Re: IGMP Non Querier - Querier Transition

Hi Rajasekar,

       Non-querier routers and hosts learns the QQIV, Robustness Variable from the querier's query and use them till the querier change. When the querier change, they again learned the new values. This is done to make sure that all the non-queriers and hosts on the LAN behaves in a similar way. The usage of these values are anyway available in the RFC.

       Once a non-querier becomes a querier, it should start using its configured values [or default values] and other non-queriers and hosts will learn these new values and use them.

Thanks,
Bharat
________________________________________
From: [email protected] [[email protected]] On Behalf Of rajasekar bonthala [[email protected]]
Sent: Wednesday, November 11, 2009 12:34 PM
To: Indranil Bhattacharya
Cc: [email protected]
Subject: Re: [magma] IGMP Non Querier - Querier Transition

Thanks for the reply.
But I do not understand the intention of adopting query interval and robustness value from the querier.

I guess that it adopts values from the Querier so that the NonQuerier should continue with the adopted values so as to avoid any change because of down of current querier.

Please mail me your analysis on this.

Thanks,
RajaSekhar

On Wed, Nov 11, 2009 at 12:13 PM, Indranil Bhattacharya <[email protected]<mailto:[email protected]>> wrote:
Hi RajaSekhar,

                     When a non-qurier becomes a querier, it should always use configured query interval and in absense of a configured value default should be used.

Thanks,
Indranil
On Tue, Nov 10, 2009 at 12:28 PM, rajasekar bonthala <[email protected]<mailto:[email protected]>> wrote:
RFC 3376 says that IGMP Non-Querier should adopt the robustness and Query interval from the Querier.
Those sections are pasted below for reference.

4.1.6. QRV (Querier’s Robustness Variable)

If non-zero, the QRV field contains the [Robustness Variable] value

used by the querier, i.e., the sender of the Query. If the querier’s

[Robustness Variable] exceeds 7, the maximum value of the QRV field,

the QRV is set to zero. Routers adopt the QRV value from the most

recently received Query as their own [Robustness Variable] value,

unless that most recently received QRV was zero, in which case the

receivers use the default [Robustness Variable] value specified in

section 8.1 or a statically configured value.

4.1.7. QQIC (Querier’s Query Interval Code)

The Querier’s Query Interval Code field specifies the [Query

Interval] used by the querier. The actual interval, called the

Querier’s Query Interval (QQI), is represented in units of seconds

and is derived from the Querier’s Query Interval Code as follows:

If QQIC < 128, QQI = QQIC

If QQIC >= 128, QQIC represents a floating-point value as follows:

0 1 2 3 4 5 6 7

+-+-+-+-+-+-+-+-+

|1| exp | mant |

+-+-+-+-+-+-+-+-+

QQI = (mant | 0x10) << (exp + 3)

Multicast routers that are not the current querier adopt the QQI

value from the most recently received Query as their own [Query

Interval] value, unless that most recently received QQI was zero, in

which case the receiving routers use the default [Query Interval]

value specified in section 8.2.




The above sections says that these values need to adopted as their own values.
But the RFC does not explain on whether the Non-Querier should continue with the adopted values,when transitions to Querier state (if the existing querier is down due to any reason).

Can any one please clarify me on this.

Thanks,
RajaSekhar

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