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Configuring DCC
Overview
Dial Control Center (DCC) is a routing technology used when routers interconnect through a public
switched network, such as a PSTN or an ISDN. It can provide the dial-on-demand service where any
two routers dial to set up a connection when data needs transferring instead of setting up a
connection before that. When the link becomes idle, DCC automatically disconnects it.
Under certain circumstances, connections between routers are instantly established whenever there
is data to be transferred, so data transfer is time-independent, bursty, and small sized. DCC is a
flexible, economical, and efficient solution for such applications. In DCC, backup mechanisms are
available to guarantee communications. In case a primary line fails, DCC switches traffic over to a
secondary line to ensure ongoing services.
Approaches to DCC
Two approaches are available to DCC: circular DCC (C-DCC) and resource-shared DCC (RS-DCC).
They are suitable for different applications. In practice, the two parties in a call do not necessarily
adopt the same approach.
Terms used in DCC configuration are as follows:
• Physical interface—An interface that physically exists. Examples are serial, BRI, and
asynchronous interfaces.
• Dialer interface—A logical interface created for configuring DCC parameters. A physical
interface can inherit the DCC configurations after it is assigned to a dialer interface.
• Dialup interface—Any interface used for dialup connection. It can be a dialer interface, a
physical interface assigned to a dialer interface, or a physical interface directly configured with
DCC parameters.
C-DCC
1. Features of C-DCC.
C-DCC delivers the following features:
{ A logical dial (dialer) interface can contain multiple physical interfaces, but a physical
interface can be assigned to only one dialer interface. A physical interface can provide only
one type of dial service.
{ You can assign a physical interface to a dialer interface to inherit DCC parameters by
assigning it to a dialer circular group, or directly configure DCC parameters on the physical
interface.
{ All the physical interfaces in a dialer circular group inherit the attributes of the same dialer
interface.
{ You can associate a dialer interface with multiple call destination addresses by configuring
the dialer route command or with a single call destination address by configuring the dialer
number command.
C-DCC is powerful and has broad applications. However, it lacks flexibility and extensibility.
For example, on an ISDN BRI interface, all the B channels inherit its configuration in the C-DCC
approach. The static binding between call destination address settings and physical interface
configurations will restrict using C-DCC, because dialer routes are becoming increasingly
complicated as a result of network growth and support to more protocols.
2. Association of physical interfaces and dialer interfaces in C-DCC.
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