)" <[e-mail]> wrote:

    Hi Ben, 
    Thanks for your comments, and happy new year! 
    
    Please see below. 
    
    On 12/30/19, 11:49 AM, "Benjamin Kaduk via Datatracker" <[e-mail]> wrote:
    
        Benjamin Kaduk has entered the following ballot position for
        draft-ietf-lisp-gpe-12: No Objection
        
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        ----------------------------------------------------------------------
        COMMENT:
        ----------------------------------------------------------------------
        
        Thanks for the updates in -10 through -12 to leave nonce/versioning to
        additional shim headers/extensions; that does alleviate the concerns that
        left me balloting Abstain on the -09.
        
        I do have some (new) comments on the -12.
        
        Section 3
        
        Conceptually, I'm thinking about this document as allocating the 'P' bit in
        the header and specifying its format when the P bit is set to 1; I don't
        expect it to be making changes to generic non-GPE LISP behavior.  So it's
        a little surprising to see that bits 0-3 are now marked as Reserved (though
        that could probably be wordsmithed away, and the existing Section 2 probably
        sets the reader up to do the right thing already), and fairly surprising to
        see the following in the P-Bit description:
        
              If the P-bit is clear (0) the LISP header is bit-by-bit equivalent
              to the definition in [I-D.ietf-lisp-rfc6830bis] with bits N, L, E
              and V set to 0.
        
        Is the claim that once an implementation supports GPE, it will never use the
        non-shim-header versions of echo-nonce, map-versioning, etc?  If not, then I
        don't think it's appropriate to say "with bits N, L, E, and V set to 0"
        here.
        
    [FM] I think you make a good point, especially that we don't want to alter the behavior of the protocol when P=0. We can re-word the document accordingly: we leave NLEV bits in the header definition, and we limit the document to specify the behavior for the case when P=1. 
    
        I'm also not sure I fully understand the motivation for pulling out
        the Locator-Status-Bits, as that field's width is unchanged from stock
        6830bis.  Leaving them to a TBD shim-header does prevent the conflict with
        the Instance ID field, and perhaps the current usage patterns justify such a
        shift, so this may be more of a side note than an indication of a flaw in
        the document.
    
    [FM] Indeed, there isn't a strong rationale to prevent the use of LSBs with GPE. Following your suggestion of specifying GPE as "allocating the P bit in LISP" we can leave that feature available even when P=1. 
    
        
        Section 7
        
           LISP-GPE, as many encapsulations that use optional extensions, is
           subject to on-path adversaries that by manipulating the g-Bit and the
           packet itself can remove part of the payload.  Typical integrity
        
        Is "g-Bit" supposed to be "P-Bit"?  I am failing to remember what the g-Bit
        is, at least...
    
    [FM] yes, typo. Will fix in next rev. 
        
           With LISP-GPE, issues such as data-plane spoofing, flooding, and
           traffic redirection may depend on the particular protocol payload
           encapsulated.
        
        I'd consider adding another clause, "noting that an attacker that is
        spoofing LISP-GPE traffic can claim to encapsulate any protocol payload
        type" -- the risk here is based on what types the receiver's implementation
        supports, not just what the legitimate sender is encapsulating.
    
    [FM] Ok, we will address this in the next rev. 
    
    I'll post an updated version to reflect the comments above asap. 
    
    
    Thanks,
    Fabio