Avaya Configuring Dial Services Instrukcja Użytkownika Pobierz pdf (Strona 136)

Configuring Dial Services

6-2

117353-B Rev. 00

Standby circuits support asynchronous (RS-449), synchronous (RS-449, V.35,

RS-422, and X.21), and ISDN interfaces. PPP is the only data link layer protocol

that you can configure over a standby circuit; you cannot use frame relay.

Comparing Standby Circuits with Dial Backup Circuits

Both standby circuits and dial backup circuits can back up failed primary circuits;

however, they differ in the following ways:

• Each standby circuit has a unique configuration; it does not adopt the primary

circuit’s configuration. In contrast, most dial backup circuits inherit the

primary circuit’s configuration.

This unique standby configuration offers flexibility when setting up other

paths to remote sites. For example, you may want the standby circuit to have a

different destination than the primary circuit, or you may enable compression

on the standby circuit but not on the associated primary circuit.

• Standby circuits let you control when the router switches from the standby

circuit back to the recovered primary circuit. You do not have this option with

dial backup circuits. In dial backup configurations, the router terminates the

backup circuit when the primary circuit recovers. For example, to ensure the

stability of a recovered primary circuit before bringing down the standby

circuit, you can delay the return of data to the primary circuit.

• Standby circuits support PPP multilink.

You can assign a bandwidth-on-demand pool to the hot standby circuit to

relieve congestion. Bandwidth-on-demand connections use PPP multilink,

which lets the router use multiple dial-up lines simultaneously to transmit

data. You do not have this option with dial backup circuits.

If you associate a bandwidth-on-demand pool with a hot standby circuit, the

router monitors the hot standby circuit for congestion. If the circuit becomes

congested, the router activates lines from the bandwidth-on-demand pool until

congestion is relieved.

For maximum flexibility and control when setting up alternative connections, and

for quick responses to failed primary circuits, standby circuits are the best choice.

However, for more straightforward applications, where you do not need to

configure an alternative site for the backup connection, dial backup circuits are

more suitable. Either option ensures that critical data reaches its destination.

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Avaya Configuring Dial Services Instrukcja Użytkownika Strona 136