Re: [pim] RFC 4541

Hi

OK, I think I understand. Isn't it a problem if a protocol expects to
be able to receive before sending though? If you look at
https://www.iana.org/assignments/multicast-addresses/multicast-addresses.xhtml#multicast-addresses-1
you will see that there are quite a few different protocols, it is
difficult to say how all of them behave. Also, we don't know how
future protocols might behave.

Also, I hope you aren't assuming that a router/host that wants to
receive for a specific group, would be sending messages to the same
group address. There could be client-server link-local protocols that
don't work that way.

Stig

On Thu, Nov 8, 2018 at 12:40 AM <Ganesh.ChennimalaiSa@dell.com> wrote:
>
> Hi Stig,
>
> I understand the point. My question is: when all protocols are chatty we theoretically can use an alternate mechanism to learn their existence and forward only to group members. For instance OSPF is chatty and OSPF PDUs can be forwarded only within OSPF routers by leveraging its chatty nature. But when we have passive listeners in a link-local group, there is no opportunity for the network to know about the existence of such receivers.
>
> Do we have passive receivers (or protocols) in this 224.0.0.* range ?
>
> regs
> Ganesh
>
> -----Original Message-----
> From: pim <pim-bounces@ietf.org> On Behalf Of Stig Venaas
> Sent: Thursday, November 8, 2018 1:58 PM
> To: ChennimalaiSankaran, Ganesh
> Cc: pim@ietf.org
> Subject: Re: [pim] RFC 4541 - 224.0.0.*
>
>
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>
> Hi
>
> The problem is that many stacks don't send IGMP reports for link-local
> groups, making the assumption that only routers need to know about
> membership, and link-local groups are not routed. Hence, you cannot
> rely on IGMP to determine which ports have interested receivers.
>
> Stig
>
> On Sun, Nov 4, 2018 at 4:55 PM <Ganesh.ChennimalaiSa@dell.com> wrote:
> >
> > Hi,
> >
> >
> >
> > Looking at RFC4541 and specifically the discussion 2..1.2 (2) on data forwarding rules. It says
> >
> >
> >
> > “Packets with a destination IP (DIP) address in the 224.0.0.X range
> >
> >       which are not IGMP must be forwarded on all ports.”
> >
> >
> >
> > As I see, there may not be explicit joins in this range and looking at IANA registry most protocols look chatty.
> >
> >
> >
> > Are there any groups with silent listeners that use this range ?
> >
> >
> >
> > regs
> >
> > Ganesh
> >
> >
> >
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