RE: IGMPv3 question

Hi,

 

In the case EXCLUDE( X, Y ),  Y are the sources from where router has
explicitly got an exclude report.

Router has received include report from some host(s) for sources in X
while exclude reports from some other host(s) for the sources in X.

So, X has been added in conflicting list.

The sources from which no request has been received are assumed to be
excluded implicitly.

 

On receiving IS_IN ( A ), include report has been received for sources
in A, that means they should be put into the conflicting list, i.e. ( X
+ A ).

The ( X + A) comes from the implicit EXCLUDE for the sources for which
no report has been received.

If exclude reports had ever been received for the sources in A, the
sources should be removed from exclude list Y, i.e. ( Y - A ).

 

Warm Regards,

Ashish Yadav

 

-----Original Message-----
From: [email protected] [mailto:[email protected]] 
Sent: Saturday, October 28, 2006 7:13 PM
To: [email protected]
Subject: [magma] IGMPv3 question

 

 

Hello, 

I would like kindly ask to answer my question.  Section 6.4.1 of RFC
3376 contains the following description of a router behavior in response
to Current-State Record:

 

Router State   Report Rec'd  New Router State         Actions

   ------------   ------------  ----------------         -------

 

   INCLUDE (A)    IS_IN (B)     INCLUDE (A+B)            (B)=GMI

 

   INCLUDE (A)    IS_EX (B)     EXCLUDE (A*B,B-A)        (B-A)=0

                                                         Delete (A-B)

                                                         Group Timer=GMI

 

   EXCLUDE (X,Y)  IS_IN (A)     EXCLUDE (X+A,Y-A)        (A)=GMI

 

   EXCLUDE (X,Y)  IS_EX (A)     EXCLUDE (A-Y,Y*A)        (A-X-Y)=GMI

                                                         Delete (X-A)

                                                         Delete (Y-A)

                                                         Group Timer=GMI

Entry Exclude(X,Y) means that all sources in set Y will not be forwarded
by a router. Entries in set X are all sources that were requested by
some hosts to be excluded, but router also received from other hosts
Include report for the same souurces X. It means that there is a
conflict because some receivers wish to receive data form sources X and
some not. 

In the light of those facts case number two in the cited text is clear.
Router is in state Include(A), gets request to exclude B so it transits
to state Exclude (A*B, B-A).

However I do not understand intention of case 3. Router is in state
Exclude(X,Y) and gets report IS_IN(A). The result is Exclude(X+A,Y-A).
Set Y-A is straightforward, some of sources in set A required to be
forwarded can also be in set Y. Though, I do not understand meaning of
X+A. This set should contain only the conflicting sources. So it seems
to be that it should be X + (common part of A and Y). In order words it
should be X + (A*Y). Can you please explain that to me?

Thank you in advance for your help

Tomasz Bartczak

 

 

 

----------------------------------------------------------------------

PS. >>> http://link.interia.pl/f19a6

 

 

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