Subject: [pim] A new draft on "PIM GR Enhancement for BSR, PIM-Bidir and PIM-SM"

From: "Archana J Patel (archanap)" <[email-masked]>
Date: Sat, 17 Nov 2007 12:52:06 +0530

Hi,
 
We have submitted a new Draft "PIM GR Enhancement for BSR, PIM-Bidir and
PIM-SM".
http://www.ietf.org/internet-drafts/draft-kulkarni-pim-gr-enhancement-00
.txt
 
It attempts to address the following Issues :
 
-If Rebooted Router was E-BSR, some of the Group-to-RP mappings will be
cleared, once
 it transitions back to E-BSR, and which might take, in worst case, upto
BS_Period interval
 to get restored, because C-RP Router will not come to know that E-BSR 
 has rebooted, hence the C-RP adv message will be sent only after C-RP
Adv Timer expiry.
 BSM generated by Rebooted Router will have only those Group-to-RP
mappings which 
 received during BS_Min_Interval after it transition to E-BSR.
 
-Rebooted BIDIR Router will ignore the triggered joins from Downstream
Routers, 
 if they are received almost immediately after hello with New Gen-ID is
sent.
 As BIDIR Router might not have received the RP info or DF election
might not 
 be complete yet(as unicast route information is absent).
 
-Same applies to PIM-SM router also, It might choose to ignore triggered
(*, G) join in
 the absence of RP-Info.
 
This draft also suggests the mechanism to refresh active-source
information 
on Rebooted C-RP(if acting as active RP), and to refresh assert-loser
and
assert-winner state on Rebooted PIM-SM Router.
 
Please review the draft and provide your suggestions and comments.

Thanks,
Archana
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---

From: Su Haiyang <[email-masked]>
Date: Mon, 19 Nov 2007 10:53:11 +0800

Dear All,

Since PIM is a soft-state protocol, it should be the responsibility of the
rebooted router to collect PIM joins or RP-Set after it boot up again.

It shouldn't count on more cooperation from its neighborhood.

And most of the enhancement mentioned at the following draft depends on
timer adjustment, which can't give precise control of the router behavior.
No prior negotiation may cause compatibility issues of PIM implementations
from different vendors.

Regarding the issue of RP-Set information inconsistence between rebooted
routers, the current protocol definition has given solution:

1.     A PIM-SM router can use the RP stored at the PIM join if it just boot
up and hasn't got the copy of RP-Set from its neighbor.

2.     The Group-RP Mapping expiry timer avoids the Non-BSR router purging
its RP-Set after it receives an empty BSM from the rebooted BSR router.

Thanks

Su Haiyang

  _____  

From: Archana J Patel (archanap) [mailto:[email-masked]] 
Sent: Saturday, November 17, 2007 3:22 PM
To: [email-masked]
Subject: [pim] A new draft on "PIM GR Enhancement for BSR, PIM-Bidir and
PIM-SM"

Hi,

We have submitted a new Draft "PIM GR Enhancement for BSR, PIM-Bidir and
PIM-SM".
http://www.ietf.org/internet-drafts/draft-kulkarni-pim-gr-enhancement-00.txt

-If Rebooted Router was E-BSR, some of the Group-to-RP mappings will be
cleared, once
 it transitions back to E-BSR, and which might take, in worst case, upto
BS_Period interval
 to get restored, because C-RP Router will not come to know that E-BSR 
 has rebooted, hence the C-RP adv message will be sent only after C-RP Adv
Timer expiry.
 BSM generated by Rebooted Router will have only those Group-to-RP mappings
which 
 received during BS_Min_Interval after it transition to E-BSR.

-Rebooted BIDIR Router will ignore the triggered joins from Downstream
Routers, 
 if they are received almost immediately after hello with New Gen-ID is
sent.
 As BIDIR Router might not have received the RP info or DF election might
not 
 be complete yet(as unicast route information is absent).

-Same applies to PIM-SM router also, It might choose to ignore triggered (*,
G) join in
 the absence of RP-Info.

This draft also suggests the mechanism to refresh active-source information 
on Rebooted C-RP(if acting as active RP), and to refresh assert-loser and
assert-winner state on Rebooted PIM-SM Router.

Thanks,

Archana

---

From: "Archana J Patel (archanap)" <[email-masked]>
Date: Mon, 19 Nov 2007 11:10:57 +0530

Hi Su Haiyang,
 
Thanks for your Comment.
 
Enhancements mentioned for BSR, BIDIR and PIM-SM Assert-Winner do not
depend on timer adjustment.
 
PIM-SM enhancements for Assert-loser and Joins depend on timer
adjustment. There can be
better solution. We want to address these issues, hence mentioned here. 

>>1.     A PIM-SM router can use the RP stored at the PIM join if it
just boot up and hasn't got the copy of RP-Set 
>>from its neighbor
As per RFC, PIM-SM router may chose to ignore the join, if it doesnt
have RP-Info.  One of the solution can be it must accepts the joins,
if it is rebooted router and it does not have RP-Info OR
Downstream-router first send BSM with No-Forward
bit first before sending Joins so Upstream routers can have RP-Info
first.
 
>>2.     The Group-RP Mapping expiry timer avoids the Non-BSR router
purging its RP-Set after it receives an empty BSM >>from the rebooted
BSR router.
Group-RP mapping expiry timer is used, if Non-BSR router is receiving
empty BSM but consider the case where Rebooted BSR router
has received one CRP-Adv message and BSM has sent with one Group-to-RP
mapping. Non-BSR routers will cleared all other
remaining group-to-rp mappings. 

Thanks,
Archana
________________________________

From: Su Haiyang [mailto:[email-masked]] 
Sent: Monday, November 19, 2007 8:23 AM
To: Archana J Patel (archanap); [email-masked]
Cc: [email-masked]
Subject: RE: [pim] A new draft on "PIM GR Enhancement for BSR, PIM-Bidir
and PIM-SM"

Dear All,

Since PIM is a soft-state protocol, it should be the responsibility of
the rebooted router to collect PIM joins or RP-Set after it boot up
again.

And most of the enhancement mentioned at the following draft depends on
timer adjustment, which can't give precise control of the router
behavior. No prior negotiation may cause compatibility issues of PIM
implementations from different vendors.

1.     A PIM-SM router can use the RP stored at the PIM join if it just
boot up and hasn't got the copy of RP-Set from its neighbor.

2.     The Group-RP Mapping expiry timer avoids the Non-BSR router
purging its RP-Set after it receives an empty BSM from the rebooted BSR
router.

Thanks

Su Haiyang

________________________________

Hi,

Thanks,

Archana

---

From: Stig Venaas <[email-masked]>
Date: Tue, 27 Nov 2007 09:31:40 +0100

Archana J Patel (archanap) wrote:
[...]
> remaining group-to-rp mappings. 

The new BSR spec solves this IMO. When the BSR sends an empty BSM, it
will trigger the C-RPs to send advertisements. The BSR is supposed to
wait until it has had time to receive all the triggered advertisements
before it sends a non-empty BSM.

Stig