Subject: (*,G) kernel entry

From: "Jyotheeswara Rao Kurma" <[email-masked]>
Date: Wed, 11 Apr 2001 11:07:45 +0500

Hi All :

   I am Jyotheesh. 
   Recently I subscribed to this list. I have a small question . I am
thankful to those guys who gives me some pointers on this.
 
  Is it good to have a (*,G) entry in the kernel ? What do you feel is 
the 
  optimized structure of the kernel forwarding table (entry ) ? I came 
to 
the conclusion that it will be good if kernel has (*,G) etries also. The
reason is some thing like this.

 suppose say a directly attached host send IGMP mebbership request, then
 the PIM router on that subnet must create a (*,G) entry in its kernel 
with
 oif-list set to the interface on which IGMP request came. Later when a
multicast packet comes from RP down the RP shared tree, this packet will
be forwared on all interfaces in oif-list of this (*,G) entry . (As 
there 
is no (S,G) entry ) .  

  If we don't have kernel (*,G) entries, i.e only (S,G) entries are 
allowed,
 then , if a directly connected host joins a group G1, and if there are
say some 1000 senders(S1-S1000) to this group G1 , then kernal has to be
loaded with 1000 (S1,G1),(S2,G1) ...(S1000,G1) entries on all
intermediate PIM routers. I think this is not desirable.Instead of 1000
(S,G) entirs, if kernel has a single (*,G1) entry, that's enough. 

 I feel it is desirable to create a (S,G) entry, when this router is
going to join SP Tree.  This switch is initiated by the DR of the
receiver towards the Source(when data threshold exceeds some specified
limit) or by RP when it wants to join SP Tree towards sender (source.)

 Then if we decide to have (*,G) entries also, then what happens to the
data packet forwarding rules, Section 4.2 . Should we look for (S,G)
entry first,
if succeede go ahead with computing inherited_olist(S,G), and if we 
dont find
(S,G), search for (*,G) and if we have that then how to get the list of
interfaces to forward ? Is it directly immediate_olist(*,G) or some 
thing 
else ?

Once agian advanced thanks to all who replies to this mail,
Thanks,
Jyotheesh

---

From: Hitoshi Asaeda <[email-masked]>
Date: Wed, 11 Apr 2001 17:11:42 +0900

> reason is some thing like this.

Yes, I agree.
Actually, old pimd's kernel patch has several experimental codes which
might introduce (*,G) routing entry. But we decided the first step was
to deploy stable kernel supporting PIM, so current kernel patch for
pimd doesn't include that new function.
It would be our next step.

Thank you.
--
Hitoshi Asaeda