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308 C
HAPTER
10: ATM N
ETWORK
B
ASICS
Using this connection-oriented networking technology, centered by a
switch, you can set up a great number of virtual connections to support
multiple applications through the same physical connection. The
switching technology enables dedicated bandwidth for each application,
overcoming the problems that exist in a shared-media networking
technology, like Ethernet, Token Ring, and Fiber Distributed Data Interface
(FDDI). ATM allows different types of physical layer technology to share
the same higher layer — the ATM layer.
ATM Cell Structure
Unlike Ethernet - which transfers variable length packets - ATM switches
transfer fixed length cells. The ATM cell is 53 bytes in length: 5 bytes of
header and 48 bytes of payload information. The header contains
enough information to allow the network to forward each cell to its
proper destination. The cell header also provides the network with the
ability to implement congestion control and traffic management
mechanisms.
Figure 4 presents the structure of the ATM cell.
Figure 4 Layout of the ATM Cell
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