+1

On 6/12/12 4:46 PM, "Stig Venaas" <[email protected]> wrote:

>On 6/12/2012 1:11 PM, Behcet Sarikaya wrote:
>> I think that a decision should be made on this draft. If it is going
>> to present a generic solution it could be fine but then such a draft
>> does not meet Softwire charter item so it can not stay in Softwire.
>>
>> My suggestion is to make it specific to DS-Lite so that it stays in
>> Softwire and meets the charter item.
>
>What do you mean by making it specific to DS-Lite? Are you talking
>about a different technical solution, or just wording? Right now the
>technical solution is generic, and I think that is great. While the
>wording seems DS-Lite specific to me.
>
>I don't like the idea of doing something DS-Lite specific, unless one
>can come up with a better technical solution that way.
>
>I think the technical solution in this draft is fine. Please let's not
>change it into a poor technical solution just to satisfy possible
>charter considerations.
>
>Stig
>
>> I believe this was Alain's intention when he asked the two drafts to be
>>merged.
>>
>> Regards,
>>
>> Behcet
>>
>> On Tue, Jun 12, 2012 at 3:34 AM, Jacni Qin<[email protected]>  wrote:
>>> Hi Stig,
>>>
>>> Sorry I missed the discussion, and your comments, inline please, hope
>>>it
>>> won't be too late.
>>>
>>> On 6/8/2012 Friday 1:43 AM, Stig Venaas wrote:
>>>
>>> Here are my last call comments. I think substantial changes are
>>> needed to the draft.
>>>
>>> I understand that this draft is focusing on dslite. But it appears that
>>> it is a generic solution. As it says in the draft:
>>>
>>>     An IPv4 receiver accesses IPv4 multicast contents over an IPv6-
>>>     only multicast-enabled network.
>>>
>>> Based on this, I think the scope of the draft, the title and
>>> introduction etc should be updated to actually show that it is
>>> a generic approach. And then instead list dslite as one of the
>>> scenarios where this is needed.
>>>
>>> Since it is a generic approach, I think it should also be reviewed,
>>> perhaps an additional WGLC, in mboned. pim wg may also have some
>>> interest in reviewing it. There are some errors regarding pim in
>>> this document.
>>>
>>>
>>> In particular, it discussed translation of IGMP/MLD. This is a
>>> topic that has been discussed in mboned/pim, and there is also
>>> another draft discussing this.
>>>
>>> It refers to draft-ietf-mboned-64-multicast-address-format-01. If that
>>> is to stay, I think this draft needs to wait to see what happens with
>>> the address-format draft in 6man. Changes may be needed in this draft
>>> depending on what happens. If only minor changes, the examples in this
>>> draft may need to be updated.
>>>
>>> Thanks, it's true. We'll wait for the comments from 6man, and update it
>>> accordingly if needed.
>>>
>>>
>>>
>>> Technical issue:
>>>
>>> In 4.2 it says:
>>>     The mB4 uses the G6 (and both S6 and G6 in SSM) to create the
>>>     corresponding MLD Report message.  The mB4 sends the Report message
>>>     to the MLD Querier in the IPv6 network.  The MLD Querier (typically
>>>     acts as the PIMv6 Designated Router) receives the MLD Report
>>>message
>>>     and sends the PIMv6 Join to join the IPv6 multicast distribution
>>>     tree.  The MLD Querier can send either PIMv6 Join (*,G6) in ASM or
>>>     PIMv6 Join (S6,G6) in SSM to the mAFTR.
>>>
>>> As is noted, the MLD querier and the DR may be different routers.
>>> It is the DR and not the MLD Querier (if they are different) that
>>> sends the PIM join. Also note that they are often different. If
>>> there are two routers, then the one with the lowest address is the
>>> MLD querier, while the one with the highest address (unless DR
>>> priority is configured) is the DR.
>>>
>>> I understand your concern. I guess the Proxying spec solved this issue.
>>>
>>>
>>>
>>> Near the end of 4.2:
>>>
>>>     A branch of the multicast distribution tree is then grafted,
>>>     comprising both an IPv4 part (from the mAFTR upstream) and an IPv6
>>>     part (from mAFTR downstream to the mB4).
>>>
>>> It says "is then grafted". So it sounds like the branch is added
>>> to the tree after the procedure has finished. But basically it is
>>> being added to the tree bit by bit as the joins are sent hop by
>>> hop. Maybe it could say "is in this way grafted" or something.
>>> I'm also a bit unsure whether "grafted" is a good term, as "graft"
>>> has a specific meaning for PIM Dense Mode.
