Avaya G430 Manual page 258

WAN interfaces
Root level
command
interface
(fastethernet|
loopback| tunnel)
Modem dial backup
The modem dial backup feature allows the Branch Gateway to utilize a modem to provide
redundant connectivity between a Branch Gateway and IP phones in a small branch office and
their primary Media Gateway Controller (MGC) at the headquarters or a regional branch
office.
Even if the Branch Gateway has Standard Local Survivability (SLS), or Enhanced Local
Survivability (ELS) using a local S8300 in Survivable Remote Server mode, it is always
preferable to continue working with the primary MGC, since features are lost when the system
is fragmented.
Analog modems have limited bandwidth and high latency, and are therefore unfit for carrying
VoIP traffic. However, using Dynamic Call Admission Control (CAC), the Branch Gateway can
be configured to report zero bandwidth for bearer traffic to the MGC when the primary WAN
link fails. A matching configuration on the MGC allows it to block new calls, if their bearer is
about to go over the modem dial backup interface, and to alert the user with a busy tone. In
this case, the user is still able to place external calls manually if local PSTN trunks are available.
Furthermore, Avaya Aura
(IGAR) may be configured to become active in such a case and to use the PSTN for
transporting the voice bearer transparently between the sites, transparently to the user. For
information about Dynamic CAC in the Branch Gateway, see
information about IGAR, see Administrator Guide for Avaya Aura
Modem dial backup is a generic data dial backup feature that can carry not only signalling but
every type of IP traffic. However, the low bandwidth of an analog modem would be likely to
cause congestion. The administrator must therefore ensure that VoIP signaling has priority
over the Dialer interface. This can be performed using access control lists (ACL), QoS lists,
and Weighted Fair Queuing (WFQ) priority schemes. The administrator should apply these
tools in both the Branch Gateway and the Remote Access Server (RAS). For information on
258 Administering Avaya G430 Branch Gateway
Command
Enter FastEthernet,Loopback, or Tunnel
interface configuration context
backup delay Set the time to wait before switching over to the
backup interface, in case of failure. You can also
use this command to set a delay before reverting
back to the primary interface.
backup Set a backup interface for the current interface
followed by the interface type and number. You
interface
must use this command from the context of the
interface for which you are setting a backup
interface.
®
Communication Manager 3.0 Inter-Gateway Alternate Routing
Comments? infodev@avaya.com
Description
Dynamic CAC on page 280. For
®
Communication Manager.
October 2013