Re: Question about IGMPv3 state machine

Hi,  

What Bharat said is correct.   The following complement is my personnal
understanding:

In the first item please note that if A=1,2,3 and B=2, then A*B=2 and A-B=1,
3

TO_EX(B) means "change to receive from sources except B", because A-B=1,3
are not in the set B that are to be "excluded",  then traffic from 1 and 3
will be received. Delete (A-B) means A-B should not be kept in the source
list under exclude mode, because traffic from them will be forwarded, the
same as all other sources except B. 

The host sending this report at present does not what to receive from B, but
the router does not know  whether there is other host on the same network is
interested in  A*B, then it keeps the source list for it (i.e. EXLUDE(A*B,
...) ) and send a query to make the confirmation (Send Q(G,A*B)). 

(B-A) are sources that should not be forwarded, their source timers will be
set to 0, corresponding to EXCLUDE (..., B-A).  In this case B-A is 0 then
non-forwarding list should be empty.

And similarly for  the second item:

Only traffic from Y*A=4 is not forwarded, traffic from X-A=1,2 will be
forwarded because X-A are not in the non-forwarding source-list. And because
they are forwarded normally they need not be kept in the source-list, thus
they should be delete.

Formerly Y-A=5,6 are requested not to be forwarded so kept in
EXCLUDE(...,Y),but a new request of TO_EX(A) only exclude Y*A=4, then
traffic from 5 and 6 should be forwarded, thus they should not be kept in
the non-forwarding list, and they are deleted as the "Delete (Y-A)"
operation indicates.

As a summary for the above two cases:

1) the first source list in EXLUDE() stores the  sources that are formerly
requested to be forwarded but currently requested not to be forwarded.
Because these request may come from different host, the router keeps them in
case there is requester for the sources. The traffic from them will
currently be forwarded.

2) The second source list in EXCLUDE stores the sources that are to be
excluded (i.e.not forwarded). The traffic from them will not be forwarded.

3)The traffic from all other sources not listed in these two list will be
forwarded (as this is in EXCLUDE mode).
 

Best Regards,

Liu Hui 

> -----Original Message-----
> From: [email protected] [mailto:[email protected]] 
> On Behalf Of Bharat Joshi
> Sent: 2009年3月25日 9:31
> To: Kunal Shah
> Cc: [email protected]
> Subject: Re: [magma] Question about IGMPv3 state machine
> 
> Hi Kunal,
> 
>     In section 6.4, RFC 3376 has defined the meaning of roles 
> the two source list in EXCLUDE( A, B) plays. Sources 
> available in A are those sources for which a host has asked 
> for data to be forwarded and sources in B has been explicitly 
> asked to be excluded.
> 
>     In section 6.3, RFC 3376 has defined the forwarding 
> rules. Now if its exclude mode, and source timer is running 
> [i.e. the sources in list 'A'], it should forward the data 
> and if it is not in exclude list [i.e. it is not in source 
> list B], it should forward the traffic.
> 
>     In the first example, source '2' exist in list of sources 
> whose source timer will be running and so will get forwarded 
> and now (B-A) in this case will be 0 and so sources 1 and 3 
> will get forwarded.
> 
>     Similarly in the second example, source '3' will get 
> forwarded as its source timer will be running and all sources 
> except source 4 will get forwarded as only source 4 needs to 
> be excluded.
> 
>     I hope this helps.
> 
> Thanks,
> Bharat
> ________________________________________
> From: [email protected] [[email protected]] On 
> Behalf Of Kunal Shah [[email protected]]
> Sent: Wednesday, March 25, 2009 4:27 AM
> To: [email protected]
> Subject: [magma] Question about IGMPv3 state machine
> 
> Hi,
> 
> This is Kunal. I am trying to understand IGMPv3 router side 
> functionality and have the following questions about the RFC 3776:
> 
> In section 6.4.1
> 
> INCLUDE (A)    TO_EX (B)    EXCLUDE (A*B,B-A)       (B-A)=0
>                                                     Delete (A-B)
>                                                     Send Q(G,A*B)
>                                                     Group Timer=GMI
> 
> If A=1,2,3 and B=2, A*B=2. How does the host that has 
> requested sources 1 and 3 still get them?? And If we delete 
> A-B=2 in this case, how does the host interested in 2 get 
> traffic from it??
> 
> And similarly for
> 
> EXCLUDE (X,Y)  TO_EX (A)    EXCLUDE (A-Y,Y*A)       
> (A-X-Y)=Group Timer
> 
>                                                     Delete (X-A)
> 
>                                                     Delete (Y-A)
> 
>                                                     Send Q(G,A-Y)
> 
>                                                     Group Timer=GMI
> 
> If X=1,2,3, Y=4,5,6, and A=3,4 the A-Y=3 and Y*A=4 What about 
> hosts that want 1,2 sources. If X-A=1,2 is deleted how will 
> the hosts get traffic from 1,2 .
> 
> I will really appreciate if you can answer these two 
> questions. I have contacted a lot of people to get these two 
> questions answered but have not heard from any one yet.
> 
> Thanks
> Kunal
> 
> 
> **************** CAUTION - Disclaimer ***************** This 
> e-mail contains PRIVILEGED AND CONFIDENTIAL INFORMATION 
> intended solely for the use of the addressee(s). If you are 
> not the intended recipient, please notify the sender by 
> e-mail and delete the original message. Further, you are not 
> to copy, disclose, or distribute this e-mail or its contents 
> to any other person and any such actions are unlawful. This 
> e-mail may contain viruses. Infosys has taken every 
> reasonable precaution to minimize this risk, but is not 
> liable for any damage you may sustain as a result of any 
> virus in this e-mail. You should carry out your own virus 
> checks before opening the e-mail or attachment. Infosys 
> reserves the right to monitor and review the content of all 
> messages sent to or from this e-mail address. Messages sent 
> to or from this e-mail address may be stored on the Infosys 
> e-mail system.
> ***INFOSYS******** End of Disclaimer ********INFOSYS*** 
> _______________________________________________
> magma mailing list
> [email protected]
> https://www.ietf.org/mailman/listinfo/magma

_______________________________________________
magma mailing list
[email protected]
https://www.ietf.org/mailman/listinfo/magma