3com 3031 Instruccion De Instalación
25
ATM C
ONFIGURATION
Introduction to ATM
Technology
Technology
Asynchronous Transfer Mode (ATM) is a transmission and switching mode of
broadband ISDN specified by ITU-T in June 1992. It has been the core technology
to implement broadband communications based on its flexibility and support over
multimedia service.
broadband ISDN specified by ITU-T in June 1992. It has been the core technology
to implement broadband communications based on its flexibility and support over
multimedia service.
As defined by ITU-T, ATM transmits, multiplexes and switches information in terms
of ATM cells. An ATM cell has a fixed length of 53 bytes, out of which 5 bytes
make up the cell header for route and priority information. The other 48 bytes are
payloads.
of ATM cells. An ATM cell has a fixed length of 53 bytes, out of which 5 bytes
make up the cell header for route and priority information. The other 48 bytes are
payloads.
ATM is connection-oriented. Each virtual circuit (VC) is identified by the virtual
path identifier (VPI) and the virtual channel identifier (VCI). One VPI/VCI value has
partial significance on a segment of link between ATM nodes. It is translated on
ATM nodes. When a connection is released, the relevant VPI/VCI values will also
be released. It will be put back into the resource table, available for other
connections.
path identifier (VPI) and the virtual channel identifier (VCI). One VPI/VCI value has
partial significance on a segment of link between ATM nodes. It is translated on
ATM nodes. When a connection is released, the relevant VPI/VCI values will also
be released. It will be put back into the resource table, available for other
connections.
Basic ATM protocol architecture consists of three planes -- User Plane, Control
Plane and Management Plane. User Plane and Control Plane can be divided into
four layers respectively, i.e. Physical Layer, ATM Layer, ATM Adaptation Layer (AAL)
and Upper Layer. Each layer can be further divided into several sub-layers.
Management Plane may also be divided into Layer Management and Plane
Management. The former is responsible for the management of every layer in
each plane. It has layered structure corresponding to other planes. The latter is
responsible for the system management and the communications between
different planes. The Control Plane mainly uses signaling protocols to establish
and release connections. The relationships among layers and planes are shown as
follows:
Plane and Management Plane. User Plane and Control Plane can be divided into
four layers respectively, i.e. Physical Layer, ATM Layer, ATM Adaptation Layer (AAL)
and Upper Layer. Each layer can be further divided into several sub-layers.
Management Plane may also be divided into Layer Management and Plane
Management. The former is responsible for the management of every layer in
each plane. It has layered structure corresponding to other planes. The latter is
responsible for the system management and the communications between
different planes. The Control Plane mainly uses signaling protocols to establish
and release connections. The relationships among layers and planes are shown as
follows:
Figure 55 ATM protocol model
Physical layer
ATM layer
ATM adaptation layer
Upper layer
protocol
protocol
Upper layer
protocol
protocol
Control plane
User plane
Management plane
Plane
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ana
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Hierarc
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Physical layer
ATM layer
ATM adaptation layer
Upper layer
protocol
protocol
Upper layer
protocol
protocol
Control plane
User plane
Management plane
Plane
m
ana
gem
ent
gem
ent
Hierarc
hic
hic
al m
anag
em
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ent