Re: [pim] ABOUT Update_SPTbit(S,G,iif)

[Rishabh Parekh <rishabh at ipinfusion.com>]

Chunyan,
Consider the following:


		R1			R2
		|			|
		|			|
	--------------------------------------
		|			|
		|			|
		R3			R4

Assume that R3 has JoinDesired(*,G) == TRUE and RPF'(*,G) = R1 and that 
traffic from source S is arriving on the RPT. Now, R3 receives a (S,G) join 
from downstream and so JoinDesired(S,G) == TRUE. Assume that RPF'(S,G) = R2. 
In this case since RPF_Interface(S) == RPF_Interface(RP(G)) AND RPF'(S,G) != 
RPF'(*,G), there is no way determine when the traffic from S starts arriving 
on the SPT (i.e. from R2). Therefore, to set the SPT bit R3 can only depend 
on R2 winning the (S,G) Assert and by implication R3 losing the Assert i.e 
I_Am_Assert_Loser (S,G,iif).

Regards,
Rishabh.
 
On Monday 27 November 2006 03:13, CTO YAO Chunyan wrote:
> Dear all, SPTbit is updated as follows:
>
>      void
>      Update_SPTbit(S,G,iif) {
>        if ( iif == RPF_interface(S)
>              AND JoinDesired(S,G) == TRUE
>              AND ( DirectlyConnected(S) == TRUE
>                    OR RPF_interface(S) != RPF_interface(RP(G))
>                    OR inherited_olist(S,G,rpt) == NULL
>                    OR ( ( RPF'(S,G) == RPF'(*,G) ) AND
>                         ( RPF'(S,G) != NULL ) )
>                    OR ( I_Am_Assert_Loser(S,G,iif) ) {
>           Set SPTbit(S,G) to TRUE
>        }
>      }
>
>
> I don't understand HOW the last one condition "
> I_Am_Assert_Loser(S,G,iif)" along with "iif == RPF_interface(S)AND
> JoinDesired(S,G) == TRUE" can show that source-specific-tree is OK?
>
> Could you tell me what the condition " I_Am_Assert_Loser(S,G,iif)"mean?
>
>
> Thanks a lot in advance!
>
>                        Chunyan

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