Subject: RE: Comments on draft-ietf-pim-v2-dm-01.txt

From: vishwas <[email-masked]>
Date: Tue, 15 Dec 98 11:35:00 PST

>Routers with no group state do nothing on  receipt  of  IGMP  reports,
>since   dense-mode   PIM  will  deliver  multicast  datagrams  to  all
>interfaces when creating state for a group
>
>>From an implementation point of view, is this exactly correct? When a   
router
>receives IGMP join request from a directly connected ( say on interface   
1)
>host for group X, and has no (S,G) state for group X,
>it needs to record the request somehow that there is a
>membership request on interface 1 for group X. Then when the router gets   
a
>datagram packet for group X, it would create and (S,G) entry and create
>a outgoing interface list containing interface 1.

    Isnt it the responsibility of the IGMP running on the router to keep
    this state?

    How a multicast protocol gets that information from IGMP would depend   

    on the router implementation.
[vishu]  -------------------------------------------------
TRUE. PIM-DM need not bother about local joins, until actually traffic   
for that group arrives. Forward state is only created when traffic for   
that group arrives. But IGMP MUST and SHOULD have the info about local   
joins, so that PIM can peep into host membership table to create an   
outgoing interfaes list.
[vishu]  ------------------------------------------------------
 For eg: PIM-DM might be started after
    IGMP has already been started. In which case there has to be a   
separate
    mechanism to inform PIM-DM about the group memberships which were
    expressed by hosts before PIM-DM was started.

 - Ravi Shekhar.

[vishu]  ----------------------------------------------------------
IGMP is integral part of IP and must be enabled before any multicast   
routing module starts up in the router. I am not so sure what other   
mechanisms exist to cache group membership info.

---

From: vishwas <[email-masked]>
Date: Tue, 15 Dec 98 11:37:00 PST

Firstly, it would be nice if all the PIM control message formats
specific to PIM-dm was in this spec itself rather than being
referenced to PIM-sm spec. We want to make sure this is a standalone
draft.
[vishu]  ------------------------------------------
I had similar view but did not receive any +ve replys from the authers.
 ------------------------------------------------

The second one is more of a clarification. Section 5.3 states:

router

Should this be stated in the draft in some form?

Sangeeta

[vishu]  --------------------------------------
The draft is RIGHT in this case. no changes need to be done.