
ATM Features and Implementation Notes
5-7
ATM Implementation Notes
This section describes special features regarding how we implement ATM.
Service Records and Virtual Circuits
ATM devices communicate using virtual circuits. These virtual circuits transmit
and receive ATM cells containing upper-layer protocols. Service records provide a
way of creating logical interfaces (within the physical ATM interface) for these
upper-layer protocols. In essence, these service records allow you to
• Organize multiple VCs into logical groups
• Create direct, point-to-point connections
• Assign, delete, and modify upper-layer protocols for just one PVC, or for a
group of VCs, at any given time
PVC Access Methods
You can set up PVCs to access an ATM network in the following ways:
• Multiple PVCs per service record
• One PVC per service record
• Hybrid access PVCs
The following sections describe each form of access.
Multiple PVCs
Upper-layer protocols treat each service record on an ATM network interface as a
single access point. These protocols use a single network address to send all traffic
destined for the network to the ATM network interface. Figure 5-3 shows a
conceptual drawing of multiple PVCs accessing an ATM network through one
service record.
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