
Data Compression Overview
117352-B Rev. 00
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Frame Relay Hybrid Access
Hybrid access enables you to combine bridging and routing over a single frame
relay interface.
When you enable data compression for frame relay on a hybrid circuit, both the
bridged and the routed traffic over that circuit are compressed. Note that
compression applies only to the hybrid permanent virtual circuit (PVC), and not to
the other PVCs from the main circuit, unless you have also enabled compression
for those interfaces. Conversely, if you enable data compression for other PVCs,
but not on a PVC you have configured for hybrid mode, the hybrid circuit does not
use compression.
Frame Relay Dial-on-Demand
Frame relay enables you to configure dial-on-demand service. Dial-on-demand
enables the router to activate a dial-up line only when there is data to send or when
you configure the router to force the activation of a dial-up line. Using frame relay
dial-on-demand ensures that you establish connections only when you need them,
as opposed to using leased lines, which are active regardless of data activity. This
helps you reduce line costs.
Frame Relay Dial Backup
Frame relay enables you to configure dial backup service. If a primary frame relay
circuit fails and you enable dial backup, the router automatically establishes a
backup circuit. The backup circuit can be a PPP circuit, a frame relay circuit that
uses direct mode (a service record with only one PVC), or a frame relay circuit
that uses group mode (a service record with two or more PVCs).
The backup circuit can inherit the primary’s configuration, or it can use its own.
When the frame relay primary and backup use the same configuration, they have a
shared configuration. The backup circuit uses the same network-layer address as
the primary circuit. The data-link layer configuration, that is, the backup PVCs,
Data Link Connection Identifiers (DLCIs), and filters can be the same or different
from the primary.
If the backup uses a unique configuration, it is a secondary configuration. A
secondary configuration uses a different network-layer address, PVCs, and filters
from the primary.
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