Broadcast and collision Domains

Discussion in 'Cisco' started by cjblair, Apr 10, 2007.

  1. cjblair

    cjblair Guest

    Could someone explain to me what each of these are, I am having
    difficulty with the subject. I guess I would understand it better if
    you can tell me why they are needed and when they should be
    implemented. I would really appreciate it.
    cjblair, Apr 10, 2007
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  2. cjblair

    Bod43 Guest

    from an on-line dictionary
    1 a : complete and absolute ownership of
    land -- compare EMINENT DOMAIN b : land so owned
    2 : a territory over which dominion is exercised
    3 : a region distinctively marked by some
    physical feature <the domain of rushing streams,
    tall trees, and lakes>
    4 : a sphere of knowledge, influence, or
    activity <the domain of art>
    5 : the set of elements to which a mathematical
    or logical variable is limited; specifically : the set
    on which a function is defined
    6 : any of the small randomly oriented regions
    of uniform magnetization in a ferromagnetic substance
    8 : the highest taxonomic category in biological
    classification ranking above the kingdom
    9 : any of the three-dimensional subunits of a
    protein that are formed by the folding of its linear
    peptide chain and that together make up its
    tertiary structure
    10 : a subdivision of the Internet consisting of
    computers or sites usually with a common
    purpose (as providing commercial information)
    and denoted in Internet addresses by a unique
    abbreviation (as com or gov); also : DOMAIN NAME

    4 (and 3) is the best fit here I think (and of course 10
    is about the worst fit).

    4 : a sphere of activity

    Collision domain
    The region of a network over which a single
    collision is detected and propagated. In
    a modern switched network
    it is consists simply of a single wire and the two ports at
    either end of it.

    Broadcant domain (typos is us)
    The region of a network over which a single
    Layer 2 broadcast frame is propagated.
    In a modern switched network it consists of
    all ports and links comprising a single VLAN.
    (A single subnet).
    Bod43, Apr 10, 2007
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  3. A collision domain is basically an area where 2 or more nodes on a
    network might send a signal at the same time, causing neither side to
    actually receive that signal. Collision domains are not really a
    problem with modern equipment, since switches give each node it's own
    collision domain (and have a ton of other benefits) . However, people
    that have not upgraded might still have a hub. A hub puts everything
    attached to it on essentially the same wire, so collisions can occur
    and screw up your network. Collisions are a layer 1 and 2 issue,
    electrical signals are the problem, and the CSMA/CD solves it.

    Remember that a broadcast is a type of message, broadcast domain is
    the area that the broadcast signal is allowed to go. Just like your
    local news doesn't go to Australia. So broadcasts are used whenever
    the a node wants to send info but doesn't know who should receive it,
    or when it wants everyone to get a signal. DHCP for instance, the
    computer sends out a broadcast hoping that someone in the broadcast
    domain is a dhcp server. Broadcasts don't cross routers (there are
    exception but you'll learn that later), so all the switches nodes and
    hubs between routers are in the same broadcast domain (unless there
    are vlans, but you'll learn about that later too :).

    So collisions domains you want to make smaller whenever you can, it
    helps the network. Broadcast domains vary depending on which clients
    and server you want to receive broadcasts.

    Hope that helps
    Matt nickerson, Apr 10, 2007
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