understand multicasting from the client/host perspective .

Discussion in 'Cisco' started by April, Jun 25, 2006.

  1. April

    April Guest

    Trying to understand multicasting from the client/host perspective ..

    What client software is needed?
    What configurations are required?
    Is there web based client, and any configuraton required?
    How a client start using a typical multicast service?
    How does a client/host works behind the scene to get multicast service,
    in conjunction with what have been set up on the router and switch?

    Any good reference on this, I mean from client/host perspective, or
    something that provide the"whole" picture, including protocol, router,
    switch, and client/host?
    April, Jun 25, 2006
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  2. A TCP/IP stack.
    If the multicasts need to be sent to multiple LANs, you need
    multicast-enabled routers.
    Client for what? Multicasting is a general-purpose mechanism, not a
    single application.
    If it's transmitting, it just sends messages to the multicast address.
    Multicast routers take care of sending to all the members of the group.

    If it's receiving, it "joins" the multicast address. This involves
    sending out a message that the local router receives, so that it can
    inform other multicast routers that there's a member on this LAN and
    they'll forward messages here.
    Do a google search for multicast routing protocols.
    Barry Margolin, Jun 25, 2006
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  3. April

    April Guest

    Thanks Barry .. however I'd like to see something like a user

    Treat me like a 4th grader who needs to use this technology to attend a
    Global Future Leaders Conference, what should I do? I'm using an XP
    April, Jun 25, 2006
  4. A "user guide" implies a particular application, not a general
    technology. Your question is like asking for a user guide for TCP/IP,
    as opposed to Internet Explorer.
    Barry Margolin, Jun 26, 2006
  5. April

    April Guest

    Thanks..but I guess you really don't know the technology really well,
    otherwise you would be able to tell a 4th grader how to use this
    technology and attend the conference. :)
    April, Jun 26, 2006
  6. April

    erik.freitag Guest

    I would say you are not guessing very well today. I suggest you re-read
    the patient and thoughtful responses responses you've received and try
    to make them apply to your situation.

    I look forward to hearing your posts from the 5th grade.
    erik.freitag, Jun 26, 2006
  7. April

    April Guest

    ok .. what I'm asking is how the technology works from a client
    perspective..here are too many people know how it work from the router
    ans switch sides.

    If you think you are just as good, give it a try .. like For example,
    April, Jun 26, 2006
  8. April

    erik.freitag Guest

    Do you know what multicast is used for? That might explain why you are
    having trouble asking a useful question.
    erik.freitag, Jun 26, 2006
  9. April

    April Guest

    you are not helping .. don't bother

    April, Jun 26, 2006
  10. Ok. Speaking on "4th grade language", multicast is like a radio. There are a
    radio waves (IP addresses in the Each wave (IP
    address) is an individual "radiostation", where there is one Speaker (Radio
    Translation Station), and multiple Receivers (Radio receivers). To be able
    to listen the "station", your "radio" should be tuned to proper frequency
    (listen proper IP address). There are some "standard defined" stations
    (mostly in range), used for specific needs (routing
    protocols, etc.). But some applications can send multicast traffic for their
    own needs. For example, you may multicast a radio or video, you may
    multicast software updates or application data. In most cases "Sender" is
    not aware if there are any listeners - multicast just goes out. When
    "receiver" wants to "subscribe" to certain "frequency", it sends special
    "Join" request to local switch and router. Router then examines, if it
    already has "the subscription", or, if not, if any neighbor has
    "subscription" to this "frequency". If it's possible to find "bandwidth",
    all routers on the way between "Sender" and "Receiver" keep the
    subscription. When "Receiver" does not want to receive the frequency, it
    sends a special "Leave" message, and routers, if there are no more
    "Subscribers" for this particular frequency, remove it from the route.

    Multicast, as I described, is "one-way traffic". So, to use it, you should
    have the multicase sender, your should know the multicast IP address, used
    by sender, and have an application, which should receive this traffic. One
    example, how you may use it. Install Windows 2000/2003 Server with Media
    Streaming Server. Create specific Media Source (for example, convert a
    couple MP3s into the Media), and define it as a Multicast. Then use specific
    URL to pont your Microsoft Media Player to this Media. the communication
    between your Server and multiple workstations will be through Multicast.

    Good luck with your study,

    HeadsetAdapter.com, Jun 26, 2006
  11. No, you're just not asking the right question.

