Subject: [pim] Question about TTL field in dense mode state refresh message

From: <[email-masked]>
Date: Tue, 27 Jun 2006 15:31:11 -0700

Hello,

The PIM-DM rfc 3973 describes the pseudo code for forwarding the state
refresh message in section 4.5.1. In the pseudo code there is a for loop
where we walk the list of interfaces with pim nbrs and inside the loop
we check if the TTL in the state refresh message is 0, we skip
refreshing the prune state of this interface and skip forwarding the
state refresh message out this interface. 

Is it safe to skip processing the state refresh message when the TTL in
the state refresh message is 0? 

Could do this check outside the for loop in the pseudocode? 

Thanks,
Sowmya

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From: <[email-masked]>
Date: Tue, 27 Jun 2006 15:41:54 -0700

To simplify my question: 
 
Would we ever see a TTL of 0, in the received state refresh message?
 
Thanks,
Sowmya
 
________________________________

From: ext [email-masked] [mailto:[email-masked]] 
Sent: Tuesday, June 27, 2006 3:31 PM
To: [email-masked]
Subject: [pim] Question about TTL field in dense mode state refresh
message

Hello, 

Could  we do this check outside the for loop in the pseudocode? 

Thanks, 
Sowmya

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From: Beau Williamson <[email-masked]>
Date: Tue, 27 Jun 2006 18:23:40 -0500

Sowmya,

Why are you worrying about PIM-DM???

It is safe to say that PIM-DM is a dead-end protocol as it is defined 
now.  No production network should be using it as it's non-deterministic 
behavior often results in route loops that have been known to melt down 
networks as well as blackhole traffic.  (Other than those draw backs, I 
guess it is just fine.)

PIM-DM is now just an academic exercise or a protocol to test single 
routers on a lab bench to see how fast they can replicate multicast packets.

As for questions on TTL, there is no longer any need to set the TTL of a 
multicast packet to anything but 255 when the application transmits 
it.  This is because we have deprecated the use of TTL Thresholds as a 
method of scoping multicast in favor of administratively scoped zones.

Beau Williamson
At 6/27/2006 05:31 PM, [email-masked] wrote:
>Content-class: urn:content-classes:message
>Content-Type: multipart/alternative;
>         boundary="----_=_NextPart_001_01C69A39.655555D8"
>
>Hello,
>
>where we walk the list of interfaces with pim nbrs and inside the loop we 
>check if the TTL in the state refresh message is 0, we skip refreshing the 
>prune state of this interface and skip forwarding the state refresh 
>message out this interface.
>