Avaya Communication Manager Administrator's Manual page 1770

Feature Reference
Wideband Switching
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
The algorithms have the ability to select trunks from low B-channel to high B-channel or from high
B-channel to low B-channel with an ISDN facility. This is a per ISDN trunk group option, but infers the
direction of search within all ISDN facilities (or portions of those facilities) administered within that
trunk group. This is necessary so the selection of trunks are not prone to as much glare as they otherwise
would be if trunks were chosen in the same direction by both user and network sides of the ISDN
interface. Note that in previous Avaya software releases, the order in which trunks were selected, whether
through linear or circular hunting, would always be with respect to the order in which trunks were
administered within the trunk group. Now, with the support of wideband services, all trunks within an
ISDN trunk group optioned for wideband are ordered based on this new "direction of trunk/hunt with
facilities" parameter, and without regard to the order in which trunks are administered within the trunk
group. 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 a
nonfacility-associated signaling (NFAS) arrangement (B-channels 1-24 are used).
•
E1: Although the 1,536-kbps bandwidth could be satisfied using a number of fixed starting points
(for example, 1, 2, 3, etc.) the only fixed starting point being supported is 1. Hence, B-channels
1–15 and 17–25 are always used to carry an H11 call on an E1 facility.
If the algorithm cannot find an available facility within the trunk group 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).
This same hunt algorithm, when offered any other call (other than a 1,920-kbps call) attempts to preserve
idle facilities by selecting trunk(s) in a partially contaminated facility if one exists. If the bandwidth
required by this call cannot be satisfied by any partially contaminated facility, then the call is placed on
available trunk(s) within an idle facility, thus contaminating the facility. Again, facilities are selected via
the trunk group's facility list and with PN preference, and trunk(s) within a facility are selected based on
the direction of channel search administered. 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.
1770 Administrator's Guide for Avaya Communication Manager
November 2003