Subject: Multicast

From: #PATHIK GUPTA# <[email-masked]>
Date: Wed, 7 Mar 2001 21:59:19 +0800

Hi,

regarding the statement made by Jon that SSM is a subset of PIM-SM, Isnt it
true that SSM just refers to providing a host with the multicast session
from one particular source even if the underlying protocol scheme is DVMRP
or even OSPF. As far as I know, SSM has more to do with the IGMPv3 then to
PIM-SM.

Regards
Pathik Gupta

-----Original Message-----
From: Jon Crowcroft [mailto:[email-masked]]
Sent: Wednesday, March 07, 2001 7:11 PM
To: Ali Boudani
Cc: [email-masked]; [email-masked]
Subject: Re: Multicast

In message <[email-masked]>, Ali Boudani typed:

 >>Isnt SSM just a particular case of PIM??

the right place for this discussion is
  SSM <[email-masked]>, 

SSM is a subset of PIM SM, roughly, and relies (sort of) on IGMPv3 (at
least on a subset of equiv. functionality).

 >>It is the specifications for just specific sources but they arent
adressing
 >>the multicast in general.
 >>am I right ?

not quite - i dont think the whole IETF list is the right place for
this one - see
http://www.ietf.org/html.charters/ssm-charter.html

i think since the ssm work is close to done, we'll see work resume on
bidir (s/cbt/pim-bidir:-) soon , and similalrly in the RMT work
see
http://www.ietf.org/html.charters/rmt-charter.html
a lot of building blocks are close to done (prob. about a year) then
we'll see some work on multiple source (the latent demand for multiple
source applications is imho underestimated, but until we can fix the
more immediate problems with supporting 1-many, we can't really expect
people to deploy many-to-many extensively- other problems being
addressed are concerned with having good solutions for multicast security
(see 
http://www.ietf.org/html.charters/msec-charter.html
and for many-to-many, for congestion control (to meet transport area
requirements)....

i think (but of course i am usually wrong) that we may see progress on
this in 2002...

 >>Jon Crowcroft wrote:
 >>
 >>> In message <[email-masked]>, Ali Boudani typed:
 >>>
 >>>  >>First the CBT protocol was created to use shared tree solutions
because
 >>>  >>DVMRP and the other dense mode protocols werent scalable. there were
 >>>  >>many problems with CBT (which is bidirectional) so PIM-SM was
cretaed
 >>>  >>which provide some switching (between shared tree and source tree).
and
 >>>  >>after that there is some discussions about the bidirectional PIM,
which
 >>>  >>is like CBT.
 >>>  >>Are we in circle here or what ??
 >>>
 >>> not really. the mainstream current multicast action is concentrating on
 >>>  single source (and on single source reliable multicast transport)
 >>> since we didn't feel we understood all the complications of ANY of the
 >>> multiple source schemes for IP or reliable....(e.g. interdomain
 >>> routing, and multiple source semantics for reliable) -
 >>>
 >>> there were'nt really "problems" with CBT apart from we never managed
 >>> to get a router vendor to committ to an implmenetation which we could
 >>> deploy and learn from - tony ballardie got a lot of the details out,
 >>> but the two implementaions i know of never saw light of day.....bidir
 >>> pim is cool, bgmp is cool, but action in implementation/details/spec
 >>> is waiting on getting the PIM SSM stuff completely shaken down....
 >>>
 >>> its all part of a good learning experience and (as any good s/w
 >>> engineer might say) its the norm:-)
 >>>  >>
 >>>
 >>>  cheers
 >>>
 >>>    jon
 >>

 cheers

   jon