Avaya Communication Manager Administrator's Manual page 540

Managing Data Calls
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.
H11
When a trunk group is administered to support H11, the algorithm to satisfy a call requiring
1,536 Kbps of bandwidth uses a fixed allocation scheme. That is, the algorithm searches for an
available facility using the following facility-specific channel definitions:
T1: H11 can only be carried on a facility without a D-channel being signaled in an NFAS
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arrangement (B-channels 1-24 are used).
E1: Although the 1,536 Kbps bandwidth could be satisfied using a number of fixed starting
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points (for example, 1, 2, 3, and so forth), the only fixed starting point being supported is 1.
Hence, B-channels 1-15 and 177-25 always are used to carry an H11 call on an E1 facility.
If the algorithm cannot find an available facility within the trunk that meets these constraints,
then the call is blocked from using this trunk group. In this case, the call may be routed to a
different trunk group preference via Generalized Route Selection (GRS), at which time, based
on the wideband options administered on that trunk group, the call would be subject to another
hunt algorithm (that is, either the same H11 algorithm or perhaps an N x DS0 algorithm
described in a later paragraph).
Note that on a T1 facility, a D-channel is not considered a busy trunk and results in a facility with
a D-channel always being partially contaminated. On an E1 facility, however, a D-channel is not
considered a busy trunk because H11 and H12 calls may still be placed on that facility; an E1
facility with a D-channel and idle B-channels is considered an idle facility.
540 Administrator Guide for Avaya Communication Manager