All things related to multicast

quicktime.merit.edu is a unicast address.
 Unless you specifically told the system to go to 233.0.236.30.  Some
systems will attempt to start up a multicast stream then "fall back"
to unicast.  If you really want to find out do a /usr/sbin/tcpdump

Sincerely,
Sidney Eaton, CCNA, Network+, NCSS, NCDE, CCSE
Network Technician
Ferris State University
205 West Building
Big Rapids, Mi 49307
(231) 591-5388
For Support Call (231) 591-4822 or www.ferris.edu/tac

Laurence Kirchmeier <>

10/19/2009 11:57 AM

To	Research Channel Working Group <>, Internet2 Multicast Working Group <>
cc
Subject	multicast connundrum

Merit is streaming a number of unicast and multicast streams
from NANOG 47 in Dearborn Mi.
We are sending one high quality unicast quicktime stream
back to a QuickTime streaming server at Merit which then reflects out the
stream to unicast connected viewers. Also  I have set up a unicast
to multicast relay so that one can receive the reflected stream via multicast.

The URLs for these two streams are:
rtsp://quicktime.merit.edu/nanog.sdp
rtsp://quicktime.merit.edu/nanogmult.sdp

The multicast address being used is 233.0.236.30, port
8000


My connundrum is this:
I am sitting on a wireless network in the hotel in Dearborn
and when I load "rtsp://quicktime.merit.edu/nanogmult.sdp"
in Quicktime Player, I actually get the video stream.  Now I ask myself
how is that possible - perhaps the wireless network is allowing multicast
traffic.  Our network engineering staff are sceptical that I am actually
seeing multicast traffic and somehow I am receiving a unicast stream.
SO the question is - how can one figure out (on a Macintosh
or linux box) whether a stream that is being received by the machine is
a multicast stream. I know that  "netstat -rn" shows all
the active tcp and udp connections.  In that list how might one detect
that a stream is a multicast stream.  Is there some other way to figure
out if a stream is a multicast stream?
Any comments, ideas would be helpful - am I missing something
obvious?

Laurie

_______________________________________________
Laurence Kirchmeier
Video Services Manager & Senior Engineer, Networking
R&D
Merit Network, Inc.
1000 Oakbrook Drive, Suite 200, Ann Arbor, MI 48104
Tel.  +1 734 527-5741 Fax. +1 734 527-5790
Email: 
    
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