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DEFINITY ECS Release 8.2
Administrator’s Guide
555-233-506
Issue 1
April 2000
Managing data calls
427Wideband Switching
15
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.