Avaya Communication Manager Administrator's Manual page 465

Networking
All of the wideband networking is over ISDN-PRI facilities (and the emulation of them by ATM-CES)
but may connect to a variety of networks, other domestic interexchange carriers' services, private line,
RBOC services, and services in other countries.
ISDN-PRI trunk groups and channel
allocation
Only ISDN-PRI trunks (and the emulation of them by ATM-CES) support wideband calls to the network.
Wideband's bandwidth requirements have necessitated modification of the algorithms by which trunks
look for idle channels. The following section describes the search methods and their relationship to the
available wideband data services.
Facility lists
The system always sends a wideband call over a single trunk group and a single DS1 facility (or other
ISDN-PRI-capable facility). Since a trunk group may contain channels (trunk members) from several
different DS1 facilities, the system maintains a facility list for each trunk group.
A facility list orders the trunk members based on signaling group. If the system is using non-facility
associated signaling groups with multiple DS1 facilities, the system sorts trunk members in that signaling
group according to the interface identifier assigned to the corresponding DS1 facility.
When searching for available channels for a wideband call placed over a given trunk group, the system
starts with the channels in the lowest-numbered signaling group with the lowest interface identifier. If the
system cannot find enough channels in a given signaling group with that interface identifier, it checks the
next higher interface identifier. If no more interface identifiers are available in the current signaling
group, the system moves its search to the channels in the next higher signaling group.
For example, if three facilities having signaling group/interface identifier combinations of 1/1, 1/2, and
2/1 were associated with a trunk group, then a call offered to that trunk group would search those
facilities in the order as they were just listed. Also note that since trunks within a given facility can span
several trunk groups, a single facility can be associated with several different trunk groups.
Given this facility list concept, the algorithms have the ability to search for trunks, by facility, in an
attempt to satisfy the bandwidth requirements of a given wideband call. If one facility does not have
enough available bandwidth to support a given call, or it is not used for a given call due to the constraints
presented in the following section, then the algorithm searches the next facility in the trunk group for the
required bandwidth (if there is more than one facility in the trunk group).
In addition to searching for channels based on facilities and required bandwidth, Port Network (PN)
preferential trunk routing is also employed. This PN routing applies within each algorithm at a higher
priority than the constraints put on the algorithm by the parameters listed later in this section. In short, all
facilities that reside on the same PN as the originating endpoint are searched in an attempt to satisfy the
bandwidth of a given call, prior to searching any facilities on another PN.
Direction of trunk/hunting within facilities
You can tell the system to search for available channels in either ascending or descending order. These
options help you reduce glare on the channels because the system can search for channels in the opposite
direction to that used by the network. If an ISDN trunk group is not optioned for wideband, then a
cyclical trunk hunt based on the administration of trunks within the trunk group is still available.
Administrator's Guide for Avaya Communication Manager
November 2003
Managing Data Calls
Wideband Switching
465