[Xorp-users] PIM/SM: Missing Join and Register-Stop from RP

Williams, Mark william at losrios.edu
Thu Mar 13 10:56:21 PDT 2014


>From what I understand, JOINs aren't send towards the source, they are sent to the RP. 

Sources don't know where receivers are; they just forward the traffic at layer two to their nearest multicast neighbor/router. It's up to the neighbor/router and upstream RP to build the tree. The register-stop message occurs once the source/tree is built. I think this is the normal function of the RP, and how it works regardless of implementation. Behaves the same way in Alcatel-Lucent and Cisco.

-Mark Williams

-----Original Message-----
From: xorp-users-bounces at xorp.org [mailto:xorp-users-bounces at xorp.org] On Behalf Of Ben Greear
Sent: Thursday, March 13, 2014 10:45 AM
To: Holger Kummert
Cc: xorp-users at xorp.org
Subject: Re: [Xorp-users] PIM/SM: Missing Join and Register-Stop from RP

On 03/13/2014 10:31 AM, Holger Kummert wrote:
> 
> Hello,
> 
> I do not understand XORP's behavior when running PIM/SM and Register 
> messages (that encapsulate multicast traffic) are received by the RP 
> from S.
> What I am really missing is the Join msg towards S in order to avoid 
> the encapsulating overhead. Therefore the Register-Stop (in order to 
> stop sending the Register msgs) is also not sent by RP.
> 
> Shouldn't both messages be sent according to RFC 4601, ch. 3.2?
> 
> The only situation where I could force the Register-Stop to be sent 
> was by enabling and setting 'switch-to-spt-threshold' to '0'.
> This sending is independent of any Join'ed receivers and happens 
> immediately after the receive of the first Register message.
> But this is obviously not the intended usage.
> 
> Anyhow under no circumstances any Join messages are sent by RP to S.
> 
> Could someone give more insight on this?

I'm afraid I never knew much about multicast, and what I did learn while hacking on xorp mcast logic I have mostly forgotten.

But, if you figure out a patch that makes xorp work better, please post it and I will try to review it.

Thanks,
Ben

> 
> 
> Thanks in advance,
> Holger
> 
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> Xorp-users at xorp.org
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> 


--
Ben Greear <greearb at candelatech.com>
Candela Technologies Inc  http://www.candelatech.com

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