Subject: [pim] Question regarding the PIM Register source address

From: Pavlin Radoslavov <[email-masked]>
Date: Mon, 24 Jan 2005 18:15:56 -0800

Section 4.9.3 (Register Message Format) of the lastest PIM-SM spec
(draft-ietf-pim-sm-v2-new-11.{txt,ps}) says:

"A Register message is sent by the DR or a PMBR to the RP when a
multicast packet needs to be transmitted on the RP-tree.  The IP source
address is set to the address of the DR, the destination address to the
RP's address."

My interpretation of the above is that "the address of the DR" is
the primary IP address of the interface toward S.

Such interpretation may create some operational issues in case of
PMBR (e.g., if the PIM Register messages have the IP address of the
"external" interface, and that address does not belong to the
address range of the domain with the RP).

Do other people have different interpretations of what the Register
message source address should be set to?
E.g., do some implementations use, say, the primary IP address of
the interface toward the RP (or just the IP address of any PIM-SM
enabled interface on the router).

Thanks,
Pavlin

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---

From: Prashant Jhingran <[email-masked]>
Date: Tue, 25 Jan 2005 19:04:31 +0800

Hi Pavlin,

As you mentioned, the draft says..... 
"The IP source address is set to the address of the DR, 
the destination address to the RP's address."

Since Register  is a Unicast Message, it MAY be sent towards RP 
in the same manner as other unicast packets  
i.e. even on a non PIM-SM enabled interface.

Hence it could be the primary IP address of the interface towards the
RP.
Although this is slightly implementation specific, 
the interface towards the RP MAY be decided 
by unicast routing table [RIB] instead of MRIB.

The above implementation would also prevent any 
"operational issues in case of PMBR" which you have pointed out. 

Regards,
Prashant Jhingran

Huawei Technologies 
Beijing, China
Ph# 00-86-10-82882016  (O)  
 
"You see, all the problems in the world are created by those who want
'perfection.' "
   -- Sri Sri Ravi Shankar  www.artofliving.org  

-----Original Message-----
From: [email-masked] [mailto:[email-masked]] On Behalf Of
Pavlin Radoslavov
Sent: Tuesday, January 25, 2005 10:16 AM
To: [email-masked]
Subject: [pim] Question regarding the PIM Register source address

Thanks,
Pavlin