Re: Igmp Group-Source specific Retransmission

Hi Deepak-san,

I comment only one point.
Please observe S flag. (RFC3376 4.1.5.)


""Kudachi, Deepak S" <[email protected]>" wrote:

> Hi Bharat,
> 
> I am still not clear on the part that you said all the queries have different src addresses.
> 
> May be I can give an example for this case.
> 
> Let us assume following values.
> 
> 
> Robustness = 2
> LMQI = 10 sec
> 
> Group = G1 = 224.0.2.1
> Srouces
>         S1 = 10.10.10.10
>         S2 = 10.10.10.20
>         S3 = 10.10.10.30
>         S4 = 10.10.10.40
>         S5 = 10.10.10.50
> 
> Our interface's current state is INCLUDE for group G1.
> 
> So 
> INCLUDE{S1,S2,S3,S4} for G1
> 
> Now we received Block message for the same group on same interface
> 
> Consider the message received is 
> BLOCK {S3}.
> 
> now according to RFC 3376 sec 6.4.2
> INCLUDE (A)    BLOCK (B)    INCLUDE (A)             Send Q(G,A*B)
> 
> We need to send a group-source specific query for A*B 
> which is nothing but send a query for source S3.
> 
> So query will be sent at Time = T1
> Send Q(G1, S3) 
> We have started the timer (LMQI)10 sec with repeat 1 so that 
> When timer expires we need to send one more query for this G1,S3. 
> ( query is send out for group G1= 224.0.1.2 ,S3 = 10.10.10.30.)
> 
> now at time  interval T2 < (T1+LMQI)
> we received TO_EXC{ S1 , S2, S5 } on same interface for the same group G1.
> 
> Now according to RFC following function need to be performed.
> INCLUDE (A)    TO_EX (B)    EXCLUDE (A*B,B-A)       (B-A)=0
>                                                     Delete (A-B)
>                                                     Send Q(G,A*B)
>                                                     Group Timer=GMI
> 
> 
> Interface moves to exclude mode 
> EXCLUDE { (S1,S2),(S5)} for group G1.
> 
> Now immediate query has to be sent for S1,S2.
> 
> Since S3 retransmission is still pending we need to merge S3 with S1,S3 in this query.
> Now Q(G1,S1,S2,S3) will be sent at interval T2.

Q(G1,S1,S2)w/SFlag=0 and Q(G1,S3)w/S Flag=1


> 
> Now for S3 we have sent two queries and its query count is set to 0 and will be
> removed from retransmission list.
> 
> For S3 we sent out second query much before T1+LMQI and no more queries will be sent for S3.
> 
> This is what we infer from the RFC and just want to know others view on this.
> 
> (please Note: I am only considering router side processing).
> 
> 
> Thanks and Regards
> Deepak
> 
> -----Original Message-----
> From: Bharat Joshi [mailto:[email protected]] 
> Sent: Wednesday, June 02, 2010 6:07 PM
> To: Kudachi, Deepak S; [email protected]; [email protected]
> Subject: RE: [magma] Igmp Group-Source specific Retransmission
> 
> Deepak,
> 
>       It would be better if you handle the example with IP addresses. Also consider how the state in the hosts are and what final state should be there after things stabilize.
> 
>       For the below example, I think you should attach the robustness count as query count with the source addresses and then as and when timer fires, you prepare a group-source specific query, send it out and reduce the query count for each source address you include in the query. Once the query count for a source address reaches zero, it is removed from the list and when all sources are removed from the list, we do not restart the timer.
> 
>       So we will end up sending three queries. But all the three queries will carry different sources in the list.
> 
>       I hope this helps.
> 
> Regards,
> Bharat
> ________________________________________
> From: [email protected] [[email protected]] On Behalf Of Kudachi, Deepak S [[email protected]]
> Sent: Wednesday, June 02, 2010 5:50 PM
> To: [email protected]; [email protected]
> Subject: [magma]  Igmp Group-Source specific Retransmission
> 
> Hi All,
> 
> I was going through the IGMPv3 RFC 3376  and was not clear on the below
> Mentioned section.
> 
> /*---------------------------------------------------------------------------------------------------------*/
> 6.6.3.2. Building and Sending Group and Source Specific Queries
> 
>    When a table action "Send Q(G,X)" is encountered by a querier in the
>    table in section 6.4.2, the following actions must be performed for
>    each of the sources in X of group G, with source timer larger than
>    LMQT:
> 
>    o Set number of retransmissions for each source to [Last Member Query
>      Count].
> 
>    o Lower source timer to LMQT.
> 
>    The router must then immediately send a group and source specific
>    query as well as schedule [Last Member Query Count - 1] query
>    retransmissions to be sent every [Last Member Query Interval] over
>    [Last Member Query Time].  The contents of these queries are
>    calculated as follows.
> /*-----------------------------------------------------------------*/
> 
> 
> This section talks about how the group-source specific queries are build and
> Send out.
> 
> Suppose our robustness variable is set to 2(default value).
> And Last Member Query Interval is 10 Sec.
> 
> Any group-source specific query need to be transmitted robustness number of times
> That is 2 times in our case and separated by LMQI which 10 sec.
> So 2 queries has to be sent across Last Member Query Time which is 20 sec.
> 
> 
> Now suppose we already sent Q(G,X) query for a group at T1 with set of sources. And we received
> A report which causes new Q(G,(X+Y)) needs to be sent and T2( before T1+LMQI). Where Y is new set of sources to be
> Queried. New Query will be sent with all sources merged from previous and new(x + y).
> 
> So the sources x already two queries will be sent and not separated by LMQI in this scenario.
> 
> My question is whether we need to send one more query after LMQI ( at T1+LMQI) for x
> Set of sources for this group?
> 
> If we need to then we will be sending 3 queries for x set of sources as follows.
> 
> Time interval T1
> Time interval T2
> Time interval T1+LMQI
> 
> Which is not correct.
> 
> Let me know whether we should send query for x set of sources for this group
> At T1+LMQI interval.
> 
> Thanks and Regards
> Deepak
> 
> 
> 
> 
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Best Regards
--
Kiyoaki Kawaguchi