RE: mboned: RE: [magma] suggestion for simplifying IGMPV3/MLDV2 to discard EXCLUDEmode

the proposal should provide an interoperable subset of the full versions
of IGMPv3/MLDv2, which i do not believe the draft does in failing to
adhere to core elements of RFCs 3376/3810.  among other things:

  * abandoning the Filter-Mode-Change records, TO_IN and TO_EX,
    misinterprets the role of these records in signaling state change
    to the routers and the subsequent handling of state change in the
    routers, e.g., the generation of appropriate group and
    group-specific queries and the accompanying lowering of timers.

    consider this very simple example:
       - host joins group G, generating IS_EX() at 0s
       - host leaves group G, generating IS_IN() at 5s
       - since no query is generated by receipt of IS_IN(), 
         group record for G persists for GMI - 5s

    along these lines, the older version interoperability section of
    RFC 3376 maps IGMPv2 Leaves to TO_IN(), not IS_IN() -- and there is no
    such thing as a "v1 Leave".

    rather, i believe the proposal should specify the following "Action on
    Change of Interface State":

Old State      New State             State-Change Record Sent
---------      ---------             ------------------------

INCLUDE (A)    INCLUDE (B)           ALLOW (B-A), BLOCK (A-B)

INCLUDE (A)    EXCLUDE ( )           TO_EX ( )

EXCLUDE ( )    INCLUDE (B)           TO_IN (B)


  * one of the key points of the proposal should be to eliminate the
    excluded sources list; further removing the router's filter-mode
    or re-labeling the group's timer for ASM purposes is ultimately
    superfluous, constituting more of an implementation optimization than
    a protocol simplification.

    in considering the handling of group and source timer values, the only
    material consideration in the proposal should involve handling the
    expiration of source timers, which should always result in removing
    the source record regardless of the mode of the group or the value of
    the group timer.


from my understanding of the "full" versions of IGMPv3/MLDv2, i do not
believe that a "lite" version of the protocols requires a lot of
significant alterations, and is more adequately summarized by a couple of
simple modifications to what's already been described in RFCs 3376/3810:

  * do not allow excluded sources in interface state
  * do not process source lists in IS_EX and TO_EX messages
  * remove source records when their respective timer expires

where other areas and alterations can be reduced safely to implementation
concerns.  and again, here's a reposting of my earlier thoughts on what
the proposal's router state should look like:

Router State   Report Rec'd  New Router State    Actions
------------   ------------  ----------------    -------

INCLUDE (A)    IS_IN (B)     INCLUDE (A+B)       (B)=GMI

INCLUDE (A)    IS_EX ( )     EXCLUDE ( , )       Delete (A)
                                                 Group Timer=GMI

EXCLUDE (X, )  IS_IN (A)     EXCLUDE (X+A, )     (A)=GMI

EXCLUDE (X, )  IS_EX ( )     EXCLUDE ( , )       Delete (X)
                                                 Group Timer=GMI

INCLUDE (A)    ALLOW (B)     INCLUDE (A+B)       (B)=GMI

INCLUDE (A)    BLOCK (B)     INCLUDE (A)         Send Q(G,A*B)

INCLUDE (A)    TO_EX ( )     EXCLUDE ( , )       Delete (A)
                                                 Group Timer=GMI

INCLUDE (A)    TO_IN (B)     INCLUDE (A+B)       (B)=GMI
                                                 Send Q(G,A-B)

EXCLUDE (X, )  ALLOW (A)     EXCLUDE (X+A, )     (A)=GMI

EXCLUDE (X, )  BLOCK (A)     EXCLUDE (X+A, )     (A-X)=Group Timer
                                                 Send Q(G,A)

EXCLUDE (X, )  TO_EX ( )     EXCLUDE ( , )       Delete (X)
                                                 Group Timer=GMI

EXCLUDE (X, )  TO_IN (A)     EXCLUDE (X+A, )     (A)=GMI
                                                 Send Q(G,X-A)
                                                 Send Q(G)


mark

On Thu, 15 Jun 2006, Hui Liu wrote:

> Hi, all,
> 
> Thank you for previous dicussions of  the ideas. 
> 
> A draft "Simplifying Process for IGMPv3 and MLDv2 Protocols" has just been
> prepared and submitted to the IETF database. This draft suggests the discard
> of EXCLUDE(S,G) mode on the hosts and the filter-mode on the router. The
> changes introduced to the original full IGMPv3/MLDv2 and appropriate
> processing are described. Interoperation issues with full IGMPv3/MLDv2 and
> IGMPv1/IGMPv2/MLDv1 are also discussed.
> 
> Any comments for this draft is welcome. If there are any incorrectness,
> please feel free to indicate.
> 
> 
> Thanks,
> 
> Hui  Liu
>  
> 
> 


_______________________________________________________________
user interface: http://darkwing.uoregon.edu/~llynch/mboned.html
web archive:  http://darkwing.uoregon.edu/~llynch/mboned/