ACL and QoS lists, see Policy lists on page 557. For information on WFQ, see Weighted Fair
VoIP Queuing on page 242.
You can configure modem dial backup to dial to an enterprise-owned RAS or to the Internet
via an Internet Service Provider (ISP). Most ISPs mandate the use of the internal IPSec VPN
gateway process to encrypt the traffic as it goes over the Internet.
Note:
IPSec VPN adds overhead to each packet, further reducing available bandwidth.
Under ideal conditions, the bandwidth of the analog modem can reach 56 kbps for downlink
(53 kbps in the US) and 33.6 kbps for uplink. However, sub-optimal PSTN quality may degrade
the downlink bandwidth to 33.6 kbps, or even 28 kbps. This may not be enough to carry a
single ISDN-PRI 64 kbps D-Channel for signalling over H.248 to and from the MGC, even
without considering the need to support IP phones and/or analog or DCP trunks.
VoIP signaling consumes bandwidth when setting up and tearing down calls. However,
calculations, testing, and field experience show that an analog modem can easily support a
small branch office when the expected Busy Hour Call Completion (BHCC) is limited.
Note:
The low bandwidth and high Round-Trip-Time (RTT) of analog modems (~100 ms) may lead
to acceptable changes in Post-Dial-Delay (PDD) and offhook-to-dialtone delays.
Modem dial backup uses the Branch Gateway’s backup interface functionality to activate the
Dialer interface for modem dial backup when the primary interface fails and to deactivate the
Dialer interface when the primary interface is up again. Currently, modem dial backup does
not support such features as Dial On Demand Routing (DDR), callbacks, or RAS. Modem dial
backup cannot receive backup calls. For more information about backup interfaces, see
Backup interfaces on page 256.
Note:
You can only backup one interface with modem dialer backup.
Using the Branch Gateway’s backup interface functionality, you can designate the Dialer
interface as the backup for the main WAN link. However, this method is not always available,
since an 'up' WAN link status does not ensure connectivity, and the main WAN link may not
even be directly connected to the Branch Gateway.
The workaround is to use the Branch Gateway’s object tracking feature to verify connectivity
to the primary MGC using Respond Time Reports (RTRs) and object trackers. Configure object
tracking to change the state of the Loopback interface accordingly, and configure the Dialer
interface as a backup to the Loopback interface. For more information about object tracking,
see
Object tracking on page 282.
Modem dial backup uses a modem connected directly to the Branch Gateway’s USB or
Console port. The modem can also be used to access the Branch Gateway CLI from a remote
WAN interfaces
Administering Avaya G430 Branch Gateway October 2013 259
To Next Page
Loading...
