Subject: RE: [pim] Query on BSR draft?

From: Bandi Sarveshwar-G19441 <[email-masked]>
Date: Thu, 14 Aug 2003 17:42:05 +0530

-----Original Message-----
From: bharat_joshi [mailto:[email-masked]]
Sent: Thursday, August 14, 2003 5:14 PM
To: Bandi Sarveshwar-G19441; [email-masked]
Subject: RE: [pim] Query on BSR draft?

Hi,

Please see inline.

Thanks & Regards,
Bharat

Hi,
   I have a query on the manner in which group to rp mappings are advertised using the bsr. Say I have a single BSR router in a domain. This BSR router learns of C-RP-ADV for a group address range G from A. Inturn BSM messages are broadcast with <G, Rp Count =1, RP addr = A>. When the A stops acting as an RP for G, will BSR send a BSM message with <G, Rp Count=0>???  Thus implicitly indicating that no RPs are available to serve G.

>>> Yes, Elected BSR must send this group-prefix with rpCount equal to zero.
This will help non-BSR routers to remove the group-prefix faster.

   Other question is, When the BSR router goes down, leading to the timing out of BSR timer followed by the expiry of ScopeZone timer in Non-C-BSR routers, do they clean up the group-rp mapping information given by the BSR? or do they continue to cache  (which could go stale sooner or latter) the information and use it??

>>> When an elected BSR goes down, he must send a BSM with bsr priority
equal to zero. Now all the group-prefix will be updated from this BSM. Now
because this is the last BSR in the domain, so there will not be any more
BSMs because of which when BS timer will timesout. Every router will remove
this Elected BSR after BS timesout and all the group-prefix will also be removed. So the group-prefix will still be there till the BS timeout.

<Sarvesh> The draft doesnt explicitly say this. Infact the draft seems to imply (not explicitly) that it should continue to use the previous group to rp mapping information till a new BSR overrides it. Probably treating it as cached information( i think a few mails on the archive seem to have mentioned this) I guess that would be a pretty bad if no other BSR comes up.

Thanks in Advance,
Sarvesh

> Sarveshwar Bandi	                                                 
> Senior Software Engineer,
> Motorola Computer Group, 
> http://www.netplane.com
> Ph: +91-40-355 3709/10/11/12 Extn: 1126
> Fax: +91-40-355 3713
> 
> 
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From: prashant <[email-masked]>
Date: Thu, 14 Aug 2003 18:16:57 +0530

Hi,
    This issue was discussed long time back on the list....& if I remember
correctly it was in accordance to what Bharat  told i.e. delete the complete
BSR related info on BSR timer expiry...
Draft may need some amendment and is left to the authors to do the needful.

BTW one hardly uses BSR mechanism ...mostly static RP configuration is
deployed

regards,
Prashant

-----Original Message-----
From: [email-masked] [mailto:[email-masked]]On
Behalf Of Bandi Sarveshwar-G19441
Sent: Thursday, August 14, 2003 5:42 PM
To: 'bharat_joshi'; [email-masked]
Subject: RE: [pim] Query on BSR draft?

-----Original Message-----
From: bharat_joshi [mailto:[email-masked]]
Sent: Thursday, August 14, 2003 5:14 PM
To: Bandi Sarveshwar-G19441; [email-masked]
Subject: RE: [pim] Query on BSR draft?

Hi,

Please see inline.

Thanks & Regards,
Bharat

Hi,
   I have a query on the manner in which group to rp mappings are advertised
using the bsr. Say I have a single BSR router in a domain. This BSR router
learns of C-RP-ADV for a group address range G from A. Inturn BSM messages
are broadcast with <G, Rp Count =1, RP addr = A>. When the A stops acting as
an RP for G, will BSR send a BSM message with <G, Rp Count=0>???  Thus
implicitly indicating that no RPs are available to serve G.

   Other question is, When the BSR router goes down, leading to the timing
out of BSR timer followed by the expiry of ScopeZone timer in Non-C-BSR
routers, do they clean up the group-rp mapping information given by the BSR?
or do they continue to cache  (which could go stale sooner or latter) the
information and use it??

equal to zero. Now all the group-prefix will be updated from this BSM. Now
because this is the last BSR in the domain, so there will not be any more
BSMs because of which when BS timer will timesout. Every router will remove
this Elected BSR after BS timesout and all the group-prefix will also be
removed. So the group-prefix will still be there till the BS timeout.

<Sarvesh> The draft doesnt explicitly say this. Infact the draft seems to
imply (not explicitly) that it should continue to use the previous group to
rp mapping information till a new BSR overrides it. Probably treating it as
cached information( i think a few mails on the archive seem to have
mentioned this) I guess that would be a pretty bad if no other BSR comes up.

Thanks in Advance,
Sarvesh