Carrier Ethernet

Discussion in 'Cisco' started by Mark, Oct 6, 2012.

  1. Mark

    Mark Guest

    Mark, Oct 6, 2012
    #1
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  2. Anyone remember back in the 80's when the telecoms thought that they
    could build nationwide networks as a single (or maybe a few large) ATM
    cloud?
     
    Barry Margolin, Oct 6, 2012
    #2
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  3. Mark

    Michelot Guest

    Hi, Mark
    Bridges are indeed used in network providers.

    Spanning tree is generally not used. If the provider is adding a
    bridge, STP would disrupt its network too long time, to converge.

    In Ethernet WAN, we consider connectionless paths (CL) and oriented
    connection paths (CO). With CO paths, address learning process is
    useless.

    Best regards,
    Michelot
     
    Michelot, Oct 6, 2012
    #3
  4. Mark

    Stephen Guest

    Bridging has some tables and overheads that grow faster than linear
    with the number of connections and devices across the entire set of
    indirectly connected switches.

    Every end point connected to a bridged system has at least 1 MAC
    address, and any traffic to that device implies that MAC has entries
    in some or all the devices that make up the network.

    This means linear scaled up table space is needed, but the maintenance
    overheads that occur grow more quickly as well.

    The other practical problem is that a network needs to be stable to
    operate well, and in practice that means that you need ways to limit
    changes to parts of the system so their effect stay local.

    in bridging a topology change can propagate across the system.
    Think of the hierarchy in routing as being selective information
    hiding.

    Instead of 1 entry per MAC address for 100,000 devices in table for a
    big corporate network, you may need just 1 or a few routing entries
    saying "xxx corp is that way".

    This means any topology change in xxx corp stays within their system -
    the rest of the system doesnt need to see it
     
    Stephen, Oct 6, 2012
    #4
  5. Mark

    Michelot Guest

    Hi Stephen,
    In the user plane, a bridge is not a MAC end point.

    Best regards,
    Michelot
     
    Michelot, Oct 7, 2012
    #5
  6. Mark

    Rick Jones Guest

    Wording quibble. Given the loaded nature of the word "broadcast" it
    might be better to put that as "frames get transmitted out all
    connected ports" or "frames get flooded out all connected ports" lest
    some new folks think the frames get transformed into actaul broadcast
    frames.

    rick jones
     
    Rick Jones, Oct 8, 2012
    #6
  7. The meaning of "scale" is in the sense of how one quantity must
    change when you change another.

    One can, for example, discuss the change in the size of the legs
    of an animal with its weight. That is:

    "How does an animal's leg scale with its weight?"

    In many interesting and useful cases, the answer is an exponent.

    How does a tree trunk diameter scale with tree height?

    How does the speed of a transistor scale with its size?

    How does the cost of a transistor scale with it speed or size?

    Doesn't scale means that something else happens, such that
    the scaling laws aren't useful anymore.

    Transistors (and animals) don't scale well down to atomic size.
    They also don't scale well up to planetary size.

    -- glen
     
    glen herrmannsfeldt, Nov 1, 2012
    #7
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