Subject: doubts regarding Pimsm (CRPs)

From: sabarivel s <[email-masked]>
Date: Fri, 9 Jun 2000 00:48:23 +0530

hi,
  i have some doubts regarding the Candidate RPs

1)  RFC 2362 section 3.6.1 states that the "C-RPs should send C-RP-Adv 
messages with the prioirity field
set to zero".
 If so , what is the use of the candidate RP priority ?

2) In the section 3.6.2 it states that "the BSR may override the prefix 
indicated in a C-RP-Adv unless the priority field is not zero".

As per the previous statement if the candidate rps sends the CRP message 
with priroity field set to zero,
where does the above situtation arise ?

then what does it mean by overriding the prefix ?

3) in the section 3.6.1 what does the statement " the advertising router 
may enfore this scope acceptance when receiveing register or join/prune 
messages " mean ?

thanks in advance
with regards
sabaris

---

From: Dave Thaler <[email-masked]>
Date: Thu, 8 Jun 2000 14:13:59 -0700 (PDT)

>  If so , what is the use of the candidate RP priority ?

If prefixes are allocated to domains (e.g. via MASC or GLOP or
IPv6 prefix-style addressing), border routers will send C-RP-Advs
with non-zero priority for ranges which are reached through them.
This is not part of the base PIM-SM spec.  Only the required behavior
of internal PIM-SM routers, BSRs, etc is discussed.

> then what does it mean by overriding the prefix ?

The BSR is always free to override normal C-RP-Advs by say static configuration
to apply to whatever subset of groups it wants them to.  This should not 
be a normal situation though.

> may enfore this scope acceptance when receiveing register or join/prune 

I believe it means an RP can drop Registers for groups it didn't claim
to be an RP for (in which case a BSR should only be narrowing the range
of groups for which a given RP is valid, not arbitrarily changing it).

> sabaris

-Dave