Subject: [MBONED] Some questions and suggestions on Lightweight IGMPv3 and MLDv2 Protocols

From: Bharat Joshi <[email-masked]>
Date: Thu, 26 Jul 2007 19:43:09 +0530

Hi Hitoshi and all,

      I have some questions and suggestions on this draft. Some of them are for the text of the draft. I also feel that when a shorter version of protocol is defined in a new document, its always difficult to restrict yourself on what all details must be referenced and what details should be mentioned in the draft.

* I would suggest to reword the following sentence in Introduction:

"IGMPv3 and MLDv2 add the capability for a multicast router to also learn which sources are of interest to neighboring systems, for packets sent to any particular multicast address."

to

"IGMPv3 and MLDv2 add the capability to learn the sources which are of interest or which are of not interest for a particular multicast address. This information is used during forwarding of multicast data packets.

* I would suggest to reword the following sentence in Introduction:

"When a multicast router receives the report messages from its downstream hosts, it forwards the corresponding multicast traffic by managing requested group and source addresses."

to

"When a multicast router receives the report messages from its downstream hosts, it creates required state. This state is used to forwards the corresponding multicast traffic to the hosts.

* In the following statement:

"Group timers and source timers are used to maintain the forwarding state of desired groups and sources under certain filter modes."

I would suggest to replace "sources under certain filter modes" with "sources under filter modes defined in IGMPv3 and MLDv2".

* In following sentence:

"With all of the above factors correlating with each other, the determination rules become relatively complex, as the interface states could be frequently changed."

What are the determination rules here? I think its the forwarding state for each group per interface.

* In following sentence under 5th paragraph of Introduction:

"the protocol operations made by data receiver hosts and routers or"

I think 'end hosts' would be better than 'data receiver hosts'.

* Under section 2.1, typo in "(as known as (*,G) join )" , two 'as'

* Under section 2.2, in following sentence:

"The elimination of the filter-mode will greatly simplify the router"

I think 'exclude' is missing between 'the' and 'filter-mode'.

* In section 3.1, if the final source list is empty, an LW-xxx hosts must not send a State-Change Record except for TO_EX(). Right?

* In last section of 3.2, its mentioned that we can augment the source list if we receive a group-source specific query when a previous response with a non-empty source list exist. But should not we take a union of the list of sources here?
* I have an opinion to keep IS_EX and IS_IN instead of replacing them with TO_EX and ALLOW. I understand that operation on receipt of both types are same but this makes the protocol simple and easy to understand. IMHO, there is no difference in implementation.

* Last paragraph of section 3.3, typo in following sentence:

"used the following situation: the host first launches an application

I think a 'in' is missing between 'used' and 'the'.

* In section 4.1, source timer is always updated as and when a (S,G) join is received. Can we make this explicit?

* In section 4.2, I suggest to add following entries in the table:

While making forwarding decision, if data packet is coming from source 'S'.

 G_Timer == 0    Source 'S' does not          Do not forward traffic.
                 exist in the list

 G_Timer > 0     Source 'S' does not          Do not forward traffic.
                 exist in the list

* Under section 5.5.1, I would suggest reword the following sentence:

"The Host Compatibility Mode of an interface is set to IGMPv2 and IGMPv2 Querier Present is set to Older Version Querier Present Timeout second (defined in [2]) whenever an IGMPv2 General Query is received on that interface."

I did not understand "Older Version Querier Present Timeout second".

Thanks,
Bharat

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