Synchronization; E911; Inter-Gateway Alternate Routing (Igar) - Avaya ESS User Manual

Synchronization

In an IP connected environment, each Port Network may have its own primary and secondary
external source that provides synchronization for the DS1. Synchronization is not supported
across IP networks.
In a CSS or ATM-PNC environment, there is only one primary and secondary synchronization
source for all DS1s in the CSS/ATM-PNC Port Networks. If a DS1 looses the primary and
secondary synchronization source, it uses the Tone Clock in the Port Network where it resides.
Use of Tone Clock synchronization may result in audible artifacts due to slips.
H.320 Video applications require synchronization. In the event that the H.320 Video application
looses synchronization, the call would be expected to drop.

E911

An E-911 call or other emergency call handling can only be routed if the trunk facility is under
the control of the same ESS server as the person originating the call.

Inter-Gateway Alternate Routing (IGAR)

Inter-Gateway Alternate Routing (IGAR) provides an alternate inter-region routing mechanism
that is used when the IP network cannot, or should not, carry bearer. IGAR preserves the
internal makeup of a call, so the call's use of non-IP bearer facilities is transparent to the end
user. IGAR can be triggered by Call Access Control via Bandwidth Limitation (CAC-BL), or can
be forced to use an alternate route. IGAR can use Public Switched Telephone Network (PSTN)
facilities, or private switched facilities to carry the inter-region audio bearer.
After failover, if an ESS server controls Port Networks or media gateways in one or more
network regions where IGAR is administered, IGAR continues to work. However, if Port
Networks or media gateways across different network regions are controlled by separate ESS
servers, calls between these systems are not seen as internal calls and therefore, IGAR does
not apply.
For example, an ESS customer with 8 Port Networks, administers each Port Network in a
separate network region (1 through 8). IGAR is administered between all 8 regions. A network
fragmentation failure occurs. Port Networks 1 through 4 failover to ESS server 1. Port Networks
5 through 8 failover to Local Only ESS servers. ESS server 1 uses IGAR to establish inter-port
network bearer between Port Networks 1 through 4. Each Local Only ESS server controls one
Port Network (5 through 8). IGAR does not apply for the Local Only servers.
All Port Networks within a CSS must be in network region 1. When an ESS server obtains
control of Port Network from the CSS, all Port Networks remain in network region 1. IGAR does
not apply within the same network region.
Trunking considerations
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