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Figure 64 ATM switching
ATM interfaces support only manually created permanent virtual circuits (PVCs) and permanent
virtual paths (PVPs), not switched virtual circuits (SVCs) created through the exchange of signals.
ATM architecture
ATM has a three-dimensional architecture. It consists of three planes: user plane, control plane, and
management plane. Both the user plane and the control plane are divided into four layers: physical
layer, ATM layer, ATM Adaptation Layer (AAL), and upper layer, each of which are further divided into
the following sub-layers:
• The control plane establishes and tears down connections with signaling protocols.
• The management plane consists of layer management and plane management. The former
manages the layers in each plane and has a layered structure corresponding to other planes.
The latter manages the system and the communications between different planes.
Figure 65 illustrates the rela
tionships between layers and planes in ATM.
Figure 65 ATM architecture
The functions of the four ATM layers are as follows:
• Physical layer—Provides transmission channels for ATM cells. At this layer, cells received
from the ATM layer are transferred into a continuous bit stream after transmission overheads
are added to them. Meanwhile, continuous bit streams received from physical media are
restored to cells, which are then passed to the ATM layer.
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