From: Scott Morris (smorris@ipexpert.com)
Date: Wed May 09 2007 - 13:05:58 ART
Beau's book is very good... And he's a very energetic speaker if you ever
get to see him at Networkers!
Scott Morris, CCIE4 (R&S/ISP-Dial/Security/Service Provider) #4713, JNCIE
#153, CISSP, et al.
CCSI/JNCI-M/JNCI-J
IPexpert VP - Curriculum Development
IPexpert Sr. Technical Instructor
smorris@ipexpert.com
http://www.ipexpert.com
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
DWINKWORTH@wi.rr.com
Sent: Wednesday, May 09, 2007 11:44 AM
To: ccielab@groupstudy.com
Subject: Re: multicast funny question!! shared trees leads to source tree at
the end of story!!!
An answer to your question is found on page 156 of Beau Williamson's book
"Developing IP Multicast Networks." Here are some relevant quotes:
"By joining the SPT, multicast traffic is routed directly to the receivers
without having to go through the RP, thereby reducing network latency and
possible congestion at the RP."
"...the overall amount of (S,G) information maintained by the routers in a
PIM-SM network that uses SPTs is generally much less than is necessary for
dense mode protocols."
"By joining SPTs in PIM-SM, we gain the advantage of an optimal distribution
tree without suffering from the overhead and inefficiencies associated with
other dense mode protocols."
"...without the shared tree to deliver the first few multicast packets from
a source, routers have no way of knowing that a source is active."
You should really buy the book. This is one of the only books I read
from cover-to-cover when I was studying.
Derick Winkworth, CCIE #15672
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