[pim] Errata 4375 RFC 3376 Older Version Querier Present Timeout

Stig Venaas <stig@venaas.com> Fri, 17 July 2015 15:57 UTC

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Date: Fri, 17 Jul 2015 08:57:33 -0700
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From: Stig Venaas <stig@venaas.com>
To: "pim@ietf.org" <pim@ietf.org>
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Subject: [pim] Errata 4375 RFC 3376 Older Version Querier Present Timeout
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Hi

I would like your thoughts on this errata for IGMPv3. It states:

  Section 8.13 says:

  8.12. Older Version Querier Present Timeout

     The Older Version Querier Interval is the time-out for transitioning
     a host back to IGMPv3 mode once an older version query is heard.
     When an older version query is received, hosts set their Older
     Version Querier Present Timer to Older Version Querier Interval.

     This value MUST be ((the Robustness Variable) times (the Query
     Interval in the last Query received)) plus (one Query Response
     Interval).

  It should say:

  8.12. Older Version Querier Present Timeout

     The Older Version Querier Interval is the time-out for transitioning
     a host back to IGMPv3 mode once an older version query is heard.
     When an older version query is received, hosts set their Older
     Version Querier Present Timer to Older Version Querier Interval.

     This value MUST be ((the Robustness Variable) times (the Query
     Interval )) plus (one Query Response Interval in the last Query
     received).

  Notes:

  The last query received is older version query.
  As such - it does not include query interval.
  It looks like it should be operator responsibility to configure
identical robustness variable and query interval values network-wide
for supporting older versions.

As mentioned in the notes, IGMPv1/v2 don't have a query interval. One
way of reading this is that it is the last IGMPv3 query, but what if
there are no v3 queriers present? It makes sense that it refers to the
query interval of the current querier, but would you expect the hosts
to try to measure what the query interval is? That doesn't sound good.
Would you configure what the query interval is on the hosts? We have
the same issue with MLDv2 as well.

Stig

[pim] Errata 4375 RFC 3376 Older Version Querier … Stig Venaas