>>>
>>> Thanks for your suggestion, we'll reword it, and make it clarified.
>>>
>>>
>>>
>>> At the end of 4.2:
>>>
>>>    The mAFTR MUST advertise the route of uPrefix64 with an IPv6 IGP, so
>>>    as to represent the IPv4-embedded IPv6 source in the IPv6 multicast
>>>    network.
>>>
>>> Yes, probably in the IGP. Perhaps say more explicitly that there must
>>> be a route due to PIM's use of RPF. I see this is mentioned in 7.1
>>> though.
>>>
>>> Ok.
>>>
>>>
>>>
>>> In 6.1 it talks about IGMP messages being translated to MLD. I would
>>> argue that this is not necessarily how this would be done.
>>>
>>> Right, I agree with you. Please see my response to Simon, we can
>>>update the
>>> text to clarify that.
>>>
>>>
>>> If you look at a pure MLD proxy, you build state for various (*,G)
>>> or (S,G) based on the reports you receive. Then based on this state
>>> you create reports that you send upstream. It is not the message
>>> from downstream that is just sent upstream. In this case, when
>>> receiving downstream IGMP reports, they could be used to create the
>>> IPv6 state. And then independent of whether the state was created
>>> due to IGMP or MLD reports, reports are sent upstream, created from
>>> that state. If you do this, messages are not translated.
>>>
>>>
>>> In 7.1 it says:
>>>
>>>     information to discover the source.  In order to pass the Reverse
>>>     Path Forwarding (RPF) check, the IPv6 routers MUST enable PIM on
>>>the
>>>     interfaces which has the shortest path to the uPrefix64.
>>>
>>> Note that the shortest path might change due to topology changes, links
>>> going down or coming up etc. So one would typically enable PIM on all
>>> the routers. If one wants to constrain multicast to only some of the
>>> topology, there are ways to build a separate multicast RIB for those
>>> routers, and then enable PIM on all of them.
>>>
>>> The text just focuses on the special configuration, I understand your
>>> concern that it's a little confusing.
>>> Maybe we can add some text like "... as prerequisites, basic multicast
>>> related configurations should be done accordingly ..."
>>>
>>>
>>>
>>> In 7.2 it says something about (*,G6) in mRIB6. The multicast RIB
>>> is something different. I think it should say TIB. Check the terms
>>> MRIB and TIB in RFC 4601.
>>>
>>> I'll check the terms again.
>>>
>>>
>>> The draft assumes PIM-SM is used. I think the approach could also
>>> be used with e.g. PIM Bidir (RFC 5015).
>>>
>>> Ok, we'll discuss this and come back to you on this point.
>>>
>>>
>>>
>>> 7.5 talks about scope, and mentions E and 8. Then it says that
>>> this specification does not specify which scope to use. I would
>>> perhaps not mention E and 8 then, it seems now to indicate that
>>> those are the only alternatives.
>>>
>>> Fine.
>>>
>>>
>>>
>>>
>>> The security considerations should probably be extended a bit.
>>> E.g. what about scoping? Can one traverse a scoped boundary by
>>> say joining a v4 scoped group using a join for a global v6
>>> prefix?
>>>
>>> Ok, we'll consider that.
>>>
>>>
>>>
>>> The draft should point out that it is just plain IPv4 in IPv6. At
>>> least that seems to be the intention. However, one might use the
>>> same solution with other tunnel types, e.g. GRE.
>>>
>>> We have a similar intention as the DS-Lite spec., we can some text.
>>>
>>>
>>> Minor nits:
>>>
>>> Thanks, done.
>>>
>>>
>>>   o  PIMv4: refers to PIM when deployed in an IPv4 infrastructure
>>>        (i.e., IPv4 transfer capabilities are used to exchange PIM
>>>        messages).
>>>
>>>     o  PIMv6: refers to PIM when deployed in an IPv6 infrastructure
>>>        (i.e., IPv6 transfer capabilities are used to exchange PIM
>>>        messages).
>>>
>>> Replace transfer with transport?
>>>
>>> Section 6.4 starts with this:
>>>
>>>     If the mB4 function is implemented in the host which is directly
>>>     connected to an IPv6-only network.  If an IPv4 application running
>>>in
>>>
>>> I'm not exactly sure what the first "if" refers to. This needs to be
>>> reformulated.
>>>
>>> Also in 6.4 there is this typo: "implemntation".
>>>
>>> Stig
>>>
>>>
>>> Thanks again for your careful review and comments.
>>>
>>>
>>> Cheers,
>>> Jacni
>>>
>>>
>>>
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>>>
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