User manual

21/1551-ASP 113 01 Uen N2 2014-01-28 51

OLUTION ARCHITECTURE

A remote gateway is usually referred to as a media gateway which

belongs to a multi-gateway MX-ONE system (e.g. located in the main

HQ site) but installed in a remote site without local server. It is a cost

effective way to facilitate a remote MX-ONE node, for instance to build a

branch node or to collapse a private network into a single system. Local

PSTN access can be provided, but the configuration does not offer

survivability.

Survivable Branch Gateway (SBG)

The MX-ONE survivable branch gateway is configured as a stand-alone

single server MX-ONE. During normal operating conditions, the SBG

simply acts as gateway between the PSTN and IP trunk handled by the

central MX-ONE. All IP extensions in the branch are registered with the

central MX-ONE.

During WAN failures, the IP telephones register temporarily with the

SBG. The SBG uses a specific license file which cannot be used for a

normal MX-ONE system. The SBG provides local PSTN access and

survivability.

Considerations for remote deployment:

There are several issues that must be taken into consideration for

remote component deployment.

• Bandwidth

• If WAN access link for the remote site is provided with narrow band-

width connection, the bandwidth may not be enough to carry

incoming and outgoing media traffic depending on the system size

(number of users). For remote Telephony Server deployment,

bandwidth needed to handle operation and maintenance without

too much delay, may be significantly higher than what is needed for

telephony.

• Care must be taken that there is enough bandwidth for a worst case

scenario.

• Latency

• The latency or packet delay in terms of the call and media control

orders and responses is crucial with remote components. The

maximum round trip delay should not exceed the allowed time limit

for time-out (normally < 100 ms is required) for proper operation.

• Availability/redundancy

• It is not straight-forward to support server and network redundancy

with remotely installed components. Even if a standby link can be

assigned (i.e. network redundancy), the down-time can be substan-

tial in the presence of WAN failure.

• Emergency (SOS) call service