Subject: Local_Only Flag usage in RFC 2209

From: Sarraju Narasinga Rao <[email-masked]>
Date: Fri, 05 Nov 1999 09:59:51 +0530

Hi

In RFC 2209, after a new PSB is created (and it's LOCAL_ONLY flag is
set) further processing for PATH message is as quoted below

o    If the PSB is new or if there is no route change
             notification in place, then perform the following routing
             manipulations, but not if the cPSB is from the local API.

             1.   Invoke the appropriate Route_Query routine using
                  DestAddress from SESSION and (for multicast routing)
                  SrcAddress from Sender_Template.

                  Call the results (Rt_OutL, Rt_InIf).

             2.   If the destination is multicast and Rt_InIf differs
                  from IncInterface in the cPSB, but fPSB points to the
                  cPSB, then do the following.

                  If the destination is multicast and Rt_InIf differs
                  from IncInterface in the cPSB, but fPSB points to the
                  cPSB, then do the following.

                  -    Turn on the Local_Only flag and clear the
                       OutInterface_list of the fPSB.  Set the fPSB
                       pointer to NULL.

                  -    Search for a PSB for the same (session,
                       sender_template) pair whose IncInterface matches
                       Rt_InIf.  If one is found, set fPSB to point to
                       it.

             3.   If the destination is multicast and Rt_InIf is the
                  same as IncInterface in the cPSB, but fPSB does not
                  point to the cPSB, then do the following.

                  -    Copy into the cPSB the OutInterface_list from the
                       PSB, if any, pointed to by fPSB.  Clear
                       OutInterface_list and turn on the Local_Only flag
                       in the PSB pointed to by fPSB, if any.

                  -    Turn off the Local_Only flag in the cPSB and set
                       fPSB to point to cPSB.

Here  my question 
--------------------
Is there a case where
 
                  the destination is multicast and Rt_InIf differs
                  from IncInterface in the cPSB, and fPSB 
                  points to NULL.

This seems possible in the case that the first PATH message arrives on
IncInterface and route query returns Rt_InIf != IncInterface. 

The result of the message processing would be that we now have a
interface for which there is no PSB with the Local_Only flag turned off.
Consequently state refresh messages will not be propogated on this
interface. Is that OK? Is there an unstated assumption here about how
multicasting is expected to work?

Could somebody out there please clarify??

Regards
-SNR

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