R3303-HP HSR6800 Routers Layer 2 - WAN Configuration Guide

2
Figure 2 ATM switching
ATM interfaces support only manually created permanent virtual circuits (PVCs), not switched virtual
circuits (SVCs) created by exchanging signals and permanent virtual paths (PVPs).
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 3 illu
strates the relationships between layers and planes in ATM.
Figure 3 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