Subject: Re: [pim] Query about Bootstrap Message

From: Subinoy Das <[email-masked]>
Date: Thu, 24 May 2007 21:45:18 -0700 (PDT)

Hi Subinoy,

> I have some confusion about Bootstrap Message in draft
> "draft-ietf-pim-sm-bsr-10".
> According to Section 4.2 page 32 C-RP-Adv message has single priority
> field for every group. Then is it possible that in a Bootstrap Message
> one C-RP has different Priority and Holdtime for different group?
> 

     No. Its the same priority and holdtime, a C-RP uses when it
generated the C-RP advertisements.

     Priority and Holdtime is for the candidate RP and not for the
group-prefixes it handles. An Elected BSR uses this priority and
Holdtime for the Candidate RP. Based on the holdtime, E-BSR knows
whether a Candidate RP is still available or not. 

     Both the Holdtime and RP priority is used in BSMs an E-BSR creates.

Thanks,
Bharat

Hi,

Assume the case when one C-RP send 10 groups in one C-RP-Adv message with priority 10, after that it send 9 groups in C-RP-Adv with priority 20. So, E-BSR has the C-RP with priority 20 for 9 groups and same C-RP with priority 10 for one group. (Holdtime is also different). If the E-BSR include all group-to-C-RP mappings then in a BSM we can see one C-RP has different priority for different group.
Is it possible?

Thanks,
Subinoy

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From: Bharat Joshi <[email-masked]>
Date: Fri, 25 May 2007 10:20:06 +0530

Hi Subinoy,

> Assume the case when one C-RP send 10 groups in one C-RP-Adv message
> with priority 10, after that it send 9 groups in C-RP-Adv with
> priority 20. So, E-BSR has the C-RP with priority 20 for 9 groups and
> same C-RP with priority 10 for one group. (Holdtime is also
> different). If the E-BSR include all group-to-C-RP mappings then in a
> BSM we can see one C-RP has different priority for different group.
> Is it possible?

    No. Did you see the following paragraphs in section 3.3 the draft:

If the mapping is not already part of the C-RP-Set, it is added to the
C-RP-Set and the associated Group-to-C-RP mapping Expiry Timer (CGET) is
initialized to the holdtime from the C-RP-Adv message.  Its priority is
set to the Priority from the C-RP-Adv message.

If the mapping is already part of the C-RP-Set, it is updated with the
Priority from the C-RP-Adv message and its associated CGET is reset to
the holdtime from the C-RP-Adv message.  If the holdtime is zero, the
mapping is immediately removed from the C-RP-Set.

<<<

    In your case, as per second paragraph, RP priority and Holdtime is
updated from C-RP advertisement for the 9 group-prefix that are
available in the C-RP-Adv message. As the 10th group-prefix in not
available in the C-RP-Adv message, the C-RP set will be available only
till its "Group-to-C-RP mapping Expiry Timer (CGET)" expires and after
that it will be removed.

    IIRC, some implementation do remove the 10th group-prefix when they
do not find it in the C-RP-Adv message.

    Hope this helps.

Thanks,
Bharat

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