Re: [pim] Call for adoption: draft-venaas-pim-igmp-mld-extension

[Hitoshi Asaeda <[e-mail]>]

Hi,

While I've not received any reply for my previous mail regarding the IGMP/MLD extension, I have a few ideas to make the proposal better, IMO.

Currently, this draft just mentions Extension Type and Extension Value at the bottom as the optional field. This optional field should be TLV fields. And the top of the TLV field contains the total length of the extension fields and multiple sub-TLV fields can be allocated.
For example, figure 4 should be;

        0                   1                   2                   3
        0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |  Type = 0x11  | Max Resp Code |           Checksum            |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                         Group Address                         |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       | Resv  |S| QRV |     QQIC      |     Number of Sources (N)     |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                       Source Address [1]                      |
       +-                                                             -+
       |                       Source Address [2]                      |
       +-                              .                              -+
       .                               .                               .
       .                               .                               .
       +-                                                             -+
       |                       Source Address [N]                      |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |       Extension Type          |    Extension Total Length     |
       +-------------------------------+-------------------------------+
       |             Type              |             Length            |
       +-------------------------------+-------------------------------|
       /                             Value                             /
       +-------------------------------+-------------------------------+
       .                               .                               .
       .                               .                               .
       +-------------------------------+-------------------------------+

This TLV extension gives the possibility to distinguish the version related consideration because the Extension Type field can specify the IGMP/MLD version if any, and support multiple TLV fields.

Regarding the contradiction of the current IGMPv3/MLDv2 RFCs, we should fix the several statements/specifications in the draft standard documents we have been thinking of.

Any comments?

Regards,

Hitoshi


> On Mar 17, 2020, at 11:24, Hitoshi Asaeda <[e-mail]> wrote:
> 
> Hi,
> 
> I like the idea and also wanted to add such optional fields in IGMPv3/MLDv2 that can be used for various purposes. The reasons why I hesitated to propose the additional optional fields in IGMPv3/MLDv2 are as follows;
> 
> This I-D says;
>   The extension will be part of additional data as mentioned in
>   [RFC3810] Section 5.1.12 (resp.  [RFC3376] Section 4.1.10) for query
>   messages and [RFC3810] Section 5.2.12 (resp.  [RFC3376]
>   Section 4.2.11) for report messages.
> However, for example, sect.4.1.10 in rfc3376 says;
>   If the Packet Length field in the IP header of a received Query
>   indicates that there are additional octets of data present, beyond
>   the fields described here, IGMPv3 implementations MUST include those
>   octets in the computation to verify the received IGMP Checksum, but
>   MUST otherwise ignore those additional octets.  When sending a Query,
>   an IGMPv3 implementation MUST NOT include additional octets beyond
>   the fields described here.
> From this last sentence, I understand hosts accepts the longer IGMPv3 query (if the checksum is correct) but ignores the additional fields for the further processes. This may be Ok for existing (conventional) implementations as they simply ignore the additional fields, which they don't understand/proceed. However, you should investigate and mention the situations and conditions in which conventional hosts (that don't support this I-D) and new hosts (that support this I-D) exist in a LAN. Moreover, according to rfc3376, the new hosts that support this I-D must also support rfc3376, which seems a contradiction.
> 
> One more another thing is that since IGMP/MLD classifies their version by the packet length, we cannot propose IGMPv4/MLDv3 if you allow this variable length fields in IGMPv3/MLDv2.
> 
> If lucky this I-D is accepted, don't forget to refer Lightweight-IGMPv3/MLDv2 [RFC5790] as they also define the standard IGMPv3/MLDv2 formats.
> 
> Regards,
> 
> Hitoshi
> 
> 
>> On Mar 17, 2020, at 8:38, Michael McBride <[e-mail]> wrote:
>> 
>> Hope everyone is doing well hunkering down.
>> 
>> Today begins a two week call for adoption for https://tools.ietf.org/id/draft-venaas-pim-igmp-mld-extension-01.txt.
>> 
>> Please give it a read (just six pages) and let us know whether or not you support the adoption of this proposal for defining the extensions of IGMP/MLD using a new message type.
>> 
>> Thanks,
>> mike
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