Subject: RE: sending NULL Bootstrap message ??

From: Narayanan Vidya-CVN065 <[email-masked]>
Date: Thu, 9 Aug 2001 08:59:48 -0500

If you are referring to the GenID action to unicast the BSM, that is not going to happen here. The E-BSR might just be elected the new BSR, but it might not necessarily be a new router (neighbor). 

But, my understanding was that if a newly elected BSR sent out a NULL BSM (this could happen if a BSR rebooted or a new router added to the PIM domain became the E-BSR or at system startup), all the PIM routers in the domain do not necessarily replace their existing RP-Set with a NULL set. They simply note the change in the BSR IP address and send C-RP advertisements to the new BSR, but retain the RP-Set information without changes. As I recall, this was specifically intended to accommodate scenarios like BSR reboot. Note that GenID should help in cases like that, but it might become a race condition between the unicasted BSM from the DR and the NULL BSM from the BSR. Also, it would become uninteroperable with routers that do not support the GenID option. 

This is my recollection of the whole NULL BSM operation. I don't recall it being changed in the new spec. Is this not how it is supposed to work? 

-Vidya

> -----Original Message-----
> From: Sridhar Vallepalli [mailto:[email-masked]]
> Sent: Tuesday, August 07, 2001 1:26 PM
> To: ramamurthy.pani; pim
> Subject: Re: sending NULL Bootstrap message ??
> 
> 
> When the standalone BSR is enabled for PIM on the network 
> (sending its first
> hello to neighbors). It receives a unicasted BSM with the 
> current RP-set and
> current BSR from the PIM DR neighbor on that interface. This 
> might prevent
> it from sending the null BSM.
> 
> -Sridhar
> 
> ----- Original Message -----
> From: <[email-masked]>
> To: "pim" <[email-masked]>
> Cc: <[email-masked]>
> Sent: Tuesday, August 07, 2001 6:11 PM
> Subject: sending NULL Bootstrap message ??
> 
> 
> > Hi,
> >    If a router is configured to be a stand alone BSR, and 
> becomes the
> E-BSR
> > of the domain,
> > is it OK for the BSR to send a BSM with no RP-SET, i.e a 
> null BSM. As a
> > result of sending
> > a NULL BSM, all the routers in the domain will be down for 
> some time, is
> > this acceptable ?
> >
> > Normally elected routers will inherit the RP-SET ( C-RP 
> list ) from the
> > active RP-SET used
> > by the router, but for stand alone routers, expected to 
> function just a
> BSR,
> > they will not
> > have the RP-SET, and so cannot inherit RP-SET, in which 
> case they are
> forced
> > to send a
> > NULL BSM message ( just advertising their BSR address, so 
> that C-RPs can
> > send their C-RP-ADV
> > msgs to the new BSR).
> >
> >            regards and thanks
> >        Ram
> >
> >
> >
> >
>