    Are you asking how to write multicast applications, implement a
    multicast network infrastructure, or what multicast applications exist
    and how to use them?
    Barry Margolin, Jun 26, 2006
  12. April

    April Guest

    Mike, thank you very much for the excellent explanation .. you explan
    things just like my favorite teacher.

    I guess when I join a webinar, once I got on the site, the step I was
    authenticated is also the process I was joining the group - if I
    understand a webinar is a multicasting session correctly?

    As a result I'll also get aother MAC address, besides the one I'm using
    to connect to the site, as a multicasting recepient?
    April, Jun 26, 2006
  13. April

    April Guest

    Mike, thank you very much for the excellent explanation .. you explan
    things just like my favorite teacher.

    I guess when I join a webinar, once I got on the site, the step I was
    authenticated is also the process I was joining the group - if I
    understand a webinar is a multicasting session correctly?

    As a result I'll also get aother MAC address, besides the one I'm using
    to connect to the site, as a multicasting recepient?
    April, Jun 26, 2006
  14. April

    April Guest

    Thank you as you have tried ..

    April, Jun 26, 2006
  15. Webinar may go by Multicast, but most likely it will go by Unicast. In case
    of Unicast, the "Publisher" opens one stream for each individual
    "Subscriber". Why Multicast is not used everywhere? Most (if not every)
    firewalls are not aware or do not honor Multicast. So, to ensure that all
    recipients are able to receive a Webinar, Publishers usually either do "try
    Multicast, then do Unicast". Plus, if one router in the path between
    "Source" and "Receiver" will not understand Multicast, whole "subscription"
    will fail.

    Multicast could be used within one ISP's network, where they control every
    router and swtich in the network. Then ISP can put, for example, TV
    channels, each in the individual "bandwidth". This will allow them to put
    better quality Video with lower Bandwidth utilisation (you may have
    thousands recipients, but your bandwidth will stay the same). To avoid
    problems with user's firewalls, they usually "drop" this multicast directly
    from their DSL or Cable modem into the "decoder box".

    Practical use for multicast today is limited by local LAN boundaries or
    MAN/WAN networks if you have control over your equipment. At the local level
    (access switches), multicast either converted to a Broadcast (if switch does
    not understand Multicast), or, if switch is "multicast-aware", it goes only
    to specific ports on the switch, where "subscribers" reside.

    Conversion from the specific Multicast IP address to a special MAC addresses
    happens on the "last router". When multicast packet reaches the last router
    before the client, router, prior to put the frame to the switch, converts it
    to a special MAC address. And the switch will either treat this frame as a
    broadcast and send to all ports, or will determine, which port should
    receive this frame and will send it to specific port(s).

    Good luck,

    HeadsetAdapter.com, Jun 26, 2006
  16. You may wish to investigate Cisco Systems IP Multicast:


    as well as the Cisco Press Book - Developing IP Multicast Networks,
    Volume I:


    Hope this helps.

    Brad Reese
    BradReese.Com - Cisco Network Engineer Directory
    1293 Hendersonville Road, Suite 17
    Asheville, North Carolina USA 28803
    USA & Canada: 877-549-2680
    International: 828-277-7272
    Fax: 775-254-3558
    AIM: R2MGrant
    Website: http://www.bradreese.com/contact-us.htm
    www.BradReese.Com, Jun 26, 2006
  17. April

    Sam Wilson Guest

    Nitpick. No actually it's more than a nitpick. There is a class of
    applications, like multicast TV, which work that one-to-many way and
    there is a developing technique called source specific multicast (SSM)
    which enforces it, but it's a refinement. In general any system can
    send traffic to a multicast group address and some applications
    (conferencing, monitoring applications) require multiple senders.

    Sam Wilson, Jun 26, 2006
  18. April

    Sam Wilson Guest

    The multicast traffic will be sent to a multicast MAC address. If your
    system joins the group then it will receive traffic sent to that MAC
    address, but you won't "get" the address as such.

    Sam Wilson, Jun 26, 2006
  19. April

    April Guest

    Thanks Mike and Sam ...

    The multicast MAC part is where I have difficulty to understand well ..
    like why this is needed? As the sender, it seems to me it only needs
    to send to an IP ... I can think this signifies the frame is multicast,
    and somehow the switch can relate the multicast MAC to the MAC of a
    host that joined the group, but not sure this is all it about?
    April, Jun 26, 2006
  20. April

    April Guest

    Mike, thanks again!

    Why this conversion is needed, it seems to me it's purpose is not to
    help on deciding to do broadcasting.
    April, Jun 26, 2006
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